NUREG/CR-3629, 'The Effect of Thermal and Irradiation ...

NUREG/CR-3629SAND83-2651RVPrinted April 1984

The Effect of Thermal and IrradiationAging Simulation Procedures onPolymer Properties

L. D. Bustard, E. Minor, J. ChenionF. Carlin, C. Alba, G. Gaussens, M. LeMeur

Prepared bySandia National LaboratoriesAlbuquerque, New Mexico 87185 and Livermore, California 94550for the United States Department of Energyunder Contract DE-AC04-76DP00789

Prepared forU. S. NUCLEAR REGULATORY COMMISSION

NOTICEThis report wasprepared as an account of work sponsored by anagency of the United States Government. Neither the UnitedStates Government nor any agency thereof, or any of their em-ployees, makes any warranty, expressed or implied, or assumesany legal liability or responsibility for any third party's use, or theresults of such use, of any information, apparatus product orprocess disclosed in this report, or represents that its use by suchthird party would not infringe privately owned rights.

Available fromGPO Sales ProgramDivision of Technical Information and Document ControlU.S. Nuclear Regulatory CommissionWashington, D.C. 20555andNational Technical Information ServiceSpringfield, Virginia 22161

NUREG/CR-3629SAND83-2651

RV

THE EFFECT OF THERMAL AND IRRADIATIONAGING SIMULATION PROCEDURES ON POLYMER PROPERTIES

L. D. Bustard and E. MinorSandia National Laboratories

Albuquerque. New Mexico 87185, USA

J. Chenion. F. Carlin, C. Alba. and G. GaussensCEA-ORIS LABRA at Saclay

91190 Gif-sur-Yvette. France

M. LeMeurCEA-DAS-SAF

92260 Fontenay-aux-Roses. France

Printed April 1984

Sandia National LaboratoriesAlbuquerque. New Mexico 87185

Operated bySandia Corporation

for theU.S. Department of Energy

Prepared forElectrical Engineering Branch

Division of Engineering TechnologyOffice of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission-Washington. DC 20555

Under Interagency Agreement 40-550-75NRC FIN No. A-1051

PREVIOUS PUBLICATIONS IN THIS SERIES

1. K. T. Gillen. R. L. Clough. G. Ganouna-Cohen. J. Chenion.and G. Delmas. Loss of Coolant Accident (LOCA)Simulation Tests on Polymers: The Importance ofIncluding Oxygen. NUREG/CR-2763, SAND82-1071, July 1982.

2. K. T. Gillen, R. L. Clough. G. Ganouna-Cohen, J. Chenion,and G. Delmas, "The Importance of Oxygen in LOCA Simu-lation Tests," Nuclear Engineering and Design. 74 (1982).pgs. 271-285.

ii

ABSTRACT

Prior to initiating a qualification test on safety-related equipment, the testing sequence for thermal andirradiation aging exposures must be chosen. Likewise. thetemperature during irradiation must be selected. Typically.U.S. qualification efforts employ ambient temperatureirradiation, while French qualification efforts employ 700 C

irradiations. For several polymer materials, the influenceof the thermal and irradiation aging sequence, as well as theirradiation temperature (ambient versus 70 0 C). has beeninvestigated in preparation for Loss-of-Coolant Accidentsimulated tests.

Ultimate tensile properties at completion of aging arepresented for three XLPO and XLPE, five EPR and EPDM, twoCSPE (HYPALON), one CPE, one VAMAC, one polydiallylphtalate.and one PPS material.

Bend test results at completion of aging are presentedfor two TEFZEL materials.

Permanent set after compression results are presented forthree EPR. one VAMAC, one BUNA N. one Silicone, and one Vitonmaterial.

iii/iv

TABLE OF CONTENTS

Executive Summary 1

1.0 Introduction 3

2.0 Samples 4

2.1 U.S. Samples 42.2 French Samples 5

3.0 Facilities i0

3.1 Radiation Aging Facility 103.2 Thermal Aging Facility 18

4.0 Experimental Techniques 20

4.1 U.S. Samples 204.2 French Samples 26

5.0 Results 41

5.1 U.S. Samples 41

5.1.1 CSPE and CPE Jacket Materials 415.1.2 EPR Insulation Materials 475.1.3 XLPO Insulation Materials 475.1.4 TEFZEL Materials 475.1.5 Compression Set Tests 60

5.2 French Samples 60

5.2.1 PRC (82 Ii) 635.2.2 EPDM (82 12 and 82 19) 63

5.2.2.1 EPDM (82 12) 635.2.2.2 Fire-proof EPDM (82 19) 63

5.2.3 EPR (82 H4 and 82 J4) 675.2.4 VAMAC (82 H3 and 82 J3) 675.2.5 HYPALON (82 G10) 685.2.6 PPS (82 H6) 685.2.7 Polydiallylphtalate (82 H5) 68

6.0 Conclusion 76

References 77

V

LIST OF FIGURES

2.1 Dimensions for 82 GlO. 82 H3, and 82 H4 French 7Dumbbell Samples

2.2 Compression Set Fixtures Used for 82 J3 and 8

82 J4 French O-ring Seal Samples

2.3 Dimensions for 82 H5 and 82 H6 ISO Dumbbell Samples 9

3.1 Artist's Rendition of Low Intensity Cobalt 11Array (LICA) Facility

3.2 Arrangement of Low Intensity Cobalt Array (LICA) 12Facility for U.S.-French Aging Program

3.3 Locations of Thermoluminescent CaF 2 Wafers 13Inside LICA Irradiation Can During Dose RateGradient Mapping

3.4 A LICA Irradiation Test Cell 16

3.5 EPR 1 and EPR 2 Insulation Specimens Prepared 17to be Inserted into the Sample Aging Region ofa LICA Irradiation Test Cell

3.6 Oven Aging Cell 19

4.1 U.S. Compression Set Fixture 24

4.2 Orientation of U.S. Compression Set Fixtures 25in Radiation Field

4.3 82 H5 and 82 H6 Samples Prepared for Aging 32

4.4 82 H5 Samples Prior to Insertion into LICA 33Irradiation Cell

4.5 Orientation of 82 H5 and 82 H6 Samples During 34Irradiation

4.6 Preparation of 82 H3. 82 H4, and 82 G1O Samples 35for Aging

4.7 82 H3. 82 H4. and 82 G1O Samples Shown as Prepared 36to be Inserted into LICA Irradiation Cell

4.8 Orientation of 82 H3. 82 H4. and 82 G1O Samples 37During Irradiation

vi

LIST OF FIGURES (Continued)

4.9 82 J3 Samples Prepared to be Irradiated 38

4.10 Irradiation Aging Configuration Used for 3982 J4 Samples

5.1 Ultimate Tensile Elongation of CSPE in 42Various Environments

5.2 Ultimate Tensile Strength of CSPE in Various 43Environments

5.3 Ultimate Tensile Elongation of CPE in Various 44Environments

5.4 Ultimate Tensile Strength of CPE in Various 45Environments

5.5 Ultimate Tensile Strength of CPE in Various 46Environments

5.6 Repeatability of Ultimate Tensile Elongation 48Results for CPE During Two R2 7 Exposures

5.7 Repeatability of Ultimate Tensile Strength 49Results for CPE During Two R2 7 Exposures

5.8 Ultimate Tensile Elongation of EPR 1 in 50Various Environments

5.9 Ultimate Tensile Strength of EPR 1 in Various 51Environments

5.10 Ultimate Tensile Elongation of EPR 2 in 52Various Environments

5.11 Ultimate Tensile Strength of EPR 2 in Various 53Environments

5.12 Ultimate Tensile Elongation of XLPO 1 in 54Various Environments

5.13 Ultimate Tensile Strength of XLPO 1 in Various 55Environments

5.14 Ultimate Tensile Elongation of XLPO 2 in 56Various Environments

vii

LIST OF FIGURES (Continued)

5.15 Ultimate Tensile Strength of XLPO 2 in 57Various Environments

5.16 Ultimate Tensile Properties for PRC (82 Ii) 64

5.17 Ultimate Tensile Properties for EPDM (82 12) 65

5.18 Ultimate Tensile Properties for Fire-Proof 66EPDM (82 19)

5.19 Ultimate Tensile Properties for EPR (82 H4) 69

5.20 Permanent Set After Compression for EPR (82 J4) 70

5.21 Ultimate Tensile Properties for VAMAC (82 H3) 71

5.22 Permanent Set After Compression for 72VAMAC (82 J3)

5.23 Ultimate Tensile Properties for HYPALON 73(82 G1O)

5.24 Ultimate Tensile Properties for PPS (82 H6) 74

5.25 Ultimate Tensile Properties for 75Polydiallylphtalate (82 H5)

viii

LIST OF TABLES

2.1 Nominal Insulation and Jacket Thicknesses for 5U.S. Samples

3.1 Relative Dose Rate Gradients, R/RA. for Several 14LICA Irradiation Positions

4.1 Radiation Dose and Thermal Exposure Time for 23U.S. Insulation and Jacket Specimens

4.2 Radiation Doses and Thermal Aging Conditions 26

for Each U.S. Compression Set Fixture

4.3 Thermal Exposure Temperatures for French Samples 29

4.4 Total Radiation Dose and the Thermal Exposure 30Time for Each Group of French Samples

4.5 Accuracy of French Measurements 40

5.1 Bend Test Results for TEFZEL 1 58

5.2 Bend Test Results for TEFZEL 2 59

5.3 U.S. Compression Set Test Results 61

5.4 Tensile and Compression Set Results for 62French Samples

ix

ACKNOWLEDGMENTS

Our appreciation is extended to Mike Luker, who ablyassisted throughout the experimental aging program. JohnLewin. Tim Gilmore. Jerry Seitz, Jack Bartberger, Pat Drozda.and Lowell Jones also provided valuable assistance during theexperimental effort.

