HTGR Knowledge Base

Conference Article: Fission Product Transport in the Primary System of a Pebble Bed High Temperature Reactor with Direct Cycle

Abstract

Transport and deposition of fission products in the primary system of a small pebble bed high temperature reactor with directly coupled gas turbine have been investigated. The reactor has a thermal power of 40 MW and is intended for heat and power cogeneration. Four radionuclides have been identified as most relevant because of volatility and radiotoxicity: 137Cs, 90Sr, 110mAg, 131I.
With the code PANAMA the fraction of failed coated fuel particles has been calculated. The diffusion of the fission products to the fuel element outer surface has been calculated with the FRESCO code. Transport and deposition of the fission products within the primary system has been analysed with the code MELCOR.
Under normal operating conditions the release rate of the short-lived 131I reaches a constant level rather quickly, contrary to the longer lived 137Cs and 90Sr which show a steady increase of the release rate during burn-up.

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Reference:

IAEA Technical Committee Meeting on “Gas Turbine Power Conversion Systems for Modular HTGRs”, held from 14-16 November 2000 in Palo Alto, California

International Atomic Energy Agency, Vienna (Austria). Technical Working Group on Gas-Cooled Reactors

IAEA-TECDOC--1238, pp:138-148