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Toyooka, Junichi; Kamiyama, Kenji; Tobita, Yoshiharu; Suzuki, Toru
Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11
Tsujimoto, Kazufumi; Tazawa, Yujiro; Oigawa, Hiroyuki; Sasa, Toshinobu; Takano, Hideki
JAERI-Tech 2003-085, 158 Pages, 2003/11
JAERI-Tech-2003-085.pdf:7.79MB
A safety analysis was performed for the Transmutation Physics Experiment Facility which was to research and develop the reactor physics aspects of the nuclear transmutation technology using the accelerator driven subcritical system. Design policies were evaluated for design of each equipment and system which had important role from view point of safety. Classification of safety class for reactor building, system, and equipment was also reconsidered. Based on the results of safety design policy, acceptance criteria for safety evaluation were reestablished and preliminary analysis were performed. Public exposure by the accident for site appropriateness assessment was evaluated based on revised guidelines in safety evaluation contained in the 1990 Recommendations of ICRP. A recritical event was analyzed by utilizing the newest knowledge for core disruptive accident and calculation code as the beyond design basis accident. The analytical results showed that the isolation capability of the container buildings was ensured against the recritical accident.
JNC TN9400 2000-038, 98 Pages, 2000/04
JNC-TN9400-2000-038.pdf:7.49MB
As an effort in the feasibility study on commercialized Fast Breeder Reactor cycle systems, an evaluation of the measures to prevent the energetic re-criticality in sodium-cooled large MOX core, which is one of the candidates for the commercialized reactor, has been performed. The core disruptive accident analysis of Demonstration FBR showed that the fuel compaction of the molten fuel by radial motion in a large molten core pool had a potential to drive the severe super-prompt re-criticality phenomena in ULOF sequence. ln order to prevent occurrence of the energetic re-criticality, a subassembly with an inner duct and the removal of a part of LAB are suggested based on CMR (Controlled Material Relocation) concept. The objective of this study is the comparison of the effectiveness of CMR among these measures by the analysis using SIMMER-III. The molten fuel in the subassembly with inner duct flows out faster than that from other measures. The subassembly with inner duct will work effectively in preventing energetic re-criticality. Though the molten fuel in the subassembly without a part of LAB flows out a little slower, it is still one of the promising measures. However, the UAB should be also removed from the same pin to prevent the fuel re-entries into the core region due to the pressurization by FCl below the core, unless it disturbs the core performance. The effect of the axial fuel length of the center pin to CMR behavior is small, compared to the effect of the existence of UAB.
; ; *;
JNC TN9400 2000-043, 23 Pages, 2000/03
ln the feasibility study on commercialized fast breeder reactor (FBR) cycle systems conducted in JNC, it is required for candidate FBR plants that the level of safety should be enhanced so as to assure: (1)Comparative or superior safety level to that of light water reactors (LWRs), and (2)releaf of the public from anxiety about potential nuclear hazard. Adopting Passive safety characteristics is one of the measures. To attain the above safety objective, we considered implication of the basic safety principles for nuclear power plants that were created by the international nuclear safety advisory group of IAEA. The way to relieve from the anxiety was also taken into account. Then a definite safety objective was set from the standpoint of prevention of core disruptive accident (CDA). Furthermore, as a definite safety goal relating to reactor coresafety, elimination of re-criticality issues under CDA was set by considering characteristics of FBR in comparison with those of LWR. To examine measures for elimination of re-criticality issues, we developed a quick method to estimate possibility of re-criticality under CDA, by drawing a map about criticality characteristics under CDA in various degraded cores. Then hopeful measures were proposed for elimination of re-criticality issues in sodium-cooled FBR with mixed-oxide fuel. Molten fuel discharge behavior of their measures was preliminarily analyzed. We concluded that discharge capability of "a subassembly with an internal duct" was effective, and that "partial removal of axial blanket" was also effective as one of the measures though it has small effect on core performance.
; ; ; Miyake, Osamu
PNC TN9410 92-068, 73 Pages, 1992/03
ln order to be useful for selecting specifications about the safety of the large scale fast breeder rector on and after Monju, following items were studied. (1)Design conditions of the reactor containment, (2)scenarios as to evaluation of core disruptive accident, and (3)applicability of the method of PSA. Technical documents provided for these studies are su㎜arized in this report.
Fuel by Calculation with a Transport Code XSDRN*; ; ; Inabe, Teruo; ; *; ;
JAERI-M 7085, 19 Pages, 1977/05
no abstracts in English
Moriwaki, Hiroyuki*; Kan, Taro*; Oki, Shigeo
no journal, ,
no abstracts in English
Tachi, Yoshiaki; Takaki, Naoyuki*; Wakabayashi, Toshio*; Takahashi, Makoto*
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.
Tachi, Yoshiaki; Takaki, Naoyuki*; Yano, Mari*; Wakabayashi, Toshio*
no journal, ,
Advanced MOX fuel pellets which has neutron absober at central axis have been studying to prevent re-criticality at CDA. Particle dispersibility in molten metal was examined through the experiment using alternative substances. In order to uniformly disperse the neutron absorber during fuel melting, an appropriate fuel structure was examined through evaluation tests using alternative materials, and material feasibility of the core fuel was evaluated.