General study on new MA burner concept being capable of flexible control of Plutonium inventory

在第一年的研究中，研究了一种新的概念，即用次锕系元素（MA）和金属稀释剂装载超长寿命堆芯，并从中子特性的角度证明了其可行性。对这两个核心概念进行了多项参数调查！混合氧化物燃料-钠冷却堆芯和金属燃料-铅冷却堆芯的燃耗特性，以阐明中子谱的影响。比较是使用三个参数来描述核反应的直接裂变，间接裂变和捕获过程。在第二年的研究中，引入了一种新的半理论方法来描述MA对燃耗特性的影响。结果表明：1）Np-237在高中子注量率水平下对堆芯的燃耗有不良影响，应在低中子注量率水平下装填。2)包层中Np-237（57%，U238）的加入可以显著降低Pu积累引起的功率分布变化。在去年进行的研究中，在KUCA B组件中测量了几种金属稀释剂候选物Nb、Cr、W、Pb的中子特性。在确定了堆芯装样量的基础上，采用周期法成功地测量了样品的反应性。这类实验最重要的问题是由于样品的加载和卸载而引起的反应性误差。通过五次试验，发现除了第一次测量外，误差都很小。

In the study done in the first year, a new concept of ultra-long life core loaded with minor actinide(MA) and metal diluent was examined, and the feasibility from the neutronic characteristics point of view was proved. Several parametric surveys were performed for the two core concepts! MOX fuel- sodium cooled core, and metal fuel-Pb cooled core, for burnup characteristics in order to clarify the effect of neutron spectrum. The comparison was done using three parameters that describe the process of nuclear reactions' direct fission, indirect fission, and capture. In the study done in the second year, a new semi-theoretical method was introduced to describe the effect of MA on burnup characteristics. The method was applied to an ultra-long life core, and the optimized initial MA loading was evaluated As the conclusions, the followings are obtained; 1) Np-237 shows bad effect on bumup in high neutron flux level So, it is desirable to load in low neutron flux level. 2) Blanket loaded with large amount of Np-237(57%,remainder is U-238) may drastically reduce the power distribution change due to Pu buildup. In the study done in the last year, neutronic characteristics of several candidates for metal diluent, Nb, Cr, W, Pb were measured in the KUCA B-assembly. The sample reactivity was successfully measured through the period method after determining the proper amount of sample loaded in the core. The most important issue of this kind of experiment is the error of reactivity due to the loading and unloading of the sample. Through the five trials, it was found that the error was negligibly small except the first measurement.