X

EXECUTIVE SUMMARY

As part of a joint French/U.S. sponsored researchprogram, the influence of accident testing conditions on thebehavior of polymer materials is being investigated. Testvariables in the accident program include: irradiation tem-perature, oxygen presence during accident simulations, andsimultaneous versus sequential accident exposures. In prep-aration for the accident tests, polymer materials were ex-posed to irradiation and elevated temperatures to produce an"accelerated age". Test variables in the aging program wereirradiation temperature, the order of the aging sequence, andsimultaneous versus sequential aging techniques. The influ-ence of aging dose rate and accident oxygen concentration haspreviously been documented1 and our current work is anextension of this previous effort.

In this report, test results at completion of the agingexposures are presented for several commercial insulation andjacket materials, compression and gasket materials, andthermosetting and thermoplastic materials. Our goals for theaging portion of the research program were:

1. To investigate whether polymer materials are sensi-tive to the sequential order in which they are ir-radiated and thermally aged. Previously publishedresults2 for low-density polyethylene (LDPE) andpolyvinylchloride (PVC) indicated that irradiationfollowed by a thermal aging exposure was the morespvere sequence. We wished to establish the appli-cability of this conclusion for a broader class ofmaterials. Both irradiation followed by thermal ex-posure and thermal exposure followed by irradiationaging sequences were part of the testing program.

2. To investigate the importance of irradiation temp-erature during sequential aging exposures. Frenchregulatory documents 3 require aging and accidentirradiations for qualification testing to be per-formed at 70 0 C. In contrast, typical U.S. qualifi-cation efforts perform ambient temperature irradia-tions. Irradiations at ambient (-270C) and 700 Cwere performed as part of the testing program.

3. To provide a variety of aged samples for use duringLOCA simulation experiments.

Our experimental results at completion of the aging pro-gram indicate:

1. If sequential ordering of irradiation and thermalexposures was important to the aging degradation oftensile properties, usually the irradiation followedby thermal exposure sequence was most severe.

2. In general, the choice of irradiation temperature wassecondary to the choice of aging sequence in its ef-fect on polymer properties.

3. For several materials, tensile properties at comple-tion of aging were only slightly affected by both theirradiation temperature and the order of the sequen-tial aging environmental exposures.

4. At most, only slight differences in permanent setwere noted as a result of the various aging tech-niques.

Ultimate tensile properties at completion of aging arepresented for three cross-linked polyolefin (XLPO) and crosslinked polyethylene (XLPE). five ethylene propylene rubber(EPR) and ethylene propylene diene terpolymer (EPDM), twochlorosulfonated polyethylene (CSPE, HYPALON). one chlori-nated polyethylene (CPE), one acrylic polyethylene (VAMAC),one polydiallylphtalate. and one phenylene polysulfide (PPS)material.

Bend test results at completion of aging are presentedfor two TEFZEL materials. o

Permanent set after compression results are presented forthree ethylene propylene rubber (EPR), one acrylic poly-ethylene (VAMAC), one BUNA N, one Silicone, and one Vitonmaterial.

2

1.0 INTRODUCTION

When used as part of a safety-related system, equipmentmust meet certain qualification criteria. Several documentsdescribe or suggest the tests and data necessary to establishqualification. For example. IEEE standards. USNRC Rules(1OCFR50.49) 5 and documents (NUREG-0588) 6 and FrenchDocuments (HM/63-7195/6) 3 provide guidance concerningqualification. These documents generally require qualifica-tion efforts to account for aging of components under normaloperating conditions by performing accelerated aging ofequipment or components prior to simulation of accidentconditions.

The aging environment inside a nuclear reactor contain-ment is a multistress environment including thermal andradiation stresses. Historically, aging in this multistressenvironment is simulated by a sequential application ofsingle stress environmental exposures. For example, IEEE323-19747 suggests a thermal aging followed by irradiationaging exposure. This exposure is considered the most severesequence for most equipment and applications. "However, thesequence used shall be justified as the most severe for theitem being tested.''7

As part of a joint French/U.S. sponsored research pro-gram, we are investigating the influence of testing condi-tions on the behavior of polymer materials. Variables in thetest program include: aging sequence, irradiation tempera-ture, oxygen presence during accident simulations, andsimultaneous versus sequential accident and aging exposures.The influence of dose rate and oxygen concentration has pre-viously been documented1 and our current work is an ex-tension of this previous effort.

In preparation for LOCA research experiments, we haveaged several commercial insulation and jacket materials.compression and gasket materials, and thermosetting andthermoplastic dumbbells. We have accumulated sufficientaging data to demonstrate that some materials are sensitiveto the order and manner in which they are irradiated andthermally aged. Properties of other polymer materials didnot depend on the order and technique of radiation andelevated temperature exposures. In this report we summarizeour data and discuss its significance toward qualificationtesting of nuclear grade safety-related equipment.

3

2.0 SAMPLES

2.1 U.S. Samples

The U.S. samples consisted of six insulation materials,two jacket materials, and five compression materials. Theinsulation and jacket materials were carefully obtained bydisassembling cable received from five U.S. manufacturers ofClass 1E cables. The materials are:

EPR 1 A radiation crosslinked fire-retardant EPDM in-sulation obtained from a shielded instrumentationcable.

EPR 2 A chemically crosslinked fire-retardant EPDM in-sulation obtained from a 600V, 3-conductor controlcable.

XLPO 1 A crosslinked polyolefin insulation obtained froma shielded instrumentation cable.

XLPO 2 A crosslinked polyolefin insulation obtained froma 600V, 3-conductor control cable.

TEFZEL 1 A TEFZEL insulation removed from a thermocoupleextension cable.

TEFZEL 2 A TEFZEL insulation removed from a shielded in-strumentation cable.

CSPE A chlorosulfonated polyethylene jacket removed froma 600V. 3-conductor control cable.

CPE A chlorinated polyethylene jacket removed from a600V, 3-conductor control cable.

Each of the jacket and insulation specimens were cut toa length of 10.9 + .3 cm (except for EPR 1 which had aninitial length of 10.2 + .3 cm). The insulation specimenswere tubular in shape. The nominal insulation thickness issummarized in Table 2.1. The jacket specimens were cut witha die into rectangular pieces. The width of each specimenwas .56 cm. The nominal jacket thicknesses are also pre-sented in Table 2.1.

The five compression materials were obtained from thesame U.S. manufacturer. Samples, received from the manu-facturer as compression molded sheets with nominal thick-nesses of .178 and .191 cm, were cut into small rectangleswith approximate dimensions: .6 cm x 1.6 cm. The fivematerials were: EPR A. EPR B. BUNA N. SILICONE, and VITON.

4

Table 2.1

Nominal Insulation and Jacket Thicknessesfor U.S. Samples

Material

EPR 1EPR 2XLPO 1XLPO 2TEFZEL 1TEFZEL 2CSPECPE

Nominal Thickness (cm)

.064

.076

.076

.076

.038

.051

.114

.114

2.2 French Samples

The French samples consist of six elastomer materialsused in the manufacture of electrical cables (insulation andjacket materials), two O-ring seal materials and two thermo-plastic and thermosetting materials used in the manufactureof connectors.

The electrical cable materials are in the form of either110 mm-long pieces of insulating material stripped from thecopper conductor (identified by "I"). dumbbells cut fromjacket material and identified by "G". or standard dumbbellscut from compression molded sheets (identified by "H").Elastomer dumbbell dimensions are shown in Figure 2.1. Thesix cable materials are:

82 Ii PRC

82 12 EPDM

82 19 EPDM

82 G1O HYPALON

Chemically crosslinked polyethylene in theform of conductor insulation for 3-conductorcables.

Ethylene propylene diene terpolymer con-ductor insulation. Samples taken from a3-conductor cable.

Alumina-loaded. ethylene propylene dieneterpolymer conductor insulation. Thismaterial was removed from a 3-conductorcable.

Chlorosulfonated polyethylene used in themanufacture of cable jackets.

