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Journal Articles

Fuels and materials irradiation test plan at JMTR

Ise, Hideo; Ogiyanagi, Jin; Nakamura, Jinichi; Sasajima, Hideo; Takasa, Akira; Hanawa, Satoshi; Kawaguchi, Yoshihiko; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko

FAPIG, (180), p.22 - 25, 2010/02

Refurbishment of Japan Materials Testing Reactor (JMTR) is conducted in Japan Atomic Energy Agency (JAEA) in order to solve irradiation related issues for safe long-term operation of current light water reactors (LWRs) and development of advanced LWRs. JMTR will restart its operation in FY 2011. Manufacturing and installation of the irradiation test facilities on safety research of fuels and materials are also in progress. The outline of the fuels and materials irradiation test plan is described in this report.

Journal Articles

Identification of radical position of fission gas release in high-burnup fuel pellets under RIA conditions

Sasajima, Hideo; Sugiyama, Tomoyuki; Chuto, Toshinori; Nagase, Fumihisa; Nakamura, Takehiko; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 47(2), p.202 - 210, 2010/02

 Times Cited Count:5 Percentile:37.58(Nuclear Science & Technology)

Fission gas release positions in high burnup fuel pellets were examined after the pulse-irradiations which simulated reactivity initiated accident (RIA) conditions in the Nuclear Safety Research Reactor (NSRR). The ratio of xenon to krypton ((Xe/Kr) ratio) in the released gas showed that fission gas was released from the entire region of the pellets of the examined PWR fuels during the pulse-irradiations. On the other hand, most fission gas was released from the center and/or intermediate regions of the examined BWR fuel pellets. Consequently, it is likely that fission gas is not released selectively from the rim structure at the pellet periphery under RIA conditions.

Journal Articles

Applicability of NSRR room/high temperature test results to fuel safety evaluation under power reactor conditions

Sugiyama, Tomoyuki; Umeda, Miki; Udagawa, Yutaka; Sasajima, Hideo; Suzuki, Motoe; Fuketa, Toyoshi

Proceedings of OECD/NEA Workshop on Nuclear Fuel Behaviour during Reactivity Initiated Accidents (CD-ROM), 12 Pages, 2009/09

Journal Articles

Effect of initial coolant temperature on mechanical fuel failure under reactivity-initiated accident conditions

Sugiyama, Tomoyuki; Umeda, Miki; Sasajima, Hideo; Suzuki, Motoe; Fuketa, Toyoshi

Proceedings of Top Fuel 2009 (DVD-ROM), p.489 - 496, 2009/09

Journal Articles

Behavior of LWR/MOX fuels under reactivity-initiated accident conditions

Fuketa, Toyoshi; Sugiyama, Tomoyuki; Umeda, Miki; Sasajima, Hideo; Nagase, Fumihisa

Proceedings of Top Fuel 2009 (DVD-ROM), p.465 - 472, 2009/09

Journal Articles

Newly-designed capsules for fuel ramp tests in the JMTR

Hanawa, Satoshi; Ogiyanagi, Jin; Inaba, Yoshitomo; Sasajima, Hideo; Nakamura, Jinichi; Nakamura, Takehiko

Proceedings of Top Fuel 2009 (DVD-ROM), p.350 - 356, 2009/09

In order to perform power transient tests of new design LWR's fuels, new power transient test capsules, the natural convection capsule and the forced convection capsule, are being developed. The natural convection capsule has relatively simple structure, and the test fuel rod is cooled by the natural convection of the coolant. The basic technologies for the natural convection capsule have already been established and the power transient tests will be started by using this capsule. The forced convection capsule has relatively complicated structure for circulating the cooling water and controlling the cooling water temperature. By performing several mock-up test, we confirmed that the target linear heat rate is achievable by the capsules, and elemental technologies to realize the forced convection capsule is feasible.

Journal Articles

Failure of high burnup fuels under reactivity-initiated accident conditions

Sugiyama, Tomoyuki; Umeda, Miki; Fuketa, Toyoshi; Sasajima, Hideo; Udagawa, Yutaka; Nagase, Fumihisa

Annals of Nuclear Energy, 36(3), p.380 - 385, 2009/04

 Times Cited Count:19 Percentile:78.52(Nuclear Science & Technology)

