HTGR Knowledge Base

Conference Article: The THTR-300 coolant gas activity, an indicator of fuel performance

Roellig, K. (Hochtemperatur-Reaktorbau GmbH, Mannheim (Germany))

Abstract

During incommissioning and the following 423 full power days (fpd) of THTR operation, the activities of 9 noble fission gas nuclides in the primary coolant have been measured quasi continuously. The radioactive decay times of these nuclides cover a range of more than 3 orders of magnitude. The sources and the mechanisms of the fission gas release can be derived from the dependence of the steady-state release fractions (R/B-values) on the half life times t1/2 of the various nuclides. Thus, the assessment of the fuel performance under operational conditions is primarily based on the routine measurements of the coolant gas activity. From the measured coolant gas activity data a fraction of coated particle failures less than 8 10-5 due to external forces was evaluated. In-service failures of particles embedded in the matrix can be neglected. This evaluation demonstrates its capability to identify specific fuel failure modes during operation. In this way, the coolant gas activity can be used as an indicator of the fuel performance.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Behaviour of gas cooled reactor fuel under accident conditions. Proceedings of a specialists meeting held in Oak Ridge, 5-8 November 1990
International Atomic Energy Agency, Vienna (Austria). International Working Group on Gas-Cooled Reactors
IWGGCR--25, pp:99-108