裂变-聚变中子源

Fission-fusion neutron source

为适应聚变堆的发展和处理高放废物的需要,提出裂变-聚变中子源的概念,它是采用LiD组件放在高通量反应堆中或中国先进研究堆(CARR)重水区中,通过慢中子与6Li(n,α)反应产生2.739 MeV氚离子,它与LiD中的D发生聚变反应,产生聚变中子;随着LiD中氚的快速积累,14 MeV中子产生的D反冲粒子流与氚发生聚变反应,增长聚变中子产额,使14 MeV中子注量率逐渐升高。当氚浓度接近0.5×1022时,D反冲粒子流与氚的聚变反应率的产额接近于1,聚变中子将成倍的增长,类似于连锁反应,使聚变中子产额达到饱和,即t时刻产生氚,都被用于产生聚变反应,形成裂变-聚变中子源。这时的通量非常高,必须在接近饱和前对设定的通量(如3.5×1014n/cm2.s)下逐步降低反应堆功率,如降低CARR中子注量率,使其在设定的通量下达到饱和,适应聚变堆中子注量率的需求。论述了裂变-聚变中子源的原理,聚变中子产生率,氚的积累速率和浓度,D反冲粒子流和与氚的聚变反应速率,以及其影响因素。在均匀中子场下(即不考虑中子降抑的情况下)计算了外径180 mm、内径100 mm的LiD管道中聚变中子注量率。

In order to meet the requirement of fusion reactor development and nuclear waste treatment, a concept of fission-fusion neutron source has been proposed with an assembly of LiD rods in high flux reactor, or in a heavy water region of CARR （China Advanced Research Reactor） by slow neutrons to transfer to fusion neutron. The principle is the reaction of ^6Li（n,α） to produce energetic tritium ion with 2. 739 MeV in LiD by slow neutron, which will be bombarding the deuteron of LiD to induce fusion reaction to produce 14 MeV neutron. The fusion reaction rate will be increasing with the accumulation of tritium in LiD by the reaction between tritium and deuteron recoils produced by 14 MeV neutrons. When the concentration of tritium reaches 0.5 × 10^22 and the fraction of fusion reaction between tritium and deuteron recoils approach to 1, the 14 MeV neutron flux will be doubled and redoubled to increase to approach saturation in which the produced tritium at t time is exhausted by fusion reaction to keep the constant of tritium concentration in LiD. At this case the 14 MeV flux is too high, it has to decrease the slow neutron flux with decreasing reactor power progressively when the fusion neutron flux approach to presetting value, for example 3.5 × 10^14 n/cm^2 · s and will approach to saturation at low level. This paper describes the principle of fission-fusion neutron source, production rate of fusion neutron, accumulation rate and concentration of tritium, the fusion reaction rate between tritium and recoil deuteron, and the influence factors. When a cylinder with outer and inner diameter as 180 mm and 100 mm put in uniform neutron field without the neutron depression effect, the 14 MeV neutron flux of the inner surface of LiD cylinder is calculated with the operation time in the heavy water region of CARR.