Pulse irradiation tests of high burnup fuels were performed to assess the fuel failure limit in a postulated reactivity-initiated accident (RIA). A BWR-UO$$_{2}$$ rod at a burnup of 69 GWd/t failed due to pellet-cladding mechanical interaction (PCMI). The fuel enthalpy at failure was close to those for PWR-UO$$_{2}$$ rods of 71 to 77 GWd/t with more corroded cladding. Comparison of cladding metallographs between the BWR and PWR fuels showed the morphology of hydride precipitation, which depends on the cladding texture, affects the failure limit. Two tests with PWR-MOX rods of 48 and 59 GWd/t also resulted in PCMI failure. The fuel enthalpies at failure were consistent with results obtained in the previous tests with UO$$_{2}$$ fuel rods, if the failure enthalpy is plotted as a function of the cladding oxide thickness. Therefore, the PCMI failure limit under RIA conditions depends on the cladding corrosion states, and the same limit is applicable to UO$$_{2}$$ and MOX fuels below 59 GWd/t.

Journal Articles

New JMTR irradiation test plan on fuels and materials

Nakamura, Takehiko; Nishiyama, Yutaka; Chimi, Yasuhiro; Sasajima, Hideo; Ogiyanagi, Jin; Nakamura, Jinichi; Suzuki, Masahide; Kawamura, Hiroshi

Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10

In order to maintain and enhance safety of light water reactors in long-term and up-graded operations, proper understanding of irradiation behavior of fuels and materials is essentially important. Japanese government and the Japan Atomic Energy Agency have decided to refurbish the JMTR and to install new tests rigs, in order to play an active role for solving irradiation related issues on plant aging and high-duty uses of the current LWRs and on development of next-generation reactors. New tests on fuel integrity under simulated abnormal transients and high-duty irradiation conditions are planned in the JMTR. Power ramp tests of new design fuel rods will also be performed in the first stage of the program, which is expected to start in year 2011 after refurbishment of the JMTR. Combination of the JMTR tests with simulated reactivity initiated accident tests in the NSRR and loss of coolant accident tests in hot laboratories would serve as the integrated fuel safety research on the high performance fuels at extended burnups, covering from the normal to the accident conditions, including abnormal transients. For the materials irradiation, fracture toughness of reactor vessel steels and stress corrosion cracking behavior of stainless steels are being studied in addition to basic irradiation behavior of nuclear materials such as hafnium. The irradiation studies would contribute not only to solve the current problems but also to identify possible seeds of troubles and to make proactive responses.

Journal Articles

Failure of high burnup fuels under reactivity-initiated accident conditions

Sugiyama, Tomoyuki; Umeda, Miki; Fuketa, Toyoshi; Sasajima, Hideo; Udagawa, Yutaka; Nagase, Fumihisa

Proceedings of International Conference on the Physics of Reactors, Nuclear Power; A Sustainable Resource (PHYSOR 2008) (CD-ROM), 8 Pages, 2008/09

Pulse irradiation tests of high burnup fuels were performed to assess the fuel failure limit in a postulated reactivity-initiated accident (RIA). A BWR-UO$$_{2}$$ rod at a burnup of 69 GWd/t failed due to pellet-cladding mechanical interaction (PCMI). The fuel enthalpy at failure was close to those for PWR-UO$$_{2}$$ rods of 71 to 77 GWd/t with more corroded cladding. Comparison of cladding metallographs between the BWR and PWR fuels showed the morphology of hydride precipitation, which depends on the cladding texture, affects the failure limit. Two tests with PWR-MOX rods of 48 and 59 GWd/t also resulted in PCMI failure. The fuel enthalpies at failure were consistent with results obtained in the previous tests with UO$$_{2}$$ fuel rods, if the failure enthalpy is plotted as a function of the cladding oxide thickness. Therefore, the PCMI failure limit under RIA conditions depends on the cladding corrosion states, and the same limit is applicable to UO$$_{2}$$ and MOX fuels below 59 GWd/t.

Journal Articles

Behaviour of high burnup PWR fuels during simulated reactivity-initiated accident conditions

Fuketa, Toyoshi; Sugiyama, Tomoyuki; Umeda, Miki; Tomiyasu, Kunihiko; Sasajima, Hideo

Proceedings of 2006 International Meeting on LWR Fuel Performance (TopFuel 2006) (CD-ROM), p.273 - 277, 2006/10

By using pulse-irradiation capability of the NSRR, JAEA continues to perform experiments simulating fuel behaviour during reactivity-initiated accidents (RIAs). The recently-tested fuels include those irradiated in European PWRs and have burnups of 67 to 79 MWd/kgU. Cladding materials of these tested rods are Zirlo, M5, MDA and NDA. The tests resulting in the PCMI failure indicate that the fuel enthalpy at failure correlates closely with the thickness of the hydride rim, and in turn with the oxide layer thickness. Fission gas release during the RIA transient is highly dependent on the peak fuel enthalpy, and a higher enthalpy causes a larger fission gas release. Pellets with a larger grain size may have a suppression effect on the release. When DNB occurs during the transient, the large cladding deformation is caused by the increase of the rod internal pressure in combination with the decreased yield stress of the cladding at an elevated temperature. In the phase of the PCMI, the deformation is driven only by solid thermal expansion of fuel pellets.

