The 5th International Conference "Safety Assurance of NPP with WWER” FSUE OKB “GIDROPRESS”,...

The 5th International ConferenceThe 5th International Conference"Safety Assurance of NPP with WWER”"Safety Assurance of NPP with WWER”

FSUE OKB “GIDROPRESS”, Podolsk, RussiaFSUE OKB “GIDROPRESS”, Podolsk, Russia29 May-1 June, 200729 May-1 June, 2007

UNIVERSITÀ DI PISAUNIVERSITÀ DI PISADIPARTIMENTO DI INGEGNERIA MECCANICA,DIPARTIMENTO DI INGEGNERIA MECCANICA,

NUCLEARE E DELLA PRODUZIONENUCLEARE E DELLA PRODUZIONEVIA DIOTISALVI 2, 56100 PISAVIA DIOTISALVI 2, 56100 PISA

Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

COMPARATIVE STUDY OF THECOMPARATIVE STUDY OF THETH-SYS CODES PERFORMANCESTH-SYS CODES PERFORMANCES

IN PREDICTING EXPERIMENTSIN PREDICTING EXPERIMENTSPERFORMED IN VVER-1000 SIMULATORPERFORMED IN VVER-1000 SIMULATOR

A. Del NevoA. Del Nevo, F. D’Auria, F. D’Auria

The 5th Int. Conf. “Safety Assurance of NPP with WWER” FSUE OKB “GIDROPRESS”, Podolsk, Russia 29 May-1 June, 2007 2

Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

LIST OF CONTENTFRAMEWORK OF THE ACTIVITYOBJECTIVE OF THE ACTIVITYPROCEDURE FOR CODE APPLICATION AND

ASSESSMENTTHE COMPUTATIONAL TOOLSPSB-VVER NUMERIC SIMULATIONSQUALITATIVE ACCURACY EVALUATIONQUANTITATIVE ACCURACY EVALUATION CONCLUSIONS


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

FRAMEWORK OF THE ACTIVITY

PROJECT TACIS 2.03/97PROJECT TACIS 2.03/97: Development and qualification of : Development and qualification of accident management (AM) procedures for the accident management (AM) procedures for the VVER1000/320 Balakovo NPP (2004–2006)VVER1000/320 Balakovo NPP (2004–2006)

THE KEY-ELEMENTS OF THE PROJECT The AM status in VVER-1000 safety technology

The ‘creation’ of the PSB-VVER EXP database The Ideal Test Matrices (considering ATWS, RIA and ‘all-over-the world’ ITF experiments)

15+1 ‘long-lasting’ PSB-VVER-1000 experiments (12 committed)

The demonstration of SYS-TH code capabilities The qualification of computational tools (code, nodalisation, BIC)

Addressing the Scaling Issue

Calculating the Uncertainty

User Qualification and Training

The proposal of AM strategy for VVER-1000

Putting the bases for ‘preserving the expertise’ Final Report

Final Meeting

Electronic database (exp-data, input decks, output, comparison exp/calc)


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado


The reference facility is the PSB-VVER ITF, simulator of VVER-1000 (V-320 design) NPP, operated at EREC

The AM TM includes 12 experiments Loss Of Coolant Accident (LOCA) – 5 Loss Of Feed Water (LOFW) – 3 Station BlackOut (SBO) – 1 PRImary to SEcondary side leak (PRISE) – 1 Main Steam Line Break (MSLB) – 1 Natural Circulation (NC) – 1

The experiments performed in the Project were actually 16 The AM TM (12) 1 test for the demonstration of repeatability of the

experimental results 3 single variant experiments.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado


INSTITUTIONS INVOLVED IN THE PROJECT University of Pisa (UNIPI) Electrogorsk Research and Engineering Center (EREC) Gidropress (GP) RRC-Kurchatov Institute (RRC-KI)

Several other Key Experts were involved in the Project

SCIENTISTS INVOLVED IN THE ANALYTICAL SIMULATIONS & ANALYSES

UNIPI - A. Del Nevo, F. D’Auria, G.M. Galassi, W. Giannotti, M. Cherubini, D. Araneo, N. Muellner

EREC - O.I. Melikhov, Y. Parfenov, V.I.Melikhov, I.V.Elkin, A. Kapustin

GP - M. Bykov, E. Lisenkov, M. Zakutaev

RRC-KI - A. Suslov, A. Andryushchenko, A. Drush, L. Gilvanov


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

OBJECTIVE OF THE ACTIVITY

GENERAL OBJECTIVES RELATED WITH THE APPLICATION OF THE TH-SYS AGAINST PSB-VVER EXPERIMENTS

Support the design of the experiments executed in PSB-VVER ITF (TACIS 2.03/97 Projects);

