効果的なPu利用や使用済燃料削減に向けた軽水炉MOX燃料の高度化に関する研究

Study on advanced LWR MOX fuel for effective Pu utilization and reduction of spent fuel assemblies

永沼 正行  ; 生澤 佳久   ; 周治 愛之 ; 鈴木 紀一  

Naganuma, Masayuki; Ikusawa, Yoshihisa; Shuji, Yoshiyuki; Suzuki, Kiichi

軽水炉MOX燃料の高度化に向けた一つの研究として、既存炉で効果的なプルトニウム利用や使用済燃料の削減に貢献できる燃料概念の検討を行った。本検討では、その目的に資するため、PWRを対象に現行のMOX燃料の指針の範囲で集合体中のPu装荷量増加の可能性を有する燃料候補概念を抽出し、その特性について比較評価を行った。結果として、ガドリニウム含有UO燃料ピンを集合体コーナーに配置し集合体内出力ピーキング・反応度を調整するタイプの燃料が有望であり、Pu装荷量は現行MOX燃料炉心より15%程度の増加が可能となることが分かった。年間にMOX燃料として使用するPu量が同一の条件では、製造するMOX燃料集合体数を15%程度削減でき、その結果、使用済燃料も同程度削減できる見通しが得られた。

As one of the studies for advancement of LWR MOX fuel, fuel concepts that can contribute to effective plutonium utilization and reduction of spent fuel assemblies in existing reactors were studied. To contribute to this purpose, candidate fuel concepts with the potential to increase the amount of Pu loading in the assembly for PWRs were devised within the current MOX fuel guidelines, and their characteristics were compared and evaluated. As a result, it was found that a fuel type with GdO-doped UO fuel pins installed at the assembly corners to adjust the power peaking in the assembly and the reactivity in the BOC is promising and the amount of Pu loading can be increased by approximately 15% compared to the current MOX fuel core. Under the condition that the amount of Pu used for MOX fuel per year is constant, the number of MOX fuel assemblies to be fabricated can be reduced by approximately 15%, therefore, the spent fuel can be also expected to be reduced by the same amount.