CSNI2106: CABRI-REPNa-10 TEST, Assessment of fuel behaviour mechanisms relevant for RIA transients

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CSNI2106 CABRI-REPNA-10 TEST. (Abstract last modified 02-MAR-2006)

CABRI-REPNa-10 TEST, Assessment of fuel behaviour mechanisms relevant for RIA transients

Abstract Table of Contents:

1. NAME OR DESIGNATION - CABRI-REPNa10 TEST

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

To request or retrieve programs click on the one of the active versions below. A password and special authorization is required.

Explanation of the status codes.

Program-name Package-ID Status CABRI-REPNA-10 TEST CSNI2106/01 Arrived

Machines used: Package-ID Orig.Computer Test Computer CSNI2106/01

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 REPNa10 test, performed on July 30th 1998, was the 10th test of the CABRI REPNa programme, devoted to the study of RIA in PWRs. The REPNa10 rod is a stub of an UO2 rod irradiated in the Gravelines 5 power plant up to about 63.5 GWd/tox. The rod stub was manufactured according to the FABRICE process.
The REPNa10 rod (with oxidised and spalled clad) was submitted to an overpower transient with a half-height width (31 ms) intermediate between the REPNa1 (9.5 ms) and REPNa8 (75 ms) ones. The main objective of this test was to study the effect of the pulse width on the behaviour of an oxidised, spalled and highly irradiated clad during a RIA. The REPNa10 transient deposited 107.6 cal/g in the tested fuel at the Peak Power Node.
A rod failure was detected by the microphones 455.9 ms after the TOP onset, which corresponds to a deposited energy of 65.8 cal/g at the Peak Power Node. The failure location deduced from the microphone analysis is 25.9 cm above the Bottom of the Fissile Column. This detection is confirmed by the DND signal close to the REPNa8 one and by the flowmeters.
However, no fuel or gas ejection was detected by the instrumentation (VD, gas passing through the flowmeters,...).
The first visual examinations in a hot cell of the CABRI REPNa10 rod confirm the presence of a crack at the level deduced from the microphone signal analysis.

5. EXPERIMENTAL LIMITATIONS OR SHORTCOMINGS -

6. PHENOMENA TESTED -

7. SPECIAL FEATURES OF EXPERIMENT -

8. COUNTERPART EXPERIMENTS -

9. STATUS
CSNI2106/01: 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
CSNI2106/01:
- Ch. Marquie, C. Hee, F. Hueber and E. Ragagli:
Analysis Report of the CABRI REPNa10 Test
Note Technique LEAC no.34/99
- Ch. Marquie, C. Hee, F. Hueber and E. Ragagli:
Quick Look Report of the CABRI REPNa10 Test
Note Technique LEAC no.3/98
- REPNa10 Data Sheet
- E. Herzog, J. Larosa and M. Vouillot:
Compte-Rendu de Refabrication du Crayon CABRI REPNa10 P17/5
Note Technique LERES 76/96 - Rapport DMT 96/290 - SEMI/LECM 96/053
- R. Marsol, L. Caral and C. Pesce:
CABRI REP Na10 Examens Visuels apres Essai dans CABRI
Note Technique PECSA no.00/01, NT SECI 99.074
- E. Ragagli:
Resultats Experimentaux des Examens Non Destructifs relatifs a l'Essai CABRI
REPNa10
Note Technique LEMRA no.3/99
- Th. Martella:
REP Na10 Examens Non Destructifs apres Tir
Note Technique PECSA no.01/07, NT DEC/S3C/01-027
- X. Iltis and P. Lhuillery:
REP Na10 Metallographic Examination
NT PECSA no.212 A7 2831 NT 02 02 - NT DEC/S3C/01-130

11. TEST DESIGNATION - REP Na10

12. PROGRAMMING LANGUAGE -CSNI2106/01:

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

16. MATERIAL AVAILABLE -CSNI2106/01:
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
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