Enclosure 2: Presentation (D. Weaver Memorandum re ...

YGR OLUTIONSENE S

8-120B RAI#2 Meeting

April 18th, USNRC, Rockville, MD

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Agenda

• Meeting objectives

• RAIs that are basis of new analysis method (5-6 and 5-7)

– New analysis methodology description

– New approach for payload specification

– Shielding analysis details

• Other RAIs

• Conclusion

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New Analysis Methodology

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New Analysis Method Discussion

• New method primarily driven by RAIs 5-6 and 5-7

• We will discuss:

– Our understanding of RAIs 5-6 and 5-7

– Primary features of new analysis method

– Fundamental principles that form basis of new methodology

– How the new method addresses concerns raised in RAIs 5-6 and 5-7

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Our Understanding of RAI 5-6

• Distributed-case analyses modeled uniform source

distribution

• Loading spec allowed source density variation

• Analysis did not consider potential source distribution

changes under HAC

• We agree that the last shielding analysis/qualification

method made it difficult to demonstrate conservatism

under NCT and HAC conditions.

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• Distributed source analyses specified maximum source

strength (gammas/sec)

– Adjusted based on payload density

– Not adjusted based on payload volume

• RAI questioned that this approach was bounding for

partial-cavity payloads

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• We concur that smaller payload volumes may not be

bounded

– Source (gammas/sec) not reduced

– Less self-shielding (for given density)

– Distributed-Case analysis did not account for shifting of

smaller payloads under HAC

• Source limit (gammas/sec) based on full-cavity analysis

• Same total source could be concentrated in section of cavity

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New Analysis Approach – Primary Features

• Point Source Analyses

– Same general approach used

– Used to establish limits on source strength for concentrated

sources

– Non-centered NCT point source case added

• Distributed Source Analyses

– Determine limits on activity density, in gammas/sec per gram

of material

– Maximum activity density of the payload material must meet

limit (not smeared density)

– Analysis conservatively based on cavity filled with maximum

activity density material

– Centrally shored small-volume containers evaluated for NCT

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New Analysis – Basic Principles

• Point source bounding for a given activity (gammas/sec)

– Concentrated (higher local dose rates)

– No self-shielding

– Worst-case location within cavity

• Cavity filled with maximum activity density material

bounding for any distributed source

– Bounds lower source strength density material

– Bounds any partially filled cavity

– Issues of source strength variation within payload, or

location of payload within cavity all disappear

• For a given activity density (Ci/g), lower g/cc payloads are

bounded when modeled at a higher g/cc

– Objects with g/cc higher than that analyzed must be qualified

as point sources. 9

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New Analysis – Basic Principles

• Demonstration of effect of g/cc changes while holding

specific activity (Ci/g) constant

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New Analysis Addresses RAIs

• RAI 5-6 (source distribution)

– Distributed source qualification based on maximum activity

density material within payload

– HAC distributed source analyses conservatively assume

cavity filled with maximum activity density material

• RAI 5-7 (smaller volume payloads)

– Analyses determine limit on activity density (γ/sec per gram),

not activity (γ/sec).

– Reducing payload volume reduces allowable activity

– Reducing payload density reduces allowable activity

– Full cavity bounds smaller volume of “same stuff”

– Reduced g/cc payloads bounded by modeled g/cc

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Analyzed Configurations

• Point Source Cases

– Centered NCT

– Non-centered NCT (worst-case location)

– Non-centered HAC (worst-case location)

• Distributed Source Cases

– Full Cavity - NCT

– Centered 55 gallon (drum) - NCT

– Centered 2.5 ft3 container – NCT

– Full Cavity - HAC

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Analyzed Configurations Basis

• Full Cavity Cases

– Bounding for any waste configuration that meets Ci/g limit

– Do not rely on shoring

• Reduced Volume Container NCT Cases (55 gal & 2.5 ft3)

– Assume waste is placed within smaller, shored container

– Allows higher source density

– HAC still based on full cavity case (no reliance on shoring)

• Point Source Cases

– Centered NCT: Shored container allows higher source

– Non-Centered NCT: Allows loose concentrated sources

– HAC: Non-centered (no shoring credit)

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New Approach for Payload Specification

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Basis for Payload Qualification

• For analyzed configuration, source limit is based on NCT

or HAC case, whichever is worse

– HAC cases do not take credit for shoring

• Gamma-energy-dependent activity and activity density

limits are determined for payload configuration

– Payload size (full, 55 gal, 2.5 ft3)

– Shored at cavity centroid, or not

• 7 analyzed configurations – 5 columns of source limits

– One set for each configuration (governed by NCT or HAC)

– Full cavity, center 55 gal, center 2.5 ft3, center pt., gen pt.

