Abstract During a loss-of-coolant-accident (LOCA) transient in a pressurized water reactor (PWR), water from the primary circuit is lost at the break. PWR designs are equipped with safety systems (SS) such as safety injection or accumulators to inject water into the primary circuit and prevent the core from being degraded. Depending on the size, position, and orientation of the break, a part of the safety system injection (SSI) into the primary circuit will be lost at the break. This parameter has a significant influence on the time the core uncovers in case the SS are lost. MAAP5.04 enables users to define the part of SSI that is lost at the break. Apart from a double-ended–break LOCA transient, users struggle to define precisely the part of SSI lost at the break, but this choice can have an important impact on the transient key event times. Thanks to its detailed equations and nodalization, the reference Code for Analysis of Thermal Hydraulics during an Accident of Reactor and safety Evaluation (CATHARE) enables one to evaluate the part of SSI lost at the break. Numerous CATHARE calculations have been performed taking into account different break sizes, positions, and orientations to determine the part of SSI lost at the break in each case. A metamodel has been created from the constituted database and implemented in EDF MAAP5.04. This paper also presents the impact of these improvements on LOCA transients where SS are lost.

中文翻译：

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EDF MAAP5.04 LOCA 瞬态仿真改进

摘要 在压水反应堆 (PWR) 中发生冷却剂损失事故 (LOCA) 瞬变期间，一次回路中的水会在中断处丢失。PWR 设计配备了安全系统 (SS)，例如安全注入或蓄能器，以将水注入一次回路并防止堆芯退化。根据断路的大小、位置和方向，安全系统注入 (SSI) 的一部分将在断路处丢失。在 SS 丢失的情况下，此参数对核心露出的时间有重大影响。MAAP5.04 使用户能够定义在中断时丢失的 SSI 部分。除了双端中断 LOCA 瞬态外，用户很难准确定义中断时丢失的 SSI 部分，但这种选择会对瞬态关键事件时间产生重要影响。由于其详细的方程和节点化，反应堆事故和安全评估期间的热力水力分析参考规范 (CATHARE) 使人们能够评估在中断时丢失的 SSI 部分。考虑到不同的断点大小、位置和方向，已执行了大量 CATHARE 计算，以确定在每种情况下断点时损失的 SSI 部分。元模型已从构成的数据库中创建并在 EDF MAAP5.04 中实现。本文还介绍了这些改进对 SS 丢失的 LOCA 瞬变的影响。考虑到不同的断点大小、位置和方向，已执行了大量 CATHARE 计算，以确定在每种情况下断点时损失的 SSI 部分。元模型已从构成的数据库中创建并在 EDF MAAP5.04 中实现。本文还介绍了这些改进对 SS 丢失的 LOCA 瞬变的影响。考虑到不同的断点大小、位置和方向，已执行了大量 CATHARE 计算，以确定在每种情况下断点时损失的 SSI 部分。元模型已从构成的数据库中创建并在 EDF MAAP5.04 中实现。本文还介绍了这些改进对 SS 丢失的 LOCA 瞬变的影响。