Fuel Pin Behavior under the Slow Power Ramp Transients in the CABRI-2 Experiments

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In the CABRI-FAST experimental program, four in-pile tests were performed with slow-power-ramptype transient-overpower conditions (called hereafter as ''slow TOP'') to study transient fuel pin behavior under inadvertent control-rod-withdrawal-type events in liquid-metal-cooled fast breeder reactors. The slow TOP test with a preirradiated solid-pellet fuel pin under a power ramp rate of approximately 3%Po/s was realized as a comparatory test against an existing test in the CABRI-2 program where approximately 1%Po/s was adopted with the same type of fuel pin. In spite of the different power ramp rates, the evaluated fuel thermal conditions at the observed failure time are quite similar. Three slow TOP tests with the preirradiated annular fuel resulted in no pin failure showing a high failure threshold. Based on posttest examination data and a theoretical evaluation, it was concluded that intrapin free spaces, such as central hole, macroscopic cracks, and fuel-cladding gap, effectively mitigated the fuel cladding mechanical interaction. It was also clarified that cavity pressurization became effective only in the case of a very large amount of fuel melting. These CABRI-FAST slow TOP tests, in combination with the existing CABRI and TREAT tests, provided an extended slow TOP test database under various fuel and transient conditions.

Section: Bcf1 Test With a High-smear-density Fuelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fuel Pin Behavior under Slow-Ramp-type Transient-Overpower Conditions in the CABRI-FAST Experiments

Fukano

Onoda

Sato

et al. 2009

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“…This paper describes the models in FEMAXI-FBR and the results of fuel pin performance analysis under steady state and transient CABRI-2 [5] program. The object of CABRI-2 program is to clarify the limit of fuel failure under abnormal transient and accident conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The measured data showed that the melting cavity extended from 0.2 m to 0.6125-0.66 m [5] and failure site is 0.67 m from bottom of the fissile column. The analysis results were consistent with the measured data.…”

mentioning

confidence: 96%

Analysis of fuel pin behavior under slow-ramp type transient overpower condition by using the fuel performance evaluation code ‘FEMAXI-FBR’

Tsuboi

Endô²,

Ishizu³

et al. 2012

FEMAXI-FBR has been developed as the one module of the core disruptive accident analysis code 'ASTERIA-FBR' in order to evaluate the mixed oxide (MOX) fuel performance under steady, transient and accident conditions of fast reactors consistently. On the basis of light water reactor (LWR) fuel performance evaluation code 'FEMAXI-6', FEMAXI-FBR develops specific models for the fast reactor fuel performance, such as restructuring, material migration during steady state and transient, melting cavity formation and pressure during accident, so that it can evaluate the fuel failure during accident. The analysis of test pin with slow transient over power test of CABRI-2 program was conducted from steady to transient. The test pin was pre-irradiated and tested under transient overpower with several % P 0 /s (P 0 : steady state power) of the power rate. Analysis results of the gas release ratio, pin failure time, and fuel melt radius were compared to measured values. The analysis results of the steady and transient performances were also compared with the measured values. The compared performances are gas release ratio, fuel restructuring for steady state and linear power and melt radius at failure during transient. This analysis result reproduces the measured value. It was concluded that FEMAXI-FBR is effective to evaluate fast reactor fuel performances from steady state to accident conditions.

“…In these pulse-type TOPs, energies of more than 1.0 kJ/g were injected within 1 s. Four types of high-smeardensity fuel pins (solid pellet design) with burnup of 0 to 5 at% irradiated in the Phénix reactor were used in this program. The experimental database in the pulse-type TOP domain was enlarged by the CABRI-2 program [5][6][7][8] with two additional types of fuel pins as shown in Table 1. One is the high-smear-density Viggen-4 fuel (solid pellet design) pins with the burnup level of $12 at%.…”

Section: Introductionmentioning

confidence: 99%

Fuel Pin Behavior up to Cladding Failure under Pulse-Type Transient Overpower in the CABRI-FAST and CABRI-RAFT Experiments

Fukano

Onoda

Sato

2010

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In the CABRI-FAST and CABRI-RAFT programs within a collaboration with the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and Forschungszentrum Karlsruhe (FZK), five pulse-type transient overpower tests were performed in order to study fuel pin behavior and failure condition in the Unprotected Loss-of-Flow (ULOF) accident. In these tests, two types of low-smear-density fuels irradiated in the French Phénix reactor at different burn-up levels were used so that an experimental database extension from the former CABRI-1 and CABRI-2 programs can be obtained. Pin failure took place in three of these tests giving information on the failure threshold. In two tests, no pin failure took place and useful information related to the transient fuel behavior up to failure and failure mechanism was obtained. These test results were interpreted through detailed analysis of experimental data and PAPAS-2S code calculations. In these calculations, pretransient fuel characteristics obtained from the sibling fuels were reflected, such that the uncertainty of the boundary condition can be minimized. Through the comparison among these tests and formerly existing CABRI tests, generalized understanding on the transient fuel behavior was obtained. It was concluded that the low-smear-density fuel mitigates cavity pressurization, thereby enhancing the margin-to-failure. It was also understood that this failure-thresholdenhancing capability is dependent on the type of transient.