• Payload must meet source strength density or source

strength limit

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Shielding Analysis – Analyzed Configurations

• Allowable sources based on conservative modeling

assumptions

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New Approach – Qualification (User’s Standpoint)

• Qualification

Flowchart

• 5 Columns in

Allowable Source

Table

– Ci limit

– Ci/g limit

• 2 Qualification

Paths

– General

– Discrete/shored

Payload

Qualification

Type

Determine payload

activity and mass data.

Discrete Sources

(shored at centroid)

General Sources

(most conservative)

Meets

Ci/g Limit

?

Meets

Applicable

Ci/g Limit

? No

Yes

SHIP

STOP

Centered Activity Limit (Ci)

Centered Activity Density Limit (Ci/g), 2.5 ft3

Centered Activity Density Limit (Ci/g), 55 gal

General Activity Density Limit (Ci/g)

No

Yes

SHIP

STOP

General Activity Limit (Ci)

Meets

Ci limit

?Yes

No

SHIP Meets

Ci limit

? Yes

No

SHIP

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Preview of Payload Qualification Table

Energy

(MeV)

G

en

era

l A

ctivity L

imit (

Ci)

C

en

tere

d A

ctivity L

imit (

Ci)

G

en

era

l A

ctivity D

en

sity

Lim

it (

Ci/g

)

C

en

tere

d A

ctivity D

en

sity

Lim

it,

2.5

ft3

Pa

ylo

ad (

Ci/g

))

C

en

tere

d A

ctivity D

en

sity

Lim

it,

55

-ga

l P

aylo

ad (

Ci/g

)

0.5 TBD TBD TBD TBD TBD









Co-60 1.3E+11 5.8E+11 8.1E+06 5.8E+07 3.3E+07

Cs-137 TBD TBD TBD TBD TBD

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New Approach – Example 1

• Sealed source,

centrally shored

– Discrete source

path

– Check Column 2

for allowable

source

– Sum fractions

for each energy

• We’ll return to this

example to

discuss the

shielding models

Payload

Qualification

Type

Determine payload


Discrete Sources


General Sources

(most conservative)

Meets

Ci/g Limit

?

Meets

Applicable

Ci/g Limit

? No

Yes

SHIP

STOP





No

Yes

SHIP

STOP


Meets

Ci limit

?Yes

No

SHIP Meets

Ci limit

? Yes

No

SHIP

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New Approach – Example 2

• Resin liner with

small, hot filter

– Find liner

fractions using

Column 3.

– Find filter

fractions using

Column 1

– Sum fractions

• We’ll return to this

example to

discuss the

shielding models

Payload

Qualification

Type

Determine payload


Discrete Sources


General Sources

(most conservative)

Meets

Ci/g Limit

?

Meets

Applicable

Ci/g Limit

? No

Yes

SHIP

STOP





No

Yes

SHIP

STOP


Meets

Ci limit

?Yes

No

SHIP Meets

Ci limit

? Yes

No

SHIP

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Shielding Analysis Details

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Method of Determining Source Limits

• Peak per-source-particle dose rate determined on each

regulatory surface

– NCT: 2-meter side plane, package side, bottom and top

– HAC: 1-meter side, top and bottom plane

• Determine maximum per-source-particle dose rate that

applies for each regulatory limit (2-m NCT, Package NCT,

1-m HAC)

• Divide dose rate limit by max per-source-particle dose rate

to yield allowable source strength

• For distributed cases, divide allowable source strength by

modeled payload mass to determine allowable source

strength density

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Example Shielding Results for Co-60

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Preview of Payload Qualification Table

Energy

(MeV)

G

en

era

l A

ctivity L

imit (

Ci)

C

en

tere

d A

ctivity L

imit (

Ci)

G

en

era

l A

ctivity D

en

sity

Lim

it (

Ci/g

)

