IAEA-SM-360/47
CURRENT STATUS OF RESEARCH REACTOR AT THE TOKAI RESEARCH ESTABLISHMENT
T. YAMADA, S. KOBAYASHI, F. SAKURAI, K. KAIEDA Department of Research Reactor, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai-mura, Nakagun, Ibaraki-ken, Japan
Abstract
Since 1957, several research reactors have been sequentially constructed in Japan Atomic Energy Institute(JAERI), and they have been extensively utilized for various studies. At present, two reactors, the upgraded Japan Research Reactor No.3 (JRR-3M), the Japan Research Reactor No.4 (JRR-4) are in operation. This paper describes the present circumstance concerning those utilization and utilization facilities, including a development of new facility and instruments.
1. INTRODUCTION
The JRR-3M is reactor upgrading from old Japan Research Reactor JRR-3. The modification works of JRR-3 were started in 1986 for get higher performance of reactor utilization, and started full power operation again for utilization in 1990. JRR-3M is a light water moderated and cooled swimming pool type reactor with beryllium and heavy water reflector with the maximum thermal power of 20 MW. Its operation cycle is basically consist of four weeks of full power operation and one week of shut down for refueling, irradiation capsule handling and maintenance works. Normally, the annual operation consists of seven or eight operational cycles mentioned above. The integrated thermal power of 26,520 MWday was attained at the end of fiscal year 1998. Fuel conversion 3 program from U-Alx dispersed MTR type fuels with a U-density 2.2 g/cm to U3Si2-Al dispersed MTR type fuel with a U-density of 4.8 g/cm3 and a burnable poison of Cd wire is progressing. By this conversion, the number of spent fuels can be reduced, and it will supply stable neutron beam to many users. The JRR-3M is the first neutron source which is equipped with a large scaled cold neutron source(CNS) and neutron guide tubes with a total length of more than two hundred meters in Japan. This remarkable feature makes it possible to open up new research field such as soft material science, and also makes it possible to install many instruments along the guide tubes.
The modification works of JRR-4 were started in October 1996 for core conversion to LEU, utilization facilities upgrading and renewal of some reactor program, the new fuel is manufactured as 20% lower enriched uranium silicide fuel without changing of structure and any size. At the same time, a medical irradiation facility for Boron Neutron Capture Therapy (BNCT) was additionally installed, and were modified a Neutron Activation Analysis (NAA) system for short life nuclides and a large scale pipe irradiation system. Furthermore many works were conducted such as the renewals of instrument and control system, repairing of reactor building etc. JRR-4 is a light water moderated and cooled swimming pool type reactor with graphite reflector with the maximum thermal power of 3.5MW. Its operated six hours a day, four days a week and about 43 weeks a year. The full power operation of JRR-4 was resumed with LEU fuel in October 1998, and started the joint use of it from the beginning of 1999.
The characteristics of these reactors are shown in Table I. And the operation schedules of the two reactors in FY 1999 are shown in Fig. 1.
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1999Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec.2000Jan. Feb. Mar. Apr. J 530 10 4 14 9 19 13 23 3 2217 3125 6 31 R 10 weeks 4 weeks R 1 2 3 4 5 6 7 8 * - Characteristic measurement 3 Governmental inspection of silicide fuel core * Overhaul and inspection M Vacation
1999Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec.2000Jan. Feb. Mar. Apr. 4234 31 4 2 J 7 weeks 17 weeks 13 weeks R 6 weeks 8 weeks R * *
- Nuclear Engineering School training * Overhaul and inspection 4 Governmental inspection Vacation
FIG.1. Operation schedules of reactors JRR-3M and JRR-4 (FY 1999).
2. UTILIZATION FACILITIES
JRR-3M and JRR-4 have both of irradiation facilities and neutron beam experimental facilities. Fig.2 shows the arrangements of the experimental holes and tubes of JRR-3M, and reactor core configulation of JRR-4 are shown in Fig.3. And characteristics of these facilities are showns Table II and III.
