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
Core FP release model
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
5/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
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
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
lev2
S3 Source Term
FP release from a PWR core2.Multi-zone calculations/temperature data
6/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Fast Core melting3h
Slow Core melting10h
242322212019181716151413121110987654321
1
54
32
-VULCAIN Code-
24 axial meshes
5 radial meshes
120 temperature transients
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
lev2
S3 Source Term
FP release from a PWR core3.Multi-zone calculations/ MFPR 8 zones
7/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
8 MFPR Calculations (neutral
H2O/H2 atmosphere)
“S3” normalisation for each FP (highest VERCORS release)
4 axial meshe
s
2 radial meshes
242322212019181716151413121110987654321
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
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
8/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
lev2
S3 Source Term
Fast Core melting3h
Slow Core melting10h
Activity and Power release to containment
9/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
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
10/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
lev2
S3 Source Term
•Containment activity
comparison for different
refloodings
FP Release model for PSA lev21. FP classification
11/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
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
12/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
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
13/13INTERNATIONAL VERCORS SEMINAR October 16th, 2007 Gréoux les Bains FRANCE
Partners
Core FP release model
Activity and Power
Reflooding efficiency
Expectations on ST
estimation
FP release model for PSA
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