5

82 H3 VAMAC

82 H4 EPR

Acrylic polyethylene in the form of sheets fromwhich dumbbells (Figure 2.1) were cut. Mate-rial is used in electrical cable jackets.mechanical parts, and connectors.

Copolymer ethylene-propylene rubber in the formof 3 mm sheets from which dumbbells (Figure2.1) were cut. Material is used in the manu-facture of insulation for electrical cablessheathed with fire-proof EPDM.

The two O-ring seal samples (identified by "J") have aninner diameter of 12 mm and an outer diameter of 17 mm. Theywere enclosed and held under compression in aluminum groovesas shown in Figure 2.2. The O-ring seal materials are:

82 J3 VAMAC

82 J4 EPR

Same material as 82 H3. used in the manufactureof O-ring seals.

Same material as 82 H4. used in the manufactureof O-ring seals.

The two thermoplastic and thermosetting materials usedin the manufacture of connectors were in the form of Inter-national Organization for Standardization (ISO) dumbbells.The dimensions for these dumbbells is illustrated in Figure2.3. The two materials are:

82 H5 Polydiallyl-phtalate

Thermosetting polyester used in con-nectors and mechanical parts.

Phenylene polysulfide used in themanufacture of switches and con-nectors.

82 H6 PPS

The French sample identification code (82 Il. 82 H5,etc.) will be used in the remainder of this report. The codepresents:

" The year of the starting investigation," The sample shape code letter." A number identifying the material type.

6

EEEEco oRh.

4mm

IL

Figure 2.1. Dimensions for 82 G1O, 82 H3. and 82 H4 FrenchDumbbell Samples - H3 French Standard(Commission of Normalization NO NF.T51-034-June 1968)

7

A 06.2 mm

AA' SECTION

Figure 2.2. Compression Set Fixtures Used for 82 J3 and82 J4 French O-ring Seal Samples

8

0

Figure 2.3. Dimensions for 82 H5 and 82 H6 ISO DumbbellSamples

9

3.0 FACILITIES

3.1 Radiation Aging Facility8

Figure 3.1 shows an artist's rendition of the LowIntensity Cobalt Array (LICA) radiation facility. Approxi-mately 16,000 curies of Co-60 is positioned at the bottom ofa water-filled tank. Radiation aging is carried out inwater-tight test cells by lowering the cells to the bottomof the tank. Water, separating the Co-60 from experimentersat the top of the tank, provides radiation shielding.

Approximately 10.000 curies of Co-60 is positioned in acircular array to provide high dose-rate exposures. Thisportion of the radiation facility was not used in this test.The remaining 6,000 curies of Co-60 is positioned in twoparallel arrays as shown in Figure 3.2. Test cell holders.each containing four cylindrical holes, are oriented parallelto the linear cobalt holders. One holder is located betweenthe two linear arrays of cobalt; the remaining holders arelocated on the two sides of the cobalt-60 sources at variousdistances from them. Test cells placed in any of the holesof a given holder receive comparable radiation dose rates.

The dose rate is governed by the distance of the cellfrom the cobalt array. Center-of-can dose rates are givenin Figure 3.2. Gradients in dose rates occur in the indi-vidual test cells; for example, there is a dropoff in doserates between the parts of the cell closest to, and furthestfrom, the cobalt. A Victoreen Model 550 Radicon III Inte-gration/Rate Electrometer with a Model 550 air ionizationprobe was used to measure the dose rate at the center of thetest cell. Accuracy was ± 5 percent. Harshaw TLD-400's(calcium fluoride manganese activated thermoluminescentdetectors) were used to map the radiation gradients forseveral of the LICA positions. Figure 3.3 illustrates thepositioning of the CaF 2 Mn wafers during gradient mapping:Table 3.1 summarizes the measured gradients. Accuracy of theCaF 2 wafers was + 10 percent. For LICA can positions IIIA. III B. IV A. IV B. V A. and V B. center-of-can dose ratesonly were measured. Gradients are similar (by symmetry) tothose measured for the respective C and D positions. Gradi-ent effects were reduced by rotating the cans during theexposure or by appropriate positioning of the samples withinthe test cell.

10

Figure 3.1. Artist's Rendition of Low Intensity CobaltArray (LICA) Facility

11

DOSE RATEKRD/H

LEVEL 5/28/82

COBAL 71PENCILS

00000000

000000000000000

VI

V85

19

IV 114

65

19

6

D C B A

Figure 3.2. Arrangement of the Low Intensity Cobalt Array

(LICA) facility for U.S./French aging program.

French samples were aged using positions

IV A-IV D. U.S. Samples were aged using

positions III A-III D and V A-V D.

12

2 CENTERLINEZ AXIS OF F

Z IRRADIATION0 CAN 14.0 cm

Z5 8c9cm> 2

0 -4ca <

W BOTTOM OF LICA IRRADIATION BRASS CAN

Figure 3.3. Locations of thermoluminescent CaF 2 wafersinside LICA irradiation can during dose rategradient mapping. CaF 2 wafers were placed atPositions A. B. C. D. E. F. and G.

13

Table 3.1

Relative Dose Rate Gradients. R/RA. for SeveralLICA Irradiation Positions. MeasurementLocations A-G are Shown in Figure 3.3.

LICA Position

MeasurementLocation IIIC HID IVC IVD VC VD

A 1.00 1.00 1.00 1.00 1.00 1.00

B 0.97 1.14 1.01 1.03 1.09 0.92

C 0.69 0.77 0.96 0.98 1.37 1.32

D 0.93 0.83 0.91 1.02 1.02 0.95

E 1.29 1.27 0.96 1.08 0.83 0.76

F 1.05 1.04 0.94 0.94 1.04 0.95

G 0.93 0.85 0.92 0.96 1.06 0.90

14

A detailed sketch of a test cell is shown in Figure 3.4.The cylindrical sample aging region (10 cm diameter and 23 cmlong) is located inside a brass can, which in turn is sus-pended from the lid of a double-walled stainless-steel can.(The double-walled design provides some thermal insulation.)When the stainless-steel lid is lifted free of the stainless-steel can, a brass lid at the bottom of the brass can iseasily removed, allowing access to the sample aging region.Figure 3.5 illustrates insulation specimens prepared to beinserted into the sample aging region.

The sample region is heated using an insulated nichromewire wrapped around the sides of the brass can and alsoaround a pancake heater which lies between the brass can andthe stainless-steel lid. The auxiliary pancake heater wasfound to be useful for reducing rather substantial tempera-ture gradients at the top of the sample aging region causedby the heat-sink effect of the massive top of the stainless-steel can. To accurately control and monitor the temperaturein the sample region, two resistance temperature devices(RTDs) were incorporated in the design. A control RTD isdirectly clamped to the inside wall of the brass can and amonitor RTD is positioned close to the center of the sample-aging region. A 2.9 cm OD plastic tube runs from the top ofthe stainless-steel can up through the water tank. Leadwires for the heater and the two RTDs feed through this tube.In addition, a small tube inside the outer plastic tube isused to circulate air or other gaseous environments past thesample region at controlled flow rates. The temperaturecapabilities of the test cells are room temperature to 150 0 C.

15

0

STESTSPECIMENS

AIR DIFFUSIONPLATE .Jt-

Figure 3.4. A LICA Irradiation Test Cell

16

Figure 3.5. EPR 1 and EPR 2 insulation specimens preparedto be inserted into the sample aging-region ofa LICA irradiation test cell.

17

3.2 Thermal Aging Facility8

The Thermal Aging Facility uses air circulating ovens.each modified to accommodate a number of self-contained agingcells. A detailed sketch of one of these aging cells isshown in Figure 3.6. It consists of a bell jar glass chamberwhich rests on an aluminum stand. A gas inlet line entersthe sample aging region from the bottom through a hole in thealuminum base. A small hole at the top of the glass chamberserves as a gas exit and as a means of introducing a per-manently positioned thermocouple into the center of thesample region. Metal collars surrounding the glass bell jarsimprove the thermal stability and reduce temperature gradi-ents in the sample aging region. Sample holders fit insidethe glass chamber. The aging cells used for this test wereconstructed in three sizes with internal volumes of .9 liter.2.5 liters, and 3.9 liters.

18

,THERMOCOUPLEGLASS CHAMBER7/SAMPLE BASKET

/;/.ALUMINUM COLLAR

r-AMPLES

IJ

GAS INLETI A iLUMINUM BASE

... ... LEGS

---- .

Figure 3.6. Oven Aging Cell

19

4.0 EXPERIMENTAL TECHNIQUES

4.1 U.S. Samples

The U.S. insulation and jacket samples were exposed tofive different aging procedures. These procedures (and theshorthand codes used in the rest of the report to describethem) are:

A = R7 0 -+ 120*C.: A 16-day irradiation at-65 krd/h and 700C followed by a 16-daythermal exposure at 120 0 C.

