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Chikazawa, Yoshitaka; Kubo, Shigenobu; Shimakawa, Yoshio*; Kaneko, Fumiaki*; Shoji, Takashi*; Nakata, Shuhei*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04
Sodium-cooled reactor (SFR) has superior characteristics thanks to sodium coolant features such as low pressure and high natural convection capability. Involving lessons learned from the 1F accident, requirements on design base DHRS have been modified. In that modification, safety requirements on design extended conditions have been clarified and sodium temperature criteria have been changed taking into account design margin even for design extended conditions. With the new DHRS configuration including ACS, designs of component cooling water system and emergency power supply have been updated.
Yang Jin An*;
JNC TN9400 99-013, 89 Pages, 1998/12
This report presents a variance reduction technique to estimate the reliability and availability of highly complex systems during phased mission time using the Monte Carlo simulation. In this study, we introduced the variance reduction technique with a concept of distance between the present system state and the cut set configurations. Using this technique, it becomes possible to bias the tansition from the operating states to the failed states of components towards the closest cut set. Therefore a component failure can drive the system towards a cut set configuration more effectively. JNC developed the PHAMMON (Phased Mission Analysis Program with Monte Carlo Method) code which involved the two kinds of variance reduction techniques : (1) forced transition, and (2)failure biasing. However, these techniques did not guarantee an effective reduction in variance. For further improvement, a variance reduction technique incorporating the distance concept was introduced to the PHAMMON code and the numerical calculation was carried out for the different design cases of decay heat removal system in a large fast breeder reactor. Our results indicate that the technique addition of this incorporating distance concept is an effective means of further reducing the variance.
Doda, Norihiro; Ohshima, Hiroyuki; Kamide, Hideki; Watanabe, Osamu*
no journal, ,
A safety criterion for the core structural integrity under decay heat removal operations is the hottest cladding temperature, which is evaluated by conservative consideration of various uncertainties. Under natural circulation, the coolant flow rate and temperature distributions in the core change dynamically, and the uncertainty does not always affect in the same way, so it should be treated differently from the situation when under forced convection. We have developed a new core hot spot evaluation method based on the statistical safety evaluation method which can treat the uncertainties under natural circulation conditions in a rational and accountable way. This paper presents the new method and the results applied to the event of loss of external power in a sodium cooled fast reactor.
Nabeshima, Kunihiko; Doda, Norihiro; Ishikawa, Nobuyuki; Amano, Katsunori; Ohshima, Hiroyuki
no journal, ,
AtheNa-SA project in JAEA is planned to evaluate the availability of cooling system in the reactor vessel under the severe accident of loop-type or pool-type sodium-cooled fast reactor. This report describes the design study of large scale sodium test facility AtheNa-RV, which could simulate natural circulation decay heat removal system in normal or damaged core.
