Research Reactor Group

CRP on Conversion of Miniature Neutron Source Research Reactors (MNSR) to Low Enriched Uranium (LEU)

1. Background

The Chinese-built Miniature Neutron Source (MNSR, 27 kW) reactors (four in China, five abroad) are low-power, neutron source research reactors used primarily for neutron activation analysis, education, and training. These reactors have cores consisting of less than 1 kilogram of HEU, enriched to 90% or greater, U-235.

Since 1978, various national and international activities have been underway to convert research and test reactors from the use of HEU to LEU fuel. These activities support the objective of reducing and eventually eliminating the civil use of HEU. Achieving the conversion of all MNSR reactors would be a helpful step forward in this international effort to reduce and eventually eliminate the civil use of HEU.

The China Institute of Atomic Energy (CIAE) has designed a new MNSR using LEU to operate in hospitals and has been studying conversion of the existing MNSR cores to LEU. China has also designed and built, with commissioning expected in 2006, a large 60MW research reactor that will have LEU fuel. It is generally accepted that conversion of the MNSRs is feasible and it is likely that China or other fuel fabricators will be able to produce LEU cores for the MNSR reactors in the near future.

At a Technical Meeting at IAEA Headquarters in May 2005, all the participating MNSR operators indicated their desire to convert to LEU fuel. It was acknowledged that to successfully carry out MNSR core conversions, a number of preparatory steps, including additional analysis and various calculations have to be made, in order to confirm the feasibility of conversion.

2. Overall Objective

The overall objective is to assist institutions in Member States with MNSR reactors with HEU cores to convert to LEU fuel with minimal reduction of the utilization capacity of the reactors in concert with international non-proliferation initiatives to reduce and eventually eliminate the use of HEU in civil commerce.

3. Specific Research Objective

The objectives of the CRP are as follows:

To establish a common approach for the conversion to LEU of the existing MNSR reactors through a comparative analysis of the feasibility of conversion;
To provide the basis for individual MNSR reactors to safely convert to qualified LEU fuel;
To carry out calculations and conduct studies necessary to plan and implement MNSR conversion to LEU; and
To disseminate information on the various technical and other steps necessary to safely convert MNSR reactors to LEU fuel.

4. Expected Research Output

At the end of the CRP, it is expected that all of the participants will have acquired an appropriate understanding of the technical and other steps necessary as well as the documentation that will be required in order to meet national regulatory requirements to carry out the conversion of their HEU-fuelled MNSR reactors to LEU cores.

Information acquired through the CRP will be published by the Agency in the form of a technical publication that will serve as an addendum to the IAEA’s existing core conversion handbook.

5. Action Plan

The following steps of the CRP will consist of:

establishment of the technical information requirements, including core conversion analyses, necessary to provide a sound basis for the safe conversion of the MNSRs to LEU fuel;
establishment of a program of neutronic and thermalhydraulic calculations and analyses, including determination of the codes needed to perform the calculations;
provision of technical resources to MNSR reactors in order to perform the necessary calculations themselves or to adopt analyses performed by other participating organizations;
provision of technical assistance or training to the MNSR reactors in order to successfully utilize computer codes to perform the calculations;
comparison of results of the core calculations carried out by the individual MNSR reactors;
selection of the suitable LEU fuel design, including optimal enrichment and uranium loading, necessary to carry out the conversion with the minimum possible reduction of the utilization
capacity of the reactor; preparation of guidelines for generic mandatory reports and related documentation, specifying the limits and conditions of the LEU fuel, which will need to be
provided to national licensing authorities; and
preparation and publication of a comprehensive document to be used as a guideline applicable to the conversion of all the MNSRs.

The schedule for meetings is expected to be:

First RCM end 2006;
Second RCM end 2007;
Third RCM end 2008-beginning 2009; and
Preparation and distribution of RCM reports, and publication in 2009 of a technical publication incorporating the CRP results and constituting a guide for MNSR conversion.

6. IAEA Scientific Officers

For further information please contact:

Pablo Adelfang, p.adelfang@iaea.org (phone +43-1-2600-22770,
Ira N. Goldman, i.goldman@iaea.org (phone) +43-1-2600-22782,