CIAU METHOD FOR UNCERTAINTY EVALUATION · 5 GENERAL FRAME OF UNCERTAINTY EVALUATION Historical...

DIPARTIMENTO DI INGEGNERIA MECCANICA, NUCLEARE E DELLA PRODUZIONE

UNIVERSITA' DI PISA 56100 PISA -ITALY

Tel +39-050-8366-53 Fax +39-050-8366-65

E-mail [email protected]

CIAU METHOD FOR UNCERTAINTY EVALUATION

F. D’Auria

OECD/NEA/CSNI - Wgama “Exploratory meeting of experts on BE calculations and uncertainty analysis”

Aix-en-Provence (France) – May 13-14, 2002

2

CONTENT

a) General frame of Uncertainty Evaluation - needs for uncertainty - historical remarks

b) Flow diagram of UMAE c) CIAU definition & needs d) The idea at the basis of CIAU e) CIAU diagram f) CIAU application & developments

- “Bifurcation” study - Licensing process of the Angra-2 NPP LBLOCA (an outline) - BE analysis of Kozloduy-3 NPP LBLOCA (an outline)

3

GENERAL FRAME OF UNCERTAINTY

EVALUATION

Needs for Uncertainty p1/2

CONSISTENT APPLICATION OF A THERMOHYDRAULIC SYSTEM CODE

CODE DEVELOPMENT & IMPROVEMENT (1)

CODE ASSESSMENT (4)

CODE USE (NPP) (5)

UNCERTAINTY EVALUATION

(6)

EXPERIMENTAL DATA (2)

PROCEDURES FOR

CODE USE (3)

PART I – UMAE

4

GENERAL FRAME OF UNCERTAINTY EVALUATION

Needs for Uncertainty p2/2

The predictions of the system codes are not exact but remain uncertain. Reasons are:

− the assessment process depends upon data almost always measured in small scaled facilities and not in the full power reactors;

− the models and the solution methods in the codes are approximate: in some cases, fundamental laws of the physics are not considered.

Consequently, the results of the code calculations may not be applicable to give ‘exact’ information on the behaviour of a Nuclear Power Plant during postulated accident scenarios. Therefore, best estimate predictions of nuclear power plant scenarios must be supplemented by proper uncertainty evaluations in order to be meaningful.

PART I – UMAE

5

GENERAL FRAME OF UNCERTAINTY EVALUATION

Historical Remarks YEAR ACTIVITY REF. (*)

1980-1982 Scaling analysis for the design of the PIPER-ONE BWR simulator 6 1982 Proposal for design criteria for PIPER-ONE 7 1985 Analysis of SBLOCAs in PWR on the basis of ‘similar’ tests 10

“ Proposal for criteria for accuracy quantification 11 1987 (1) Publication of OECD/CSNI ITF-CCVM 12a & 12b

1988 Proposal of criteria for planning ‘Counterpart’ tests (CT) 13 1989 Issue of US NRC Compendium on ECCS Research 16

“ Issue of OECD/CSNI SOAR onTECC 15 “ ‘Use’ of CT data related to BWRs 14

1989-1992 Papers dealing with the basis of the UMAE uncertainty methodology 14, 17, 18 1990 Publication of CSAU 22 “ (6) Studies on user effect, bringing to a CSNI publication in 1992 19

“ Proposal for the FFTBM for accuracy quantification 20 “ Analysis of Natural Circulation in PWR on the basis of ‘similar’ tests 21

1991 (2) Proposal for a methodology for independent assessment of codes 4 & 23 1992 Analysis of LOFW in PWR on the basis of similar tests 24

“ Proposal for a procedure for nodalisation qualification 25 1993 Simplified flow-sheet of UMAE and differences with respect to CSAU 26

“ Analysis of SBLOCA in PWR on the basis of performed CT (4) “ Application of UMAE to a SBLOCA in Krsko PWR 27 “ Publication of OECD/CSNI SETF-CCVM 28

1994 Completion of the 2D-3D Research Program and planning of TRAM 29 1995 Issue of UMAE-ET (to account for ‘unrecoverable’ code errors) 30 & 31 “ (2) Comparison between features of uncertainty methodologies (4) 1996 Issue of UMAE-SETF (to exploit SETF data) 32

