PROPOSALS FOR UNIVERSITY REACTORS OF A NEW GENERATION

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1 PROPOSALS FOR UNIVERSITY REACTORS OF A NEW GENERATION Introduction R.P. Kuatbekov, O.A. Kravtsova, K.A. Nikel, N.V. Romanova, S.A. Sokolov, I.T. Tretiyakov, V.I. Trushkin (NIKIET, Moscow, Russia) Worldwide, there is a growing number of countries being aware that a continued economic growth accompanied by an increase in the electricity consumption requires less dependence on fossil sources, with nuclear power, as the only alternative, finding increasingly greater acceptance. However, large-scale evolution of nuclear power requires a larger number of expert personnel possessing skills in handling of nuclear materials, an experience in operation of nuclear installations, and, certainly, a safety culture, which is especially important for the countries that have started or just plan to develop their own nuclear power. Apart from personnel training, there is also a need for an adequate experimental framework for studying the properties of materials, radiation and nuclear safety, and isotope production. In other words, there is a need for scientific centers to provide for the hands-on training of nuclear personnel, keep them professionally skilful and train scientific staff to be capable to conduct independently fundamental and applied researches using nuclear radiation. Fig. [] illustrates the fact that hands-on or vocational training is instrumental to nuclear education and the development of the nuclear power infrastructure. Moreover, official training and educational programs need to be developed for all those involved in the national nuclear power infrastructure, i.e. students, engineers, operators, inspectors, managers and even, in general, the public at large. Academic background Extra educational programs PhDs 50+ experts 2 24 months Masters / Higher education Fig.. Requirement for basic extra educational training levels in the construction, management of NPPs 400+ Project management + maintenance and operating staff 6 2 months academic education and programs for staff at all operation and with two reactor Bachelors / units [] months Tecnicians Apart from construction and operating staff personnel training, the experience of research reactor operation gained by a country planning to develop its own nuclear power will make it possible to take a conscious decision, about the long-term commitments required for nuclear power. A milestones approach was developed by the IAEA [2], which identifies 9 infrastructural issues to be addressed by countries developing nuclear power programs. The experience of research reactor operation in a given country indicates that it has already achieved a certain progress in such issues as proliferation resistance, nuclear safety and regulatory supervision.

2 Key requirements to training research reactors A research reactor market study shows that the target consumers for a small research reactor are the countries that are mastering nuclear technologies (Southeast Asian, African, Latin American and CIS countries). This is confirmed by Table which presents data on the major research reactors used for nuclear personnel training. Table. Role of research reactors in education and training of nuclear personnel [] Country, research reactor Power, kw Personnel number Austria*, TRIGA Mark II Brazil, IPEN/MB Czech Republic**, VR France***, ISIS (%) + (7%) + (32%) + (30%) + France, MINERVE Germany, AKR Italy, TRIGA Mark II Malaysia, TRIGA Mark II Slovenia, TRIGA Mark II * for personnel of Slovakia. ** for personnel of Slovakia and the Czech Republic. *** depending on missions at hand, the training course duration is 3 to 24 hours. + In brackets share of international students. The key requirements to training research reactors are as follows: since the research reactor will be supplied to foreign countries, it is expected to meet the international recommendations as to the compliance with nonproliferation guarantees; simplicity of maintenance and ease of use as intended; the research reactor shall possess intrinsic safety properties for the stable operation in conditions of potential unscheduled operation (operating errors); reference, proven fuel assemblies based on LEU-fuel shall be used in the core. Besides, an efficient use of the research reactor shall be ensured, namely: a high neutron flux in experimental devices (per unit of power); a long life; high burn-up of fuel; low capital and operating cost. Two modifications of small research reactors have been developed at JSC NIKIET as the base university facilities: 400kWt research reactor with natural coolant circulation; MWt research reactor with forced coolant circulation. The design was developed under international recommendations and Russian safety standards, because Russian safety requirements frequently exceed the requirements of national regulators in other countries. The developed research reactors are intended for a broad range of research and applied activities with the use of experimental devices both installed directly in the reactor core and reflector and operating on the neutron beams extracted from the reactor. 2