B = R27 -+ 120°C: A 16-day irradiation at-65 krd/h and ambient temperatures (-270C)followed by a 16-day thermal exposure at 1200C.

C = 120 0C -4 R7 0 : A 16-day thermal exposure at1200C followed by 16-day irradiation at-65 krd/h and 700C.

D = 120 0 C -+ R2 7 : A 16-day thermal exposure at1200C followed by a 16-day irradiation at-65 krd/h and ambient temperatures ( 27 0 C).

E = R1 2 0 : A 16-day simultaneous exposure to 120 0Cthermal and -65 krd/h irradiation environments.

The 120 0C. 16-day deviated temperature exposure waschosen based on Arrhenius calculations which assumed a40-year service operation at 45 0 C and cable material acti-vation energy of 1.0 eV.

The insulation specimens were placed in sample fixturesas illustrated by Figure 3.5. EPR 1 and EPR 2 samples wereirradiated together. Likewise. XLPO 1 and XLPO 2 sampleswere irradiated together. The jacket specimens (CSPE andCPE) were irradiated separately. During irradiations, airflow to the 1.8 liter irradiation cell was approximately40 cc/min.

For thermal aging, 0.9 liter thermal aging cells wereemployed for the insulation specimens. Sample holders simi-lar to those shown in Figure 5 (but smaller in diameter) wereused to support each individual insulation specimen. EPR 1.EPR 2. XLPO 1. and XLPO 2 samples were each aged separately.The jacket specimens were aged using the 2.5 liter thermalaging cells. CPE and CSPE were thermally aged separately.Air flow to the thermal aging cells was -20 cc/min forboth the insulation and jacket specimens. This corresponds to

20

.5 to 2 "complete" air changes an hour. The air flow removesfrom the vicinity of the samples any thermal decompositionproducts that are outgassed by the samples.

For each material, approximately 80 sample specimensstarted each aging sequence. Several times during both theirradiation and thermal exposures, aging was momentarilyinterrupted to allow for removal of several sample specimens.These specimens were used to determine the degradation his-tory during the aging exposures. Midway during the irradia--tion exposure, the sample cell was rotated -1800 to aver-age radiation gradient effects. All samples pulled from thecell prior to completion of the irradiation were removedfrom the center of the cell. This minimized the effect ofradiation gradients on intermediate exposure results.

Table 4.1 summarizes the total radiation dose and thethermal exposure time for each group of U.S. insulation andjacket specimens.

Tensile tests were performed at Sandia NationalLaboratories on the EPR 1, EPR 2, XLPO 1, XLPO 2, CSPEo andCPE samples. For each experimental condition, three or foursamples were tested to determine the ultimate tensileelongation, e. and the ultimate tensile strength, T.Tensile measurements were performed at ambient temperatures(-23 0C) using Instron 1125 (EPR 2 specimens; agingenvironments A. B. D. and E) and Instron 1130 machines (allother specimens). Samples were gripped using pneumaticjaws: initial jaw separation was 5.1 cm and samples werestrained at 12.7 cm/min. The strain was monitored with anInstron electrical tape extensometer clamped to the sample.The systematic difference in normalized elongation andtensile strength due to the use of two different tensilemacchines was approximately 12%. Data obtained on the 1130was higher than that obtained by the 1125.

Bend tests were performed on the TEFZEL 1 and TEFZEL 2samples rather than tensile tests since aged specimen tubesshattered when gripped by the pneumatic jaws of the Instrontensile testing machine. Bend radii between 75 and 6 timesthe radii of the TEFZEL specimens were employed. Eachspecimen was successively wrapped around tubes of smallerdiameter until insulation cracking was visually observed.

21

The U.S. Compression Set Samples were exposed to threedifferent aging procedures. These procedures (and theshorthand used in the rest of the report to describe them)are:

R27 -* 120*C = A 16-day irradiation at -60 krd/hand ambient temperatures (-270C) followed bya 16-day thermal exposure at 120 0 C.

120 0 C R27 = A 16-day thermal exposure at 1200Cfollowed by a 16-day irradiation at -60 krd/hand ambient temperatures (-27 0 C).

R20= A 16-day simultaneous exposure to 120 0Cthermal and -60 krd/h irradiation environments.

The compression set samples were exposed using a fixtureas shown in Figure 4.1. Each layer of the fixture containedthree .127 + .001 cm spacers and four compression setsamples. Each of the five layers of one fixture was used fora different compression sample material; namely EPR A. EPRB. BUNA N. VITON, or SILICONE. Two sample fixtures were ir-radiated in an aging cell. The fixtures were oriented sothat the compression fixture surfaces were perpendicular tothe Cobalt-60 array (see Figure 4.2). Air flow to the ir-radiation cell was approximately 40 cc/min. Thermal agingwas performed using a 2.5 liter aging cell containing fourfixtures. Air flow to the thermal aging cell was also40 cc/min. Table 4.2 summarizes irradiation doses and ther-mal aging times for each fixture.

The compression set samples ranged in thickness between.165 and .205 cm. Prior to compression, each individualsample was measured for thickness and its position in thefixture noted. After exposures to radiation and thermalenvironments, the sample thickness was again measured. Priorto the final measurements, the fixture was disassembled(releasing the compressive strain) and a 30-minute recoverytime allowed.

Our compression set samples have much smaller thicknessesthan those recommended by ASTM Standard D395-78. 9 ThisStandard recommends (for Method B) test specimens with1.25 cm thicknesses. Our sample thicknesses more realisti-cally simulate use conditions, but generate much largererrors in the calculated values for compression set.Absolute error for our compression set values is + 0.1.

22

Table 4.1

Radiation Dose and Thermal Exposure Timefor U.S. Insulation and Jacket Specimens

Sample GroupXLPO 1AXLPO 1BXLPO iCXLPO 1DXLPO IE

XLPO 2AXLPO 2BXLPO 2CXLPO 2DXLPO 2E

EPR 1AEPR lBEPR 1CEPR IDEPR 1E

EPR 2AEPR 2BEPR 2CEPR 2DEPR 2E

CSPE ACSPE BCSPE CCSPE DCSPE E

CPE ACPE BCPE CCPE DCPE E

Total RadiationDose[Mrd(air equiv.)]

24.2*24.223.423.124.3

22.7*24.223.423.024.3

Thermal ExposureTime (HRS)

385 hours385 hours384 hours385 hours386 hours

25.725.525.025.325.7

25.725.525.025.325.7

25.025.424.224.224.6

23.923.423.123.123.4

22.322.922.322.322.4

22.322.922.322.322.4

386385384385386

385385384384384

385385384384384

389380389389384

389389385385384

386377383384381

386377383384381

hourshourshourshourshours







TEFZELTEFZELTEFZELTEFZELTEFZEL

TEFZELTEFZELTEFZELTEFZELTEFZEL

1A1BIC

ID1E

2A2B2C2D2E

* XLPO 1A and XLPO 2A were irradiated separately.

23

A A

Figure 4.1. U.S. Compression Set Fixture

24

CO-60

Figure 4.2. Orientation of U.S. Compression SetFixtures in Radiation Field

Table 4.2

Radiation Doses and Thermal Aging Conditionsfor Each U.S. Compression Set Fixture

CompressionSet Fixture

Total Dose(Mrd)

Thermal AgingTime (hrs)Aainc Seauence

#38

#12

#37

#32

#13

#14

#20

#50

Unaged NA NA

NA23.8

120 NA

R27 4 120

R27 - 120

120 4 R27

120 - R27

22.9

23.8

23.8

23.4

23.0

386

382

386

386

386

386

4.2 French Samples

The French samples were exposed to four different agingprocedures. These procedures (and the shorthand codes usedin the rest of the report to describe them) are:

A = T 4 R70:

B = R 7 0 4 T:

C = T 4 R27:

D = R 2 7 4 T:

A 10-day thermal exposure followed by a9- or 10-day irradiation at -115 krd/hand 70 0 C.

A 9- or 10-day irradiation at -115 krd/hand 70 0 C followed by a 10-day thermalexposure.

A 10-day thermal exposure followed by a9- or 10-day irradiation at -115 krd/hand ambient temperatures (-27 0 C).

A 9- or 10-day irradiation at -115 krd/hand ambient temperatures (~27 0 C)followed by a 10-day thermal exposure.

The 10-day thermal exposure temperature depended on thespecimen material. Table 4.3 lists each of the French

26

Samples and the appropriate thermal aging temperature.Various sample groups were irradiated over a several monthperiod. Co-60 decay during this time period necessitatedvarying the irradiation exposure time from 9 days to 10 daysso that each sample group was irradiated to a similar dose(-25 Mrd).

