REACTOR P I K
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WHAT ARE NEUTRONS NEEDED FOR
NEUTRON SOURCES: PRESENT SITUATION
PIK REACTOR: CHARACTERISTICS AND POTENTIAL
PIK REACTOR: STATUS AND PERSPECTIVES
PIK REACTOR: Research program and experimental facilities
PIK REACTOR: possibilities for applied work
_ REACTOR PIK AS A BASIS FOR AN INTERNATIONAL NEUTRON RESEARCH CENTER
WHAT ARE NEUTRONS NEEDED FOR
If you want to see an object, you have to illuminate it. If you want to discern details of an object, you will have to illuminate it with "light" of a wavelength equal to or smaller than the distance between the object details you are interested in. For most solids (or condensed media), such details of interest to physicists (for example, lattice sites) lie at about a few angstroms (10-8 cm) distance from one another. This means that the "light" required for studying the structure of solids should have a wavelength of the order of a few angstroms. Such light does exist. It is X- and gamma rays, as well as beams of elementary particles, for instance, neutrons.
The exclusive role X- and gamma rays play in scientific research and everyday life is only too well known. Less known among nonspecialists are the properties and advantages inherent in neutron radiation. At the same time they are quite significant.
First, neutrons, as particles having a mass, possess an energy much smaller than the X- or gamma rays with the same wavelength, and this energy becomes comparable with the energy of thermal vibrations of atoms and molecules in a substance, which offers a possibility of studying not only the averaged, static atomic structure of matter but the dynamic processes occurring in it as well.
Second, neutron possesses a magnetic moment, and this permits investigation of magnetic structures and magnetic excitations, which has turned out to be very important for understanding the nature of, and the processes occurring, for example, in such new and promising materials as high-temperature superconductors.
Third, neutrons interact with atomic nuclei rather than with electrons in atomic shells, as X- and gamma rays do, and this factor accounts for their significantly higher "contrast" (sensitivity) in discriminating among neighboring elements in the Periodic Table. This is particularly true for light elements (hydrogen, oxygen etc.), whose identification in solids containing heavy elements by conventional X- or gamma ray techniques meets with staggering difficulties, and which, if present in a material, may dominate its properties. More than that - neutrons can be used to probe even the isotope composition of matter.
Apart from this, neutrons are electrically neutral, and their interaction with nuclei is weak, which permits neutrons to penetrate deep into matter; this property of neutrons gives them an advantage over the X- and gamma rays, as well as beams of other, charged elementary particles.
These and other, not mentioned here, properties of neutron radiation make it a unique tool for probing condensed matter, and it can be used to advantage in various areas of science, such as physics, chemistry, biology, geology, materials science, to say nothing of its potential in medicine, industry, and other fields.
Note, however, that all these possibilities have not been provided by Nature, so to say, free of charge; indeed, building a good, modem source of neutron radiation is a very expensive endeavor, its cost amounting to hundreds of millions of US dollars.
Nevertheless, neither the trend to progress inherent in science, nor the vital needs of industry and national economy could permit any developed nation to reject the perspectives promised by the use of neutron methods in the investigation of matter, and, hence, the construction of neutron sources.
Now what kind and scale should be the source - that is another question. The answer to it is determined by the specific capabilities of a given country, namely, by the level of its scientific and technological potential, available finances, and personnel, essential not only in the design and construction stage but in the course of using the source as well.
The concept accepted presently universally consists in that each developed region in the world should have at least one high-power (high-flux) neutron source (in a supranational-scale center), complemented by a network of medium-power sources located in national centers of the countries in this region. In Western Europe, such a supranational source is the high-flux reactor HFR at the Institut Laue-Langevin (Grenoble, France), which has been successfully used for many years not only by the European countries but by the World community as well.
The East-European and Asiatic region does not yet have such a source, although medium-power national sources have been already operated successfully and for a long time by different countries in the region. The possibilities offered by these sources are, however, limited.
At the same time the experience gained during the nearly 25 years of HFR operation in Grenoble, and particularly its unplanned shutdown in 1991, have shown convincingly that one high-flux neutron source is certainly too little for the world.
NEUTRON SOURCES: PRESENT SITUATION
The efficiency of neutron methods is determined to a considerable extent by the quality of the available neutron-radiation sources, primarily by their neutron flux density. In this context, it is instructive to analyze the current situation in the world.
The main type of neutron source employed presently is still the nuclear reactor, i.e. a continuous source using the chain reaction of uranium fission for neutron production. While spallation-type sources based on knocking neutrons out of a heavy target by fast protons have certain advantages in some studies, their low average flux (they operate in pulsed mode) compared to a reactor does not make them really competitive, particularly if one takes into account the comparatively high cost of their construction.
