CSNI2103: CABRI-REPNa-4 TEST, Assessment of fuel behaviour mechanisms relevant for RIA transients

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CSNI2103 CABRI-REPNA-4 TEST. (Abstract last modified 02-MAR-2006)

CABRI-REPNa-4 TEST, Assessment of fuel behaviour mechanisms relevant for RIA transients

Abstract Table of Contents:

1. NAME OR DESIGNATION - CABRI-REPNA-4 TEST

2. COMPUTER FOR WHICH PROGRAM IS DESIGNED AND OTHER MACHINE VERSION PACKAGES AVAILABLE -

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Explanation of the status codes.

Program-name Package-ID Status CABRI-REPNA-4 TEST CSNI2103/01 Arrived

Machines used: Package-ID Orig.Computer Test Computer CSNI2103/01

3. DESCRIPTION OF TEST FACILITY -
The CABRI REP Na test data provide a very consistent basis for the assessment of fuel behaviour mechanisms relevant for RIA transients. For the CABRI REP Na rods that did not fail, valuable information on fission gas release and especially on cladding deformation have been generated in the test programme. REP Na cladding strain data have been used as a start point for deriving an admittedly simple RIA failure criterion. This is based on a maximum strain which can be tolerated by the cladding, i.e. failure can occur only when this strain level is exceeded.
- For cladding that still retains ductility, failure at high burn-up (50-60 MWd/kg) is predicted beyond a 1% (permanent) diameter strain.
- For cladding that has been embrittled due to e.g. large corrosion, spalling and hydriding, a zero ductility is assumed, i.e. the failure threshold is at onset (0%) of permanent strain.

The conditions under which the ductility decreases from 1% to zero are provisionally set in the paper, taking into account the evidence from the CABRI tests and from ANL laboratory tests. Based on the above, one derives that the lowest failure limit at 60 MWd/kg is ~65-70 cal/g, which applies to heavily corroded/hydrided fuel, i.e. for oxide thickness of ~80 mm and in presence of oxide spalling. For corrosion resistant fuel, i.e. for oxide thickness well below 80 mm and in absence of spalling, the failure threshold at the same burnup is ~100 cal/g.

This failure criterion predicts well three of the four failed REP Na tests, but not the REP Na-1 test. For this, the predicted failure threshold is 63 cal/g, whereas the reported experimental value is 30 cal/g. For CABRI unfailed rods, the predicted failure limit is very close to the enthalpy achieved during the test. When used at its higher degree of conservatism (i.e. ductility = 0), the proposed failure threshold predicts reasonably well also the failed NSRR PWR and BWR rods. In general, more data at prototypical conditions are needed in order to arrive to comprehensive, best-estimate failure predictions. The PIE data of unfailed REP Na rods show a remarkable similarity between the trend exhibited by the cladding strain and by the fission gas release. This is briefly discussed in this paper with regard to a possible FGR mechanism (i.e. it is implied that the gas may mostly be released upon cooling, when cladding constraints are reduced). In any case, it appears that FGR as such has little to do with the mechanism of failure when this occurs at low enthalpy.

For more detailed information visit
http://www.nea.fr/html/dbprog/cabrirepna/CABRI-REPNa.htm  and
http://www.nea.fr/html/dbprog/ccvm/csni-rest.html

4. DESCRIPTION OF TEST -
The REPNa4 CABRI test, performed on July 28th 1995, was the fifth test which objective was to study the behaviour of a PWR pin under a RIA type power transient.
The tested pin was extracted from a pin irradiated in the Gravelines reactor (span no.5, high oxidation) and had a mean calculated burn-up of 62300 MWd/t. The power transient, irradiated from a 100 kW power plateau, was supposed to be representative of the real reactor Reactivity Initiated Accident; its mid height width was approx. 70 ms instead of 10 ms for the 4 previous REPNa experiments. It led to an energy release into the pin at peak power node of 70 cal/g at the end of the pulse and of 95 cal/g at scram.
No clad rupture was detected during the test. Some fissile and clad elongation has been measured during the power transient. The first post-test examinations have shown a maximum residual clad swelling of 0.4% accompanied by a strong spalling of the zirconia layer.

5. EXPERIMENTAL LIMITATIONS OR SHORTCOMINGS -

6. PHENOMENA TESTED -

7. SPECIAL FEATURES OF EXPERIMENT -

8. COUNTERPART EXPERIMENTS -

9. STATUS
CSNI2103/01: 02-MAR-2006 Masterfiled restricted

10. REFERENCES -
A RIA Failure Criterion based on Cladding Strain by C. Vitanza
OECD Halden Reactor Project
Paper presented at the IAEA Technical Committee Meeting on Fuel Behaviour under Transient and LOCA Conditions
CSNI2103/01:
- F. Arreghini, C. Hee and F. Hueber:
Analysis Report of the CABRI REPNa4 Experiment
Note Technique LERES No.20/96
- REPNa4 Data Sheet
- M. Vouillot:
Compte-Rendu de Refabrication du Crayon CABRI REP-Na4 1065-5
Rapport DMT 95/202
- J.P. Breton:
CABRI REP-Na 4 and REP-Na 5 Data
Note Technique SEMAR 98/28
- J.M. Girard:
Resultats Experimentaux des Examens non Destructifs relatifs a l'Essai REPNa4
Note Technique LERES NO.42/95
- J. Noirot, B. Pasquet and V. Cuisset:
Microprobe Examination of REPNa4 Fuel at Level 312 MM/BFC
Note Technique LERES NO.22/98, NT SDC/LEC 97/2015 Ind.0
- D. Lespiaux:
REPNa5 and REPNa4 Examinations performed at the LECA:
- fission gas release,
- metallographic examinations.
Note Technique LERES no.20/98, NT SDC/LEC 97.2020 Ind.0
- Th. Martella and A. Giuliani:
Examens Non Destructifs de REP_Na4
Note Technique SDC/LCND no.96-2005 (DR) Indice 0
- J. Noirot, I. Rochas and N. Lozano:
SEM Examination of REPNa4 Fuel Fractography at level 298 mm/bfc
NT no.97-2001 Ind:0

11. TEST DESIGNATION - REP Na4

12. PROGRAMMING LANGUAGE -CSNI2103/01:

15. ESTABLISHMENT -
Institute de Radioprotection et de Surete Nucleaire
CE Cadarache
13108 St PAUL-LEZ-DURANCE Cedex

16. MATERIAL AVAILABLE -CSNI2103/01:
Data\ data files + software for plotting curves and extracting to other formats
Experimental reports\ Technical notes on the test results (PDF format)
FABRICE\ Technical notes on the tested rod before test
Other reports\ Other technical notes
Post-test examinations\ Technical notes on the post-test examinations
Read Me First.pdf Description of the files

17. CATEGORIES -

- Y. Integral Experiments Data, Databases, Benchmarks

Keywords: FUEL BEHAVIOUR, TRANSIENTS