Table 4.4 summarizes the total radiation dose and thethermal exposure time for each group of French samples. Theinsulation specimens (82 Ii. 82 12. 82 19) were irradiatedand thermally aged using fixtures similar to that shown inFigure 3.5. 82 Il and 82 12 samples were irradiated togetherin the same aging cell. 82 19 samples were irradiated alone.Air flow to each of the 1.8 liter irradiation cells was-60 cc/min. Thermal aging of each group of insulationspecimens was performed separately using a 0.9 liter agingcell and an air flow of -30 cc min. The 82 H5 samples wereirradiated as shown in Figures 4.3 through 4.5. Metallicwashers were used to keep each dumbbell separate from allothers. A similar arrangement was used for the 82 H6 samples(but without the basket). Air flow to the irradiation cham-bers was -60 cc/min. The 82 H5 samples were thermally agedusing 0.9 liter thermal cells and ~30 cc/min air flow. The82 H6 samples were thermally aged using 3.9 liter aging cellsand a -100 cc/min air flow. 82 H3, 82 H4, and 82 G10dumbbells were assembled as shown in Figures 4.6 and 4.7 andoriented for irradiation as shown in Figure 4.8. Air flowto the 1.8 liter irradiation cell was -60 cc/min; air flowto the 0.9 liter thermal aging cell -30 cc/min. The 82 J3compression set assemblies were randomly placed in a basketand irradiated as shown in Figure 4.9. The 82 J4 com-pression set assemblies were stacked in a basket and irradi-ated as shown in Figure 4.10.

Air flow to the 1.8 liter irradiation cell was -60cc/min for the 82 J3 and 82 J4 samples. These samples weretherm- ally aged using 0.9 liter aging cells with an airflow of -30 cc/min.

The ultimate tensile elongation, e. and ultimate tensilestrength, T. were measured at CEA-ORIS-LABRA in Saclay forFrench elastomer samples 82 If. 82 12, 82 19, 82 H3, 82 H4,and 82 G10. the thermoplastic material 82 H6. and the ther-mosetting material 82 H5. A ZWICK Model 7025/3 test machine.located in a room with controlled temperature of 210 C. wasused for the tensile tests. Dumbbells and conductor insula-tion samples were gripped in the jaws of the test machine.Initial spacing between the jaws was 40 mm for the 82 GIO.82 H3, and 82 H4 dumbbells, approximately 150 mm for the82 H5 and 82 H6 dumbbells, and on the average 110 mm for the

27

82 I1, 82 12. and 82 19 insulation specimens. An extenso-meter was located at the center of each test piece. Its gapwas 10.0 mm. The strain rate was 50 mm per minute.

Compression set measurements were performed atCEA-ORIS-LABRA in Saclay for French elastomer samples 82 J3and 82 J4.

Table 4.5 summarizes the accuracy of the French measure-ments. Each measurement is made on five test pieces. If ameasurement showed excessive discrepancy from the average itwas rejected and a new average was computed.

28

Table 4.3

Thermal Exposure Temperatures For French Samples

SampleDescription

1. PRC Insulation

2. EPDM Insulation

3. EPDM Insulation

4. PPS Dumbbells

5. PolydiallylphtalateDumbbells

6. VAMAC AcrylicPolyethyleneDumbbells

7. EPR Dumbbells

8. HYPALON Dumbbells

9. VAMAC Acrylic Poly-ethylene O-ringseal samples

10. EPR O-ring sealsamples

SampleCode

82 II

82 12

82 19

82 H6

82 HS

82 H3

ExposureTemperature (OC)

140

140

140

160

160

120

140

140

120

82

82

82

H4

GIO

J3

82 34 140

29

Table 4.4

Total Radiation Dose and the Thermal Exposure Timefor Each Group of French Samples

Radiation Exposures

RadiationDose

Thermal ExposureTime

82 IIABCD

82 12ABCD

82 19ABCD

82 H6ABCD

82 H5ABCD

82 H3ABCD

82 H4ABCD

82 G1OABCD

24.724.724.724.9

24.724.724.724.9

24.025.323.925.6

26.026.025.826.2

24.124.623.824.0

25.425.425.425.4

25.125.124.924.9

25.525.524.424.4

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

MrdMrdMrdMrd

240.5240.2240.5240.2

240.5240.2240.5240.2

258.5238.8258.5241.1

238.6238.7238.6238.7

240.2238.6240.2241.0

240.0240.2240.0240.2

258.5268.8258.5268.8

239.0243.9239.0243.9

hourshourshourshours








30

Table 4.4 (Continued)

Total Radiation Dose and the Thermal Exposure Timefor Each Group of French Samples

Radiation Exposures

RadiationDose

Thermal ExposureTime

82 J3ABCD

82 J4ABCD

25.4 Mrd25.4 Mrd24.5 Mrd24.5 Mrd

24.0 Mrd24.6 Mrd24.1 Mrd24.3 Mrd

240.0 hours241.3 hours240.1 hours240.2 hours

245.5 hours243.9 hours245.5 hours239.0 hours

31

Figure 4.3. 82 H5 and 82 H6 Samples Prepared for Aging

32

Figure 4.4. 82 H5 Samples Prior to Insertion into LICA

Irradiation Cell

33

Co--60

Figure 4.5. Orientation of 82 H5 and 82 H6 SamplesDuring Irradiation

34

Figure 4.6. Preparation of 82 H3, 82 H4, and 82 G10Samples for Aging

35

Figure 4.7. 82 H3, 82 H4. and 82 G10 Samples Shown asPrepared to be Inserted into LICAIrradiation Cell

36

Co-60

Figure 4.8. Orientation of 82 H3, 82 H4, and 82 GI0Samples During Irradiation

37

Figure 4.9. 82 J3 Samples Prepared to be Irradiated

38

CO-60

Figure 4.10. Irradiation Aging Configuration Used for82 J4 Samples

39

Table 4.5

Accuracy of French Measurements

Measured Parameter Accuracy

Dimensions

Dumbbell SizeInsulation Outer DiameterInsulation Inner DiameterWire Thickness

Tensile Strength

DumbbellsConductor Insulation

Tensile Elonqation

+ 0.1 mm+ 0.5 mm+ 0.3 mm+ 0.2 mm

+ 5%+ 15%

DumbbellsConductor Insulation

Compression Set (Permanent Set)

+ 5%+ 5%

+ 9%

40

5.0 RESULTS

5.1 U.S. Samples

Sequential exposures to irradiation and thermal environ-ments were employed for aging sequences A. B, C, and D(Section 4.1). Each environmental exposure lasted for -380hours (Table 4.1). Thus the total sequential exposure timefor both the irradiation and thermal aging environments was-760 hours. Several times during this 760-hour exposureperiod, aging was momentarily interrupted to allow for removalof several sample specimens. These specimens were used todetermine the degradation history during the aging exposures.In this section we plot tensile property degradation versusexposure time for the CSPE, CPE, EPR 1, EPR 2. XLPO 1, andXLPO 2 materials. For each aging sequence, the first 380hours of our plots represents one of the environmental stressexposures (irradiation or thermal), while the second 380 hoursrepresents the second environmental stress exposure of thesequence. Aging exposure E was a simultnaeous exposure toirradiation and 1200C thermal environments. It lasted -380hours (see Table 4.1). Tensile property degradation duringthe E aging exposure is also shown in our figures.

5.1.1 CSPE and CPE Jacket Materials

The ultimate tensile properties of CSPE and CPE dependedon the order of the sequential exposures. Figures 5.1 and5.2 illustrate tensile property degradation of CSPE as afunction of exposure time to radiation and thermal environ-ments. The R7 0 -' 120 0 C exposure most severely degradesboth the ultimate tensile elongation and the ultimate tensilestrength. The R1 2 0 exposure yields comparable results.The 120C -+ R2 7 sequence is the least degrading sequence.For CSPE, jacket degradation during sequential sequencesdepends on whether the irradiation is performed at ambient or700C temperatures; 700C irradiations are more severe.

CPE elongation degradation does not depend on irradiationtemperatures (see Figure 5.3). The R -+ 120 sequences pro-duces more elongation degradation than does the 120 -ý Rsequence or the R1 2 0 simultaneous exposure. Ultimate ten-sile strength results, Figures 5.4 and 5.5. indicate thatthermal exposures reduce tensile strength while ambientirradiation exposures increase tensile strength. Irradiationexposures at elevated temperatures do not strongly affectCPE's tensile strength properties.

41

1.2

1.0

0.8

e/e00.6

0.4

0.2

0.0-0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.1. Ultimate Tensile Elongation of CSPE in VariousEnvironments. Sample tensile elongation dividedby initial (unaged) elongation is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

42

1.2

lO

0.8T/To "

0.6

0.4 CSPE*=A:o=B:

0.2- O=C:t=D:EI=E:

0.0 - I -0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.2. Ultimate Tensile Strength of CSPE in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

43

1.2

1.0

0.8

0.6

0.4

0.2

0.00 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.3. Ultimate Tensile Elongation of CPE in VariousEnvironments. Sample tensile elongation dividedby initial (unaged) elongation is plotted-versusaging time. Each portion of the sequentialexposures lasted ~380 h.