About ten years ago, there were in the world more than 300 research reactors, which were used primarily in materials science studies, i.e. for sample irradiation, and for production of radionuclides. The number of reactors designed specifically for physical research, i.e. providing neutron beams, did not exceed 100. About 25 of them had a flux density at the level of 1014 n/cm2s, and only two (one in USA, in Brookhaven National Laboratory, and one in Europe, certainly the best, at the international Institut Laue-Langevin) with a density of ~ 1015 n/cm2s.
The 1980s have witnessed a trend to a reduction of the number of reactors through decommissioning of low-power and outdated machines, which have reached the end of their service life. The reactors of a new generation intended to replace them were equipped by modem systems, such as sources of cold and hot neutrons and neutron guides, which permit obtaining and leading out beams of neutrons of a given energy.
It was only in the 1990s that new reactors in Germany, Japan, Korea, and Egypt were commissioned, some reactors in France, USA, Hungary, and Poland were upgraded, and several research reactors in Canada, Germany, Iran etc. are presently in the stage of design or construction. But all of them are medium-power installations (national sources). Only two high-flux reactor projects existed at the time in the fairly advanced stage of development:
As we shall see below, the beam parameters and experimental capabilities of the PIK reactor are such that its commissioning would permit us not only satisfy the needs of our country in neutrons, but also set up around it an international center for neutron studies of the type of the ILL facilities which have been used successfully already for more than two decades.
Building a second International neutron center, which would be orientated geographically toward countries of Eastern Europe and Asia, appears reasonable, if one takes 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.
Our estimates, which were made as far back as 1992, show that the construction of this complex could be completed in 2.5 - 3.0 years under conditions of proper financing. The economic situation in Russia has not been favorable enough to allow doing this up to now, and there is still no confidence that the required funds would be allocated in the nearest future.
In these conditions, it appears reasonable to invite foreign partners to participation in financing the final stage of construction, which would imply their right to participate in future neutron research programs at the PIK reactor.
PIK REACTOR: CHARACTERISTICS AND POTENTIAL
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 HFR at Institut Laue-Langevin, presently the best research reactor in the world.
The main concepts underlying the technical project were formulated as far back as the late 1960s (practically at the time of the Grenoble project), but its construction was started only in 1976, when the Grenoble reactor was already put in operation.
By 1986, the original project was completed to about 70%, but after this (after the Chernobyl disaster) the construction was practically frozen to bring the project in compliance with the revised nuclear safety requirements. The revised project was approved only in 1990, when our country found itself faced by grave economic problems.
The PIK reactor represents a compact neutron source (core volume _50 l) surrounded by a heavy-water reflector. It is fueled by Uranium-235 (enriched to 90%) of total weight ~ 27 kg. Light water is used both as coolant and as moderator.
The design parameters:
The reactor will by provided by sources of hot, cold (2), 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 300 m 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 location of experimental setups is as large as 50 (in Grenoble, there are 25 of them presently), which will permit simultaneous operation of 50 groups; in other words, many hundreds of researchers could profit from carrying out their experiments (in Grenoble, about 1000 proposals for neutron beam studies are accepted annually).
Despite the long period taken up by its construction, the project (after its revision) meets the highest world standards, which has been confirmed by a technical appraisal carried out in 1993 by leading specialists from USA, France, Germany, Great Britain, and EC Committee. The comments of the experts aimed at bringing the project in compliance with the universally accepted nuclear safety requirements have been carefully analyzed, and the corresponding technical solutions implemented. The project has been approved by all organizations exercising State supervision over the construction and operation of objects presenting radiation hazard, including State Committee for Ecology.
Presented below is a graph of thermal-neutron flux-density distribution in the PIK reactor and the HFR reactor in Grenoble. Also shown for comparison are the graphs for the currently operating WWR-M reactor at PNPI and for the FRM-II reactor in Munich (Germany), the best of the new projects approved for building.
PIK REACTOR: STATUS AND PERSPECTIVES
Most of the 27 buildings of the complex are already constructed, although the painting and decoration work have not been completed.
Awaiting construction are:
All these installations, with the exception of the first, are not included in the startup complex and can be completed at a later stage.
All problems relevant to energy power supply are practically solved:
In 1996, an enclosure around the territory of the complex has been constructed and provided by a special protection and alarm system in full compliance with present-day nuclear-safety requirements.
In 1996, work on strengthening the ceilings over the main and technological halls (conteinment) has been completed, thus providing conditions for installation of the reactor itself and of the primary-coolant systems (clean conditions area).
Installation of equipment relating to the intermediate-coolant circuit, just as that of the electric power supply unit, is practically complete.
