STUDIES ON DEVELOPMENT OF AUTOMATIC FUEL MONITORING SYSTEM FOR A POOL-TYPE RESEARCH REACTOR

对池式研究堆燃料元件可能释放裂变产物(FP)的灵敏监测方法进行了研究。它包括在反应堆冷却水中引入气泡，以有效地提取在堆芯某处产生的溶解的裂变稀有气体^&lt；89；Kr和^&lt；138；Xe，并高效地计算它们各自的子核素^&lt；89；Rb和^&lt；138；Cs。测量采用以下两种方法之一：(方法一)在滤纸上通过吸入反应堆水箱的气泡气体和空气进行测量；或(方法二)在清洗水中将气泡气体采样到水面的瓶子中。研究了两种方法中影响子体核素检测效率的各种因素。这些参数包括引入气体的流量、气体出口在水中的位置(深度和径向)、冷却剂是否循环、以及(对于方法II)采样气体从采样到用水洗涤气体之间的停留时间。在这些实验数据的基础上，我们设计并构建了一套常规使用的连续模式实验的燃料自动监测系统，该系统采用方法II，由间歇采样进入水面的气瓶，将气瓶输送到探测器附近，放置一定时间，摇瓶，测量水中的核素组成。作为常规的燃料监测系统，该系统已经有效地测量了138&gt；Cs。

Studies on developing a sensitive monitoring method of possible release of fission products (FP) from a fuel element have been made for a pool-type research reactor. It consists of introducing gas bubbles into reactor coolant water to extract effectively the dissolved fission rare gases, ^<89>Kr and ^<138>Xe, produced somewhere in the core, and counting their respective daughter nuclides, ^<89>Rb and ^<138>Cs with high efficiency.The measurements were done by either method, (Method I) on a filter paper by sucking the bubbled gas and air covering water of the reactor tank, or (Method II) in the washing water of bubbled gas sampled into a bottle at the water surface. Various causes that influence the detection efficiency (DE) of the daughter nuclides in both methods were studied. These include the flow rate of introducing gas, position (depth and radial direction) of gas exit in the water, whether the coolant was circulated or not, and (for Method II) standing time of the sampled gas between the sampling and washing the gas with water. On the basis of these experimental data, we have designed and constructed an automatic fuel monitoring system of the continuous mode experiment, for routine use by adopting Method II.It is composed of an intermittent sampling of the bubbling gas into bottle at the water surface, conveying the bottle until near the detector, standing the bottle for a definite time, shaking the bottle, and measuring the nuclides contained in the water. The system have performed effectively measuring ^<138>Cs as a routine fuel monitoring system.