Pu Vector sensitivity Study for a Pu burning fast reactor

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Hunter, S.

Hunter, S.

動燃事業団では、核種分離・消滅処理研究の一環として、大電力電子加速器を用いて長寿命核分裂生成物を消滅する可能性を研究している。電子加速器を用いると、二次的な放射化が少ないこと、広範な加速器技術を利用することができることという利点がある。現在開発中のエネルギー10MeV進行波還流型大電力CW電子線形加速器の前段部分を設置し、入射部試験を実施している。これまでに、進行波加速管にビーム電流100mAのビーム負荷を加えることができた。またパルス幅が3msecという長い電子ビ-ムを安定に加速することができた。平成9年3月に、残りの加速管6本を設置が完了し、平成9年度から全加速器の運転試験に向けて準備・調整を行っている。また、消滅処理システムして電子線加速器による単色光子の発生装置についても触れる。

This study used a "pancake" type fast reactor core design of 600 MW(e) which had been optimised for Pu burning with a feed Pu vector appropriate to once-through irradiation of MOX fuel in a PWR. The purpose of the study was to investigate the feasibility of using different qualities of Pu vector within the same basic core design. In addition to the reference (once-through) Pu vector, two extreme Pu vectors were examined: high quality Pu from military stockpiles; low quality Pu corresponding to the equilibrium point of multiple recycling in a Pu burning fast reactor. The calculations used a 2D R-Z model. The cell lattice code SLAROM, the diffusion & burnup code CITATION and the perturbation code PERKY were used. Cross-section data was taken from JENDL-3.2. The key results for the reference Pu vector case were a reactivity loss per cycle of 4.304% and the main safety parameters, a Na void worth of 1.631% and a Doppler constant of -0.00573 (a ratio of -285). The reactivity loss and void-to-Doppler ratio were used as targets for the calculations with the other Pu vectors. For the high quality Pu vector it was necessary to introduce an amount of diluent material into the core, to allow criticality criteria to be met. Several different classes of diluent were examined: increased fuel pin voidage, materials transparent to neutrons, moderators and neutron absorber. Compared with the initial "reference" Pu vector, with absorber as diluent there was an improvement in the reactivity loss per cycle (down to 3.4%) but a degradation in the main safety parameters with the void : Doppler ratio around -2000. With any of the other materials used as diluent the situation was reversed, with the reactivity loss increased to around 6% but Na void and Doppler improved to a ratio around -20. A mixture of absorber with another diluent material was shown to balance the above effects. A diluent of ZrH together with BC was Capable of producing an ...