3 Based on the experience of the IAEA member sates, the guidelines have been developed for experimentation in nuclear physics and engineering which of a fundamental importance for the education and training of future nuclear personnel [3]. The document includes major theoretical information on each experiment conducted, the experimentation sequence, the required equipment and safety requirements. Potential applications: Training of nuclear technology specialists: i. training of personnel in control and maintenance of nuclear reactors; ii. training laboratory activities. 2 Nuclear physics; 3 Nuclear technology; 4 Solid-state physics; 5 Radiation material science; 6 Radiation chemistry; 7 Neutron activation analysis; 8 Neutron radiography of various items; 9 Biology; 0 Optimization of the medical and industrial isotope ( 3 I, 35 S, 32 P, 99 Mo) production technology. 2 Research reactor with natural coolant circulation (400 kwt) As shown by international practice, as well as by the experience of the nuclear reactor development in Russia, natural coolant circulation is the preferred cooling concept for a small research reactor. This leads to a reduction in the capital cost of the nuclear research facility construction thanks to the absence of the reactor coolant pumps, pipelines and valves in the primary circuit. This also results in a less dependence on external power supplies. The reactor (Fig. 2) has a pool-type design with natural coolant circulation. Inside the core, the coolant flows in the upward direction. Desalinated water is used as the coolant, the moderator, the end reflector and the radiation shielding. The design service life of the reactor is 50 years. The reactor pool is divided into two parts by a horizontal partition (an FA storage balcony). The balcony is mounted inside the reactor pit and is fitted with storage cells for FAs and irradiation devices. The pool s upper portion accommodates a refueling mechanism and brackets for the vertical experimental, CPS channels and ionization chambers attachment. The pool s lower portion accommodates the reactor core with the beryllium reflector, horizontal channels with supports and a distributing header. 3

4 Fig kW training research reactor [4] The reactor facility includes 3 horizontal experimental channels (HEC) for the application in research or treatment of oncologic diseases based on different ray therapy methods. Each HEC is mounted inside a penetration in the reactor s biological shielding and has a shutter at its end. Experimental devices or a medical box with respective equipment may be installed at the beam outlet. There are eight positions provided in the stationary beryllium reflector for the installation of vertical experimental channels for isotope production. 4

5 Rabbit system channels for the neutron activation analysis may be installed instead of the eight changeable beryllium reflector blocks. There is a central trap installed in the core center instead of seven FAs. The reactor is deployed within the protective concrete block of the reactor building and comprises an aluminum tank (the pool s outer shell), the core, the reflector, the control and protection system (CPS) actuators, ionization chamber channels, the upper shielding rotary plug, the horizontal channel shutters, and experimental devices. The pool also includes an interim SNF storage. The reactor s pool design makes it possible to facilitate greatly the operations to load/unload fuel assemblies and irradiated specimens into/from the core, reshuffle the core as the fuel burns up, and modify the conditions of experiments. Besides, the pool design makes the reactor cheaper thanks to a simplified flowchart and increased reliability and safety of the reactor operation. The reactor s maximum power is limited to 400 kw, which makes it possible to use natural coolant circulation for the heat removal from the core and extend the reactor cycle to 5 years. This makes the reactor much easier to operate and, with regard for the reactor application, is greatly advantageous. On the other part, the in-core neutron flux is about cm -2 s - which enables a broad range of research and applied activities to be carried out with the use of experimental devices both installed directly in the reactor core and reflector and operating on neutron beams extracted from the reactor. 3 Research reactor with forced coolant circulation ( MWt) Also, a MW modification of a university reactor with forced coolant circulation has been developed at JSC NIKIET. In this reactor, the in-core neutron flux reaches cm -2 s - which makes it possible to expand its experimental capabilities. The reactor (Fig. 3) has a pool-type design with forced coolant circulation inside the core in the downward direction. Desalinated water is used as the coolant, the end reflector and the radiation shielding. The reactor pool is divided into two parts by a horizontal partition. The upper part accommodates a core with a beryllium reflector, a balcony with storage cells for FAs and irradiated devices, horizontal channels, and brackets for the vertical experimental, CPS and IC channels attachment. The tank s lower part consisting of a number of cylindrical volumes with holes, which perform the role of a retention tank used to reduce the 6 N intrinsic activity of the water that has passed through the core. The major peculiarity of the reactor is the use of forced circulation for the heat removal from the core. The reactor cooling circuit comprises a circulation pump a heat exchanger and a coolant purification system, all accommodated in a separate room inside the reactor building. The primary circuit water fed to the pool flows downwards through the FAs, the CPS channels and the changeable reflector blocks to enter the retention tank. Having flown through the retention tank s sections, the coolant is discharged, over the pipeline, to the circulation circuit beyond the pool. Downstream of the circulation pump and the heat exchanger, the water goes back to the pool through the supply pipeline. 5

