Chemical behavior of fission products in core heatup accidents in high-temperature gas-cooled reactors

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Nuclear Technology; (United States)

OSTI ID:5080906

Moormann, R; Hilpert, K ^[1]

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1. Forschungszentrum Juelich GmbH, KFA, Postfach 1913, D-5170 Juelich (DE)

This paper provides an overview of high-temperature gas-cooled reactor (HTR) fission product chemistry and its influence on source terms in core heatup accidents. These accidents are risk-dominating for medium-sized HTRs and are characterized by maximum core temperatures of {approximately}2500{degrees} C (2773 K) and a late-starting, slowly proceeding fission product release from the fuel particles. In these accidents, the number of chemical reactions in the core and primary circuit is limited by the low oxygen potential and preferential release of metal from the fuel. The graphite in the core acts as a very powerful barrier to metallic fission products because of its chemisorption action. Cesium iodide (CsI) formation can reduce this sorption retention for cesium when there is a high cesium burden on the graphite. This is not necessarily expected for small HTRs, which have much lower maximum accident temperatures (1600{degrees} C = 1873 K) and a much lower fractional release of fission products from coated particles. In the primary circuit, less efficient chemisorption of fission products on metals occurs. The fission product chemistry in the HTR reactor building is similar to that for other reactor types.

• OSTI ID: 5080906
• Journal Information: Nuclear Technology; (United States), Journal Name: Nuclear Technology; (United States) Vol. 94:1; ISSN 0029-5450; ISSN NUTYB
• Country of Publication: United States
• Language: English

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