To demonstrate (the availability of) acceptable prediction capabilities for existing codes to simulate transients in easter NPP

Qualifying computational tools used for performing safety analyses focused on the development of AM procedures

To compare the performances of different TH-SYS codes used for Best Estimate analyses (i.e. Cathare2, Relap5/Mod3.3, Relap5-3D©, Athlet, Korsar, etc…). This comparison is based on the application of the tools used at UNIPI in the procedure for code assessment General comparison between the codes (time evolutions) – NOT

PRESENTED The qualitative accuracy evaluation based on the analysis of the

Relevant Thermohydraulic Aspect (RTA) The quantitative accuracy evaluation performed with the FFT-BM

To contribute in providing relevant post-tests results usable for the development of the CIAU procedure for CATHARE2 and RELAP5 code


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

THE PROCEDURE FOR CODE APPLICATION AND ASSESSMENT

The activity aimed at the qualification of computational tools was based on the following steps:

Facility configuration

Check of the experimental Boundary and Initial Conditions (BIC)

Check of the experimental data

Input deck preparation and documentation

Steady state conditions

Transient analysis


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

THE COMPUTATIONAL TOOLS

UNIPI PSB-VVER nodalization by CATHARE2/V1.5B – pre/post-test phases

UNIPI PSB-VVER nodalization by RELAP5/Mod3.3 & RELAP5-3D©/v2.2.4 – pre/post test-phases

EREC PSB-VVER nodalization by CATHARE2/V1.3L – pre/post-test phases

EREC PSB-VVER nodalization by RELAP5/Mod3.3 – pre-test phase

GIDROPRESS PSB-VVER nodalization by KORSAR/v1.1 – pre/post-test phases

GIDROPRESS PSB-VVER nodalization by TRAP – pre-test phase

RRC-KI PSB-VVER nodalization by ATHLET/Mod 2.0 Cycle A – post-test phase.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

PSB-VVER NUMERIC SIMULATIONS


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

OVERVIEW OF THE POST-TESTS ANALYSES

A comparison between the results obtained by the codes and their applications to the transients of the test matrix was performed.

Different approaches were considered for this comparison in order to evaluate not only the performance of the codes and their capabilities to predict the phenomena but also the UNIPI methodology for code assessment.

These steps were performed in several subsequent phases Comparison and discussion of the results, considering the

homogeneous quantities such as: pressures, mass flow rates, integrated mass flow rate, mass inventories, fluid temperatures, structure (typically the core) temperatures, levels, pressure drops and powers (core, heaters, etc).

The figures of the results time trends (more than 50) were depicted for each test (at least CATHARE2 and RELAP5). Visual judgment of the calculation results quality and of the code capability to correctly reproduce the experiment.

The list of the resulting events or Time Sequence of Events (TSE)

Detailed tables (Qualitative accuracy evaluation) were prepared reporting the Phenomenological Windows (Ph.W.), the Relevant Thermal-hydraulic Aspects (RTA) and the related parameters. These were used to evaluate if the calculation reproduced all the main aspects/phenomena of the experiment and if these aspects/phenomena were well identified and characterized.

The quantitative accuracy was evaluated using the specific tool developed at UNIPI: the FFTBM


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

QUALITATIVE ACCURACY EVALUATION

The QUALITATIVE ACCURACY evaluation is based upon a systematic procedure consisting in the identification of phenomena and of the RTA. It derives from a visual observation of the experimental and predicted trends. The technical judgments envisaged are: the code predicts qualitatively and quantitatively the parameter

(Excellent – the calculation result is within experimental data uncertainty band);

the code predicts qualitatively, but not quantitatively the parameter (Reasonable – the calculation result shows only correct behavior and trends);

the code does not predict the parameter, but the reason is understood and predictable (Minimal – the calculation result is not within experimental data uncertainty band and sometimes does not have a correct trend);

the code does not predict the parameter and the reason is not understood (Unqualified - calculation result does not show correct trend and behavior, reasons are unknown and unpredictable).

