PIK of the bunch

1 January 2002

PIK, a high-flux heavy-water reactor, is the largest research reactor in East Europe. By Judith Perera

In 2001 Russia's Nuclear Energy Ministry (Minatom), the Ministry of Industry, Science, and Technologies, and Presidium of the Russian Academy of Sciences provided R199 million ($7 million) to continue construction of the PIK research reactor at the St Petersburg Nuclear Physics Institute (PNPI) in Gatchina. Although the sum was only 61.66% of what was allocated for 2001, it has enabled work to resume on the project which had an initial cost estimated at $150 million, according to PNPI centre director Vladimir Nazarenko. He says the reactor is 80% ready and only about $35 million worth of work remains to be done.

Construction began in 1976 but was repeatedly suspended due to the lack of finances. So far, construction of the research complex has cost $150 million. The aim is to begin operation in 2003, provided the project is financed properly. The reactor will be used for fundamental studies of solid bodies, particle interaction, and other problems of nuclear physics, radiation chemistry, and biology. The reactor's physical parameters and test capacities are such that it could become the centre of an international centre for neutron research.

Some 10 years ago, there were more than 300 research reactors worldwide, used primarily for materials science studies. The number of reactors designed specifically for physical research, - for providing neutron beams - was less than 100. About 25 of them had a flux density at the level of 1014 n/cm2s, and only two (one in the US at Brookhaven National Laboratory, and one in Europe at the international Institut Laue-Langevin in Grenoble, France) had a density of about 1015 n/cm2s.

In the 1980s many research reactors were closed and decommissioned and construction of some new units did not get under way until the 1990s. However most of these are medium-power installations. Only two high-flux reactor projects were then in the fairly advanced stage of development: PIK and the ANS supersource project in the US (with a flux at a level of (6-7) x l015 n/cm2s), which did not get beyond the design stage because its construction was blocked in the Senate.

From the standpoint of its characteristics and experimental capabilities, the high-flux research neutron-beam reactor PIK is not inferior, and in some aspects, even superior to the Grenoble reactor, currently considered the best research reactor in the world. The new research neutron source FRM-II at Garching in Germany is also a centre of excellence but its neutron flux is lower, at 8 x 1014 n/cm2s.

The main concepts underlying the PIK project were formulated in the late 1960s (at the time of the Grenoble project), but its construction began only in 1976, after the Grenoble reactor was already in operation. By 1986, it was about 70% complete, but after the Chernobyl disaster construction was practically frozen to bring the project in compliance with new safety requirements. The revised project was approved only in 1990, by which time finances were difficult.

However, the PIK reactor represents a compact neutron source surrounded by a heavy-water reflector. It is fuelled by Uranium-235 (enriched to 90%) with a total weight of around 27kg. Light water is used both as coolant and as moderator. The design parameters are as follows:

• Thermal power100 MW.

• Thermal-neutron flux: 1.2x1015 n/cm2s in reflector; 4.5x1015 n/cm2s in 10 cm-diameter central channel - four times higher. (The Grenoble reactor is not equipped with such a channel.)

• Number of horizontal beam-tubes: 10. Channel diameter: 10 cm, with a possibility of replacement by a 25-cm diameter channel.

• Number of inclined beam channels: 6.

• Number of vertical thimbles for sample irradiation: 6.

The reactor will offer sources of hot, cold, and ultracold neutrons to make available neutron beams in different energy ranges. A low-temperature loop will permit sample irradiation at helium temperatures. A system of neutron guides (four for the cold, and four for thermal neutrons) of total length 300m will provide operation with external beams in zero-background conditions of the neutron guide hall adjoining the reactor building.

The total number of work stations for setting up experiments is 50 (Grenoble has 25), which will permit simultaneous operation of 50 groups and many hundreds of researchers could profit from carrying out their experiments using PIK - in Grenoble, about 1000 proposals for neutron beam studies are accepted every year.

PNPI scientists say that building a second international neutron centre, which would be orientated geographically toward countries of Eastern Europe and Asia, appears reasonable taking into account the needs the world's scientific community feels in high-intensity neutron beams, both for pure research (investigation of ever finer effects requiring accumulation of large statistics), and for industry-oriented applications.

The intention is also to use PIK for applied work. This includes production of doped silicon for the electronics industry. PNPI scientists note that the world demand for doped silicon with ingot diameters of 150 mm or more is about 100 tonnes a year but setting up industrial-scale production on a reactor already in use would be technically difficult. The PIK reactor, with its large-volume reflector, a high and uniform thermal-neutron flux, offers the possibility of installing a beam-tube with up to 250 mm in diameter, providing an opportunity for organising production of up to 50 tonnes a year. There are also promising prospects for setting up isotope production since PIK benefits from the availability at the PNPI site of a cyclotron and of a hot-chamber building, as well as highly qualified physicists and radiochemists. Other possibilities include neutron activation analysis, non-destructive materials testing and neutron therapy in oncology.

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