环境自动监测站固定式辐射监测仪性能测试与评价

参考计量技术规范《固定式环境γ辐射空气比释动能(率)仪现场校准规范》(JJF 1733—2018),对辐射环境空气自动监测站78台高气压电离室开展辐射特性测试。现场校准方面,仅88%的电离室满足1±0.2的响应范围要求;78台电离室的重复性均不超过1%,响应的非线性均不超过6.5%,符合规范要求。针对电离室开展辐射性能测试,发现电离室在9.0×10^-2~1.0×10⁹ μGy/h范围内的响应均不超过1±0.2;电离室对164 keV以上的光子的能量响应趋于1.0,对60 keV以下的光子无响应能力,而当光子能量在60~164 keV范围内时,响应曲线会因γ光子与电离室内部惰性气体的光电效应出现"鼓包";电离室不具备对核临界事故脉冲辐射的监测与警示能力;电离室能够在2 s内给出测量范围内的准确示值,但在分段电压的交界处,响应时间会延长至180~360 s;电离室的响应受环境温度、湿度变化的影响大小不足±0.01,表明电离室的环境适应性优良。

Performance Test and Evaluation of Fixed Radiation Monitor in Environmental Automatic Monitoring Station

In this paper,the radiation characteristics of 78 high pressure ionization chambers are tested with reference to the metrological technical specification JJF 1733-2018.In the field calibration,88% of ionization chambers meet the response range of 1±0.2;The repeatability of 78 ionization chambers don''t exceed 1%,and the response nonlinearity does not exceed 6.5%,which meet the specification requirements.The radiation performance test is carried out for the ionization chamber,and it is found that the measuring range of ionization chamber in 9.0×10^-2-1.0×10⁹ μGy/h shall not exceed 1±0.2.The energy response to photons above 164 keV tends to 1.0,and has no response ability below 60 keV.The response curve in range of 60 keV to 164 keV appears "bulge" due to the γ Photoelectric effect of photon and inert gas in ionization chamber.In addition,it does not have the monitoring and warning capability for pulse radiation in nuclear criticality accidents.The response time can give accurate indication in measurement range within 2 s,but response time will be extended to 180-360 s at the junction of segmented voltage.The response change of ionization chamber is less than ±0.01 affected by ambient temperature and humidity,showing excellent environmental adaptability.