Characterisation of reactor graphite to inform strategies for the disposal of reactor decommissioning waste

Hetherington, Andrew (2013). Characterisation of reactor graphite to inform strategies for the disposal of reactor decommissioning waste. University of Birmingham. Ph.D.

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Abstract

Graphite has been used extensively in UK reactors since the 1950s. The UK nuclear decommissioning programme will result in some 90,000 tonnes of waste graphite being removed from Magnox, AGR, research reactors and plutonium production reactors.

It is necessary to understand the radiological characteristics of reactor graphite as a prerequisite for decisions about its interim management as well as final disposition. There is in particular a need to improve confidence in the disposal inventory of the long-lived radionuclides carbon-14 and chlorine-36.

Models have been developed to predict the distribution of principal radionuclides for Chapelcross reactor 1 and Wylfa reactor 1, and the calculated inventory compared with published experimental measurements on active samples. The models show good agreement with experimental values for carbon-14 and cobalt-60. However, for the highly mobile and volatile radionuclides chlorine-36 and tritium agreement is poor. The models provide a crude upper limit on the inventory, but certain radionuclides may be released during irradiation. For Wylfa it is predicted that all graphite waste arisings will be ILW. For Chapelcross of the order of 16% of the graphite core may be classified as LLW after the C&M period, but levels of carbon-14 rule out disposal to the LLWR facility.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):