Complex Approach to Study Physical Features of Uranium Multiple Recycling in Light Water Reactors. A.A. Dudnikov, V.A. Nevinitsa, A.V. Chibinyaev, V.N. Proselkov, Russian Research Center “Kurchatov Institute” A.Yu. Smirnov, G.A. Sulaberidze Moscow Engineering Physics Institute
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A.A. Dudnikov, V.A. Nevinitsa,
A.V. Chibinyaev, V.N. Proselkov,
Russian Research Center “Kurchatov Institute”
A.Yu. Smirnov, G.A. Sulaberidze
Moscow Engineering Physics Institute
(National Nuclear Research University)
International Conference on Management of Spent Fuel from Nuclear Power Reactors,IAEA, Vienna, Austria, 31 May – 4 June 2010
An initial loading is supposed enriched and fabricated from natural uranium only. Fresh fuel isotope composition obtained after gas centrifuges enrichment was calculated in following assumptions:
Then fuel is irradiated in reactor of VVER-1000 type up to given burnup level and after during 10 years is cooled and reprocessed. Uranium is separated and turns to fresh fuel fabrication.
For re-enrichment purpose quasi-ideal cascade is implemented containing natural uranium feed (F) and additional reprocessed uranium feed (E) .
The scheme of the separating cascade with an additional flow of a feed
The following set of uranium recycling scenarios is considered:
Two burnup levels were considered:
48 MW·days/kg (h.m.) and 60 MW·days/kg (h.m.)
Natural uranium relative consumption, recycled uranium relative consumption and relative separation work consumption in dependence on recycle number. Initial enrichment is 4.0% wt, burnup is 48 MW days/kg (h.m)
Natural uranium relative consumption, recycled uranium relative consumption and relative separation work consumption in dependence on recycle number. Initial enrichment is 4.4% wt, burnup is 60 MW days/kg (h.m)
U-232 concentration during irradiation in five consecutive recycles, with and without account of U-236 compensationVVER-1000 fuel cell, with and without account of Np-237 (n,2n) Np-236m reaction
There is a tendency to growth of mass concentrations of fuel in a coreU-232and Np-237 in spent fuel with growth of recycle number in case of absence of restriction on U-232 in fresh fuel.
These factors result to problems with recycled uranium usage because of increase of hard gamma rays emitters concentration.
Implementation of restriction on U-232 concentration in fresh fuel, made from recycled uranium, due to dilution of U-236 in fresh fuel, allows to moderate growth of U-232 concentration in spent fuel and makes it possible to reach equilibrium of U-232 and Np-237 concentrations in spent fuel
The existence of isotope correlation between U-232 and Np-237 is the reason of the existence of isotope correlation between U-232 and U-236 in fresh and spent fuel.
Analysis of calculated results allows the following conclusions to be formulated in connection with the scenarios considered
Results of this study lead to the conclusion that development of U-236 separation technology could reduce accumulation of U-232 in the LWR fuel cycle and improve natural uranium economy.