Issue No. 21 Summer
(July 2008)


ENS News

Word from the President

The case for nuclear energy is not solely linked to global warming

ENS Events


NESTet 2008 - YGN Reporter

PIME 2009

RRFM 2009

Member Societies & Corporate Members

High Pressure - Boiling Water Reactor, HP-BWR

NUSIM 2008

MINA 2008

Why the Bulgarian Nuclear Society insist that the “small units” at Kozloduy NPP remain operational

Annual General Meeting of KTG and the German Atomic Forum takes place in Hamburg

UK Societies announce nuclear merger

The SNE magazine analyzes the results of the nuclear power plants in 2007

MYRRHA a new future for nuclear research

Spent fuel pool emptying, drainage and purging at EUREX Plant (Italy)

YGN Report

Nestet YGN Reporter

North American Young Generation at a Nuclear Congress in Chicago

European Institutions

Nuclear Forum working on roadmap for the development of nuclear in the EU

Nuclear Energy and Greenhouse Gas Emissions Avoidance in the European Union

Position Paper on Nuclear Energy’s Contribution to a post-2012 Climate Policy

ENS World News

NucNet News

ENS Members

Links to ENS Member Societies

Links to ENS Corporate Members

Editorial staff


30.9. - 3.10. 2008
in Dubrovnic, Croatia


PIME 2009
15 - 17 February 2009
in Edinburgh, UK


RRFM 2009
22.3. - 25.3.2009
in Vienna, Austria
















Word from the President

The High Scientific Council (HSC) plays an important role within ENS. Its remit is to bring to the attention of the scientific community, as well as the wider public, information on the very latest developments in cutting edge scientific research and development. As an expert body of senior and highly-qualified scientists it provides a very authoritative and informed view of the latest scientific developments taking place in the nuclear science community. I have had the pleasure of knowing and working with a number of HSC members for some time and always attached a great deal of importance to what they have to say about the major issues that are driving the international nuclear research agenda.

Part of the High Scientific Council’s mission is to report on what was discussed and presented at each of ENS’ major conferences. RRFM is a well-established and much-respected flagship ENS conference. With the nuclear revival gathering momentum across the world the work that is being carried out into research reactor design and constantly improving fuel management is all the more relevant and significant. The following HSC position paper was written by Bernard Bonin of the CEA, in France, following RRFM 2008 (in Hamburg).

Before you read this interesting position paper I would like to take this opportunity to wish you and yours a restful and – hopefully - sunny summer break.

David Bonser
ENS President

RRFM 2008 Hamburg: An ENS High Scientific Council position paper on research reactors.

RRFM is the occasion, once a year, to review the status, operation and evolution of research reactors around the world, including material testing reactors (MTRs) and irradiation facilities, neutron sources for condensed matter studies, reactors for radioisotope production, reactors for education and training, and critical mock-ups for reactor physics. The total number of research reactors in the world is decreasing, as many reactors are ageing and are not being replaced. It is hoped that this situation will stabilise soon: a further decrease of the fleet could be detrimental to the community. With regards to the reduction of research reactors, the principle of “coalitions” is proposed and promoted by IAEA, to give access to reactor to several neighbouring countries. Such coalitions could be most effective in Latin America and in Africa.

In Europe, there are basically three major research reactors projects: the Jules Horowitz reactor in Cadarache (France), which is intended to replace the ageing Materials Testing Reactor “OSIRIS” in 2014; the PALLAS facility, which will replace the High Flux reactor in Petten (the Netherlands) and the MYRRHA project, which is dedicated to the study of accelerator-driven sub-critical cores. Good news from the Jules Horowitz Reactor (JHR) project has been reported, as the financial aspects of the project have been settled with participation confirmed from many countries, including India. Whereas the construction of the JHR has already begun, the status of the PALLAS and MYRRHA projects is more uncertain.

