Selection and Experimental Research of the Passive Start-Up Neutron Detector in Nuclear Power Plant
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摘要: 为监测核电厂首循环装料、停堆以及启动过程中的堆芯状态,国内外核电厂一般在堆芯引入2个一次中子源组件,但一次中子源均为国外进口,存在进口受限的问题。为解决此问题,研究首循环取消一次中子源组件,采用燃料组件自发裂变产生的中子作为启动用中子源。燃料组件自发裂变产生的中子强度远低于一次中子源。针对以上情况,需在堆外采用更高灵敏度的探测器进行中子注量率的监测。本文在分析各种高灵敏度探测器基本原理的基础上,给出高灵敏度中子探测器的选型建议,并对其性能进行了试验验证,试验结果表明:3He正比计数管即使在γ剂量率大于0.1 Gy/h时,设置合适的甄别电压,也可以有效甄别γ噪声,试验验证的最大γ剂量率为1.0 Gy/h。Abstract: In order to monitor the reactor core during the first cycle charging, shutdown and start-up of nuclear power plants, domestic and foreign nuclear power plants generally introduce two primary neutron source components in the core, but the primary neutron sources are imported from the United States, which has the problem of import limitations. In order to solve this problem, it is studied to cancel the primary neutron source component in the first cycle and use the neutrons produced by the spontaneous fission of the fuel assembly as the starting neutron source. The neutron intensity produced by spontaneous fission of fuel assembly is much lower than that of primary neutron source. In view of the above situation, it is necessary to use a higher sensitivity detector to monitor the neutron fluence rate outside the reactor. Based on the analysis of the basic principles of various high-sensitivity detectors, this paper gives suggestions on the selection of high-sensitivity neutron detectors, and verifies their performance by experiments. The experiment results show that even when the γ dose rate is greater than 0.1 Gy/h, the 3He proportional counter tube can be set with an appropriate discriminating voltage, and can effectively discriminate γ noise. The maximum γ dose rate verified by the experiment is 1.0 Gy/h.
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Key words:
- Passive start-up /
- Neutron /
- Detector /
- Proportional counter tube /
- High sensitivity
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表 1 三种正比计数管特性对比
Table 1. Comparison of the Characteristics of Three Proportional Counter Tubes
参数 BF3正比计数管 3He正比计数管 10B正比计数管 工作电压 最高
(2500~3200 V)居中
(1200~1800 V)最低
(700~1200 V)燃耗
寿命④最短(<1012 cm−2·s−1) 居中(<1015 cm−2·s−1) 最长
(1017 cm−2·s−1)耐γ辐照
能力居中
(10 Gy/h)最差
(1Gy/h)最好
(103 Gy/h)耐温
性能最差
(<120℃)最好
(<200℃)居中
(<150℃)中子
灵敏度居中[典型应用:8 cps①/( cm−2·s−1)] 最高[典型应用:30 cps/(cm−2·s−1)及以上] 最低[典型应用:
4 cps/(cm−2·s−1)]坪斜② 最好
(<1%/100V)较好
(<3%/100V)最差
(<40%/100V)坪长③ >500 V >200 V ≥100 V 注:①cps—每秒计数;②坪斜—高压变化100 V,cps的变化,越小越好;③坪长—探测器坪区宽度,越长越好;④燃耗寿命—表征探测器在累计中子注量率辐射下的性能 表 2 坪特性测试结果
Table 2. Test Results of Plateau
计数率/cps 工作电压/V 1150 1200 1250 1300 1350 6177 7807 8369 8441 8557 坪区①/V 1250~1350 坪斜 2.21%/100 V 注:①坪区—工作电压的设置范围 表 3 甄别特性测试结果
Table 3. Test Results of Discriminating Characteristics
甄别电压/V 0.2 0.3 0.4 0.5 0.6 0.7 计数率/cps 8494 8436 8390 8224 7839 7417 中子灵敏度/
[cps/ (cm−2·s−1)]311 309 307 301 287 272 甄别电压/V 0.8 1.0 1.2 1.5 1.8 2.0 计数率/cps 6925 5906 4865 3815 3015 2621 中子灵敏度/
[cps/ (cm−2·s−1)]254 216 178 140 110 96 表 4 0.04 Gy/h γ剂量率测量结果
Table 4. Measurement Results of 0.04 Gy/h γ Dose Rate
甄别电压/V 0.4 0.5 0.6 0.7 0.8 1.0 本底计数率/cps 5.37 4.86 4.59 4.58 3.70 3.33 有γ源时计数率/cps — — 13.29 5.17 3.74 3.08 “—”表示无数据 表 5 0.1 Gy/h γ剂量率测量结果
Table 5. Measurement Results of 0.1Gy/h γ Dose Rate
甄别电压/V 0.7 0.8 1.0 1.2 1.5 本底计数率/cps 5.3 4.0 4.5 4.1 2.5 有γ源时计数率/cps 49.1 10.0 4.1 2.7 2.6 表 6 0.2 Gy/h γ剂量率测量结果
Table 6. Measurement Results of 0.2 Gy/h γ Dose Rate
甄别电压/V 1.0 1.2 1.5 本底计数率/cps 4.60 3.82 3.07 有γ源时计数率/cps 9.31 3.85 3.10 表 7 0.4 Gy/h γ剂量率测量结果
Table 7. Measurement Results of 0.4 Gy/h γ Dose Rate
甄别电压/V 0.8 10 1.5 2.0 本底计数率/cps 5.97 4.64 3.08 2.34 有γ源时计数率/cps — 93.03 2.47 1.60 表 8 0.6 Gy/h γ剂量率测量结果
Table 8. Measurement Results of 0.6 Gy/h γ Dose Rate
甄别电压/V 1.2 1.5 1.8 本底计数率/cps 4.16 3.41 2.6 有γ源时计数率/cps 14.53 2.82 1.95 表 9 1.0 Gy/h γ剂量率测量结果
Table 9. Measurement Results of 1.0 Gy/h γ Dose Rate
甄别电压/V 1.2 1.5 1.8 本底计数率/cps 3.8 3.0 2.7 有γ源时计数率/cps 29.6 24.7 1.9 -
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