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CONSEQUENCE ANALYSIS OF THE CATASTROPHIC FAILURE OF HIGHLY ACTIVE LIQUID WASTE TANKS 
SERVING THE THORP AND MAGNOX NUCLEAR FUELS REPROCESSING PLANTS AT SELLAFIELD

INTRODUCTION

1.01 Reprocessing spent radioactive fuel at the THORP plant will produce highly
radioactive liquids. The storage of these represents a unique hazard:- there are 
potential catastrophic consequences of a failure of safety systems and loss of 
containment. Whilst the seriousness of the hazard is readily admitted by UK 
authorities, for example, by the Nuclear Installations Inspectorate, no study of the 
full consequences of failure has been made available for public discussion. This is 
in contrast to the situation in the USA and Germany, where 'accident consequence 
studies' that were originally performed within the nuclear industry, were later made 
public. These early studies (one at the US Oak Ridge National Laboratories (1) and 
another at the Institute for Reactor Safety (IRS) in Germany (2) indicated that liquid 
waste tanks had the potential to boil if cooling failed and to eventually produce a 
high temperature 'salt-melt' which would release volatile radioactive nuclides, 
chiefly caesium-137 and strontium-90, in large quantities. The consequences of 
such a release would be 10-100 times more severe than a single nuclear reactor 
melt-down, such as occurred at Chernobyl.

1. 02 Despite secrecy concerning waste stores in Britain, an attempt was made to
raise this issue at the Public Inquiry into extension of Windscale (now Sellafield) 
for Thermal Oxide (fuel) Reprocessing, the so-called THORP, in I977. Magnox 
reprocessing had already led to several tanks being filled with Highly Active Wastes 
(HAW) by 1977. At that time a group of concerned scientists (members of the 
Political Ecology Research Group in Oxford), brought to the attention of the Inquiry 
the two studies mentioned above. BNFL had presented a very limited 'worst-case' 
accident study, wherein the cooling systems to the tanks fail for unspecified reasons 
and begin to boil, venting 1/10,000th of the inventory of one tank in the process. The 
Political Ecology Research Group (PERG) requested that the studies be taken a stage 
further to where the tank boils to dryness and liberates 900A, of the volatile caesium 
and 5% of the strontium and ruthenium, as considered in the US and German 
scenarios. It was argued (by Dr Gordon Thompson, a nuclear engineer then with 
PERG) that once failure had proceeded as far as the boiling phase, there would be 
no certainty of recovery.

(1) Details of the Oak Ridge Studies were discussed at the Windscale Inquiry,
particularly documents BNFL 223, 299 and 309 submitted in evidence, see also: 
Blanco & Parker, ORNL-1465 (1966) pp35-41.
(2) Bachner et.al. Report No 290, Institut fur Reaktorsicherheit, Koln (August 1976).

Auteur	P.Taylor
	-
Datum	1994*
Classificatie	2.05.8.35/05 (GROOT-BRITTANNIË - SELLAFIELD - THORP)
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Documentatie- en onderzoekscentrum kernenergie

Publicatie Laka-bibliotheek:
Consequence Analysis of a Catastrophic Failure of Highly Active Liquid Waste Tanks Serving the Thorp and Magnox Nuclear Fuel Reprocessing Plants at Sellafield (1994)

Publicatie Laka-bibliotheek:Consequence Analysis of a Catastrophic Failure of Highly Active Liquid Waste Tanks Serving the Thorp and Magnox Nuclear Fuel Reprocessing Plants at Sellafield (1994)

Publicatie Laka-bibliotheek:
Consequence Analysis of a Catastrophic Failure of Highly Active Liquid Waste Tanks Serving the Thorp and Magnox Nuclear Fuel Reprocessing Plants at Sellafield (1994)