JAEA Reports

Summary of fuel safety research meeting 2005; March 2-3, 2005, Tokyo

Fuketa, Toyoshi; Nakamura, Takehiko; Nagase, Fumihisa; Nakamura, Jinichi; Suzuki, Motoe; Sasajima, Hideo; Sugiyama, Tomoyuki; Amaya, Masaki; Kudo, Tamotsu; Chuto, Toshinori; et al.

JAEA-Review 2006-004, 226 Pages, 2006/03

JAEA-Review-2006-004.pdf:34.43MB

Fuel Safety Research Meeting 2005, which was organized by the Japan Atomic Energy Agency was held on March 2-3, 2005 at Toshi Center Hotel, Tokyo. The purposes of the meeting are to present and discuss the results of experiments and analyses on reactor fuel safety and to exchange views and experiences among the participants. The technical topics of the meeting covered the status of fuel safety research activities, fuel behavior under Reactivity Initiated Accident (RIA) and Loss of coolant accident (LOCA) conditions, high fuel behavior, and radionuclide release under severe accident conditions. This summary contains all the abstracts and sheets of viewgraph presented in the meeting.

Journal Articles

NSRR RIA-simulating experiments on high burnup LWR fuels

Fuketa, Toyoshi; Sugiyama, Tomoyuki; Sasajima, Hideo; Nagase, Fumihisa

Proceedings of 2005 Water Reactor Fuel Performance Meeting (CD-ROM), p.633 - 645, 2005/10

LWR fuel behaviors during a reactivity initiated accident (RIA) are being studied in the NSRR program. Results from recent NSRR experiments, no failures in Tests OI-10 and -12 and the higher failure enthalpy in Test OI-11, reflect the better performance of the new cladding materials in terms of corrosion during PWR operations. Accordingly, these rods with improved corrosion resistance have larger safety margin than conventional Zircaloy-4 rods. In addition, the smaller inventory of inter-granular gas in the large grain pellet could reduce the fission gas release in RIA as observed in the OI-10. Test VA-1 was conducted with an MDA sheathed 78 MWd/kgU PWR fuel rod. Despite of the higher burnup and thicker oxide layer of $$sim$$81$$mu$$m, the enthalpy at failure remained in a same level as those for rods with of $$sim$$40$$mu$$m-oxide at 50 - 60 MWd/kgU. This result suggests high burnup structure (rim structure) in pellet periphery does not have strong effect on the failure enthalpy reduction because the PCMI load is produced primarily by solid thermal expansion of the pellet.

JAEA Reports

Behavior of irradiated PWR fuel under simulated RIA conditions; Results of the NSRR tests GK-1 and GK-2

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

JAERI-Research 2004-022, 113 Pages, 2004/12

JAERI-Research-2004-022.pdf:47.48MB

Results from power burst tests, GK-1 and GK-2, conducted at the NSRR, are summarized. The tests were performed on a 14$$times$$14 PWR fuel rod irradiated to a burnup of 42 MWd/kgU in the Genkai unit #1 of Kyushu Electric Power Co., Inc. The instrumented test fuel rod in a double-container-type capsule was subjected to the pulse-irradiation with stagnant water cooling condition at 0.1 MPa and 293 K. Deposited energy and peak fuel enthalpy were 505 J/g and 389 J/g in the Test GK-1, and 490 J/g and 377 J/g in the Test GK-2, respectively. During the pulse-irradiations, DNB occurred and the cladding surface temperature reached 581 K and 569 K in the Tests GK-1 and -2, respectively. The maximum cladding hoop strain was 2.7% in the Test GK-1 and 1.2% in the Test GK-2. However, the test fuel rods did not fail. Estimated fission gas releases during the pulse-irradiations were 11.7% and 7.0% in the Tests GK-1 and -2, respectively.

