New measurement of the242Pu(n,γ) cross section at n_TOF

J Lerendegui-Marco,A Junghans,K Eberhardt,M A Cortés-Giraldo,E Mendoza,J M Quesada,C Guerrero,N_Tof Collaboration ,D Cano-Ott

doi:10.1051/epjconf/201611102005

Abstract

The use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2 ) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. With the use of such new fuel composition rich in Pu, a better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. For the case of 242 Pu, the two only neutron capture time-of-flight measurements available, from 1973 and 1976, are not consistent with each other, which calls for a new time-of flight capture cross section measurement. In order to contribute to a new evaluation, we have perfomed a neutron capture cross section measurement at the n_TOF-EAR1 facility at CERN using four C6 D6 detectors, using a high purity target of 95 mg. The preliminary results assessing the quality and limitations (background, statistics and γ -flash effects) of this new experimental data are presented and discussed, taking into account that the aimed accuracy of the measurement ranges between 7% and 12% depending on the neutron energy region.

Highlights

Introduction and motivationThe measurement of accurate capture and fission cross sections is essential for the design and operation of current and innovative nuclear systems aimed at the reduction of the nuclear waste [1]
The spent fuel from current nuclear reactors contains a significant fraction of plutonium, which can be separated from the fuel matrix
This plutonium contains 66% of the fissile 239Pu and 241Pu, that can be combined with depleted uranium (238U) to make what is known as mixed oxide (MOX) fuel

Summary

Introduction and motivation

The measurement of accurate capture and fission cross sections is essential for the design and operation of current and innovative nuclear systems aimed at the reduction of the nuclear waste [1]. In addition to the direct measurement in the fast energy region (En>2 keV), accurate average radiation width and strength function are required to solve some ambiguous results obtained between optical model calculations and the statistical analysis of the swave resonance parameters [11]. This calls as well for an accurate measurement of the resonance region (1 to 1000 eV) with enough resolution and statistics to determine accurately the corresponding average resonance parameters.

Experimental setup

Total Energy Detection Technique

Preliminary analysis and first results

Findings

Summary and conclusions