The parameters characterizing the RTA (i.e., SVP = Single Valued Parameter, TSE = parameter belonging to the Time Sequence of Events, IPA= Integral Parameter and NDP = Non Dimensional Parameter) give an idea of the amount of the discrepancy.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado


TEST #8TEST #8


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado



Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

A comparative tables highlighted the performance of the codes Cathare2 and Relap5 in predicting the RTAs

Main conclusions regarding the comparison of the qualitative accuracy evaluations: The judgments on PRZ behavior are generally excellent or reasonable in all

transients in the CATHARE2 and in RELAP5 simulations. Number of PORV opening (pressurizer behavior) in the high pressure

transient (i.e. LOFW) always more than in the experiment. The analysis of the SG behavior is also often “minimum” in the number of

the BRU-A valves opening and closure during the high pressure transient (both codes).

A general faster pressure increase is observed in SG behavior following the main steam line closure (“reasonable” or “minimum”).

Primary mass distribution has been judged correctly simulated in almost all transients for CATHARE2 code

The dryout have been correctly predicted by the code, even if it should be noted that the timing of the occurrence of this phenomenon was generally anticipated. This occurred in particular in the post test of the experiment N. 11 and 12 conducted with RELAP5 code.

The occurrence of the loop seal clearance has been reasonable predicted by the codes. In particular, the main difference was the prediction of the loop where the clearance occurred



Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

QUANTITATIVE ACCURACY EVALUATION

The tool (FFT-BM) has been developed at University of Pisa and is based on the use of the Fast Fourier Transform.

The requirements that this tool for accuracy evaluation fulfills are: at any time of the transient this function should remember the

previous history; engineering judgment should be avoided or reduced; the mathematical formulation should be simple; the function should be non-dimensional; it should be independent upon the transient duration; compensating errors should be taken into account (or pointed out); its values should be normalized.

20-25 parameters selected between a list of 27 are used for the application of the method depending upon the transient and the availability of the experimental measurements: pressures, levels, pressure drops, cladding and fluid temperatures, mass inventory or injected and power.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

QUANTITATIVE ACCURACY EVALUATION

The FFT-BM provides a measure of the accuracy of the calculation, in particular: AA is the relative magnitude of the discrepancy WF factor characterizes the kind of error (…at low or high frequencies)

Two limits are envisaged in the UNIPI procedure for code assessment: AApp=0.1; AAtot=0.4

•‘VERY POOR/UNACCEPTABLE’(AA)tot > 0.7

•‘poor’0.5 < (AA)tot < 0.7

•‘good’0.3 < (AA)tot < 0.5

•‘very good’(AA)tot < 0.3


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

QUANTITATIVE ACCURACY EVALUATION BY R5 & C2

Relap5Cathare2

C2 - Average Accuracy Primary Pressue

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 5000 10000 15000 20000 25000

Time (s)

Av

era

ge A

ccu

racy

(-)

T#1

T#2

T#3

T#4

T#5

T#6

T#7

T#8

T#9

T#10

T#11

T#12

Acceptability limit

C2 - Average Accuracy Total

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 5000 10000 15000 20000 25000

Time (s)

Av

era

ge A

ccu

racy

(-)

T#1

T#2

T#3

T#4

T#5

T#6

T#7

T#8

T#9

T#10

T#11

T#12

Acceptability limit AAtot<04

R5 - Average Accuracy Primary Pressue

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 5000 10000 15000 20000 25000

Time (s)

Av

era

ge A

ccu

racy

(-)

T#1

T#2

T#3

T#4

T#5

T#6

T#7

T#8

T#9

T#11

T#12

Acceptability limit

R5 - Average Accuracy Primary Pressue

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 5000 10000 15000 20000 25000

Time (s)

Av

era

ge A

ccu

racy

(-)

T#1

T#2

T#3

T#4

T#5

T#6

T#7

T#8

T#9

T#11

T#12

Acceptability limit AAtot<04


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

OVERALL QUANTITATIVE ACCURACY EVALUATION

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Test#1 Test#2 Test#3 Test#4 Test#5 Test#6 Test#7 Test#8 Test#9 Test#10 Test#11 Test#12

Av

erag

e A

ccu

racy

(-)

R5 - Primary PressureR5 - TotalC2 - Primary PressureC2 - TotalA1 - Primary PressureA1 - TotalK - Primary PressureK - TotalR5 (T2-imp) - Primary PressureR5 (T2-imp) -Total

Acceptability limit AAtot<0.4

Acceptability limit AAp<0.1100 sec.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40


Aver

age

Acc

ura

cy (

-)