C

en

tere

d A

ctivity D

en

sity

Lim

it,

2.5

ft3

Pa

ylo

ad (

Ci/g

))

C

en

tere

d A

ctivity D

en

sity

Lim

it,

55

-ga

l P

aylo

ad (

Ci/g

)










Co-60 1.3E+11 5.8E+11 8.1E+06 5.8E+07 3.3E+07

Cs-137 TBD TBD TBD TBD TBD

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Shielding Analysis Details

• General (unshored) NCT and HAC point sources placed in

worst possible location

– Top corner of cask cavity

– Minimum shielding

– Minimum distance to regulatory surfaces

– Lines up with both lid (top) and lead slump (side) gaps

• Distributed case source regions modeled as hypothetical

bounding material: zirconium at ~8 g/cc.

– Minimum attenuation for zirconium (except for 3.5 MeV)

– Max density bounding for a given source density

– If a payload component has a higher density material, must

use activity limit column (based on point models)

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Treatment of Multiple Sources/Energies

• Entire process repeated for….

– Each gamma energy level

– Each payload source component

• Determine fraction of limit for each energy/component

– Using full process described earlier

– May use activity or activity density limit, whichever gives

lower fraction

• Sum fractions for all gamma energies and/or payload

components

• Sum-of-fractions may not exceed 1.0

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Shielding Analysis – Example 1

• Sealed source, centrally shored

– This is not a volumetric source case, so no self-shielding

credit Is taken.

– NCT model based on centrally shored point.

– HAC model based on worst-case point.

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• Resin liner with small, hot filter

• Resin fills cavity, but filter could be anywhere.

– Models for the liner

– Models for the filter

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• Centered 55 gallon drum

– NCT model assumes drum at cavity centroid

– HAC model assumes full cavity of drum contents

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SAR, Other RAIs

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SAR Presentation

• Chapter 7

– Payload Qualification Flowchart

– Usage rules

– Payload Qualification Table

– Examples

• Chapter 5

– Technical bases for Payload Qualification Table

– Description of shielding approach and conservatisms

• Shielding Calculation Package

– Details of shielding models

– Details of Payload Qualification Table computations

– Backup for modeling assumptions

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Other RAIs

• Structural (2-1)

• Shielding (5-x)

• Operations (7-x)

• Maintenance (8-x)

E YGREN S ITULO ONSStructural Evaluation (2-1)

• Figure 2-50 shows the total deformation of the cask during the end

drop. The relative displacement of the top of the lead-column and the

bottom of the bolting ring is the lead-slump. The data print-out from

ANSYS for this load case is included in Reference 2-15 (ST-627)

Appendix 2, Page 24 of 24.

• In Section 2.7.3 of the SAR it is stated, “A conservative evaluation of

the maximum amount of lead deformation under puncture drop test of

8-120B cask has been performed in Reference 2-15. It has been

shown that the lead shielding deformation is limited to 0.458 inch”.

• This evaluation can be found in Section 7.5 Pages 17 through 19 of

Reference 2-15 (ST-627).

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E YGREN S ITULO ONSBremsstrahlung Conservatism under HAC (5-4)

• Used HAC MCNP model with a 90Sr/90Y beta source

spectrum in e-p transport mode to simulate the production

of bremsstrahlung radiation. 90Y betas are very energetic

daughters of 90Sr, with a maximum energy of 2.245 MeV.

The bremsstrahlung response for a unit beta source was

2.3E-12 mrem/hr per β/sec. So for a 90Sr/90Y 2x1012 β/sec

source, the HAC dose rate at 1 m due to bremsstrahlung

would be 4.6 mrem/hr, or 0.5% of the HAC 1 m dose limit.

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E YGREN S ITULO ONSOther Shielding RAIs

• 5-2

Barnwell data package for 77 shipments 2008-2011;

manifest, receipt survey, usually shipper’s survey

• 5-5

• 5-8

Maximum thickness of shield ring specified

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E YGREN S ITULO ONSGamma Source due to Bremsstrahlung (7-2)

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E YGREN S ITULO ONSOther RAIs

• Operations (7-x)

• Acceptance Tests and Maintenance (8-x)

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Conclusion

• Next actions

• Schedule

• Concluding remarks/questions

YGR OLUTIONSENE S

Thank You

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