Burnup characteristics analyses of graphite impurities in HTGR fuel element. (August 2018)

• Record Type: Journal Article
• Authors: Li, Jian; She, Ding; Shi, Lei
• Is Part Of: Annals of nuclear energy. Volume 118(2018)
• Page Start: 165
• Page End: 169
• Publication Date: 2018-08
• Subjects: HTGR fuel element -- Graphite impurities -- Burnup characteristics; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2018.04.018
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: Burnup behaviors of graphite impurity isotopes are analyzed in details. Deficiency of the equivalent boron content method is figured out and an revised method is proposed. It is recommended to describe the impurity concentrations explicitly in the physics design of HTGR. Abstract: In the fuel element of high-temperature gas cooled reactors (HTGRs), there exist various impurities in the graphite matrix, which are mainly originated from the raw materials, such as naturally occurring graphite, artificial graphite and resin. These impurities can reduce the excess reactivity of the reactor core, both in the initial criticality and during the overall operation history. In the practical physics design of HTGR, the equivalent boron content (EBC) method is usually used to describe the graphite impurities, where the impurity isotopes are simply converted to some amounts of boron by preserving the neutron absorption. Although it is found to be effective in criticality calculations, EBC may introduce errors in burnup analyses. This paper investigates the burnup characteristics of the graphite impurities. According to their behaviors during burnup, the impurities are classified into three categories, i.e. the high-burnable isotopes, low-burnable isotopes and unburnable isotopes. Moreover, a revised equivalent boron content (REBC) is proposed to describe the absorption rates of impurities, which can improve the computational accuracy in the burnup analyses of HTGR fuel.