高功率研究堆低浓化物理特性研究

应用ＦＧ２ＤＢ两维两群扩散燃耗程序和带６９群中子截面库的ＣＥＬＬ栅元少群参数程序，对高功率研究堆低浓化堆芯进行了物理计算。ＬＥＵ燃料元件的铀密度为３．６－７．２ｇ／ｃｍ３，包壳厚度为０．３８－０．５６ｍｍ。结果表明：改变燃料芯体铀密度或厚度在物理上相当；各堆芯方案的控制棒价值等运行安全有关参数都可以接受。部分计算结果被拟合成线性或二次关系式以便于应用。给出了各堆芯的最小临界值、剩余反应性、运行寿期、快热中子通量和积分通量等物理参数。分析这些参数后指出：当Ｕ－２３５含量提高２０％或更多时，ＬＥＵ堆芯与ＨＥＵ堆芯的主要物理性能相近，这时快中子通量几乎不受影响，热中子通量的下降率近似正比于元件Ｕ－２３５含量增加率。但由于ＬＥＵ堆芯运行寿期的延长，对一般同位素生产与燃料元件辐照考验不会有明显影响。

REDUCED ENRICHMENT NEUTRONIC STUDY ON HIGH POWER RESEARCH REACTOR

The FG2DB two dimensional two group diffusion/burnup code and the CELL few group cell parameter code with 69 groups neutron cross section data base have been used for reduced enrichment neutronic study on high power research reactor with LEU fuel elements of uranium density 3.6-7.2g/cm 3 and cladding thickness 0.38-0.56mm. Results show the equivalence of fuel meat uranium density on thickness changing. Control rod worths and other operation safety parameters of core are acceptable. Parts of the results have been fitted to linear or quadratic expressions for easy application. The minimum critical value, excess reactivity, cycle length, fast and thermal fluxes and integrated fluxes, etc.,are given. Analysis of these parameters shows that with the U 235 content increased by 20% or more, the LEU core main physical characteristics are similar to those of the HEU core;reduced enrichment almost has no influence on the fast neutron flux; the decreasing rate of the thermal neutron flux is proportional approximately to the increasing rate of the U 235 content in fuel element; because of the cycle length prolonging, common radioisotope production and fuel element radiation testing are not influenced apparently.