低温核供热堆事故放射性释放量的计算方法及其应用

THE CALCULATION METHOD OF ACCIDENTAL RELEASE OF RADIOACTIVITY FOR NUCLEAR DISTRICT HEATING REACTOR AND THEIR APPLICATION

本文根据低温核供热堆的设计原则、堆内结构和系统设置等方面的特点，提出了该堆可能发生的向环境释放较多放射性的事故是：反应堆主冷却剂小管（取样管或仪表管）在安全壳外破裂；废气贮罐泄漏；核疏水系统贮罐泄漏；卸压箱泄漏；燃料组件操作事故；控制棒引水管破裂并迭加两道隔离阀失效。根据低温核供热堆的安全特点推导出这些事故放射性释放量的计算方法。结合拟建的大庆２００ＭＷ低温核供热堆具体给出了重要的事故假设和这些事故放射性释放量的计算结果及其对公众成员的辐射剂量，其中对环境影响最大的是控制棒引水管破裂并迭加两道隔离阀失效事故。在离排放口２５０ｍ处公众成员受到的全身剂量为２．６×１０－２ｍＳｖ、甲状腺剂量为４．５ｍＳｖ。

In the paper, on the basis of the design principle, reactor structure and process system of nuclear district heating reactor, the potential accidents to be put forward, in which the more radioactivity is released to environment, are: (1)breakage of small primary coolant tube (such as sampling tube or instrumentation tube) outside containment, (2)leakage of radioactive waste gas tank, (3)leakage of nuclear drains collecting tank, (4)leakage of depkressurized tank, (5)fuel handling accident, (6)breakage of supply water tube of control rod drive with two safety valves failure. According to the safety behavior of nuclear district heating reactor, the calculation method of accidental release of radioactivity is derived. In acordance with the design of Planned Daqing 200 MW nuclear district heating reactor, the important accidental assumptions are given, and the release of radioactivity and the dose to the member of public are calculated. The maximum dose is resulted from the beakage of supply water tube of control rod drive, the whole body dose to the member of public at the distance of 250 m from emmision point is 2.6×10 -2 mSv, thyroid dose is 4.5 mSv. (