How will the High Flux Reactor enter the third millennium?

The High Flux Reactor, located in Petten, Netherlands, is owned and licensed by the European Commission but operated under contract by Nuclear Research and Consultancy Group (NRG). It is a 45 MWt unit that produces neutrons to be used either inside the core, where there are 19 locations with high fast and thermal fluxes for irradiation; outside the core, for producing radioisotopes, carrying out ramp tests, etc; or in 12 neutron beams for applications including fundamental research and cancer treatments.

The reactor has very high availability and reliability (the most recent accident, a radioisotope capsule breakage, occurred in 1987). It is also able to make use of a variety of thermal and fast neutron fluxes. As a result, it has been able to become well-adapted to its market, particularly the medical market, and it can claim filling rates of about 75%.

MEDICAL USES

Each year approximately 10 to 15 million nuclear medical procedures are carried out in the European Union. These medical procedures are mainly based on radioisotopes: up to 14 million of them are diagnoses and more than one million are treatments.

As regards treatment procedures, they are distributed as follows: some 40% are executed in Germany; 15% in France; 11% in Italy; 8% in the UK; 8% in Spain; and 18% in the remaining EU countries. The majority of these procedures use isotopes produced by nuclear reactors; for example, technetium 99, obtained from molybdenum 99, is used for about 70% of all diagnoses in nuclear medicine. The medical therapies, in their turn, exclusively use isotopes produced in nuclear reactors.

The most common, and most important, product in the market is technetium 99 which is required in around 70% of medical procedures. This radioisotope is provided by two European companies, IRE and Mallinckrodt, in close collaboration with the three reactors – HFR (sited at the Joint Research Centre of the EU at Petten in the Netherlands), BR2 (Studiecentrum voor Kernenergie, Belgium) and Osiris (Saclay, France).

The health of the European citizen is the main objective of the research and development carried out at HFR. This reactor:

• Is the most important radioisotope producer for medical diagnosis and therapies in the European Union.

• Is the principal installation at European level for the application and development of the BNCT (a cancer treatment described below) and other similar techniques.

• Is the most important supporting installation for the development of European R&D networks in the European Union.

• Is included in the “Citizen’s Health” programmes of the European Commission.

• Contributes directly to the development of several promising medical research fields (diagnoses, cancer treatment, prosthesis’ development, etc).

For technical reasons (it has 11 production cycles per year and is well situated geographically) and because of the high priority given to medical activities in the programme, the HFR reactor is by far the most important radioisotope producer in the European Union.

Several million patients are benefiting each year from the radioisotopes for medical use produced by HFR.

Nordion, a Canadian company, currently produces about 70% of the radioisotopes used on the world market. It is not easy to relate the production of radioisotopes by a particular nuclear reactor to the number of medical treatments. Nevertheless, it seems that about 60% of nuclear medicine processes in Europe use products from HFR. In addition, some of the Mo-99 produced by HFR is used outside Europe, especially in the USA (where it supports around one million medical treatments per year).

The features of the HFR which support its highly competitive position are:

• Its very high utilisation rate (more than 280 days per year).

• The availability of high thermal flux.

• The flexibility offered by the large number of irradiation facilities available and their very different characteristics.

• The proven quality assurance system.

• Proven transport logistics and easy management of transport time, because the reactor is close to international airports and a dense road network.

Radioisotope production will continue to be a growing market in the future. The HFR reactor is the pivot of the European network for the production and distribution of radioisotopes for medical applications. Each year, several million Europeans are treated with isotope products from HFR.

The number of medical treatments is increasing, partly due to the increasing use of existing techniques and partly due to the introduction of new treatments. An example of a new treatment is boron neutron capture therapy (BNCT).

BNCT takes advantage of a characteristic of boron. When submitted to a flux of neutrons, boron disintegrates and produces highly energetic alpha particles which have a limited range of action (10 microns) in organic tissues. In the treatment a boron-containing drug, injected into the patient, selectively attaches itself to the tumour tissues. The tumour zone is then exposed to a neutron flux produced by a reactor which will selectively kill the cancer cells.

It became possible to use the HFR as a BNCT installation after its reactor vessel was replaced in 1984. The age of the reactor made the replacement necessary, and in the replacement it was possible to redesign and change two neutron beams (the HB11 and HB12 beam tubes) to incorporate a BNCT installation.

The redesigned installation, including neutron filters, beam shutter, operation room and patient access, was put in place in 1990. The construction, preliminary tests and qualification tests, and obtaining of the operation licence, took about six years. Clinical tests have been under way since October 1997, and by 27 October this year 15 patients suffering from glioblastoma (a large brain tumour) had been treated in the HFR reactor installations.

Glioblastoma, the disease currently tested in the HFR reactor, kills about 15 thousand people in Europe each year. Other cancerous diseases kill millions. In the near future, the BNCT technique might be used for the treatment of several cancers.

This work programme has always had a clear European dimension, but the importance of the role of HFR is obvious in the fact that the HFR is, at present, the only European reactor with a fully operational BNCT facility. As a result, the BNCT management co-operation team near the HFR reactor has become a truly trans-European operation, involving six hospitals from five countries. The BNCT programme is supported by and co-ordinated with the health care programmes of the European Commission. The technological developments and detailed results produced from the work at HFR are available in all the EU countries that want to build up their own BNCT facilities.

