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Endless Trouble. Britain’s Thermal Oxide Reprocessing Plant (THORP) (2019)

Author	IPFM, M.Forwood, G.MacKerron, W.Walker
	2-05-8-35-13.pdf
Date	January 2019
Classification	2.05.8.35/13 (UNITED KINGDOM - SELLAFIELD - THORP)
Front

Endless Trouble
Britain’s Thermal Oxide Reprocessing Plant (THORP)
Martin Forwood, Gordon MacKerron and William Walker
© 2019 International Panel on Fissile Materials

Dedication
For Martin Forwood (1940–2019)
Distinguished colleague and dear friend

Introduction
In November 2018, after 25 years of separating plutonium from domestic and foreign
spent fuel from nuclear power reactors, Britain’s troubled Thermal Oxide Reprocessing
Plant (THORP) at Sellafield started to wind down operations and move to a clean-out
program as part of the plant’s final shutdown. This is a prelude to the plant’s 
decommissioning and the treatment, disposal and management of its various remnants 
that may take even longer to complete.

Located on the United Kingdom’s Cumbrian coast of the Irish Sea, Sellafield—
initially called Windscale—was the place chosen in the late 1940s to produce plutonium 
for Britain’s atomic bombs. Plutonium is central to Sellafield’s story. Like uranium-235,
plutonium-239 has been valued as both a nuclear-weapon material and source of energy
in power stations. Absent in nature, plutonium-239 is a product of the irradiation
of the abundant isotope uranium-238 by neutrons in a nuclear reactor. The material is
separated by chemical means (“reprocessing”) from residual uranium and radioactive
wastes after spent fuel containing them has been discharged from a reactor. The technology
is unusually difficult given the need to shield workers and the public from inescapable,
dangerous, long-lasting radioactivity.

The site was chosen due to its distance from large cities, presence of cooling water and
access to the sea for disposing of radioactive wastes, a practice that was initially regarded
as acceptable. It was expanded to serve civil purposes when the “Magnox” design
of reactor used in the military program was adopted for nuclear power stations
built across the UK in the 1950s and 60s. Besides producing plutonium, it was considered
necessary to reprocess Magnox spent fuels on safety grounds since their cladding
corroded in water ponds used for their cooling. The B205 facility constructed at Windscale
in the 1960s was dedicated to the reprocessing of Magnox fuels.