use of fission product release results for irsn safety studies

Use of Fission Product Release results for IRSN safety studies

Dr. Grégory NICAISE

IRSN / DSR (Reactor Safety

Department)

International VERCORS Seminar

October 15-16th, 2007Gréoux les Bains, France

Partners

IRSN management of FP release(Severe Accidents)

2/13

IRSN/DPAM (FP research)

•Vercors result analysis

•FP release mechanisms

•Safety analysis and physical studies

•Probabilistic Safety Assessments

IRSN/DSR (Reactor Safety)

INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

Partners

Main uses of VERCORS results for safety analysis

INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE

3/13

Core FP release model

•FP release calculations (from the reactor core)

Activity and Power

•Kinetics of activity and power release

(to the containment)Reflooding studies

•Reflooding studiesFP release model for PSA

lev2•Generic FP release model for

PSA (level2)

Expectations on ST

estimation

•Expectations on Source Term estimation

•“S3” Source Term

S3 Source Term

Partners

S3 Source Term

4/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE


Activity and Power

Reflooding efficiency

Expectations on ST

estimation

FP release model for PSA

lev2

S3 Source Term

Release Fraction Release Fraction Element S3 Min Max Element S3 Min Max

Xe 100% 100% 100% Sr 10% 5% 35% Kr 100% 100% 100% Eu 10% 5% 35% I 100% 100% 100% Np 10% 0% 10%

Te 100% 100% 100% U 10% 0% 10% Sb 100% 50% 100% Nb 5% 0% 10% Br 100% 100% 100% Pr 5% 0% 5% Rb 100% 100% 100% La 5% 0% 10% Se 100% 100% 100% Ce 5% 0% 5% Cs 95% 95% 95% Y 1% 0% 1% Mo 90% 30% 90% Nd 1% 0% 1% Tc 90% 30% 90% Zr 1% 0% 1% Ba 50% 5% 100% Pu 1% 0% 1% Rh 30% 5% 50% Am 1% 0% 1% Ru 10% 5% 50% Cm 1% 0% 1%

“S3” FP released fraction in case of full core melting

Partners

FP release from a reactor core1.Physical scales


MFPR Code

UO2 grain

~10-6 m

VERCORS tests

UO2 pellet

~10-2 m

PWR

UO2 core

~101 m

Physical Interpretations

Meso scale Modelisation

Empirical Correlations

“MFPR Core Calculations”

“S3 Normalisation”

Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

FP release from a PWR core2.Multi-zone calculations/temperature data


Fast Core melting3h

Slow Core melting10h

242322212019181716151413121110987654321

1

54

32

-VULCAIN Code-

24 axial meshes

5 radial meshes

120 temperature transients

Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

FP release from a PWR core3.Multi-zone calculations/ MFPR 8 zones


8 MFPR Calculations (neutral

H2O/H2 atmosphere)

“S3” normalisation for each FP (highest VERCORS release)

4 axial meshe

s

2 radial meshes

242322212019181716151413121110987654321

Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

Balanced sum (mesh burnup and mass)

21,512,58,54,521,12,8,4, *63*

61*

61*

61*

2182710779*

15752*

63*

61*

61*

61*

2182727298*

157105 RRRRRRRRR mmmm

Mass balance

Burnup balance

FP release from a PWR core4.Multi-zone calculations/ Results


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

Fast Core melting3h

Slow Core melting10h

Activity and Power release to containment


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

Power released to containment

Iodine is 50%

Activity released to containment

Iodine is 30%

•FP identification of activity and power contributions

•Containment chemistry

Reflooding efficiency studies


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

•Containment activity

comparison for different

refloodings

FP Release model for PSA lev21. FP classification


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

•Need of a generic (be applied to all severe accident sequences) and simple (linear)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000time (s)

release %

CsITeXeMoBaSbRuSrZrLaCeEuNdNbU

t0 (T ric>1100°C) tB

20%

80%

GROUP 1 First aerosols I Cs Te Mo Br Rb Se Rh Tc

GROUP 2 Noble Gases Xe Kr

GROUP 3 Second AerosolsSb Sr Ba Ru Zr Nb La Ce Y Nd Eu Pr Np U Pu Am Cm

FP Release model for PSA lev22. FP release model construction


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term

tempst0 t1

Mass (kg)

Noble gases

t_DEN 100%

Second aerosols

tempst0 t1

Mass (kg)

t1ft2 t_DEN 100%

t1 t2

1% masse Classe (S3)

First aerosols

t_DEN 100%

temps

20%

80%

t0 t1

Mass (kg)

t1ft2t2 = 0.2 t_DEN100% + 0.8 t1

t1f = 0.8 t_DEN100% + 0.2 t1

t0 t1

Mass(kg)

t1ft2 t_DEN 100%

(S3)

(S3)

(S3)

t_DEN

Reflooding case

Expectations on Source Term estimations


Partners


Activity and Power


Expectations on ST

estimation


lev2

S3 Source Term •High benefits of release kinetic

acknowledgments from VERCORS tests

•FP emission to containment is better estimated

•Containment atmospheric aerosols are dynamically quantified

•Better estimation of source term in case of early containment loss

use of fission product release results for irsn safety studies

Documents

st estimationfp release

power release

cmfp release model

vercors results

psa lev2s3 source termneed

bains francemain

psa lev21

psa lev22