R5 - Primary PressureR5 - TotalC2 - Primary PressureC2 - TotalA1 - Primary PressureA1 - TotalK - Primary PressureK - TotalR5 (T2-imp) - Primary PressureR5 (T2-imp) - Total



0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50


Aver

age

Acc

ura

cy (

-)

R5 - Primary PressureR5 - TotalC2 - Primary PressureC2 - TotalC2v13L - Primary PressureC2v13L - TotalA1 - Primary PressureA1 - TotalR5 (T2-imp) - Primary PressureR5 - Total


Acceptability limit AAp<0.1

10000 sec.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40


Aver

age

Acc

ura

cy (

-)

R5 - Primary PressureR5 - TotalC2 - Primary PressureC2 - TotalA1 - Primary PressureA1 - TotalR5 (T2-imp) - Primary PressureR5 (T2-imp) - Total




Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

OVERALL QUANTITATIVE ACCURACY EVALUATION

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00A

vera

ge A

ccur

acy

(-)R5 - Primary PressureR5 - TotalC2 - Primary PressureC2 - TotalR5 (Imp-BIC) - Primary PressureR5 (Imp-BIC) - TotalC2v13L - Primary PressureC2v13L - TotalA1 - Primary PressureA1 - TotalK - Primary PressureK - Total

Acceptability limit

Acceptability limit AAp<0.1

HIGH-PRESSHIGH-PRESS LOW-PRESS NCLOW-PRESS LOW-PRESS

HIGH-PRESS LOW-PRESS

AAtot<0.4


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

CONCLUSIVE REMARKS CODE ASSESSMENT, AIMED AT CONFIRMING THE CAPABILITIES OF

TH-SYS CODES AGAINST AM TM CARRIED OUT AT EREC TEST FACILITY PSB-VVER, WAS PERFORMED

FOUR TH-SYS CODES (CATHARE2, RELAP5, ATHLET AND KORSAR) WERE APPLIED WITH A DIFFERENT EXTENT AND WITH DIFFERENT PURPOSES BY FOUR INSTITUTIONS: UNIPI, GIDROPRESS, EREC AND RRC-KI

THE COMPARATIVE ANALYSIS OF THE RESULTS BRINGS TO THE FOLLOWING CONSIDERATIONS:

The codes assessment confirmed that all codes were in general capable to predict the TH scenarios, involving the simulation of AM actions, with satisfactory results, notwithstanding the peculiarities of each code(i.e. numerical scheme, availability of cross junction, possibility to simulate the throttle of the break)

Some general minor discrepancies between the experimental evidences and the code simulations were identified, highlighted and justified

The differences in the simulation of the PRZ valve cycling

A faster pressure increase was observed in SG behavior following the main steam line closure.

General longer coupling between primary and secondary side pressure during the transient scenarios

Alex

was explained with the imperfect knowledge of the characteristics of the valves and the heaters installed in the PRZ. Nevertheless, it was also connected to the tendencies of the TH-SYS codes to over-predict the insurge of water in the PRZ. This was evidenced in the high pressure scenarios and connected to the combined effects of the uncertainties in the heat exchange (heat losses) and the condensation in the PRZ component.

Alex

This was connected with and over-estimation of the primary to secondary heat exchange, the uncertainty in the heat losses simulation, as well as the difficulties in predicting the condensation in the blind “large” steam and in the main steam line upstream the valve simulating the turbine steam valve in the facility.

Alex

This effect was justified again with the difficulties in simulating the heat losses at different facility conditions (e.g. low mass inventory, high mass inventory, hot primary water conditions, etc), the MCP heat losses but also with the unavoidable simplified simulation of the codes in predicting the complex SG PSB-VVER thermal-hydraulic behavior.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

CONCLUSIVE REMARKS …FOLLOWING CONSIDERATIONS (CONT’ED):

The analysis demonstrated that the FFT-BM is a suitable tool to measure the accuracy of the results.

The primary pressure threshold foreseen in the UNIPI methodology for the high pressure transients involving cycling of valves was highlighted to be too restrictive.

The user effect, well known in literature, was confirmed to be a key issue in the application of the TH-SYS codes.


Gru

ppo

Ric

erca

Nuc

lear

e S.

Pie

ro a

G

rupp

o R

icer

ca N

ucle

are

S. P

iero

a

Gra

doG

rado

THANKS

The 5th International Conference "Safety Assurance of NPP with WWER” FSUE OKB “GIDROPRESS”,...

Documents

Transcript of The 5th International Conference "Safety Assurance of NPP with WWER” FSUE OKB “GIDROPRESS”,...