Neutron induced fission of 237Np – status, challenges and opportunities

Ivan Ruskov,Stephan Oberstedt,Yury Kopatch,Andreas Oberstedt,Oleg Shcherbakov,Andrei Goverdovski,Franz-Josef Hambsch,Walter Furman,F.-J Hambsch,N Carjan,I Ruskov

doi:10.1051/epjconf/201816900021

Abstract

Nowadays, there is an increased interest in a complete study of the neutron-induced fission of 237Np. This is due to the need of accurate and reliable nuclear data for nuclear science and technology. 237Np is generated (and accumulated) in the nuclear reactor core during reactor operation. As one of the most abundant long-lived isotopes in spent fuel (“waste”), the incineration of 237Np becomes an important issue. One scenario for burning of 237Np and other radio-toxic minor actinides suggests they are to be mixed into the fuel of future fast-neutron reactors, employing the so-called transmutation and partitioning technology. For testing present fission models, which are at the basis of new generation nuclear reactor developments, highly accurate and detailed neutron-induced nuclear reaction data is needed. However, the EXFOR nuclear database for 237Np on neutron-induced capture cross-section, σγ, and fission cross-section, σf, as well as on the characteristics of capture and fission resonance parameters (Γγ, Γf, σoΓf, fragments mass-energy yield distributions, multiplicities of neutrons vn and γ-rays vγ), has not been updated for decades.

Highlights

For basic and applied nuclear science, 237Np continue to be amongst the most important and interesting isotopes for experimental investigation with neutrons of different energies
Figure 1. 237Np(n,f) cross-section in the vicinity of the first resonance cluster around En = 40 eV (Fig. 6 [12]) and in the neutron energy range between 1.5 MeV and 9 MeV (Fig. 7 [14]); the depicted data are from different experiments, as well as from different evaluated nuclear data libraries
Several experiments based on the time-of-flight (TOF) technique were dedicated to the measurement of fission cross section data in a wide neutron energy range (0.7 eV–1 GeV), using different fission-fragment detectors [12,13,14]

Summary

Introduction

For basic (fundamental) and applied nuclear science, 237Np continue to be amongst the most important and interesting isotopes (minor actinides) for experimental investigation with neutrons of different energies. This is because, as it is a long-lived (T1/2 = 2.144 × 106 years) isotope, which is present in spent fuel of light-water nuclear reactors, it contributes significantly to the long-term radio-toxicity of nuclear waste. For its successful incineration (transmutation, σf ∼ 0.01–10 barn), neutrons of different energies can be used [1,2,3,4,5,6,7]. According to one of the contemplated scenarios, a high-flux thermal reactor (σtfh ∼ 20 mb) can be used as a transmutation device [7], because the majority of the operating commercial reactors in the world are based on a thermal spectrum

Neutron-induced fission cross section of 237Np

Conclusion and outlook