Motome, Yuiko; Akiyama, Yoshiya; Murao, Hiroyuki
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07
The NSRR is a research reactor of TRIGA-ACPR type, located in the Nuclear Science Research Institute. The NSRR facility has been utilized for fuel irradiation experiments to study the behaviors of nuclear fuels under reactivity initiated accident conditions. Under the new regulation standards after the Fukushima Daiichi accident, the research reactors are being regulated according to the risk of the facility. Graded approach is introduced in the regulation. In order to apply the graded approach, the radiation effects of residents living around the NSRI under the external hazards were evaluated and the level of the risk of the NSRR facility was investigating. This report is summarized for the result of the evaluation in case the safety functions were lost by the tornado, earthquake and following tsunami. As the result, the risk is confirmed to be low, since the effective dose of the residents has been below 5 mSv per event due to the loss of the safety functions by the tornado, earthquake and following tsunami.
Department of Research Reactor and Tandem Accelerator
JAEA-Review 2014-047, 153 Pages, 2015/02
The Department of Research Reactor and Tandem Accelerator is in charge of the operation, utilization and technical development of JRR-3, JRR-4, NSRR, Tandem Accelerator and RI Production Facility. This annual report describes a summary of activities of services and technical developments carried out in the period between April 1, 2013 and March 31, 2014.
Suzuki, Motoe; Fuketa, Toyoshi; Saito, Hiroaki*
Nuclear Technology, 155(3), p.282 - 292, 2006/09
Experimental analyses were performed for the RIA-simulated tests, OI-10 and OI-11 of high burnup PWR rods, in the NSRR by the RANNS code. The rod conditions were calculated by the fuel performance code FEMAXI-6 following the actual power history from the beginning to the end of irradiation in PWR and the results were given to the RANNS code as pre-test conditions. The RANNS analysis was conducted on the basis of such test conditions in the NSRR as the pre-test conditions, pulse power enthalpy and coolant temperature. The predicted quantities such as temperature of pellet stack and cladding, stress-strain distribution in cladding, and interactions among them during pulse irradiation were discussed in terms of PCMI process and compared with the experimental observations. In the OI-10 rod, calculated cladding permanent strain has a reasonable agreement with strain profile obtained in PIE, while locally enhanced strain of cladding was pointed out. In the OI-11 rod, the process from crack initiation to split failure was accounted for by the plastic strain occurrence in cladding.
Suzuki, Motoe; Saito, Hiroaki*; Fuketa, Toyoshi
Nuclear Engineering and Design, 236(2), p.128 - 139, 2006/01
A computer code RANNS was developed to analyze fuel rod behaviors in the RIA conditions. The code performs thermal and FEM-mechanical calculation for a single rod in axis-symmetric geometry to predict temperature profile, PCMI contact pressure, stress-strain distribution and their interactions. An experimental analysis by RANNS begins with pre-test conditions of irradiated rod which are given by FEMAXI-6. Analysis was performed on the simulated RIA experiments in NSRR, FK-10 and FK-12, of high burnup BWR rods in a cold start-up conditions, and PCMI process was discussed extensively. It was revealed that pellet thermal expansion dominates cladding deformation and subjects the cladding to bi-axial stress state, and thermal expansion in the cladding makes the stress in the inner region significantly lower than that in the outer region. Simulation calculations with wider pulses were carried out and the resulted cladding hoop stress was compared with the failure stress estimated in the NSRR experiments.
Suzuki, Motoe; Saito, Hiroaki*; Fuketa, Toyoshi
Proceedings of 2005 Water Reactor Fuel Performance Meeting (CD-ROM), p.579 - 601, 2005/10
The RANNS code analyzes behaviors of a single fuel rod in reactivity-initiated accident (RIA) conditions. The code has two types of mechanical model; one-dimensional deformation model for each axial segment length of rod, and newly-developed two-dimensional local deformation model for one pellet length. Analyses were performed on the two RIA-simulated experiments in the NSRR, OI-10 and OI-11 with high burnup PWR rods, and results of cladding deformation were compared between calculations by the two models and PIE data. RANNS calculated the deformation profiles of claddings during the power transient of the experiments on the basis of the pre-pulse conditions of rods predicted by FEMAXI-6 code. In the calculations by the two-dimensional model, the plastic strain increase at the cladding ridges was compared with those in between the ridges and with the PIE data, and effect of stress variance induced by local non-uniformity of strain on the crack growth was discussed.
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 81m, the enthalpy at failure remained in a same level as those for rods with of 40m-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.
