Minor Actinide Neutron Reaction Data (MANREAD)

1. Background Information

The strategies foreseen for future employment and development of nuclear power generation underline the use of nuclear energy systems in which the nuclear fuel contains consistent amounts of the minor actinides (MA)[1]. These minor actinides, particularly neptunium and americium, are produced as normal by-products of the operation of thermal power reactors. Because of the existence of long-lived isotopes of these elements, they constitute the major sources of the residual radiation in spent fuel and in wastes resulting from reprocessing. Therefore, it is mandatory to gain availability of reliable and accurate neutron-induced reaction cross section data for the important isotopes of the MAs. Relatively low uncertainties in these data are required for core design studies, as well as for high burn-up strategies.

Most of the experimental neutron cross section data are available for the main uranium and plutonium isotopes, reflecting the past and current interest in the U/Pu fuel cycle at neutron energies ranging from thermal to fast, as required for thermal and fast reactors. Although the existing nuclear databases could be sufficient for a first evaluation of critical reactors as well as for ADS (Accelerator Driven Systems), a detailed assessment of important integral reactor quantities requires precise and complete sets of basic nuclear data, including the most important isotopes of the MA elements.

Nuclear data requirements for the minor actinides were reviewed in reasonable detail by the full membership of the International Nuclear Data Committee (INDC) as the primary external review body for nuclear data needs at their biennial meetings in May 2004 and 2006. This body of experts recommended the development and assembly of a suitable database of neutron cross sections for MA with some urgency as soon as feasible for immediate application for the evolution of accelerator driven systems and other newly-proposed power and waste-handling facilities.

A Consultants' Meeting held on 23-24 November 2006 discussed in detail all the objectives for the present CRP proposal, such as the necessary measurements to be performed at various suitable neutron installations and the identification of appropriate participants to undertake the various tasks.

The present proposal has been formulated accordingly, on the basis of the INDC and CM recommendations.

2. Overall Objectives

The overall objectives of the CRP are the critical evaluation, uncertainty assessment and production of neutron cross section data for an agreed set of minor actinides. This CRP will be composed of groups performing relevant experiments at the most appropriate facilities in Europe, United States, Japan and elsewhere, and will address these overall objectives and deliver up-to-date results on neutron reaction data for the minor actinides.

3. Specific Research Objectives/Purpose

A worldwide assessment will be made of the experimental capabilities to undertake measurements of neutron reaction cross sections for the important isotopes of the MA elements.

Report measurements of neutron-induced reaction cross section on MA just completed or planned in the period of activity of the CRP, at research laboratories worldwide (e.g. IRMM, Geel, Belgium; LANCSE, LANL, USA; n_TOF, CERN, Geneva, Switzerland; TIT, Tokyo, Japan; etc.).

Uncertainty assessment of available experimental information on MA neutron cross section data (including data from measurements to be performed in the next two-year period)

Assessment of the quality and uncertainties of MA data present in the evaluated nuclear data libraries (ENDF/B-VII, JEFF3.1, BROND-2.2, JENDL-3.3, etc.)

4. Expected Research Output/Results

Nuclear data for the main isotopes of the MA elements: these new data will undergo critical assessments, and recommended sets of data will be posted on the Agency's Nuclear Data Services webserver and made available to the nuclear physics/engineering/data communities.

6. Action Plan

[1] Minor actinides elements are considered to be Np, Am, and Cm - in addition, the less abundant isotopes of U and Pu actinides are also included in this definition.