Measurement of Neutron Capture Cross Sections of Radio-active Fission Product Nuclides

测量了裂变产物核素的中子俘获截面，以获得放射性废物核转化的基础数据。放射性核素俘获截面的数据很少，这是因为放射性核素的处理是困难的，在本研究中，通过比较靶核素和中子俘获过程中产生的核素的活度来获得截面。用大型Ge探测器同时测量了这两种核素的活度。1991年，测量了~(137)&GT；Cs(n，γ)~(-138)&GT；Cs反应的截面。由于同时测量~(137)Cs和~(138)Cs的活度，自动消除了电子系统的计数损失和化学提纯过程的分离产率等各种误差来源。得到的截面为0.250×0.013，是Stupegia值的2.3倍。1992年，用同样的方法测量了^&lt；90&gt；sr(n，γ)^&lt；91&gt；sr反应的截面。测得横截面值为15.3×1.3 mb。还测量了~(137)&gt；Cs(n，γ)~(138)&gt；Cs的共振值为0.36*0.07b，发现共振积分的影响可以忽略不计。本研究提供了新的可靠的~(137)Cs和~(90)Cs的中子俘获截面数据，结果将发表在《核科学与技术》杂志上。

Neutron capture cross sections of fission product nuclides were measured to obtain basic data for nuclear transmutation of radio-active waste. There are few data of capture cross sctions of radio-active nuclides since the handling of the radio-active target is difficult.In this study, cross sections were obtained by comparing the activities of a target nuclide and a nuclide produced by the neutron capture process. Activities of both nuclides were measured simultaneously using a large Ge detector.In 1991, the cross section of ^<137>Cs(n,gamma)^<138>Cs reaction was measured. Since the measurement of activities of ^<137>Cs and ^<138>Cs were made simultaneously, various sources of errors such as the counting loss of electronic system and the separation yield of chemical purification process were automatically canceled. The value of cross section obtained was 0.250 * 0.013 barn, and this value is 2.3 times larger than the value reported by Stupegia.In 1992, measurement of the cross section of ^<90>Sr(n, gamma)^<91>Sr reaction was performed by using the same method. The value of cross section obtained was 15.3 * 1.3 mb. The value of resonance using the integral of the ^<137>Cs(n, gamma)^<138>Cs was also measured and the value obtained was 0.36 * 0.07 b. It was found that the effect of resonance integral was negligible.This study presents new and reliable data of neutron capture cross section of ^<137>Cs and ^<90>Sr. The results will be published in Nuclear Science and Technology.