基于短半衰期核素的γ谱燃耗测量方法

Gamma spectrometry to determine burnup based on short half-life nuclides

提出了一种基于短半衰期核素平衡浓度求解燃耗的γ谱法。该方法通过将待测燃料在恒定中子通量条件下辐照一段时间,使得短半衰期标识核素建立浓度平衡,并基于核素平衡浓度与燃料中剩余235 U含量之间的关系求解得到燃耗值。理论模拟结果与"LR-0"实验堆上的燃料辐照实验均表明,当燃料经过短期辐照后,短半衰期标识核素^(88)Kr,^(92)Sr能在γ谱中出现明显可分辨的特征峰,从而证实了^(88)Kr,^(92)Sr作为燃耗测量的标识核素的可行性。模拟了不同实验条件下测量富集度为20%的乏燃料的燃耗情况,实验表明标识核素^(88)Kr,^(92)Sr与其相应的干扰核素的特征峰在相应能量段均可分辨出来,且γ谱的测量宜选在乏燃料卸料冷却11h内进行。最后通过^(88)Kr,^(92)Sr计算获得了与理论值相吻合的燃耗值。相比于其他方法,该方法测量燃耗不受辐照历史、燃料富集度、再次辐照前冷却时间的影响。

A gamma spectrometry method used to determine burnup based on the equilibrium concentration of short half- life nuclides is proposed. Spent fuel is irradiated under constant neutron flux for a period time to make the short half-life indicator isotopes reach the equilibrium concentration, burnup value can be obtained based on the relationship between the equilibrium conz centration and residual z3s U content. The theoretical simulation results and fuel irradiation experiment on the ＂LR-0＂ research re- actor show that the characteristic peaks of short half-life nuclides 88 Kr and 9z Sr can be significantly distinguished when fuel is irra- diated for a short period of time, thus confirming the feasibility of using 88 Kr and 9z Sr as indicator isotopes for burnup measure- ment. This paper simulates the burnup of 20% enriched spent fuel under different experimental conditions, the experimental re- sult shows that the characteristic peaks of indicator isotopes 88 Kr, 9z S and the corresponding interfering isotopes lazI, 88 Rb can be distinguished in the corresponding energy range, and the gamma spectrum measurement should be carried out within 11 hours after discharge. Finally, the calculated burnup values consistent with the theoretical values can be obtained via 88 Kr and 9z Sr. Compared with other methods, this burnup measurement method is not affected by the irradiation history, fuel enrichment and cooling time before re-irradiation.