44

a

T

1.8 1 1 1 1 1CPE

1.6 O=B: R2 7 -.- T IA,= D : T'RR2 IEI= E :R120

1.4

/To 1.2-

1.0 -

0.8

0.6-I I I I I II

0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.4. Ultimate Tensile Strength of CPE in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted -versusaging time. Each portion of the sequentialexposures lasted -380 h.

45

1.8

1.6

1.4

T/To 1.2

1.0 -0 1

0.8- I0.6 1

0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.5. Ultimate Tensile Strength of CPE in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted -versusaging time. Each portion of the sequentialexposures lasted -380 h.

46

For some CPE samples, irradiations were terminated whenour irradiation cells mistakenly filled with water. Theexposure sequence was restarted with new samples. Figures5.6 and 5.7 demonstrate tensile property results for the twosets of exposures: one sequence successfully completed, theother identical sequence terminated prior to completion. Thedata illustrates the extent of repeatability of results.

5.1.2 EPR Insulation Materials

Ultimate tensile property degradation for EPR 1, a radi-ation cross-linked FR-EPDM° is illustrated in Figures 5.8 and5.9. Irradiation reduces both the ultimate tensile elonga-tion and ultimate tensile strength. Degradation is worst forthe R2 7 exposure, with lesser degradation noted for theR7 0 and R1 2 0 irradiations. The opposite effect is notedfor EPR 2, a chemically cross-linked FR-EPDM (Figures 5.10and 5.11). For this material, the R1 2 0 and R70 irradia-tions more degrade the EPR tensile properties than does theR27 exposure. When irradiation and thermal stresses areapplied sequentially, neither EPR 1 nor EPR 2's ultimatetensile elongation properties depended on the sequentialordering. EPR 1 and EPR 2 tensile strength properties arealso not affected by sequential ordering.

5.1.3 XLPO Insulation Materials

XLPO 1 and XLPO 2 tensile properties are illustrated inFigures 5.12-5.15. Only the ultimate tensile strength ofXLPO 2 was sensitive (mildly) to sequential ordering ofradiation and thermal stresses. The R 4 T sequencesincreased the tensile strength more than did the T - Rsequences.

5.1.4 TEFZEL Materials

Tables 5.1 and 5.2 present bend test results for TEFZEL1 and 2 respectively. Four specimens (two white and twocolored) were tested for each aging condition. If all foursamples passed the bend test, a P is shown in the table.Those table locations where samples failed the bend test aremarked with an F. TEFZEL degradation is clearly dependenton irradiation temperature. We experienced no bend testfailures for TEFZEL specimens aged using ambient temperatureirradiations. We did observe bend test failures when agingprocedures employed either 700C or 1200C irradiations. Forboth TEFZEL materials, the 1200C -> R70 sequence was moresevere than the R7 0 -> 1200C exposure.

47

1.2

1.0

0.8

e/eo

II I I I I

CPE0= R2 7 EXPOSURE #10= R27 EXPOSURE #2

I I I t I I

0.6

0.4

0.2

0.01) 100 200 300 400 500 600 700 800

TIME (hours)

Figure 5.6. Repeatability of Ultimate Tensile ElongationResults for CPE During Two R2 7 Exposures

48

1.4

1.3

1.2

1.1

I

CPE0 = R2 7* = R2 7

I I I I I

EXPOSURE #1EXPOSURE #2

*140

T/To

I f0

1.0

0.9

0.80 I I Ia I I I I I

100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.7. Repeatability of Ultimate Tensile StrengthResults for CPE During Two R2 7 Exposures

49

1.2

e/eo

1.0

0.8

0.6

0.4

.0.2

0.0 0.1O0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.8. Ultimate Tensile Elongation of EPR 1 in VariousEnvironments. Sample tensile elongation dividedby initial (unaged) elongation is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

50

T/To

1.4

1.2

1.0

0.8

0.6

0.4

0.20 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.9. Ultimate Tensile Strength of EPR 1 in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

51

1.2

1.0

0.8

e/e00.6

0.4

0.2-

0.00 1-0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.10. Ultimate Tensile Elongation of EPR 2 in VariousEnvironments. Sample tensile elongationdivided by initial (unaged) elongation isplotted versus aging time. Each portion of thesequential exposures lasted -380 h.

52

1.4

1.2

1.0

T/To0.8

0.6

0.4

0.2-0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.11. Ultimate Tensile Strength of EPR 2 in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

53

1.2

1.0

0.8e/0o

0.6-

0.4

0.2

0.0 -0 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.12. Ultimate Tensile Elongation of XLPO 1 inVarious Environments. Sample tensile elonga-tion divided by initial (unaged) elongation isplotted versus aging time. Each portion of thesequential exposures lasted -380 h.

54

1.4

1.2

1.0T/T 0

0.8-

0.6

0.4

0.200 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.13. Ultimate Tensile Strength of XLPO I in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

55

e/eo

1.4

1.2

1.0

0.8

0.6

0.4

0.20 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.14. Ultimate Tensile Elongation of XLPO. 2 inVarious Environments. Sample tensile elonga-tion divided by initial (unaged) elongation isplotted versus aging time. Each portion of thesequential exposures lasted -380 h.

56

1.4

1.2

1.0

T/To0. 0.8-

0.6

0.4-

0.20 100 200 300 400 500 600 700 800 900

TIME (hours)

Figure 5.15. Ultimate Tensile Strength of XLPO 2 in VariousEnvironments. Sample tensile strength dividedby initial (unaged) strength is plotted versusaging time. Each portion of the sequentialexposures lasted -380 h.

57

Table 5.1

Bend Test Results for TEFZEL 1

Bend Radius/Insulation Radius

75X 69X

F:

B:

D:

A:

C:

E:

Unaged P

R2 7-4120 P

120-+R2 7 P

R7 0-+120 P

120+R7 0 P

R120 P

P = Pass Bend Test

F = Fail Bend Test

P

P

P

P

P

P

56X 50X 44X 31X

P P P P

P P P P

P P P P

P P P P

P P P F

P P F F

22X l1X 6X

P

P

P

F

F

P

P

P

F

P

P

P

F

F

58

Table 5.2

Bend Test Results for TEFZEL 2

Bend Radius/Insulation Radius

75X 69X 56X 50X 44X 31X 22X 1iX 6X

F: Unaged P P P P P P P P P

B: R2 7 4120 P P P P P P P P P

D: 1204R2 7 P P P P P P P P P

A: R7 0 4120 P P P P P P F F

C: 1204R7 0 P P P F F

E: R1 2 0 P P P. P P P F F

P = Pass Bend Test

F = Fail Bend Test

59

5.1.5 Compression Set Tests

Our compression set tests employed compression sampleswith thicknesses -. 18 cm. As mentioned in Section 4, thisthickness represents actual use conditions but produces largeuncertainties in the value of compression set, C:

t - tio -to -tn

where to = original thickness

ti= final thickness

tn= compressed thickness.

We predict our absolute uncertainties for C to exceed.10. For all five materials, our uncertainty exceeds thecompression set variation caused by aging differences. (SeeTable 5.3.)

5.2 French Samples

Each French aging sequence included two environmentalstress exposures - an irradiation exposure and a thermalaging exposure. Mechanical tensile tests and compression setmeasurements were performed at the completion of each ex-posure. Results are presented in Table 5.4.

Measurement results are shown for each material inFigures 5.16 through 5.24. Measurement values are normalizedwith respect to those relating to unaged control specimensof the same material (blank samples U). For each aging se-quence, usually two data values are plotted. The first valuereflects test results at completion of the first exposure ofthe aging sequence, while the second value indicates resultsat the completion of the aging exposure. For a few testconditions, only data at the completion of the sequence wereobtained. This single data value is plotted.

60

Table 5.3

U.S. Compression Set Test Results

EPR A EPR B BUNA A SILICONE VITON

Unaged (#38)

Partially Aged:

R2 7 (#12)

120 (#37)

Aged:

R1 20 (#32)

R27 -ý 120

#13

#14

120 -3 R2 7

#20

#50

.09 + .01

.54 + .04

.31 + .07

.74 + .03

.67 + .02

.67 + .03

.68 + .04

.79 + .06

.11 + .02

.78 + .03

.73 + .05

1.0

.96 + .03

.98 + .03

.91 + .02

.95 + .01

.07 + .01

.48 + .01

.39 + .02

.68 + .01

.63 + .01

.59 + .02

.68 + .02

.71 + .02

.07 + .03

.82 + .02

.17 + .01

1.0

.83 + .02

.86 + .01

.72 + .01

.81 + .01

.17 + .01

.80 + .05

.27 + .03

.97 + .02

.88 + .01

.89 + .01

.80 + .01

.83 + .02

*Errors Reflect + a for Four Samples. Absolute Error is + .10.

