Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Protactinium-231 – new burnable neutron absorber

10/02/2017 2017 - #03 Fuel cycle and nuclear waste management

Kulikov G.G. Kulikov E.G. Shmelev A.N. Apse V.A.

DOI: https://doi.org/10.26583/npe.2017.3.18

UDC: 621.039.544.8

To compensate reactivity excess in nuclear reactors burnable neutron absorbers such as gadolinium and erbium are used. Their daughter nuclides resulting from neutron absorption by erbium and gadolinium play no important role in terms of neutron-physical processes occurring in the reactor core. A burnable neutron absorber, daughter nuclides of which would have a beneficial effect on fission chain reaction, is of a great interest.

The aim of the work is to study neutron-physical properties of new burnable neutron absorber – 231Pa, and possibilities of its producing in significant quantities. The chain of isotopic transformations starting from 231Pa is an analogue to the chain of isotopic transformations starting from 237Np. However, gradual improvement of neutron-multiplying properties in 237Np-chain can be only achieved in fast neutron spectra while in the case of 231Pa-chain a positive neutron balance can be achieved both in fast and thermal neutron spectra. So, in this sense the chain starting from 231Pa is a unique one. In addition, 237Np can be produced in nuclear reactors as a result of neutron radiative capture by 235U while significant amounts of 231Pa can be only produced through the threshold (n,2n) and (n,3n)-reactions of 232Th under its bombardment by ultra high-energy neutrons. So high-energy neutrons are practically absent even in fast spectrum reactors, these neutrons can be produced by fusion facilities only. Production of 231Pa in fusion facilities and the further use of 231Pa in nuclear power reactors can make it possible to realize some potential capabilities of fusion facilities for radical increase of nuclear fuel burn-up. Thus, isotope 231Pa is a new and unique burnable neutron absorber that was not proposed yet.

During implementation of the work evaluated nuclear data libraries JENDL-4.0 and ENDF/B-V were used, as well as computer software system SCALE-4.3.

We obtained the following results.

  1. In contrast to conventional burnable neutron absorbers based on gadolinium and erbium, the isotope of protactinium proposed in this paper seems to be more attractive because it allows us not only to compensate initial reactivity excess, but also to provide high fuel burn-up thanks to good multiplying properties of its daughter nuclides.

  2. Significant quantities of protactinium could be produced in hybrid fusion-fission reactors, which are sources of neutrons (not sources of energy), and parameters of which have been already achieved at present time at experimental facilities in USA, Japan, UK.


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burnable absorber protactinium-231 gadolinium erbium high fuel burn-up very long fuel campaign stabilized multiplying properties