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

no abstracts in English

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

 Times Cited Count:7 Percentile:24.14(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Behavior of irradiated BWR fuel under reactivity-initiated-accident conditions; Results of tests FK-1, -2 and -3

Sugiyama, Tomoyuki; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Sasajima, Hideo; Nagase, Fumihisa; Fuketa, Toyoshi

JAERI-Research 2003-033, 76 Pages, 2004/01

JAERI-Research-2003-033.pdf:17.46MB

Boiling water reactor (BWR) fuels with burnups of 41 to 45 GWd/tU were pulse-irradiated in the Nuclear Safety Research Reactor (NSRR) to investigate fuel behavior under cold startup reactivity-initiated-accident (RIA) conditions. BWR fuel segment rods of 8$$times$$8BJ (STEP I) type from Fukushima-Daiichi Unit 3 nuclear power plant were refabricated into short test rods, and they were subjected to prompt enthalpy insertion from 293 to 607 J/g (70 to 145 cal/g) within about 20 ms. The fuel cladding had enough ductility against the prompt deformation due to pellet cladding mechanical interaction. The plastic hoop strain reached 1.5% at the peak location. The cladding surface temperature locally reached about 600 deg C. Recovery of irradiation defects in the cladding due to high temperature during the pulse irradiation was indicated via X-ray diffractometry. Fission gas release during the pulse irradiation was from 3.1% to 8.2%, depending on the peak fuel enthalpy and the normal operation conditions.

Journal Articles

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

 Times Cited Count:17 Percentile:73.59(Nuclear Science & Technology)

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.

Journal Articles

Effects of pellet expansion and cladding hydrides on PCMI failure of high burnup LWR fuel during reactivity transients

Fuketa, Toyoshi; Sugiyama, Tomoyuki; Nakamura, Takehiko; Sasajima, Hideo; Nagase, Fumihisa

NUREG/CP-0185, p.161 - 172, 2004/00

To provide a data base for the regulatory guide of light water reactors, behavior of reactor fuels during off-normal and postulated accident conditions such as reactivity-initiated accident (RIA) is being studied in the Nuclear Safety Research Reactor (NSRR) program of the Japan Atomic Energy Research Institute (JAERI). A series of experiments with high burnup fuel rods is being performed by using pulse irradiation capability of the NSRR. This paper presents recent results obtained from the NSRR power burst experiments with irradiated PWR fuels with ZIRLO and MDA claddings, and discusses effects of pellet expansion as PCMI (Pellet-Cladding Mechanical Interaction) loading and cladding embrittlement primarily due to hydrogen absorption. Separate-effect studies including tube-burst and ring-tensile tests on Zircaloy cladding also described.

JAEA Reports

Dose evaluation with ICRP Publication 60 at postulated accidents of NSRR, 2003

Kashima, Yoichi; Taki, Mitsumasa; Kikuchi, Masamitsu; Sasajima, Hideo; Nakamura, Takehiko

JAERI-Tech 2003-088, 100 Pages, 2003/12

JAERI-Tech-2003-088.pdf:5.55MB

A new experiment plan is in progress to perform pulse-irradiation experiments at the NSRR with irradiated fuel rods in the high temperature and high pressure capsules. This report describes the results of the public dose evaluation for the design basis accident and postulated accidents with the models that follow the ICRP Publication 60. It was confirmed that the results met the criteria for safety design and siting with ample margins.

Journal Articles

Morphology change of rock-like oxide fuels in reactivity-initiated-accident simulation tests

Nakamura, Takehiko; Sasajima, Hideo; Yamashita, Toshiyuki; Uetsuka, Hiroshi

Journal of Nuclear Materials, 319, p.95 - 101, 2003/06

 Times Cited Count:2 Percentile:19.48(Materials Science, Multidisciplinary)

Pulse irradiation tests under simulated RIA conditions were performed with three types of ROX fuels. Single phase YSZ, homogeneous mixture of YSZ/spinel and YSZ particle dispersed in spinel type ROX fuels were pulse irradiated in the Nuclear Safety Research Reactor (NSRR). Mode and threshold of the fuel failure including its consequences were investigated under the RIA conditions. The fuel failure occurred in a burst type mode in all the three types of ROX fuel tests with considerable fuel melting. Even though the mode was quite different from those of UO$$_{2}$$ fuel, failure threshold enthalpies of the ROX fuels were close to that of UO$$_{2}$$ fuel at about 10 GJ m$$^{-3}$$. The consequence of the failure of the ROX fuels was different from the one of UO$$_{2}$$ fuel, because molten fuel dispersal occurred at lower enthalpies in the ROX fuel tests. Change of the fuel structure and material interaction in the transient heating conditions were examined through optical and secondary electron microscopy, and electron probe micro analysis.

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