Office for Nuclear Regulation

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Inventory differences at UK civil nuclear sites in 2016/17

Site Plutonium
kg (1)
HEU
kg 235U (2)
LEU
tU (3)
Natural U
tU (3)
Depleted U
tU (3)
Dounreay -0.006 +0.167 +0.001 NIL -0.001
Harwell +0.004 +0.004 NIL NIL NIL
Windscale (4) -0.423 NIL NIL NIL -0.156
Winfrith NIL NIL NIL NIL NIL
Sellafield -38.172 <+0.001 +1.086 <+0.001 -7.915
Springfields NIL NIL -1.332 +0.928 -0.851
Capenhurst Nuclear Services NIL NIL N/A N/A N/A
URENCO
Capenhurst (5)
N/A N/A <-------------  -0.311 ---------->

Whenever nuclear material is measured, there is an uncertainty associated with the measurement. The major source of inventory differences has been the uncertainties associated with making multiple measurements of nuclear material during complex processes such as enrichment, fuel fabrication and reprocessing. These figures show no evidence of a leak, diversion or theft of nuclear material.

+    apparent increase
-    apparent decrease

  1. the figures for plutonium are the total amount of all plutonium isotopes.
  2. the figures for highly enriched uranium (HEU) are for the uranium 235 content of uranium   enriched to above 20% of that isotope.
  3. low enriched uranium (LEU), natural uranium and depleted uranium cannot be used to make explosive devices.  The published figures include these grades for the sake of completeness.
  4. for which Sellafield Ltd became the site licensee on 1 April 2008
  5. the figure for Urenco Capenhurst is a consolidated figure for Urenco UK Ltd, Enrichment Technology UK Ltd and Capenhurst Nuclear Services

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