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Chitose, Keiko*; Morii, Tadashi*
PNC TJ9214 90-004, 123 Pages, 1990/06
In the experimental fast reactor "JOYO", PNC(Power Reactor and Nuclear Fuel Development Corpolation) schedules to move two control rods from the third row of core to the fifth row, for the expansion of irradiation space, as the preparation for the shift to high power core, Firstly, only one control rod is moved. In this case, the reactivity worth of the control rod will decrease, because the control rod is shifted to outer region which has small reactivity worth. This study investigates the effect of the decrease of the reactivity worth of control rods on the transient of the accidents described in the present application of license. If the scram worth is about 0.067
K/K(decreasing from 0.074 K/K), the maximum temperatures of core increase. The change of the scram worth has an effect on the TOP(Transient overpower) accidents, but little effect on the LOF(Loss of Flow) and LOHS(Loss of Heat Sink) accidents. Then it proves that all of these maximum temperatures satisfy the safety criteria.
Chitose, Keiko*; *; *
PNC TJ9214 90-003, 107 Pages, 1990/06
In the experimental fast reactor "JOYO", PNC schedules to test the high-burnup capability of LMFBR. This study is performed for the license of the test at the shifted core (shift a control rod from the third row of core to the fifth row, for the expansion of irradiation space). Firstly, we caluculate the temperatures of the spare pins, which are adjacent to the RTCB test pin, at the anticipated transients and accident of the plant with the superposition of the FP gas blanketing released from pin failure. Then it proves that all of these maxium temperatures, that is, the fuel center and cladding middle temperature of the spare pins, and the fuel center temperature of the test pins are lower than the safety criteria (spare pin: pellet; 2680
C, claddlng; 890C, and test pin: pellet; 2620C). Secondary, we analyze the performance of the test pin to forecast the time of pin failure. The main factor of the pin failure is high pressure of the plenum gas. Contact pressure of FCMI(fuel-cladding-mechanical-interaction) is low. From the view point of CDF(cumulative-damage-factor), the results show that the pins don't fail on the condition of local maximum burnup rate lower than 26at%.
Morii, Tadashi*; *; *; Chitose, Keiko*
PNC TJ9214 89-002, 193 Pages, 1989/03
In the experimental fast reactor "JOYO", PNC (Power Reactor and Nuclear Fuel Development Corporation) schedules two new tests programs in near future in order to verify high-power and high-burnup capability of LMFBR fuel pins : PTM (Power-to-Melt) test and RTCB (Run, to-Cladding Breach) test. The following safety analysis necessary to get a license for the PTM test has been performed in this study. (1)Caluculate test conditions of fuel, cladding and coolant temperature and the cladding strain of test pins. (2)Confirm that the cladding of test pin has not been broken in touch with molten fuel which oozes from central melting zone of the pin and also that taking account of the axial movement of liquid fuel strain of the cladding caused by thermal expansion of solid fuel is about 0.6%, Which is less than 3% of the cladding breaking strain. (3)Calculate temperature increases due to a mistaken setting up of coolant flow of test assembly and fing the condition which satisfies representative safety criteria.
*; *; Chitose, Keiko*; Morii, Tadashi*; *
PNC TJ9214 89-001, 159 Pages, 1989/03
In the experimental fast reactor "JOYO", PNC (Power Reactor and Nuclear Fuel Development Corporation) schedules two new tests programs in near future in order to verify high-power and high burn-up capability of LMFBR fuel pines : PTM (Power-to Melt) test and RTCB (Run-to-Cladding Breach) test. Firstly, in the present study, the temperature rises of the spare pine sadjacent to the RTCB test pin due to FP gas blanletting have been calculated with superposition of the anticipated transients and accident of the plant. The calculated results have shown that the fuel center and cladding middle temperature of the spare pines are lower than the limited values (fuel : 2630 C, cladding : 890C). Secondary, the radiation dose to population due to the accidents described in the present application of license has been calculated to be sufficiently lower than the limited values.
Abe, Yutaka*; Fukasawa, Masanori*; Fujii, Tadashi*; Chitose, Keiko*; Hamazaki, Ryoichi*; Maruyama, Yu
no journal, ,
no abstracts in English
Chitose, Keiko*; Tachi, Yoshiaki; Wakabayashi, Toshio*; Takaki, Naoyuki*
no journal, ,
In sodium-cooled fast reactors, the core is not arranged in its most reactive configuration. In this case, when the fuel melts to form a molten pool, the recriticality may occur by positive reactivity insertion due to core compaction. To prevent such recriticality, special devices of the fuel subassembly structure for discharging the molten fuel from the core region, have been investigated by the Japan Atomic Energy Agency (JAEA). On the other hand, the inherent feature of core geometry and the neutron characteristics may provide the similar effect to prevent such recriticality. The purpose of this study is to design the core specification its deformation in CDA causes negative feedback to subcritical condition, without any fuel discharge device. The convex shaped core has the longer fuel length in the inner-core region and the shorter fuel in the outer-core region. Therefore, the core geometry as intact status has a lower neutron leakage effect. When the fuel melts in CDA, the core height is compacted and negative reactivity insertion is expected during molten pool formation. The convex shaped core is based on the large-scale cylindrical homogeneous core (3,600MWth, 4.95m in core diameter, and 0.75m in core height). The calculation showed that the compaction of cylindrical core leads to a reactivity gain, whereas the convex shaped core results in negative reactivity effect. In this geometry, both inner-core and outer-core are divided into two regions. Furthermore, we introduced the smaller diameter pin for inner-core and keep uniform Pu enrichment for all regions. The smaller diameter pins in high importance region are effective for flat-distribution. Through pin diameter survey, we confirmed the advantages of smaller diameter pin, such as reducing pressure loss of core coolant and decreasing the height of molten pool.
