反应堆无源启动对堆外核测仪表系统设计影响浅析

Analysis of the Influence of Passive Start-Up of Nuclear Reactor on Design of Nuclear Reactor Nuclear Instrument System

目前压水堆的启动主要是通过外引入中子源的方式,例如反应堆中装载初级中子源和次级中子源。引入的中子提高了反应堆的中子本底水平,使得堆外核探测器获得有效的探测计数,从而确保反应堆的反应性得到有效的监控,以便安全可控地启动核反应堆。但在实际的核反应堆中,核燃料本身可释放相当数量的中子,如何充分利用堆内核燃料自发裂变产生的中子,通过核燃料设计、燃料装填方式、探测器布置、探测器选型等一种或多种方式的综合,达到无外引入中子源的前提下仍可安全可控地启动反应堆,是目前反应堆设计的重要方向之一。本文通过对多种中子探测器的特性分析和性能比较,基于VVER无源启动实践特点,对CAP1000堆型或全新堆芯的低中子源或无源启动设计相关的堆外核探测系统提出优化建议。

At present, the start-up of pressurized water reactor is mainly through the external introduction of neutron sources, such as the loading of primary neutron sources and secondary neutron sources in reactor. The introduction of neutrons increases the neutron background level of the reactor, enabling the neutron probes of ex-core nuclear measurement instrumentation to obtain effective detection counts, thereby ensuring that reactor reactivity is effectively monitored for a safe and controllable start-up. However, the nuclear fuel itself in practical nuclear reactor can release a considerable number of neutrons. How to make full use of the neutrons generated by the spontaneous fission of the core nuclear fuel, through nuclear fuel design, fuel loading methods, detector layout, detector selection, etc. to achieve a safe and controllable start-up of the reactor without introduction of neutron sources, is one of the important research directions for reactor design. Through analyzing and comparing the characteristics and performance of a variety of neutron detectors, and practice experience on the VVER passive start-up design and implement, this paper provides some ex-core nuclear instrumentation design suggestion for CAP1000 type or new type reactor design with low or without neutron source.