Abstract

This study introduces new methodologies for integrating fission reactions induced by delayed neutrons into the Multi-Region Integral Kinetic (MIK) code by using a Monte Carlo neutron transport calculation. First, it was confirmed that it is feasible to solve the Integral Kinetic Model (IKM) with delayed neutrons by the forward Euler discretization method in terms of the number of time steps. This can be done with the help of the law of radioactive decay to reflect the delay in the emission of delayed neutrons in the discretized IKM. Second, a new Monte Carlo–based methodology was introduced for calculating the cumulative distribution functions of secondary fission induced by prompt and delayed neutrons. These functions are necessary for the discretized IKM. The results of preliminary verification using the Godiva reactor confirmed the applicability of the new Monte Carlo–based methodology. A new MIK code that has the capability of calculating the fission reaction rates for delayed neutrons is currently under development. Based on the preliminary verification results, future studies will verify the discretized IKM with delayed neutrons using kinetic analyses and compare them to experimental results for prompt and delayed supercritical transients in diverse reactor configurations.

摘要

本研究介绍了使用蒙特卡罗中子输运计算将延迟中子诱发的裂变反应整合到多区域积分动力学 (MIK) 代码中的新方法。首先，证实了通过正向欧拉离散化方法在时间步数方面求解具有延迟中子的积分动力学模型（IKM）是可行的。这可以借助放射性衰变定律来完成，以反映离散化 IKM 中延迟中子发射的延迟。其次，引入了一种新的基于蒙特卡罗的方法来计算瞬发和延迟中子引起的二次裂变的累积分布函数。这些函数是离散化 IKM 所必需的。使用 Godiva 反应器的初步验证结果证实了基于蒙特卡罗的新方法的适用性。一种能够计算延迟中子裂变反应速率的新 MIK 代码目前正在开发中。基于初步验证结果，未来的研究将使用动力学分析验证具有延迟中子的离散化 IKM，并将它们与不同反应堆配置中瞬态和延迟超临界瞬变的实验结果进行比较。