“ Publication of OECD/CSNI on Lesson Learned from SBLOCA ISP 39 (5) “ (3) Proposal for a procedure for code user training, see also (6) 33 1997 Application of UMAE utilising Relap5/mod2 and Cathare 2v1.3 codes 5

“ Application of UMAE to Angra-1 PWR 34 “ Proposal for the CIAU (idea at the basis of the method) 35

1998 Publication of OECD/CSNI UMS report 2 1997-1999 Execution of different Kv scaled calculations (4)

1999 Demonstration of feasibility of CIAU and preliminary results (4) 2000 Publication of IAEA Guidelines for Accident Analysis – Draft – (4)

“ Bifurcation analysis and CIAU matrix enlargement (4) 2001 Application of CIAU to Angra-2 and Kozloduy-3 NPP LBLOCA (4) 2002 Development of uncertainty for 3-D neutronics/thermalhydraulics coupled codes

(*) list of references in the paper presented at UIT National Conf. 1998 (1) updated in 1996 (2) updated in 1998 (3) updated in 1998 and finalised in 1999 (4) papers and reports available (not part of the same list) (5) the report related to all ISP issued in 1998

The CSNI report on User Effects has been extended in 1999 to cover countermeasures suitable for reducing user effects

PART I – UMAE

6

FLOW DIAGRAM OF UMAE

General qualification

processCode

Plant nodalization

Plant calculation

ITF nodalizations

Specific experimental data

ITF calculations

Accuracy quantification (°)

Accuracy extrapolation (°)

Nodalization and user qualification

Generic experimental

data

Demonstration of similarity (°) (Phenomena (Scaling laws)

ASM calculation

Uncertainty

ba

i

h

j

GI FG

gc

d

e

f

l

LN (°)

n

YES

FG

k

(°) Special methodology developed

(Phenomena analysis) (Scaling laws)

Stop of the process

NO

NO

PART I – UMAE

7

CIAU DEFINITION & NEEDS

CIAU = Code with capability of Internal Assessment of Uncertainty • RELAP5 IS THE CODE • UMAE IS THE COUPLED UNCERTAINTY METHODOLOGY THE WORDS ‘INTERNAL ASSESSMENT OF UNCERTAINTY’ CAME OUT AS A

NEED FOR THE SCIENTIFIC COMMUNITY DURING THE OECD/CSNI “ANNAPOLIS MEETING” ORGANISED BY US NRC AND HELD IN ANNAPOLIS

(MD) IN NOVEMBER 1996

NEEDS A) CODE RESULTS ARE AFFECTED BY USER CHOICES. THE USER OF

UNCERTAINTY METHODS MAY ALSO HEAVILY AFFECT RESULTS PREDICTED BY UNCERTAINTY METHODS. THE COMBINATION OF THE TWO EFFECTS MAY BE NOT TOLERABLE.

B) THE APPLICATION OF ANY UNCERTAINTY METHOD MAY REQUIRE

EXPERTISE AND/OR RESOURCES NOT EASILY AVAILABLE. C) THE UNCERTAINTY MUST BE A CHARACTERISTIC OF THE CODE

QUALITY OR OF THE QUALIFICATION LEVEL.

PART I I – CIAU

8

CIAU DEFINITION & NEEDS

PART I I – CIAU

9

THE IDEA AT THE BASIS OF CIAU REFERENCE SYSTEMS THE CLASS OF LWRs. THE FOLLOWING REACTORS BELONG TO THE CLASS: • BWR - ALL THE TYPES (JET PUMPS OR INTERNAL RECIRCULATION MCP

OR EXTERNAL LOOPS); • PWR EQUIPPED WITH UT-SG; • PWR EQUIPPED WITH OT-SG; • WWER EQUIPPED WITH HO-SG. EXTENSION OF THE METHODOLOGY CAN BE ENVISAGED TO COVER: • CANDU, • NEW GENERATION REACTORS EQUIPPED WITH PASSIVE ECC (AP-600,

SBWR, ETC.). REFERENCE SCENARIOS • ANY TRANSIENT SCENARIO ASSUMED FOR THE REFERENCE

SYSTEM.

- SITUATIONS WITHIN-DBA AND BEYOND-DBA ARE CONCERNED

- THE BOUNDARIES OF VALIDITY FOR THE ADOPTED CODE-NODALISATION AND FOR THE ADOPTED UNCERTAINTY METHODOLOGY ARE NOT OVERPASSED.