Formal European collaboration for the BNCT application was started, in the frame of the European BIOMED 1 programme, in 1987. This group now consists of 40 research centres in 14 countries, and it has two priority tasks :

• To initiate, as soon as possible, clinical glioma treatments at the HFR reactor. This goal was attained in 1997.

• To create conditions so that other tumours can be treated at HFR as well as at other comparable installations in the European Union.

New applications of the BNCT technique are now being studied in the HFR reactor, including its use in treating brain tumours, liver cancer, skin melanoma and non-cancerous diseases such as diabetes.

If BNCT tests are successfully executed in the HFR reactor, it is clear that new reactors will be necessary for similar treatment elsewhere in Europe.

In the medical use of isotopes, there is currently no competition between reactor operators – co-operation is the order of the day. The co-operative spirit that presently characterises research in this field is highlighted by the fact that Prof Dr Sauerwein, who is responsible for treatment at HFR, is the president-elected of the International Society for Neutron Capture Therapy.

Work on BCNT is also underway outside the EU:

• In Japan, two reactors are being modified for the introduction of the BNCT technique: JRR-4 (at the Tokai Research Establishment) and the reactor at the University of Kyoto (modification began in 1999).

• In the US, two reactors are already available for BNCT treatments: they are at the Brookhaven National Laboratory and at the Massachusetts Institute of Technology.

• In Finland, a Triga reactor at the Technical Research Centre has been modified for BNCT; the first patient was treated there in 1999.

Other work under way at HFR includes characterisation of new isotopes for companies performing research on the production of new radioisotopes. HFR carries out the necessary analysis work for the irradiation of specific targets for new products.

Neutron diffraction has also been used for many years at HFR. This is used for the characterisation of biomedical materials, particularly for measuring the stresses in medical prosthesis.

NUCLEAR ENERGY

In the nuclear power industry, the HFR reactor mainly provides experimental support in the following fields:

• The safety of power reactors, through the study of component ageing under irradiation and fuel tests.

• The development of new fuels using plutonium.

• Waste management, through tests on the transmutation of actinides.

• The study of materials for new reactor concepts and thermonuclear fusion.

Around half of the reactors now in operation have already, or will soon, reach an age of around 30 years Their conceptual design really belongs to the fifties and sixties. They have already been modified many times during the years – ie each time new information was obtained. So in many areas research & development is decreasing in the field of nuclear power.

The use of a test reactor such as HFR remains indispensable in managing the life of these plants. Electricity producers mainly want to extend the life of their reactors (from 30 years to 40 or more). Of course, it is a considerable economic opportunity, because a large number of such reactors approach this stage. The difficulties of finding a site and winning a licence for a new reactor, as well as the problems of decommissioning, have led owners to examine the large scale renewal of reactor components. This has been done with steam generators and there is speculation it may be attempted for reactor vessels.

In this context, study of the ageing of materials and components under neutron flux, as well as the evolution of their characteristics is essential for safety. HFR is heavily involved in these studies, as part of the AMES European work group and the LYRA series of materials ageing tests.

Nuclear fuel efficiency

There is a constant requirement to carry out research on high burnup of power reactor fuels, whether for PWRs or BWRs. Similarly, accident research is required.

Reactor operators may find there is a considerable economic advantage in the use of fuels made of mixed oxides of uranium and plutonium (MOX fuels).

Tests of MOX fuels are being executed at HFR. On an ongoing basis, power tests are being executed to verify whether this type of fuel can be used in power reactors. In addition, the problem of whether the production of fission gases may limit the number of utilisation cycles for this type of fuel is being studied.

Other tests at HFR have begun to study new types of MOX fuel to examine its fitness for extended use in power reactors.

Waste management

The plutonium separated during the reprocessing of spent fuel is continuing to build up, ton after ton. Burning it in MOX reactor fuel assemblies is the first use of this highly radioactive product and the first step towards eliminating it as a waste product. Unfortunately, however, this only admits of a limited number of cycles.

Only fast reactors can fully burn plutonium. The EU’s CAPRA project addresses this in a programme using fuel comprising 100% plutonium.

The first tests executed at HFR have indicated several difficulties in fuel containing 45% plutonium (using a technique known as needle fusion).

At the end of 1999, a new series of investigations will begin into this fuel and to help in the validation of this management concept.

Waste and transmutation

Waste is a major obstacle to public acceptance of nuclear energy. It is difficult to justify the liability of nuclear waste storage up to complete disintegration. Even if the residual activity is weak, the safety of the waste always remains difficult to demonstrate.

If long-lived actinides (plutonium, americium, neptunium, etc) could be destroyed in a process separate to the reprocessing of spent fuels, the residual activity in the waste would quickly – in a reasonable delay of about 200 up to 300 years – decay to a level similar to that of natural soil radioactivity. The entire nuclear waste problem would then be changed.