Tomiyasu, Kunihiko; Sugiyama, Tomoyuki; Nakamura, Takehiko; Fuketa, Toyoshi
JAERI-Research 2005-022, 128 Pages, 2005/09
In order to clarify the driving force of PCMI failure on high burnup fuels and the influence of hydrogen embrittlement on failure limit under RIA conditions, simulated-RIA experiments were performed on fresh fuel rods in the NSRR. The driving force was restricted only to thermal expansion of pellet by using fresh pellets, and fresh claddings were pre-hydrided to simulate hydrogen absorption of high burnup fuels. In seven experiments, test rods resulted in PCMI failure, which was observed on high burnup fuels, in terms of transient behavior and fracture configuration. It indicates that the driving force is sufficiently explained with thermal expansion of pellet and a contribution of fission gas is small. Many incipient cracks were generated in the outer surface of the cladding, and they stopped at the boundary between hydride rim and metallic layer. It suggests that a toughness of metallic region except hydride rim has particular importantance for failure limit. Fuel enthalpy at failure correlates with the thickness of hydride rim, and tends to decrease with thicker hydride rim.
Fuketa, Toyoshi; Nagase, Fumihisa; Sugiyama, Tomoyuki
Proceedings of IAEA Technical Meeting on Fuel Behaviour Modelling under Normal, Transient and Accident Conditions, and High Burnups (CD-ROM), 15 Pages, 2005/09
To provide a data base for the regulatory guide of light water reactors, behaviors of reactor fuels during off-normal and postulated accident conditions such as reactivity-initiated accident (RIA) and loss-of-coolant accident (LOCA) are being studied at the Japan Atomic Energy Research Institute (JAERI). A series of RIA-simulating experiments with high burnup fuel rods is being performed by using pulse-irradiation capability of the Nuclear Safety Research Reactor (NSRR). Fuel behaviors during a LOCA are also examined in an extensive program comprising of integral thermal shock tests and separate tests for oxidation rate and mechanical properties of fuel cladding.
Fuketa, Toyoshi; Nagase, Fumihisa; Sasahara, Akihiro*
Nippon Genshiryoku Gakkai-Shi, 47(2), p.112 - 119, 2005/02
Behavior of LWR fuel during reactivity-initiated accident (RIA) and loss-of-coolant accident (LOCA) is described.
Nagase, Fumihisa; Fuketa, Toyoshi
Journal of Nuclear Science and Technology, 42(1), p.58 - 65, 2005/01
Tube burst tests have been performed with artificially hydrided Zircaloy-4 specimens at room temperature and at 620 K. Pressurization rate was increased to a maximum of 3.4 GPa/s in order to simulate rapid PCMI that occurs in high burnup fuel rods during a pulse-irradiation in the NSRR. Hydrogen content in the specimens ranged from 150 to 1050 ppm. Hydrides were accumulated in the cladding periphery and formed "hydride rim" as observed in high burnup PWR fuel claddings. The hydrided cladding tubes failed with an axial crack at the room temperature tests. Brittle fracture appeared in the hydride rim, and failure morphology was similar to that observed in the NSRR experiments. The hydrides rim obviously reduced burst pressure and residual hoop strain at the tests. The residual hoop strain was very small even at 620 K when thickness of the hydride rim exceeded 18% of cladding thickness. The present result accordingly indicates an important role of the hydrides layer in high burnup fuel rod failure under RIA conditions.
Sasajima, Hideo; Sugiyama, Tomoyuki; Nakamura, Takehiko*; Fuketa, Toyoshi
JAERI-Research 2004-022, 113 Pages, 2004/12
Results from power burst tests, GK-1 and GK-2, conducted at the NSRR, are summarized. The tests were performed on a 1414 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.
Sugiyama, Tomoyuki; Fuketa, Toyoshi
Journal of Nuclear Science and Technology, 41(11), p.1083 - 1090, 2004/11
The effect of cladding surface pre-oxidation on the rod coolability under reactivity initiated accidents was investigated. NSRR tests on irradiated fuel rods have shown higher rod coolability than that of fresh rods, which arose from suppressed DNB and early quench at the surface. To identify the dominant factor, possible factors such as pellet cracking and so on, were assessed. The most probable factor, the cladding pre-oxidation, was examined by pulse irradiation tests on fresh rods with three cladding surface conditions, no oxide layer, 1m and 10m-thick oxide layers. Temperature measurements showed increased thresholds for DNB and quench at the pre-oxidized surface, leading to a reduced film boiling duration. The shifts of the critical and minimum heat flux points could be caused by the surface wettability increase. In the present tests, the wettability change was probably dominated by the chemical potential change at the surface due to pre-oxidation. The test results indicate the effects do not depend on the oxide layer thickness, but on the presence of the oxide layer.
