Thresholds for failure of high-burnup LWR fuels by pellet cladding mechanical interaction under reactivity-initiated accident conditions

Udagawa, Yutaka; Sugiyama, Tomoyuki; Amaya, Masaki

Journal of Nuclear Science and Technology, 56(12), p.1063 - 1072, 2019/12

https://doi.org/10.1080/00223131.2019.1637795

no abstracts in English

Failure thresholds of high burnup BWR fuel rods under RIA conditions

Nakamura, Takehiko*; Fuketa, Toyoshi; Sugiyama, Tomoyuki; Sasajima, Hideo

Journal of Nuclear Science and Technology, 41(1), p.37 - 43, 2004/01

https://doi.org/10.3327/jnst.41.37

Transient deformation of high burnup BWR fuel rods was measured and failure limit was examined under simulated RIA conditions. Brittle cladding failure occurred at a small strain of about 0.4% during an early phase of the pulse irradiation tests at the NSRR. Strain rates were in an order of tens %/s at the time of the failure. Comparison of the results with thermal expansion of pellets suggested that the deformation was caused by thermal expansion of the pellets. In other words, the influence of fission gases in the pellets was small in the early phase of the deformation. Separate effect tests were conducted to examine influence of the cladding temperature on the failure behavior of cladding. Influence of the pulse width on the failure threshold was discussed in terms of the strain rate, magnitude of the deformation and temperature of the cladding for high burnup BWR fuel rods under RIA conditions.

Irradiated fuel behavior under power oscillation conditions

Nakamura, Takehiko; Nakamura, Jinichi; Sasajima, Hideo; Uetsuka, Hiroshi

Journal of Nuclear Science and Technology, 40(5), p.325 - 333, 2003/05

https://doi.org/10.3327/jnst.40.325

In order to examine high burnup fuel performance and to confirm its integrity under unstable power oscillation conditions arising during an ATWS in BWRs, two tests of irradiated fuels under simulated power oscillation conditions were conducted in the NSRR. Irradiated fuels at burnups of 25 and 56GWd/tU were subjected to four to seven power oscillations, which peaked at 50 to 95kW/m with intervals of 2s. The power oscillation was simulated by quick withdrawal and insertion of six regulating rods of the NSRR with a computerized control. Deformation of the fuel cladding of the test rods was comparable to those observed in shorter transient tests, which simulated RIAs, at the same fuel enthalpy level up to 368J/g. The fuel deformation was mainly caused by PCMI and was roughly proportional to the fuel enthalpy. Enhanced cladding deformation due to ratcheting by the cyclic load was not observed. Fission gas release, on the other hand, was considerably smaller than in the RIA tests, suggesting different release mechanisms in the two types of transients.

NSRR tests under simulated power oscillation conditions of BWRs

Nakamura, Jinichi; Nakamura, Takehiko; Sasajima, Hideo; Suzuki, Motoe; Uetsuka, Hiroshi

HPR-359, Vol.2, p.34_1 - 34_16, 2002/09

In BWR, power oscillations can occur due to the void fraction fluctuation. To investigate the fuel behavior during power oscillation of BWRs, two types of irradiated fuel rods were tested under simulated power oscillation conditions in the Nuclear Safety Research Reactor(NSRR). One is high burnup BWR fuel (56GWd/t) test, with 4 power oscillation cycles, to clarify the behavior of high burnup fuel. The second one is high enriched fuel(20%,25GWd/t) test, with 7 power cycles, to perform the test under high power conditions. The fuel behavior data, such as cladding elongation, fuel stack elongation, cladding temperature, etc. were obtained in these tests. The DNB did not occur in these tests. The PCI was observed through cladding elongation and fuel stack elongation during the power oscillations, but the residual strain of cladding was very small. Fuel behavior under simulated power oscillations is discussed based on in-pile data and PIE data and is compared with FEMAXI-6 and FRAP-T6 calculation.

Proposal and analysis of the benchmark problem suite for reactor physics study of LWR next generation fuels

Research Committee on Reactor Physics

JAERI-Research 2001-046, 326 Pages, 2001/10

JAERI-Research-2001-046.pdf:14.45MB

The Working Party on Reactor Physics for LWR Next Generation Fuels in the Research Committee on Reactor Physics, which is organized by the Japan Atomic Energy Research Institute, has recently proposed a series of benchmark problems to investigate the calculation accuracy of the nuclear characteristics of LWR next generation fuels. The next generation fuels mean the ones aiming for further extended burnup such as 70GWd/t over the current design. The resultant specifications of the benchmark problem therefore neglect some of the current limitations such as 5wt%235U to achieve the above-mentioned target. The Working Party proposed six benchmark problems, which consist of pin-cell, PWR assembly and BWR assembly geometries loaded with uranium and MOX fuels, respectively. The present report describes the detailed specifications of the benchmark problems. The results of preliminary analyses performed by the eleven member organizations and their comparisons are also presented.

Post-irradiation examination of high burnup HBWR fuel rods at JAERI

Nakamura, Jinichi; Uetsuka, Hiroshi; Kono, Nobuaki; ; ; Furuta, Teruo

HPR-345 (Vol. II), 0, 13 Pages, 1995/00

no abstracts in English