A number of studies have begun on this theme, and in France a law (known as the Bataille law) has asked that propositions to implement such a programme should be put forward before 2006.

Progress has also been achieved on finding methods besides reprocessing to separate these actinides. What is the next thing that should be done with these actinides? In the same way as the CAPRA project is considering burning plutonium, transmutation studies have been launched to burn other actinides in existing PWRs.

HFR has completed seven transmutation experiments in this field. These experiences not only confirm the theoretical estimations, but to a great extent validate the technological feasibility of the concept. Take for example americium: the last experiment executed at HFR confirmed the theoretical feasibility of the process (70% of the americium disappeared), but has also revealed technical problems to be solved (swelling of the support stopped the experiment before the end).

Future HFR experiments will make it possible to refine our knowledge in this field. The objective, in the medium term, is to define the possibilities for the industrial application of this promising procedure, namely disparition of americium by a one-pass-through target.

FUTURE REACTORS – NEW CONCEPTS

Nuclear energy production is presently not competitive because of the low price of oil and gas. Nevertheless, studies show that within a period impossible to define (some say 20 years, some say 50 years), nuclear energy will be indispensable in providing electricity for the world.

In this context, teams from all over the world are working on future systems, considering designs for high temperature reactors, fast reactors, spallation reactors, fusion reactors, etc.

Technological problems, especially regarding materials or fuels, are showing up in all these fields. Such problems are sometimes so new and so difficult that they can put the real feasibility of the system into question. This is the case, for example, with the windows of the spallation reactors, with tritium breeding materials and with the first blanket of fusion reactors.

The use of a test reactor such as HFR makes it possible to test these materials and fuels in real conditions as well as to verify the feasibility of future concepts.

HFR is already used in several test programmes.

Fusion reactor

The materials of fusion reactors are technological truncheons: they have to undergo high irradiation; break off tritium; absorb tremendous thermal chokes; and evacuate enormous specific powers. The creation and/or improvement of these materials is one of the essential elements in making these projects feasible, as is solving the specific problems of nuclear physics.

For ten years about 20% of the HFR reactor capacity has been used for ten or more experiments each year in order to test these new or improved materials. In this field, HFR is the European test reactor of reference. Specific tests have studied the behaviour of certain irradiated materials that are extremely important for the future development of the fusion reactor concept. Where tritium breeding materials are concerned, unique European test loops make it possible to follow up the continual tritium release during material irradiation.

Spallation reactor

The studies on spallation reactors have identified important problems for the windows used in supporting huge irradiation doses in very delicate thermal and chemical conditions.

HFR has proposed several tests to study and optimise the behaviour of these windows.

High temperature reactor

The concept of the high temperature reactor is considered feasible, but nevertheless it has to be checked as regards fuel behaviour and materials, which must support extreme temperature conditions. These will be tested in the HFR reactor, which has already provided long-standing experience in HTR materials and fuel testing.

SCIENCE AND INDUSTRY

The characteristics of neutrons make them very useful in fundamental research into material structures.

The neutron has a magnetic moment, so it can test magnetic materials, to determine and understand their magnetic structure. It has a wavelength about the same as the spacing between atoms in molecules, so neutrons can produce interference patterns from the atomic lattice and can provide precise information on crystal and material structures. Since it is neutral it passes through the electron cloud to the nucleus and is more penetrative than electrons or X-rays.

Its weight gives the neutron specific capture sections and so can give unique information about the composition of materials in neutronography measurements.

HFR has tried recently to increase its capacity in this field by updating the beam tubes and by collaborating under a co-operation agreement with Delft University. In 1998 a new system of displacement was installed to measure the residual stress on heavy industrial sections. This tool, unique in Europe, has beeen used in several experiments in 1999. HFR is now studying the possibility of updating its neutron scattering possibilities completely in 2000.

The HFR reactor is also used for other direct industrial applications such as neutron radiography, irradiation of flower bulbs, analysis by activation, colour modification of certain materials, etc. These applications remain limited in volume because the intrinsic operating costs of the reactor are seldom compatible with the costs and working methods of industry.

HFR AND THE FUTURE

HFR has been in operation since the end of 1961. A new reactor vessel was installed in 1984, with a 30 year design life, so the reactor is expected to operate until 2015.

There are several keys to the success of HFR:

• The existence on the site of NRG, with its competency in the nuclear field and its technical facilities such as hot cells, allows integrated activities at a high technical level that are very attractive for the customers.

• The presence of IAM on the site, and its competencies in the field of material analysis, also provide good synergy.

• In the medical field the association of Mallinckrodt, with NRG, IAM and other partners in the Medical Valley, offer the site possibilities unique in Europe.

• Since the HFR is owned by the European Commission it is involved in European research and has close links with work in other countries.

• The reactor’s geographical position in the centre of Europe, with easy transportation, is also of benefit.

These points, which explain the success of HFR, also explain our confidence in the future. A group has already begun to work to analyse the future of this reactor after 2015 – should it be refurbished or replaced by a new reactor? Our children will need, in the future, medical support, cancer treatment, new safe and clean energy sources, and it is difficult to see how, in the future, all these activities can be provided in Europe without tools such as the HFR.