M310机组蒸汽发生器传热管5%破损率量化研究

M310核电机组《化学和放射化学技术规范》第3篇《放射化学规范》中规定，当“133Xe>92500 MBq/t或133Xe>37000 MBq/t和131I/133I>1.5”时，执行“如果至少1台蒸汽发生器（SG）传热管破损率超过5%，则应以50 MW/min 速率降负荷到NS/SG模式”指令。在实际运行过程中，由于无法判断传热管破损率是否超过5%，故无法确定是否执行“以50 MW/min 速率降负荷到NS/SG模式”的指令，因此，M310核电机组《放射化学规范》中该运行指令不具备可操作性。本文对国内外相关放射化学运行指令进行调研，充分理解“传热管破损率超过5%”的含义，并进行量化分析。通过对SG传热管在5、24、44 L/h泄漏率下的裂纹稳定性进行分析，发现在这些泄漏率下单根传热管都不会发生失稳断裂，进而给出了一个具有可操作性的建议，用指标“如果至少1台SG一次侧向二次侧的泄漏率超过5 L/h”，代替无法量化的“如果至少一台SG传热管破损率超过5%”，可保证核电厂运行的安全性和经济性。 

Quantitative Study on 5% Damage Rate of Steam Generator Heat Transfer Tube in M310 Unit

For M310 nuclear power unit, Part 3 ( Radiochemistry Code ) of the Technical Specification of Chemistry and Radiochemistry specifies that when “133Xe>92500 MBq/t or 133Xe>37000 MBq/t and 131I/133I>1.5”, execute the command "if the damage rate of heat transfer tube of at least one steam generator (SG) exceeds 5%, reduce the load to NS/SG mode at the rate of 50 mw/min". However, in the actual operation process, since it is impossible to judge whether the damage rate of SG tube exceeds 5%, it is impossible to determine whether to execute the instruction of "reducing the load to NS/SG mode at a rate of 50 MW/min". Therefore, for M310 nuclear power unit, the operation instruction in the Radiochemistry Code is not operable. This paper investigates the relevant radiochemistry operation instructions at home and abroad, fully understands the meaning of "the damage rate of heat transfer tubes exceeds 5%”, and makes quantitative analysis. Through the analysis of the crack stability of the SG heat transfer tube under the leakage rate of 5, 24, 44 L/h, it is found that the unstable fracture of a single heat transfer tube will not occur at these leak rates, and then an operational suggestion is given: using the indicator "If the leak rate of at least one SG from the primary side to the secondary side exceeds 5 L/h" instead of the unquantifiable "If the damage rate of at least one SG heat transfer tube exceeds 5%", the safety and economy of nuclear power plant operation can be ensured.