Amaya, Masaki; Sugiyama, Tomoyuki; Fuketa, Toyoshi
Journal of Nuclear Science and Technology, 41(10), p.966 - 972, 2004/10
Pulse irradiation simulating RIA condition was carried out for test rod prepared from fuel irradiated in a commercial reactor. After the pulse irradiation, optical microscopy (OM) and scanning electron microscopy (SEM) observations and electron probe micro analysis (EPMA) were conducted for the test rod as a part of destructive tests. Fission gas release behavior during pulse irradiation was investigated by EPMA and puncture test. Xeon depression was observed in the fuel pellet after pulse irradiation at periphery and center region. It is considered that fission gas was mainly released from the pellet center region during pulse irradiation. The amount of xenon release during pulse irradiation was estimated to be 10-12% from the EPMA results and this estimated value was comparable with the puncture test result. Comparing the estimated value with other results of out-of-pile annealing tests, it was concluded that most fission gas, which was accumulated at grain boundary during base irradiation, was released from the center region of test fuel pellet during pulse irradiation.
Sugiyama, Tomoyuki; Fuketa, Toyoshi; Ozawa, Masaaki*; Nagase, Fumihisa
Proceedings of 2004 International Meeting on LWR Fuel Performance, p.544 - 550, 2004/09
Two pulse irradiation experiments simulating reactivity initiated accidents were performed on high burnup (60 GWd/t) PWR UO rods with advanced cladding alloys. Test OI-10 was performed on an MDA cladded rod with large-grain (25 m) fuel pellets with a peak fuel enthalpy condition of 435 J/g, and resulted in a peak residual hoop strain of 0.7%. On the other hand, Test OI-11 on a ZIRLO cladded rod with conventional pellets resulted in a fuel failure at a fuel enthalpy of 500 J/g due to the pellet-cladding mechanical interaction (PCMI). A long axial split was generated on the cladding over the active length. The fuel pellets were fragmented and dispersed into the coolant water. The fuel enthalpy at failure is higher than the PCMI failure criterion of 209 J/g at the corresponding burnup. The experimental results suggest that the rods with improved corrosion resistance have much safety margin against the PCMI failure compared to the conventional Zircaloy-4 rod.
Sugiyama, Tomoyuki; Nagase, Fumihisa; Nakamura, Jinichi; Fuketa, Toyoshi
HPR-362, Vol.2, 12 Pages, 2004/05
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 loss of coolant accident (LOCA) and reactivity-initiated accident (RIA) is being studied at the Japan Atomic Energy Research Institute (JAERI). The LOCA program consists of integral thermal shock tests and other separate tests for oxidation rate and mechanical property of fuel claddings. Prior to the tests on irradiated claddings, the tests have been conducted on non-irradiated claddings to examine separate effects of corrosion and hydrogen absorption during reactor operation. The tests on irradiated claddings have recently been started and results have been obtained. As for an RIA study, 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 LOCA and RIA studies at JAERI.
Murao, Hiroyuki; Yachi, Shigeyasu; Ota, Kazunori; Muramatsu, Yasuyuki; Nakamura, Takehiko; Terakado, Yoshibumi
UTNL-R-0435, p.15_1 - 15_9, 2004/03
no abstracts in English
Murao, Hiroyuki; Yachi, Shigeyasu; Ota, Kazunori; Muramatsu, Yasuyuki; Nakamura, Takehiko; Terakado, Yoshibumi
JAERI-Tech 2003-094, 41 Pages, 2004/01
Prior to actual runs in the shaped pulse and in the combined pulse operations, the online simulation and the offline simulation must be performed to examine safety and appropriation. Actual reactor power of the NSRR can be simulated practically, but a slight difference canbe observed between the present simulation results and the actual operation during the NSRR start-up phase and power controled operation. Regulating rod worth and fuel temperature feedback reactivity were re-evaluated and installed into the simulators. As a result, the accuracy of the simulator was remarkably improved. So that the application and safety of the shaped pulse and combined pulse operation were improved.
Sugiyama, Tomoyuki; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Sasajima, Hideo; Nagase, Fumihisa; Fuketa, Toyoshi
JAERI-Research 2003-033, 76 Pages, 2004/01
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 88BJ (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.
Nakamura, Takehiko*; Fuketa, Toyoshi; Sugiyama, Tomoyuki; Sasajima, Hideo
Journal of Nuclear Science and Technology, 41(1), p.37 - 43, 2004/01
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.
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.