PART I I – CIAU

10

THE IDEA AT THE BASIS OF CIAU

THE IDEA

“THE STATUS APPROACH” FOR NUCLEAR PLANT TRANSIENT SCENARIOS: 1) ANY TRANSIENT SCENARIO ASSUMED IN THE REFERENCE

SYSTEMS CAN BE CHARACTERIZED BY THE TIME AND BY A LIMITED NUMBER OF VARIABLES. THE BOUNDARIES OF VARIATION FOR THOSE VARIABLES AND THE TIME ARE IDENTIFIED.

2) THE RANGES OF VARIATION FOR THOSE VARIABLES AND THE

TRANSIENT TIME ARE SUBDIVIDED INTO INTERVALS. HYPERCUBES RESULT FROM THE COMBINATION OF VARIABLES INTERVALS.

3) THE NPP STATUS IS FORMED BY THE COMBINATION OF ONE

HYPERCUBE AND ONE TIME INTERVAL. 4) IT IS ASSUMED THAT UNCERTAINTY CAN BE ASSOCIATED TO

ANY NPP STATUS.

PART I I – CIAU

11


THE ORIGIN OF THE IDEA

• THE NPP STATUS APPROACH FOR ACCIDENT

MANAGEMENT AND FOR EOP OPTIMISATION:

- ALREADY DISCUSSED IN A SPECIALISTS MEETING HAD IN PISA IN JUNE 1985 AS AN ALTERNATIVE TO THE EVENT APPROACH,

- CONSIDERED IN THE “CATALOGUE OF GENERIC PLANT

STATES…” ISSUED BY OECD/CSNI IN NOVEMBER 1996. • THE LOOK-UP TABLES FOR THE EVALUATION OF THE

CRITICAL HEAT FLUX (CHF) PROPOSED BY D.C. GROENEVELD AND P. KIRILLOV.

PART I I – CIAU

12


PART I I – CIAU

13

CIAU DIAGRAM

Qual. ITF and SETF data Qual.

Calc. Results

Transient evolution and status approach

CIAU development

Data documentation for each status

Quantitative accuracy Qualitative accuracy

Time accuracy Needed variables

selection

Quantity Accuracy Matrix

Time Accuracy Vector

Scenario independence

check

Transient types and Hypercubes number

Uncertainty calculation

Quantity Uncertainty Matrix Time Uncertainty Vector

CIAU

CIAU application ASM

transient result

Possible stop of the process

Transient status characterization

Quantity Uncertainty Time Uncertainty

Scenario Uncertainty

a b

e

c

d

f g

h

i

l

m n

o

p q

r t s

u

YES

NO

UMAE specific

14

CIAU STATUS

Set of tests for QUM+TUV No. 2, part 1

PART I I – CIAU

15

CIAU STATUS

Set of tests for QUM+TUV No. 2, part 2

PART I I – CIAU

16

CIAU QUALIFICATION

‘EXTERNAL’ QUALIFICATION *** DEMONSTRATION ***

THE CIAU CAN BE APPLIED FOR CALCULATING ITF OR NPP TRANSIENTS DIFFERENT FROM THOSE THAT ORIGINATED THE QUM+TUV (THIS CONDITION IS NOT MET IN THE REPORTED EXAMPLE). IN THESE CASES IT MUST BE SHOWN THAT: THE UNCERTAINTY BANDS ENVELOPE THE EXPERIMENTAL DATA.

0

2

4

6

8

10

12

14

16

18

20

0 200 400 600 800 1000 1200

Time (s)

Pres

sure

(MPa

)

Upper Uncertainty Bound

Lower Uncertainty Bound

ExpCalc

Fig. 2 - Application of the CIAU to the UMS: uncertainty bands in predicting primary system pressure.

PART I I – CIAU

17

CIAU QUALIFICATION

‘EXTERNAL’ QUALIFICATION *** DEMONSTRATION ***

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200

Time (s)

Mas

s (%

)



Exp

Calc

Fig. 3 - Application of the CIAU to the UMS: uncertainty bands in predicting primary system mass inventory.

400

450

500

550

600

650

700

750

0 200 400 600 800 1000 1200

Time (s)

Tem

pera

ture

(K) Upper Uncertainty Bound


Calc

Exp

Fig. 4 - Application of the CIAU to the UMS: uncertainty bands in predicting rod surface temperature at 2/3 core height.

