Abstract

The use of advanced uranium-based and thorium-based fuel bundles in pressure tube heavy water reactors (PT-HWRs) has the potential to improve the utilization of uranium resources while also providing improvements in performance and safety characteristics of PT-HWRs. Earlier lattice physics and reactor core physics studies have demonstrated the feasibility of using such advanced fuels; however, thermal-hydraulic (T-H) studies are required to confirm that these advanced fuels will have adequate T-H safety margins. Preliminary system T-H transient simulations have been carried out for a 700-MW(electric)–class PT-HWR in a postulated loss-of-coolant accident (LOCA) using the CATHENA code. One purpose of this work was to demonstrate that such simulations of a PT-HWR filled entirely with advanced fuels could be set up and executed successfully in a CATHENA transient simulation model. The other purpose was to evaluate the peak sheath and peak fuel centerline temperatures during a LOCA to perform an analysis that compares the relative performance of each of the proposed advanced fuels. System T-H simulations with CATHENA were performed to model a postulated LOCA event with a 20% inlet header break in a typical 700-MW(electric)–class PT-HWR using two types of advanced uranium-based and thorium-based fuel bundles in modified 37-element and 35-element geometries. Calculations were also performed for a PT-HWR using conventional natural uranium fuel in 37-element fuel bundles for comparison. In the event of a LOCA, there is a drop in the primary circuit pressure. It is assumed that there is a 2-s delay between the signal of the low primary pressure and the tripping of the reactor. When the reactor trips, the shutdown rods are inserted. The reactor trip is followed by the activation of the emergency core cooling system, which occurs 30 s after the LOCA starts, with a trip signal on the boiler crash cooling. Simulation results for the LOCA demonstrated that the peak fuel centerline temperatures (ranging from 1822°C to 2183°C) were several hundred degrees below the expected melting point of UO₂ (~2865°C). Simulations also demonstrated that the peak sheath temperatures for the advanced fuel concepts ranged from 1177°C to 1204°C, which are lower than that with conventional NU fuel in 37-element fuel bundles. Thus, the system T-H analysis of the relative results provides confidence in the proposed advanced uranium-based and thorium-based fuel concepts for potential use in PT-HWRs.

摘要

在压力管重型水反应堆（PT-HWR）中使用先进的铀基和th基燃料束具有改善铀资源利用的潜力，同时还可以改善PT-HWR的性能和安全特性。早期的晶格物理学和反应堆堆芯物理学研究已经证明了使用这种先进燃料的可行性。但是，需要进行热工液压（TH）研究以确认这些先进燃料将具有足够的TH安全裕度。初步的系统TH瞬态模拟已经使用CATHENA代码在假定的冷却液损失事故（LOCA）中对700兆瓦（电）级PT-HWR进行了仿真。这项工作的目的之一是证明可以在CATHENA瞬态仿真模型中成功建立并执行完全填充高级燃料的PT-HWR的仿真。另一个目的是评估LOCA期间的峰值鞘管和峰值燃料中心线温度，以进行比较每种提议的先进燃料的相对性能的分析。使用CATHENA进行系统TH仿真，以模拟假定的LOCA事件，在典型的700 MW（电）级PT-HWR中使用两种先进的铀基和th基燃料束，在进口总管折断20％的情况下对LOCA事件进行建模。 37元素和35元素的几何。为了进行比较，还使用常规的天然铀燃料在37个元素的燃料束中对PT-HWR进行了计算。如果发生LOCA，主回路压力下降。假设在低一次压力的信号和反应堆的跳闸之间存在2 s的延迟。当反应堆跳闸时，将插入停机杆。在反应堆跳闸之后，将激活应急堆芯冷却系统，该系统在LOCA启动后30 s内发生，并在锅炉失速冷却装置上发出跳闸信号。LOCA的模拟结果表明，峰值燃料中心线温度（范围从1822°C到2183°C）比预期的UO熔点低数百度。反应堆跳闸后，将激活应急堆芯冷却系统，该系统在LOCA启动后30 s内发生，并在锅炉失速冷却装置上发出跳闸信号。LOCA的模拟结果表明，峰值燃料中心线温度（范围从1822°C到2183°C）比预期的UO熔点低数百度。在反应堆跳闸之后，将激活应急堆芯冷却系统，该系统在LOCA启动后30 s内发生，并在锅炉失速冷却装置上发出跳闸信号。LOCA的模拟结果表明，峰值燃料中心线温度（范围从1822°C到2183°C）比预期的UO熔点低数百度。₂（〜2865°C）。模拟还表明，先进燃料概念的最高鞘层温度范围为1177°C至1204°C，低于37元素燃料束中常规NU燃料的峰值鞘层温度。因此，系统TH对相对结果的分析使人们对拟议的先进的基于铀和fuel的先进燃料概念很有信心，可用于PT-HWR。