Evaluation of the fraction of delayed photoneutrons for TMSR-SF1  

作　　者：Rui-Min Ji Ye Dai Gui-Feng Zhu Shi-He Yu Yang Zou Gui-Min Liu 

机构地区：[1]Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China [2]University of Chinese Academy of Sciences, Beijing 100049,China

出　　处：《Nuclear Science and Techniques》2017年第9期129-136,共8页核技术（英文）

基　　金：supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)

摘　　要：The 10 MW_(th) solid-fueled thorium molten salt reactor(TMSR-SF1) is a FLi Be salt-cooled pebble bed reactor to be deployed in 5–10 years, designed by the TMSR group. Due to a large amount of beryllium in the core, the photoneutrons are produced via(γ , n) reactions.Some of them are generated a long time after the fission event and therefore are considered as delayed neutrons. In this paper, we redefine the effective delayed neutrons into two fractions: the delayed fission neutron fraction and the delayed photoneutron fraction. With some reasonable assumptions, the inner product method and the k-ratio method are adopted for studying the effective delayed photoneutron fraction. In the k-ratio method, the Monte Carlo code MCNP6 is used to evaluate the effective photoneutron fraction as the ratio between the multiplication factors with and without contribution of the delayed neutrons and photoneutrons. In the inner product method, with the Monte Carlo and deterministic codes together, we use the adjoint neutron flux as a weighting function for the neutrons and photoneutrons generated in the core. Results of the two methods agree well with each other, but the k-ratio method requires much more computing time for the same precision.The 10 MWth solid-fueled thorium molten salt reactor （TMSR-SF1） is a FLiBe salt-cooled pebble bed reactor to be deployed in 5-10 years, designed by the TMSR group. Due to a large amount of beryllium in the core, the photoneutrons are produced via （γ, n） reactions. Some of them are generated a long time after the fission event and therefore are considered as delayed neutrons. In this paper, we redefine the effective delayed neutrons into two fractions： the delayed fission neutron fraction and the delayed photoneutron fraction. With some reasonable assumptions, the inner product method and the k-ratio method are adopted for studying the effective delayed photoneutron fraction. In the k-ratio method, the Monte Carlo code MCNP6 is used to evaluate the effective pho- toneutron fraction as the ratio between the multiplication factors with and without contribution of the delayed neu- trons and photoneutrons. In the inner product method, with the Monte Carlo and deterministic codes together, we use the adjoint neutron flux as a weighting function for the neutrons and photoneutrons generated in the core. Results of the two methods agree well with each other, but the k-ratio method requires much more computing time for the same precision.

关 键 词：碰撞后 分数 延迟 系数倍率法 裂变中子 评价 缓发中子 蒙特卡洛 

分 类 号：TL42[核科学技术—核技术及应用]