Study of annual tritium discharge in pressurized water reactor based on historical data
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摘要: 以压水堆核电厂中氚的产生机理和氚源项计算模型为基础,结合对国内外大量压水堆核电厂的氚排放运行数据的系统性分析,识别出冷却剂硼酸活化和次级中子源活化是压水堆氚排放量的主要来源,其中对中国广核集团运行机组,锑铍中子活化后的产氚量对氚年排放量的贡献可达到40%,而氚从完整的锆合金包壳的燃料棒中的释放是可以忽略不计的。由于优化次级中子源是降低压水堆氚排放量的唯一有效措施,通过分析建议压水堆核电厂采用双层不锈钢包壳的次级中子源或者取消次级中子源以降低压水堆氚排放。Abstract: Based on tritium production mechanism and the tritium calculation model in China General Nuclear Power Corporation (CGN), the historic tritium discharges in lots of nuclear power plants around the world have been comprehensively gathered and analyzed. It is recognized that the activation of boric acid in the primary loops and activation of Be in secondary neutron source (40% of annual tritium discharge in CGN’s operating pressurized water reactor units) are the predominant origins, and the tritium release from intact fuel rods with zirconium alloy can be neglected. It is found that use of double encapsulated secondary neutron source or cancellation of secondary neutron source is the only way to reduce significantly the tritium discharges in the pressurized water reactors.
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表 1 压水堆核电厂中产生氚的核反应
Table 1. Nuclear reaction of tritium production in PWR
region nuclear reaction fuel $ {\text{U/Pu}} + {}_0^1{\text{n}}\xrightarrow{{}}{\text{FP1 + FP2}} + {}_1^3{\text{H}} $ boric acid
(primary coolant)$ {}_{\text{5}}^{{\text{10}}}{\text{B + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{({\text{n,2α}} )}}}{\text{2}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{1}}^{\text{3}}{\text{H}} $
$ {}_{\text{5}}^{{\text{10}}}{\text{B + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,nα )}}}}{}_{\text{3}}^{\text{6}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n + }}{}_{\text{2}}^{\text{4}}{\text{He}} $ ⇨ $ {}_{\text{3}}^{\text{6}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{1}}^{\text{3}}{\text{H}} $
$ {}_{\text{5}}^{{\text{10}}}{\text{B + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{2}}^{\text{4}}{\text{He}} $ ⇨ $ {}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,nα )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{0}}^{\text{1}}{\text{n + }}{}_{\text{1}}^{\text{3}}{\text{H}} $$ {}_{\text{5}}^{{\text{11}}}{\text{B + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,T)}}}}{}_{\text{4}}^{\text{9}}{\text{Be + }}{}_{\text{1}}^{\text{3}}{\text{H}} $ ⇨ $ {}_{\text{4}}^{\text{9}}{\text{Be + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{2}}^{\text{6}}{\text{He}} $
⇨ $ {}_{\text{2}}^{\text{6}}{\text{He}}\xrightarrow{{\text{β }}}{}_{\text{3}}^{\text{6}}{\text{Li + }}_{ - 1}^{\text{0}}{\text{e}} $ ⇨ $ {}_{\text{3}}^{\text{6}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{1}}^{\text{3}}{\text{H}} $
$ {}_{\text{4}}^{\text{9}}{\text{Be + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,T)}}}}{}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{1}}^{\text{3}}{\text{H}} $ ⇨ $ {}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,nα )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{0}}^{\text{1}}{\text{n + }}{}_{\text{1}}^{\text{3}}{\text{H}} $lithium hydroxide
(primary coolant)$ {}_{\text{3}}^{\text{6}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{1}}^{\text{3}}{\text{H}} $
$ {}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,nα )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{0}}^{\text{1}}{\text{n + }}{}_{\text{1}}^{\text{3}}{\text{H}} $deuterium
(primary coolant)$ {}_{\text{1}}^{\text{2}}{\text{H + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,γ )}}}}{}_{\text{1}}^{\text{3}}{\text{H}} $ antimony-beryllium in SNS $ {}_{\text{4}}^{\text{9}}{\text{Be + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{2}}^{\text{6}}{\text{He}} $ ⇨ $ {}_{\text{2}}^{\text{6}}{\text{He}}\xrightarrow{{\text{β }}}{}_{\text{3}}^{\text{6}}{\text{Li}} $ ⇨ $ {}_{\text{3}}^{\text{6}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,α )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{1}}^{\text{3}}{\text{H}} $
$ {}_{\text{4}}^{\text{9}}{\text{Be + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,T)}}}}{}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{1}}^{\text{3}}{\text{H}} $ ⇨ $ {}_{\text{3}}^{\text{7}}{\text{Li + }}{}_{\text{0}}^{\text{1}}{\text{n}}\xrightarrow{{{\text{(n,nα )}}}}{}_{\text{2}}^{\text{4}}{\text{He + }}{}_{\text{0}}^{\text{1}}{\text{n + }}{}_{\text{1}}^{\text{3}}{\text{H}} $表 2 不同堆型的预期氚产生量的相对贡献
Table 2. Relative contribution of expected tritium production in different reactor
origin relative contribution/% EPR AP1000 VVER fuel 0 31 22 boric acid and lithium hydroxide 83 69 77 SNS 17 0 − total 100 100 100 -
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