検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

MCNPによる高速炉用MOX燃料の線出力密度の解析精度向上

lmprovement of linear heat rate calculation for fast reactor MOX fueI using Monte Carlo code "MCNP"

関根 隆; 北村 了一; 青山 卓史

not registered; Kitamura, Ryoichi; Aoyama, Takafumi

高速炉用MOX燃料の熱設計手法の合理化を目的として「常陽」で実施した燃料溶融限界線出力試験(B5D-2)における試験条件の解析精度を向上するため、連続エネルギーモンテカルロコード"MCNP"を用いて試験用燃料ピンの線出力密度を計算した。MCNPによる解析では、試験用燃料ピンが装填されたB5D-2集合体内部の非均質な構造を詳細に模擬して中性子束分布及びスペクトルを計算し、各試験用燃料ピン位置における核分裂率を求め、これに核分裂当たりの発熱エネルギーを乗ずることにより、線出力密度を算出した。ここで、$$gamma$$線による発熱分については、「常陽」MK-II炉心管理コードシステム"MAGI"を用いて$$gamma$$線発熱を計算し(遅発$$gamma$$線を含む)、これをMCNPで求めた中性子発熱に加えることにより考慮した。MCNPの解析精度を検証するため、当該試験用燃料ピンの破壊試験で測定された148乗Nd生成量に基づく実測ベースでの線出力密度を求め、MCNPの計算値と比較した結果、計算値と実測値の比(C/E)は0.955$$pm$$0.020となり、両者は良く一致した。これにより、MCNPはMOX燃料ピンの線出力密度を精度良く計算できることを確認した。得られたC/Eを用いてMCNPの計算値を補正することにより、B5D-2集合体に装填された各試験用燃料ピンの線出力密度を評価した結果、それらが最大となる炉心中心高さでの線出力密度は620$$sim$$685W/cmとなった。

A three dimensional, continuous energy Monte Carlo code "MCNP" was applied to accurately evaluate the linear heat rate of mixed oxide (MOX) fuel used in a fast reactor. The test fuel pins to be analyzed were irradiated at the core center position in the experimental fast reactor JOYO MK-II core as the power-to-melt test, which was performed in order to optimize the thermal analysis method employed in the MOX fuel pin design. ln the calculation, the heterogeneous structure of the irradiation test subassembly (B5D-2) which accommodated test fuel pins inside was modeled precisely. The neutron flux distribution within the subassembly was calculated using MCNP with the neutron source which was based on the diffusion theory by the JOYO MK-II core management code system "MAGI" The linear heat rates of fuel pins were then obtained by multiplying the fission rate and fission energy of individual fissile nuclide. The gamma heating was calculated by MAGl considering the delayed fission gamma and it was included in the neutron heating obtained by MCNP. The accuracy of MCNP was verified by the post irradiation examination. using the fission product yields ($$_{148}$$Nd) measured for the melted part of test fuel pins, the linear heat rates were evaluated and compared with the MCNP results. The average ratios of MCNP calculations to the experimental values were 0.955$$pm$$ 0.020, indicating MCNP can precisely calculate the linear heat rates. By correcting the MCNP calculation results with the C/E values obtained above, the linear heat rates of test fuel pins were evaluated to be 620 - 685 W/cm at the core center height.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.