PART I I – CIAU

18

CIAU APPLICATION & DEVELOPMENTS “Bifurcation” study

Bifurcations can be originated by: • the actuation or lack of actuation of a system (e.g.

pressurizer relief valves) • the occurrence of a physical phenomenon characterized by

a threshold (typically, the dryout). Type one and type two bifurcations, (or system and phenomenon connected bifurcations) are distinguished.

Scenarios can be imagined where bifurcations bring the transient evolution far from the best-estimate deterministic prediction, thus invalidating the connected uncertainty evaluation. Therefore, a bifurcation analysis is necessary.

Starting points for the bifurcation analysis are: A) the identification of type one and of type two

bifurcations B) the knowledge of the uncertainty characterizing the

parameters which affect the bifurcation.

PART I I – CIAU

19

CIAU APPLICATION & DEVELOPMENTS “Bifurcation” study - plan

No. EVENT ID. STATUS EVENT TIME (s)

A Test start NA 0. B Scram # 13. C MSL valves operation (closure, opening) # 13. D MFW operation (closure, opening) # 13. E Pumps trip and coast down limits #* 13.-280. F Blow down in saturation condition NC 50. G Pressurizer PORV actuation (start and end of

cycling) NO -

H Steam generators SRV operation (as above) #* 25.-135. I ECCS (Accumulators, LPIS, HPIS) start and end

of liquid delivery #*+ 335.

L Dry out occurrence (at 2/3 of the active fuel height)

NC 300.

M PCT event (at 2/3 of the active fuel height) NC 310. N Rewetting occurrence (at 2/3 of the active fuel

height) NC 420.

O Actuation of relevant ESF (PRZ heaters, CVCS, RHR, etc.)

NO -

P Neutron power peaks in case of ATWS NO - Q Test end NA 900. NA: Not Applicable NO: Not Occurring NC: Not Considered * Only the event start + Accumulator # The event is considered as source of potential bifurcation

Tab. 2 - List of events utilized for identifying comparable time spans and timing of events in the reference calculation. The same events are sources of potential

bifurcations.

PART I I – CIAU

20


Time

Pres

sure



Primary Side Pressure (Nominal Calculation )

1a 1b

PSCRAM

Fig. 5 - Planning of bifurcation studies. Bifurcation calculations 1a and 1b are originated by the events B, C, D, E in Tab. 2.

Time

Prim

ary

Side

Pre

ssur

e

Seco

ndar

y Si

de P

ress

ure

Primary Side Pressure (Nominal Calculation)

2a

2b

2c 2d

Secondary Side Pressure (Nominal Calculation)

SRV Pressure Set



SRV Actuation Time

Fig. 6 - Planning of bifurcation studies. Bifurcation calculations 2a, 2b, 2c and 2d are originated by the event H in Tab. 2.

PART I I – CIAU

21


Time

Pres

sure


Primary Side Pressure (Nominal Calculation)Time Error


3a

3b

3c

Accumulators Pressure

Fig. 7 - Planning of bifurcation studies. Bifurcation calculations 3a, 3b and 3c originated by event I in Tab. 2.

PART I I – CIAU

22

CIAU APPLICATION & DEVELOPMENTS “Bifurcation” study -plan

No. ID.+ Reference Events (Tab. 2)

Bifurcation Initial Status (BIS)

Way to reach the BIS

Notes from the Calculated Database

Dryout at level ‘9’

(time/PCT) s/K

0 LS00 - - - Reference Calculation AR = 3.97e-4

130./570.*

1 1a LS1A

B,C,D,E PPRZ = PSCRAM at 5

s

Additional break (AR = 3.5e-3) in the period

0-5 s.

A new dryout condition (loop seal controlled) occurs.

160./710.

2 1b LS1B

B,C,D,E PPRZ = PSCRAM at

45 s

Additional break (AR = 5.0e-5) in the period 0-45 s. Original break

opening at 45 s.

- 130./690.

3 2a LS2A

H PPRZ = 15 Mpa at tSRV

Additional break (AR = 1.0e-5) in the period 0-tSRV. Original break

opening at tSRV.

- 135./674.

4 2b LS2B

H PPRZ = 6 Mpa at

tSRV


0-tSRV.

Early DNB (50 s) and accumulator actuation (120 s).

Extended DNB.

350./1540.