Erection work at other installations of the complex is presently delayed primarily by lack of financing.
A critical facility representing a full-scale model of the PIK reactor operating at power levels of up to 100 W has been developed at the Institute and put in operation. This mockup permits one to check experimentally the neutron-flux and other physical parameters of the PIK reactor in real conditions, and to optimize them.
We estimate the construction work of the complex to be 80% complete, and the equipment installed up to 65-70%.
The present status of the installation can be inferred from the photographs below.
By our estimate, about 30 million USD would be needed to complete the construction (installation of the heavy-water isotope purification plant is not included in this estimate).
Attempts to internationalize the project (that is, to attract foreign investments) undertaken at government level in 1992-93 did not meet with success at the time, despite the generally positive conclusion of the international experts, who confirmed that PIK is a highest-quality project, and that its validity and substantiation do not raise any doubts.
In the years that followed, work at the complex was continued, although at a pace well behind the schedule. There is no doubt that the reactor, whose significance for the Russian science is universally recognized, will eventually be built. But this will be done in a shorter time if we succeed in finding investors from outside, whose contribution would be compensated by participation in the use of the attractive possibilities offered by the PIK reactor.
Research program and experimental facilities
From the very beginning, the PIK reactor was conceived as a high-level installation on a state scale (we have in mind the scale of the former USSR), intended to satisfy the needs of research in various areas of science. This can be readily seen from the scientific program below, which was approved by many national and international committees and meetings.
Physics of condensed states:
Structural and radiation biology and biophysics.
Radiation physics and chemistry.
Nuclear and elementary particle physics:
These areas cover the problems of all scientific groups in Russia interested in using neutron methods, and the broad experimental capabilities of the PIK reactor can be adapted to suit scientific interests of our foreign partners.
Everything is determined here by the existence of, and access to, experimental facilities which would be adequate to a given problem. The PNPI, aided by a number of other Russian Institutes, is working on building these facilities.
This relates primarily to the equipment and systems intended for joint use, such as neutron sources for different parts of the energy spectrum (thermal, hot, cold, ultracold), neutron guides, helium ducts, monochromators, polarizers etc.
We have developed and mastered the production of modem neutron optics systems, namely, conventional, focusing, and polarizing neutron guides, neutron spin flip systems, precision, including three-dimensional, polarization analysis. These techniques are currently used in both Russian and foreign laboratories. The nuclear detector and physical electronics departments are capable of equipping experimental setups with high-quality instruments. The instrumentation developed at the Institute is well known to our foreign colleagues who place many orders for instruments at our Institute.
In most research areas in the physics of condensed state, success is determined not by one instrument but rather by a set of instruments (spectrometers, diffractometers etc.) permitting investigation of various characteristics of a sample. Development of such a set comprising about 25 instruments is planned to be pursued during the years left until the PIK is put in operation. Some of them have already been built and are presently being used at our old medium-flux WWR-M reactor and in some foreign centers (France, Germany, Hungary, Egypt etc.).
In the field of nuclear physics, a number of unique installations for operation with ultracold and polarized cold neutrons have been constructed, which permit obtaining, even at the medium-flux levels of the WWR-M, world-class results in studies of the symmetry properties in elementary-particle interactions, and of the fundamental characteristics and decay correlations of the neutron (these studies are well known and widely recognized by the world scientific community).
The general situation in this area is in the stage where, should the PIK reactor be commissioned tomorrow, nearly half of the beam stations could be occupied by the already available installations. The free stations left could be offered to users chosen.
possibilities for applied work
The unique properties of the neutron and the vast irradiation potential of the PIK. reactor can be used to advantage for applied work, as this is illustrated by the examples given below.
I. Production of doped silicon
The demand of electronics industry in doped silicon for production of power valves and large-scale integrated circuits is well known, just as the high efficiency of the use of neutrons for the purpose of doping. The world demand for doped silicon with ingot diameters of 150 mm or more is about 100 tons/y. Setting up industrial-scale production of neutron-doped silicon on a reactor already in use would meet with formidable difficulties for a number of reasons of purely technical nature.
The PIK reactor, with its large-volume reflector, a high and uniform thermal-neutron flux, and a possibility of installing a beam-tube with up to 250 mm in diameter, offers an excellent opportunity for organization of such production. The output could be as high as-50 tons/y.
2. Purification and upgrading of heavy water (D2O)
Heavy water is used primarily in nuclear power production. Its production from natural raw materials being very energy-consuming, heavy water costs 200-250 USD/kg.
At the same time some countries have accumulated large amounts of D2O contaminated by tritium and with a low deuterium content. The problem is aggravated by the need of regenerating eliminated nuclear warheads, a process producing heavy-water wastes which are usually contaminated by tritium. Development of a technique of deep purification of heavy-water from tritium and of its enrichment in deuterium, as well as its implementation on an industrial scale promise a significant profit, not to mention the ecological aspects of the problem.
