ADS用振動充填型窒化物燃料要素の温度解析

Analysis of temperature distribution on sphere-pac type nitride fuels for ADS

荒井 康夫; 西 剛史; 小川 伸太*

Arai, Yasuo; Nishi, Tsuyoshi; Ogawa, Shinta*

階層型サイクル概念に基づくマイナーアクチノイド(MA)核変換燃料サイクルへの負担軽減を目的として、加速器駆動システム(ADS)用(Pu,MA)N+ZrN二粒子振動充填型燃料概念を提案し、燃料温度解析を行い、従来のペレット型燃料要素と比較・検討した。仮定した幾つかの条件の下で燃料温度分布を計算した結果、粒子振動充填型燃料では粒子充填層の熱伝導率は低くなるものの、ペレット型燃料で顕著に見られるギャップ部での温度上昇が少ないため、結果的に燃料中心温度はペレット型燃料より低くできることがわかった。この結果から、燃料製造にかかわる種々の要素技術(真球に近い高密度粒子の製造、高い充填率の達成など)が整うことを条件として、燃料製造、再処理、廃棄物などへの負担軽減が期待できる(Pu,MA)N+ZrN二粒子振動充填型燃料の概念が成立する可能性が示された。

A concept of sphere-pac type nitride fuel for ADS consisting of (Pu,MA)N and ZrN particles was proposed in order to mitigate the burden of dedicated MA-transmutation fuel cycle based on double-strata fuel cycle concept. Assuming several conditions, radial temperature distribution was compared between the sphere-pac and pellet type fuel elelments. Although the thermal conductivity of the sphere-pac particle bed is lower than that of the pellet, the maximum temperature of the sphere-pac type fuel can be lower than that of the pellet-type fuel thanks to small temperature rise in the gap region. It was suggested from the results that the concept of sphere-pac type nitride fuel is applicable when several elemental technologies for fuel fabrication, such as preparation of high dense particle and their close packing, are developed. The new concept can contribute to the mitigation of fuel cycle including fuel fabrication, reprocessing and waste management.