5 2c LS2C

H PSG = PSRV at 10 s

Early MSIV closure to achieve tSRV =10 s.

The achieved value for tSRV is 20 s (MSIV closure at t=1 s).

140./695.

6 2d LS2D

H PSG = PSRV at 70 s

Delayed MSIV closure to achieve tSRV

=70 s.

The achieved value for tSRV is 100 s (MSIV closure at t=60 s).

130./680.

7 3a LS3A

I PPRZ = PACC at 320 s


0-320 s.

Accumulator actuation achieved at 310 s.

115./705.

8 3b LS3B

I PPRZ = PACC at 600 s

Additional break (AR = 2.2e-4) in the period 0-600s. Original break

opening at 600 s.

Accumulator actuation achieved at 604 s.

200./734.

9 3c LS3C

I tACC=tNOM + ∆tACC

Delayed actuation of accumulators. Delay ∆tACC derived from

Fig. 7.

Dryout occurring at all core levels.

280./950.

Tab. 3 – Performed ‘bifurcation calculations’

PART I I – CIAU

23

CIAU APPLICATION & DEVELOPMENTS “Bifurcation” study - results

0 200. 400. 600. 800. 1000. 1200.Time (s)

0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

Pres

sure

(MPa

)

WinGraf 3.2 - 02-12-2000

XXX 00 upper uncertainty limitX

X

X

X X XX X

X XX

XX X

XX X X X X

YYY 00 lower uncertainty limit

Y

Y YY Y

YY

YY Y

Y Y Y Y Y Y Y Y Y Y

ZZZ 00

Z

ZZ Z Z Z

ZZ

ZZ

ZZ

Z Z Z Z Z Z Z Z

VVV 3C

VVVVVVVVVVVVVVVVVVV

JJJ 3B

JJJJJJJJJJJJJJJJJJ

HHH 3A

H H H H H H H H H H H H H H H H H H H

### 2D

##

##

##

## # # # # # # # # # # #

OOO 2C

OOOO

OO

OO

O O O O O O O O O O O

AAA 2B

AA

AA A A A A A A A A A A A A A A

BBB 2AB B B

BB

BB

BB B B B B B B B B B

CCC 1BC C

CC

CC

CC C C C C C C C C C C

DDD 1AD DD

DD

DD

D D D D D D D D D D D

Fig. 8 – Results of the bifurcation calculations: primary system pressure.

-100.0 0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0Time (s)

0

1000

2000

3000

4000

5000

6000

7000

Mas

s (k

g)

WinGraf 3.2 - 02-12-2000

XXX ls03 cntrlvar34X

X

X

XX

XX X X X X X X X X X X X X X

YYY ls1a cntrlvar34Y

Y

YY

YY Y Y Y Y Y Y Y Y Y

Y Y Y Y Y

ZZZ ls1b cntrlvar34

ZZ

Z

Z

ZZ

Z Z Z Z Z Z Z Z Z ZZ Z Z Z

VVV ls2a cntrlvar34

V

V

V

VV

V V V V V V V V V V V V V V V

JJJ ls2b cntrlvar34

J

J J J J J J J J J J J J J J J J J J J

HHH ls2c cntrlvar34

H

H

H

HH H H H H H

H H H H HH

HH H H

### ls2d cntrlvar34

#

#

#

## # # # # # # # # # #

##

# #

OOO ls3a cntrlvar34

O

O

OO

OO O O O O O O O O O O O O O O

AAA ls3b cntrlvar34

A

A

A

A

A A A A A A A A A A A A A A AA

BBB ls3c cntrlvar34

B

B

BB

BB B B B B B

BB

BB

B B B B B

Fig. 9 – Results of the bifurcation calculations: primary system mass inventory.

PART I I – CIAU

24

CIAU APPLICATION & DEVELOPMENTS “Bifurcation” study – results

-100.0 0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 900.0Time (s)

400

600

800

1000

1200

1400

1600

Tem

pera

ture

(K)

