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Kamiyama, Kenji
JNC TN9400 2003-039, 46 Pages, 2003/06
JNC-TN9400-2003-039.pdf:2.25MB
The SIMMER-III code has been developed to evaluate the sequences of core disruptive accidents (CDAs) in fast reactors (FRs). In order to reasonably evaluate the mass of molten fuel remained in the core region and the consequence of re-criticality, it is important especially for the code to evaluate phenomena adequately such as ejection, freezing and blockage formation inside the escape path. The freezing model for the molten fuel has been developed and improved through the SIMMER-III phase 1 and 2 assessment programs. Especially, in the phase 2 assessments, knowledge of the metallurgy area was introduced, and it was found that a molten material formed the supercooling layer in the vicinity of structure wall and that the temperature of this layer dominated the energy loss of molten material and eventually the mass ejected into flow channel. This supercooling temperature was determined for each material based on the experimental result respectively as a constant input variable. 0n the other hand, experimental data used for the assessments of freezing model did not cover the temperature condition of CDA completely. In this study, a semi-empirical correlation which is comprised of thermophysical properties is proposed to predict supercooling temperatures, in order to increase reliability and accuracy of SIMMER-III freezing model. To attain the generality of this semi-empirical correlation, not only the experimental data with molten uranium dioxide but also the data with tin and wood's metal were used in the derivation of this correlation, which have different thermophysical properties and temperature conditions. In addition, it was confirmed through the evaluation of experimental data that this correlation could be applied to the molten stainless steel freezing phenomena.
; ; Kamiyama, Kenji;
JNC TN9400 2002-031, 73 Pages, 2002/06
JNC-TN9400-2002-031.pdf:3.26MB
This report describes four researches as follows, which were carried out in JFY2001 in order to contribute to the safety design and evaluation in the phase 2 of the feasibility study on commercialized fast reactor cycle systems (F/S). (1)The qualitative and quantitative safety objectives were proposed as reference for the safety goal based on the risk concept proposed by the US NRC. In addition, for attaining it, auxiliary safety objectives were determined to each of the fast reactor system and the fuel cycle system. Based on this, tth proposals of the development target and the design requirement about safety were created. (2)The distribution of the possession radioactivity in the entire fast reactor cycle system, which consists of large fast reactor facilities and a set of aqueous fuel cycle facilities, was preliminarily calculated. (3)In order to understand the system safety characteristics independent from site conditions, the radioactive material release risk in the aqueous re-processing system and fuel fabrication system to MOX pellet fuel was quantitatively analyzed especially focusing on the abnormal events, which are considered that the large amount of radioactivity is released. (4)The toxicity of the lead and problems in dealing with the lead, which exists in lead-bismuth cooling systems, were investigated. Main products are as follows. (1)By determining the provisional proposals of the development target and design requirement of the safety which introduced the risk concept about the entire fast reactor cycle system, the direction of the safety design of each system in the phase 2 of F/S was indicated. (2)About the aqueous fuel cycle system, the safety design characteristics of the conceptual design candidate were understood from a viewpoint of a radioactive material release risk.
Niwa, Hajime; Pierre Lo Pinto*; Tobita, Yoshiharu; ; ; Kamiyama, Kenji
JNC TY9400 2002-021, 48 Pages, 2001/12
JNC-TY9400-2002-021.pdf:1.85MB
This is interim report describing the progress and the results of the collaborative research works between JNC snd CEA on the safety logic in future fast reactors under the title of "Establishment of Rationa- lizedSafety Assurance Logic Aiming at FBRs with Enhanced Social Acceptance" from 1999 to 2001. This contains JNC's contribution and common view of both partners. (1) Safety goals are proposed from JNC and CEA. Significant coherency is found such as to keep defence-in depth, mitigation measures against core melt are taken into account for containment design, "evacuation free" concept is pursued, quatitative safety target is also considered as well as deterministic approach, and improvement of social acceptance is considered from the development stage of the fuel cycle including nuclear power plants. (2) Safety characteristics of each candidate coolant were compared and discussed. Gascooled fast reactor is a common interest area. Discussions are focused