61

Table 5.4

Tensile and Compression Set Results for French Samples

MATERIAL

Elastomeric

9 TESTS" U * *

Materials:

PRC 140 T 1.3 1.1 1.2 1.1 0.9 1.1 1.1 1.0 1.082 I1 e 370 332 267 264 30 332 269 245 43EPDM 140 T 0.6 0.6 0.3 0.4 0.4 0.6 0.5 0.4 0.282 12 e 240 241 82 124 1.5 241 118 135 0.5Fire-proofEPDM 140 T 0.6 0.6 0.7 0.7 0.4 0.6 0.8 0.7 0.482 19 e 245 222 83 113 32 222 84 107 34EPR 140 T 1.7 1.5 1.3 1.5 0.8 1.5 1.4 1.6 0.882 H4 e 174 186 99 124 81 186 93 116 73EPR 140 Com-

pres- 8.2 67 -- 71 -- 58 -- 57sion

82 J4 Set

VAMAC 120 1.8 1.7 1.8 1.8 1.8 1.7 1.8 1.8 1.882 H3 312 308 245 248 238 308 207 217 215VAMAC 120 Com-

pres- 9.6 -- 56 -- 71 -- 68 64 76Sion

82 J3 Set

HYPALON52 tC10

140 T 0.9 0.7 0.7 0.6 0.7 0.7 0.8 0.7T .~ . - _ _

B A22 249 205 332 204 28A 214

Thermoplastic material:

PPS 160 IT 1 8.7 _8.0 8.4 8.1 8.0 8.4 7.882H e 0.7 1 0.6 1 0.7 10.7 1 0.6 1 0.7 1 0.

Thermoset material:

Polydial-lylphtalate 160 T 4.6 4.5 4.8 4.4 5.0 4.5 4.8 4.6 4.782 H5 I ] 10.3 10.4 0.3 0.3 10.310.40.3 0.4 0.3

*Code - U = Blank sampleA = Thermal aging at 9*C, followed by irradiation at 70*CB = Irradiation at 700C, followed by thermal aging at 8"CC = Thermal aging at G*C, followed by irradiation at 27*CD = Irradiation at 270C, followed by thermal aging at 8°C0 = Thermal aging temperature

* T = ultimate tensile strength (Units = 10 MPa)e = ultimate tensile elongation (units = %)

*** First column = Results at completion of first exposure of the sequenceSecond column = Results at completion of second exposure of the sequence

62

5.2.1 PRC (82 If)

Figure 5.16 illustrates the normalized tensile propertiesfor chemically cross-linked polyethylene (PRC). The orderof aging exposures does not seem to affect the tensilestrength. The deviation of the measured data from theaverage value is + 10 percent. which is not significant.

However, tensile elongation is influenced by sequentialexposure order to a much greater extent than the tensilestrength. The PRC material is strongly degraded by the ir-radiation then thermal exposure sequences (sequences B andD), whereas degradation is slight for the thermal exposurethen irradiation sequences (sequences A and C). In allcases, irradiation at 700C or 270C causes identical changesin tensile strength or tensile elongation, with or without aprior thermal exposure at 1400C.

5.2.2 EPDM (82 12 and 82 19)

Samples 82 19 are fire-proof EPDM material, whereas the82 12 samples are not. Figure 5.17 illustrates measurementresults for 82 12, while Figure 5.18 presents results for82 19.

5.2.2.1 EPDM (82 12)

When irradiation is performed at 700C, the order of agingexposures does not affect the tensile strength (withinmeasurement accuracy of + 15 percent - see Table 4.5). At270C however, the irradiation followed by thermal exposuresequence (exposure sequence D) degrades the tensile strengthmore than does the thermal followed by irradiation sequence(exposure sequence C). Hence for tensile strength behaviorof the 82 12 material, irradiation temperature is important.

Ultimate tensile elongation is more degraded by the ir-radiation followed by thermal exposure sequences (sequencesB and D).

5.2.2.2 Fire-proof EPDM (82 19)

Both thermal followed by irradiation sequences (A and C)increased the tensile strength, whereas both irradiationfollowed by thermal sequences (B and D) decreased the tensilestrength. Interestingly, for both of these latter sequences(B and D), the irradiation exposures at 70.C and 272C in-creased the tensile strength, contrary to the behavior of the82 12 EPDM samples when irradiated. For all sequences.elongation was decreased. The material appears to becomereticulated during aging exposures.

63

ULTIMATETENSILE STRENGTH

1.0

T/To

U A B C D

ULTIMATETENSILE ELONGATION

1.0 i-0 9

9 09

0/00

QI

9U A B C D

U = UNAGED

A= 140-,R 7 0

C = 140--,R2 7

D = R2 7 -140

B = R7 0 -- 140

Figure 5.16. Ultimate Tensile Properties for PRC (82 I1)

64


1.0

T/To

1.0

6/80

U A B C D

ULTIMATE

TENSILE ELONGATION

U A B C D

U =UNAGED

A = 140---R7 o

B =R17 0 -0-140

C = 140-0-112 -

D = R 2 7 -- 140

Figure 5.17. Ultimate Tensile Properties for EPDM (82 12)

65


1.0

T/To

U A B C D


1.0 c0 0

6/00

I I I ITU A B C D

U = UNAGED

A= 140--R 7 0

B= R 7 0 -,-140

C = 140--'R 2 7

D = R 2 7 -- 140

Figure 5.18. Ultimate TensileEPDM (82 19)

Properties for Fire-proof

66

5.2.3 EPR (82 H4 and 82 J4)

The same EPR material was used to make 3 mm-thick sheetsof EPR and also O-ring seals. Dumbbells (82 H4) as shown inFigure 2.1 were cut from the sheets and used for ultimatetensile strength and ultimate tensile elongation measure-ments. O-ring seals (82 J4) with an inner diameter of 12 mmand an outer diameter of 17 mm were supplied by the samemanufacturer as the sheet EPR material. These were used forcompression (permanent) set measurements. Ultimate tensilemeasurement results for the 82 H4 samples are shown inFigure 5.19. Permanent set after compression measurementsfor the 82 J4 samples are illustrated in Figure 5.20.

For the 82 H4 tensile specimens, irradiation at 270C andat 700C have the same effect on ultimate tensileproperties. Identical changes in tensile strength andtensile elongation were observed for the two thermalfollowed by irradiation sequences (A and C). A similarobservation is relevant for the two irradiation followed bythermal exposure sequences (B and D).

The effect of irradiation is more substantial for ulti-mate tensile elongation than for ultimate tensile strength.Both the 27°and 700C irradiations reduced the tensileelongation by -30 percent whereas the tensile strength wasonly reduced by 10-20 percent.

There are only slight differences in permanent set causedby the different aging sequences (Figure 5.20).

5.2.4 VAMAC (82 H3 and 82 J3)

The same VAMAC material was used to make 3 mm-thicksheets of VAMAC and also O-ring seals. Dumbbells (82 H3) asshown in Figure 2.1 were cut from the sheets and used forultimate tensile strength and ultimate tensile elongationmeasurements. O-ring seals (82 J3) were used for compression(permanent) set measurements. Ultimate tensile measurementresults for the 82 H3 samples are shown in Figure 5.21.Permanent set after compression measurements for the 82 J3samples are illustrated in Figure 5.22.

For the 82 H3 tensile specimens, irradiations at 270C andat 70 0 C have the same effect on ultimate tensile properties.The material tensile properties are also unaffected by theorder of the aging sequence. Both the tensile strength andthe tensile elongation are unaffected by the thermal aging

67

exposure. Only the irradiation exposure changed the tensileproperties of VAMAC.

There are only slight differences in permanent set causedby the different aging sequences (Figure 5.22).

5.2.5 HYPALON (82 G1O)

An electric cable was stripped of its HYPALON jacket.(HYPALON is the trade name of Dupont for CSPE.) Dumbbellsas shown in Figure 2.1 were cut from the material and usedfor ultimate tensile strength and ultimate tensile elongationmeasurements.

For this material (Figure 5.23). irradiations at 27 0 C andat 700C have the same effect on ultimate tensileproperties. Changes in ultimate tensile strength andelongation are also independent of the order of the agingexposures (irradiation and thermal).

5.2.6 PPS (82 H6)

Phenylene polysulfide (PPS) dumbbells as shown in Figure2.3 were injection molded by the material manufacturer. Theeffects of aging sequences on this material's ultimatetensile properties are shown in Figure 5.24. This materialis highly resistant to aging. Its mechanical properties areso little affected by the aging sequences that it isdifficult to detect any meaningful differences between thevarious aging sequences.

5.2.7 Polydiallylphtalate (82 H5)

Polydiallylphtalate dumbbells as shown in Figure 2.3 weremolded by the material manufacturer. The effects of agingsequences on this material's ultimate tensile properties areshown in Figure 5.25. The first aging exposure (1600C ther-mal exposure or 27 0 C irradiation) results in an increase intensile elongation, possibly caused by lengthening of themacro-molecular chains. Irradiation at 700C does not in-crease the elongation. The second aging exposure of theaging sequence (either irradiation or thermal exposures)causes an increase in ultimate tensile strength and a reduc-tion in ultimate tensile elongation. This possibly reflectsadditional cross linking of the material. For polydiallyl-phtalate. the order of the aging sequence does not affect theultimate tensile properties.