The PNPI has developed an original technique for this process, which has already been tested at pilot plants. An operating project for a large-scale plant of this type has been made. This project is of considerable independent interest and can be analyzed separately from the PIK. Implementation of this project would require capital investments at a level of 12 million USD. The output of such a plant (which is actually a factory) is ~ 60 tons/y of high-quality heavy water with a tritium content of about 4x10-6 Curie/kg and D2O concentration of- 99.8%.
Before the PIK startup and during the first three years of its operation, all this output and, subsequently, after that time about one half of it could be supplied to any Customer on the side.
The funds invested into the construction, including the costs of the raw materials and operation, would be recouped in about three years.
3. Production of radioactive isotopes
The demand for radioisotopes and tagged compounds for medicine and industry is ever increasing while the number of their producers decreases steadily, following the decreasing number of neutron sources suitable for these purposes.
Putting the PIK reactor possessing such a high irradiation potential in operation, the availability at the PNPI site of a cyclotron and of a hot-chamber building, of highly qualified physicists and radiochemists among the personnel of PNPI and of the Radium Institute offer promising prospects for setting up radioisotope production here.
4. Neutron activation analysis
It would be difficult to overestimate the role of neutron activation analysis in ecology, mining industry, production of rare and precious metals, and of all kinds of new materials created by technologists. Specialists believe that any country has to make annually hundreds of thousands of analyses. To be able to do this, however, one has to have neutrons, and the more analyses have to be performed, the more neutrons will be required. The PIK reactor cannot naturally solve this problem alone, but it is capable of providing a very substantial contribution.
The above examples do not naturally exhaust all problems of applied nature that are solvable with neutrons, and were meant simply to illustrate the potential of the PIK. One could add here nondestructive testing and stress study in constructions and materials, neutron therapy in oncology, and many other fields of possible applications.
AS A BASIS FOR AN
INTERNATIONAL NEUTRON RESEARCH CENTER
The neutron beam parameters and the experimental potential of the PIK reactor are indeed unique; as already mentioned, they are comparable only to those of the Institut Laue-Langevin (ILL) at Grenoble, and will not apparently be available anywhere in the world for the nearest 10-15 years.
At the same time the demand for neutrons for both scientific research and applications is growing. This is evidenced by an ever increasing interest in neutron techniques revealed in industrial laboratories all over the world. This is suggested also by the ever more stringent competition reactor experiment proposals meet at Grenoble. By an apt remark of a leading neutron physicist, there are indications of a "neutron drought" in the world, which become increasingly apparent.
Several international meetings on the PIK program held at PNPI and numerous discussions with leading foreign scientists have shown that the PIK reactor simply must be commissioned in a reasonable time (3-4 years).
There are all necessary prerequisites for this, including the available living conditions.
The Petersburg Nuclear Physics Institute is already well known all over the world. It is one of the largest Institutes of the Russian Academy of Sciences, with more than 2000 people on the stuff, including 70 Professors and more than 300 Doctors of science. The research is focused primarily on nuclear and elementary-particle physics, physics of condensed state, molecular and radiation biophysics, and physics of reactors and accelerators. The PNPI was awarded the status of State Research Center of the Russian Federation.
The Institute is located in a beautiful wooded area, three km away from Gatchina.
The closeness to St. Petersburg (43 km), the world-famed center of science and culture, with its numerous research institutes, universities, theaters and museums, its unique palaces provides wonderful possibilities for work and recreation.
The closeness to an International airport (25 km), a well-developed network of railroads, highways, and sea routes provide a convenient answer to any transportation problem.
The Institute has a developed infrastructure, including its own hotel to accommodate 100 guests, a wonderful sporting complex with a swimming pool and game halls, a restaurant-diner, and an outpatient's polyclinic. If this is complemented by a conference center whose project has been completed, and a few cottages for scientists coming with families to stay here for a prolonged period, the living conditions will meet world's standards.
On the other hand, construction of an International center of such a scale and level will be in line with the best traditions of St. Petersburg and the trend of Russia's integration into the world community.
Science, particularly fundamental science, does not recognize state boundaries. Its achievements belong to Mankind. Therefore the proposal to join efforts in constructing a world-class facility for use by all nations appears to conform with the goals of the international scientific community and with the spirit of the world we live in.
GO TOP Designer: Dr. Igor A. KONDUROV : KOND@LNPI.SPB.SU
Last modified: 02.09.98
Designer: Dr. Igor A. KONDUROV : KOND@LNPI.SPB.SU