WinGraf 3.2 - 02-12-2000

XXX ls03 httemp902000910

X X X X X X X X

X X

X X X X X X X X X X

YYY ls1a httemp902000910

YY Y Y Y Y Y

YY

Y Y Y Y Y Y Y Y Y Y Y

ZZZ ls1b httemp902000910

Z Z Z Z Z Z Z Z

ZZ

Z Z Z Z Z Z Z Z Z Z

VVV ls2a httemp902000910

V V V V V V V VV

V

V V V V V V V V V V

JJJ ls2b httemp902000910

J J

J

JJ

JJ

J

J

J

J J J J J J J J J J

HHH ls2c httemp902000910

H H H H H H H H H H

H H

H H H H H H H H

### ls2d httemp902000910

# # # # # # # # # #

#

# # # # # # # #

OOO ls3a httemp902000910

O O O O O OO

OO

O O O O O O O O O O O

AAA ls3b httemp902000910

A A A A A A A A A A AA

AA

A

A A A A A

BBB ls3c httemp902000910

B B B B B BB

B

B

B

BB

B B B B B B B B

Fig. 10 – Results of the bifurcation calculations: rod surface temperatures at 2/3

core height.

0

2

4

6

8

10

12

14

16

18

20

0 200 400 600 800 1000 1200

Time (s)

Pres

sure

(MPa

)

3b sup

3a sup

3b inf

3a inf

3b

3a



UP Pressure (Nominal Calculation)

Fig. 11 – ‘Tree’ of uncertainty bands resulting from the bifurcation study: primary system pressure.

PART I I – CIAU

25

CIAU APPLICATION & DEVELOPMENTS Licensing process of the Angra-2 NPP LBLOCA

(an outline)

Angra-2 is a 3765 MWth Siemens (Framatome-ANP) NPP – four loop PWR. LBLOCA DEGB DBA licensing analysis in the FSAR was submitted by the applicant to the regulatory authority based on BE+Uncertainty calculation. Independent evaluation of uncertainty was performed by CIAU to support the licensing authority. CIAU application ‘supported’ by extensive sensitivity study (> 150 code runs). PCT related results shown below.

PART I I – CIAU

26

CIAU APPLICATION & DEVELOPMENTS

BE analysis of Kozloduy-3 NPP LBLOCA (an outline)

Kozloduy-3 is a WWER-440/213, Gidropress – six loop reactor. LBLOCA, ‘200 mm break’ was requested by the NPP to support license renewal activity. Evaluation of uncertainty was performed by CIAU. Related to PCT, it was shown that Cathare predictions are bounded by the uncertainty bands predicted by the Relap5 BE analysis. PCT time trends reported below.

PART I I – CIAU

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800 10 00 1 200

Time (s )

Tem

pera

ture

(K

) Relap5 "reference"

Cathare CIAU upper band

27

CONCLUSIONS

1. CIAU CONSTITUTES A TOOL ORIGINATED BY THE COMBINATION OF A QUALIFIED BEST ESTIMATE CODE AND A SUITABLE UNCERTAINTY METHODOLOGY. “CONTINUOUS” ERROR BANDS ARE OBTAINED.

2. THE IDEA AT THE BASIS OF CIAU DERIVES FROM THE “NPP

STATUS” APPROACH: HYPERCUBES AND TIME INTERVALS HAVE BEEN DEFINED THAT ARE “FILLED” BY UNCERTAINTY DATA.

3. RELAP5/MOD3.2 SYSTEM CODE AND UMAE UNCERTAINTY

METHODOLOGY HAVE BEEN COUPLED. UNCERTAINTY COMES FROM THE ‘EXTRAPOLATION OF ACCURACY’.

4. FOUR SETS OF QUM+TUV (QUANTITY UNCERTAINTY

MATRICES AND TIME UNCERTAINTY VECTORS) HAVE BEEN DEFINED.

5. RECENT ACHIEVEMENTS:

• ‘EXTERNAL’ QUALIFICATION (DATA OTHER THAN THOSE

DISCUSSED); • CONSIDERATION OF BIFURCATION: ‘TREE’ OF UNCERTAINTY

BANDS; • ‘AUTOMATISATION’ (METHOD AVAILABLE UNDER WINDOWS) • APPLICATION TO ANGRA-2 (LICENSING, LBLOCA DEGB-DBA)

AND KOZLODUY-3 NPP (LBLOCA ‘200 MM’ BREAK).

6. PLANNED DEVELOPMENTS:

• COUPLED 3-D NEUTRONICS-THERMALHYDRAULIC ANALYSES; • DATABASE EXPANSION.

PART I I – CIAU

CIAU METHOD FOR UNCERTAINTY EVALUATION · 5 GENERAL FRAME OF UNCERTAINTY EVALUATION Historical...

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