RRFM 2008 partcipants

The biggest issue at the conference was the progress made in the conversion of the cores of research reactors from highly-enriched uranium (HEU) to low-enriched uranium (LEU). The programme of core conversion was initiated back in 1978 under the auspices of the US Department of Energy. It supports the minimization and, to a certain extent, the elimination of the use of HEU in civilian nuclear applications.

As of 2008, a total of 207 research reactors were involved in the project worldwide. 56 have already been converted, 78 are beyond scope, and 46 are planned for conversion with existing LEU fuel. The remaining 28 are high performance reactors, also planned for conversion but these will need fuel of a new type to comply with core conversion without losing too much in performance. The challenge for this new fuel development was extensively analysed during the conference.

The permanent challenge of research reactors devoted to testing or irradiation is to produce high neutron fluxes with limited amounts of fissile material. This in itself is a constraint as it already points to the need for fuels with a high density of fissile matter. Conversion of research reactor cores to LEU has made the need for dense fuel all the more urgent. The intermetallic compound U3Si2 is presently the reference fuel, with a well mastered production process on the industrial scale and a good behaviour profile under irradiation. But its density is only 4.8, and this is clearly not sufficient for the conversion of some of the more demanding research reactors. Higher densities can be reached by switching to UMo alloy, where the 7-10% Mo additive has been chosen for its capacity to stabilize the gamma phase of uranium. Monolithic UMo alloy has a density as high as 16; UMo can also be made of powder, sandwiched between two co-laminated plates of Al. The density of the powder (called “meat” in the specialist’s jargon) at the centre of the sandwich is then limited to about 8 The behaviour of this type of fuel plates has been tested under irradiation in various laboratories, with as yet not entirely satisfactory results. The general finding is that the Al matrix interacts with the UMo alloy to form an interaction layer where the gamma phase of the uranium crystal lattice is locally destroyed, with negative consequences on the behaviour of the fuel under irradiation (the swelling and pillowing of the fuel plate can modify the cooling of the fuel and cause its buckling; the fission gas release can cause blistering of the plate and cause its ultimate rupture). The addition of 2-5% of Si either in the Al matrix or in the UMo itself seems to limit both the development of this indesirable, mainly amorphous interaction region, and the resulting swelling. Reports from all laboratories confirm the positive role of Si on the fuel behaviour under irradiation. The phenomenology of the role of silicon is being better mastered, as silicated phases located at the interface between UMo and Al play the role of a diffusion barrier, which limits the development of the amorphous interaction layer. Cumulated fission rates as high as 5.1021 in the fuel grains, corresponding to burn-ups of 10 %, have been achieved with UMo fuels in powder form. Alternatives to the aluminium cladding have been researched (stainless steel, zirconium alloy), with promising results so far. Altogether, the UMo fuel is by no means produced, even less qualified on the industrial scale. It is hoped that the promising additon of Si will ultimately result in a well-mastered fabrication process, with satisfactory fuel performance under irradiation. But progress is slow. Some of the more advanced research reactors will have to wait for this new type of fuel to achieve core conversion.
The US National Nuclear Security Administration recently issued a request for information, or RFI, on the nuclear industry's capability to fabricate very-high-density low-enriched UMo fuel for research and test reactors. According to RFI’s very ambitious schedule, the qualification of monolithic fuel for use in US reactors by the US Nuclear Regulatory Commission is anticipated for 2011.

The RRFM conference was not entirely devoted to core conversion. A significant part of what was communicated concerned core calculation. The 2008 edition of the conference has confirmed the generalisation of the use of Monte Carlo codes for the neutronic calculations. Coupled neutronic-thermal hydraulic (NTH) calculations are more and more frequently undertaken. The IAEA has proposed to launch a Coordinated Research Project (CRP) devoted to the benchmarking of these NTH calculations. The European Nuclear Society welcomes this initiative and will follow its developments.

The High Scientific Council of the European Nuclear Society


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