68


1.0

I

00 0 0 0?

I I- . - . - a ~* - a - a ~.

U A B C D


0 C)1.0O %.- a,a'

00/00 ?

I I I I~a. - - ____________

U A B C D

U = UNAGED

A = 140-,- R7 0

C = 140-.-R2 7

D = R2 7-- 140

1B = RRto -w-140

Figure 5.19. Ultimate Tensile Properties for EPR (82 H4)

69

PERMANENT SETAFTER COMPRESSION

1.0

~2~~~ TIU A B C D

U =UNAGED

A= 140-R 70

B = R7 0 --- 140

C= 140-a-R 2 7

D =R 2 7 -e140

Figure 5.20. Permanent Set After Compression for EPR (82 J4)

70


1.0

T/T 0

aa*a~u *ma5

U A B C D

1.0

0/eo -IULTIMATETENSILE ELONGATION

0

9 00 0 0)

- a - a - a - a. a U U a a

U A B C D

U = UNAGED

A = 120-,-RTO

C =120-s-112 1

D = 1 2 -.10420

B =R 7O--120

Figure 5.21. Ultimate Tensile Properties for VAMAC (82 H3)

71

PERMANENT SET

AFTER COMPRESSION

1.0

m

U A B C D

U = UNAGED

A = 120-- R7 0

B =R 7 0 -- 120

C = 120--R 2 7

D =R27-a120

Figure 5.22. Permanent Set(82 J3)

After Compression for VAMAC

72


1.0

T/To

U A B C D

ULTIMATE

TENSILE ELONGATION

1.0

0 I

9

I I IU A B C D

U UNAGED

A = 140--R 7 0

B =R 7 0 -- 140

C = 140-,--R2 7

D =R 2 7 -- 140

Figure 5.23. Ultimate(82 G1O)

Tensile Properties for HYPALON

73


1.0

T/To

1.0

0/00

U A B C D

ULTIMATE

TENSILE ELONGATION

o 'ii Q

U A B C D

U = UNAGED

A= 160- R7 0

B =R70--160

C = 160--R2 7

D =R 2 7 --160

Figure 5.24. Ultimate Tensile Properties for PPS (82 H6)

74


1.0

T/To

U A B C D


0 0 0

1.0

0/00

--I?- -0--

U A B C D

U = UNAGED

A = 160-,- R 0

B = R 70 -'-160

C =160-aRi 7

D = Rg7 -o'-160

Figure 5.25. Ultimate Tensilephtalate (82 HS)

Properties for Polydiallyl-

75

6.0 CONCLUSIONS

As part of a joint French/U.S. sponsored research pro-gram, we are investigating the influence of testing condi-tions on the behavior of polymer materials. In this reportwe have summarized the response of several commercial insul-ation and jacket materials, compression and gasket materials,and thermosetting and thermoplastic materials to variousaging environments.

Ultimate tensile properties measured during our agingexposures exhibited several general trends:

1. If sequential ordering of irradiation and thermalexposures was important to the aging degradation oftensile properties, usually the irradiation followedby thermal exposure sequence was most severe.Examples are elongation and tensile strength forCSPE. CPE, EPDM (82 12 and 82 19). and elongation forPRC (82 Il). A counter example is TEFZEL 2 which wasmore degraded by the thermal followed by the 700Cirradiation exposure rather than the reversesequence. The observation that irradiation followedby thermal exposures is the more severe sequence isconsistent with previously published results for lowdensity polyethylene (LDPE) and polyvinylchloride(PVC).2 Neither LDPE nor PVC materials wereincluded in this study.

2. During the sequential irradiation and thermal ex-posures, we performed irradiations at both ambient(-270C) and 70 0 C temperatures. In general, thechoice of irradiation temperature was secondary tothe choice of aging sequence in its effect on poly-mer properties. Irradiation temperature did influ-ence the degradation behavior of some materials.Examples are bend test results for TEFZEL 1 andTEFZEL 2. elongation and tensile strength data forCSPE, tensile strength data for EPR 2, and tensilestrength data for EPDM (82 12).

3. For several materials, tensile properties at com-pletion of aging were only slightly affected by boththe irradiation temperature and the order of thesequential aging environmental exposures. Examplesare XLPO 1, VAMAC (82 H3), PPS (82 H6), andpolydiallylphtalate (82 H5).

76

In addition to tensile measurements, we performed per-manent set after compression measurements for several gasketand O-ring seal materials. At most, only slight differencesin permanent set were noted as a result of the various agingtechniques.

REFERENCES

1. Gillen. K. T.. Clough, R. L., Ganouna-Cohen. G..Chenion. J.. and Delmas. G.. "The Importance of Oxygenin LOCA Simulation Tests." Nuclear Engineering andDesign. 74 (1982). pgs. 271-285.

2. Clough, R. L. and Gillen, K. T.. "Radiation-ThermalDegradation of PE and PVC: Mechanism of Synergism andDose Rate Effects." NUREG/CR-2156. SAND80-2149, June1981.

3. Fremont. Ph., "Specification Generale pour la Qualifi-cation des Materiels Class 1E des Centrales Nucleaires aeau sous pression," Electricite de France document.HM/63-7195/6, July 1983.

4. Nuclear IEEE Standards, Published by the Institute ofElectrical and Electronics Engineers, Inc.

5. 1OCFR50.49 "Environmental Qualification of ElectricEquipment Important to Safety for Nuclear Power Plants."Nuclear Regulatory Commission, Federal Register. Vol. 48.No. 15, 2729. January 21. 1983.

6. Szukiewicz, A. J.. "Interim Staff Position on Environ-mental Qualification of Safety-Related Electrical Equip-ment -- Including Staff Responses to Public Comments."NUREG-0588, Rev. 1, U.S. Nuclear Regulatory Commission,Washington, DC, July 1981.

7. IEEE Standard 323-1974, "IEEE Standard for QualifyingClass 1E Equipment for Nuclear Power GeneratingStations." 1974.

8. The description of the thermal and radiation agingfacilities is a modified, updated version of the des-cription that was provided by: Gillen, K. T., Clough.R. L.. and Jones, L. H.. "Investigation of Cable De-terioration in the Containment Building of the SavannahRiver Nuclear Reactor." NUREG/CR-2877. SAND81-2613,August 1982.

9. ASTM D 395-78. An American National Standard.

77

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BIBLIOGRAPHIC DATA SHEET NUREG/CR-3629-SAND83-2651

1;LIN-0 D*01-

3 TITLE AND SU"TITLE 4 RECIPIENT S ACCESSION NUMBER

The Effect of Thermal and Irradiation Aging 5 DATE REPORT COMPLETEC

Simulation Procedures on Polymer Properties MONTH YEAR

6 AUT.4OISI 7 DATE REPORT ISSUED

L. D. Pustard F. Carlin M. LeMeur IONTM VIAA

E. Minor C. Alba February 1984J. Chenion G. Gaussens , PROJECT TASKIWORK UNIT NUMBER

S PERFORMING ORGANIZATION NAME AND MAILING ADDRESS I.,cludt iZe CeO&

Sandia National LaboratoriesAlbuquerque, New Mexico 87185 tO FIN NUMBER

A1051

11 SPONSOiRING ORGANIZATION NAME AND MAILING ADDRESS (Ifte..Ae ZP Ce0*) 12@ TYPE OF REPORT

Electrical Engineering BranchDivision of Engineering TechnologyOffice of Nuclear Regulatory Research 12 PERIOD COVERED iclus,,•,

U. S. Nuclear Regulatory CommissionWashington, D.C. 20555 March 1982-March 1984

13 SUPPLEMENTARY NOTES

14 ABSTRACT 0O0 m ;cW 9, AIt.)

Prior to initiating a qualification test onsafety-related equipment, the testing sequence for thermaland irradiation aging exposures must be chosen. Likewise.the temperature during irradiation must be selected.Typically. U.S. qualification efforts employ ambienttemperature irradiation while French qualification effortsemploy 706C irradiations. For several polymer materials.the influence of the thermal and irradiation aging sequenceas well as the irradiation temperature (ambient versus 70C)has been investigated in preparation for Loss-of-CoolantAccident simulated tests.

Ultimate tensile properties at completion of aging arepresented for three XLPO and XLPE. five EPR and EPDM. twoCSPE (HYPALON). one CPE. one VAMAC. one polydiallylphtalate.and one PPS material.

Bend test results at completion of aging are presentedfor two TEFZEL materials.

Permanent set after compression results are presented forthree EPR. one VAMAC. one BUNA N. one Silicone. and one Vitonmaterial.

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