6 Fig. 3. MW research reactor Sectional view: shielding cover; 2 refueling channel; 3 supply nozzle; 4 discharge nozzle; 5 IC channel; 6 rabbit system channels; 7 CPS guide tubes; 8 interim FA storage balcony; 9 reactor core; 0 stationary reflector; retention tank; 2 horizontal channel shutter A small amount of the pool water flows through the channels in the stationary beryllium reflector, cools it and mixes with the coolant bulk in the retention tank which it enters through the hydraulically profiled holes in the retention tank s upper plate. In the event of scheduled or emergency reactor shutdown, decay heat is removed from the fuel elements by natural circulation. When the reactor coolant pumps are tripped, the coolant flows through the channels in the stationary beryllium reflector, passes through the retention tank, and cools the core as it flows upwardly therein. The major user properties of the two reactor types are given in Table 2. 6

7 Table 2. Major user properties of the research reactors Parameter 400kW training research reactor MW training research reactor FA type VVR-M2 VVR-M2 Thermal power, MW Up to 0.4 Number of FAs in the core Core height, mm Fuel enrichment in U 235, % Undisturbed thermal neutron flux (E <0.4 ev), cm -2 s - in the central trap, no less than: Horizontal channel outlet neutron flux: - thermal (E <0.625 ev) - fast (E > 0.82 MeV) Number of horizontal experimental channels (HEC): - tangential; - radial Number of vertical experimental channels (VEC), not more than: - including the central trap Number of control rods, including: - shim rods (SR) - automatic control rods (ACR) - emergency protection rods (EPR) (4.8 6) 0 8 (.2.5) 0 9 (4 4.8) 0 8 (.0.2) Cycle duration, years Conclusion Despite a decrease in the rate of construction of new research reactors, creation of reactor facilities for the personnel education and training will remain a crucial near-term task. The presented reactors feature a simple design and proven engineering concepts which make the reactors cost-effective and safe and ensure their long-term operation without refueling. Depending on customer requirements, it is possible to change or extend the reactor s research applications; for example, a medical box for neutron capture therapy may be installed in the nuclear reactor facility. References. E. Bradley, D. Ridikas, M. Yagi, M. Ferrari, B. Molloy. Assessing the role of research reactors and related infrastructure in the development of a nuclear power programme. RRFM-202, Czech Republic. 2. IAEA, Milestones in the Development of a National Infrastructure for Nuclear Power (IAEA Nuclear Energy Series No. NG-G-3.), Vienna, IAEA, Hands-on Training Courses Using Research Reactors and Accelerators (IAEA Training course series, No. 57), Vienna, Nuclear Research Facilities of Russia. Edited by N.V. Arkhangelskiy, I.T. Tretiyakov, V.N. Fedulin. Moscow.: JSC NIKIET,