As for the JRR-3M, nine irradiation holes are located in the core region for the capsule irradiation. They are used for material irradsiation tests and radio isotope(RI) production. In the heavy water reflector region, nine vertical holes are arranged. One of the holes is used for the CNS facility and the others are used for the irradiation experiments such as an activation analysis, a semiconductor production by silicon doping, RI production and so on. The CNS facility is a vertical thermo-syphone type using liquid hydrogen at 20K as a moderator. A schematic diagram of the CNS facility is shown in Fig.4. The CNS gain at wavelength of 5 Angstrom is 10. This facility is operated all during the reactor operation. Horizontal beam tubes are arranged in the heavy water tank for neutron beam experiments, nine horizontal beam tubes(1G through 6G, 7R,8T and 9C) are arranged tangentially to the core, in order to reduce fast neutrons and gamma rays in the neutron beam. The layout of neutron beam experimental instruments are shown in Fig.5. Seven out of the nine tubes, 1G through 6G and 7R, supply thermal neutron beam for experiments in the reactor room. The 8T beam tube transmits thermal neutrons into the beam hall through two thermal neutron guide tubes. The 9C beam tube transmits cold neutron from CNS into the beam hall through three cold neutron guide tubes. It has
2 IAEA-SM-360/47 become possible to install a lot of beam experimental instruments along these neutron guide tubes. Five neutron guide tubes, T1 and T2 for thermal neutrons and C1,C2 and C3 for cold neutrons, are installed to extract neutron beams efficiently from the heavy water reflector and the liquid hydrogen moderator in the heavy water tank through the horizontal beam tube 8T and 9C respectively to the beam hall. Of the seventeen neutron beam ports, an eight are set on the thermal neutron guide tubes and another nine on the cold neutron guide tubes, are available in the beam hall, 30m wide x 50m long, which is located next to the reactor building. The characteristic wavelength of T1 and T2 are 2 Angstrom and their radius of curvature is 3,340m. The length is about 60m. C1 and C2 with a radius of curvature of 834m have a characteristic wavelength of 4 Angstrom. Their total length is about 31m and 51m respectively. C3 with a radius of curvature of 370 m has a characteristic wavelength of 6 Angstrom, and is 31 m long. Their categories by instrumental type are listed in Table IV. The total number of instruments installed in a reactor hall and a guide hall are 26, and some instruments are being developed.
As for the JRR-4, five irradiation holes located in the reflector region for the capsule irradiation. They are used for the irradiation experiments such as an activation analysis, a semiconductor production by silicon doping, RI production and so on. And also a medical irradiation facility for BNCT is installed. Figure 6 shows the cross sectional view of neutron beam facility for BNCT at JRR-4. The medical irradiation facility has been composed of a heavy water tank, a collimetor and an irradiation room. The heavy water tank has four layers of heavy water for spectrum tailoring and 75cm thickness aluminum for the shield of fast neutron. The collimator is for collimating thermal neutron by graphite also epithermal neutron by lead, as well as shielding gamma ray by bismuth. Furthermore, a prompt gamma ray analyzing(PGA) system is constructed in the reactor pool.
9C 8T 1G
2G N S
3G Pool side T
Pn D 4G
Fuel elements DD: Pipe 5G TT: Pipe 6G 7R Reflector elements NN: Pipe Control rods Vertical Irradiation Holes: Pn: Pneumatic tube HR,PN,PN3,SI,DR,RG,VT-1,BR,SH Neutron source SS: Pipe Horizontal Beam Tubes: Irradiation tubes 1G 6G,7R,8T,9C
FIG.2. Arrangement of experrimental holes FIG.3. Reactor core configuration of JRR-3M. of JRR-4.
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Reactor Pool He Refrigerator Condenser Low Temperature H2 Buffer Tank Channel Tube Subpool Heavy Water Tank
Guide Tunnel
Neutron Guide Tube Core
Vacuum Chamber
FIG.4. Schematic diagram of CNS facility in JRR-3M.
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Reactor Building Experimental Building
TAS-1 MINE SANS-J 2G BIX- E C3-1-2 PNO AGNES C3-2 CNRF C2-3-1 3G C3-1-1 PGA C2-3-2 1G-A LCE C2-3-2A HRPD C2-3-3 1G C2-3-4
GPTAS C3 NSE C2-2 4G 3G 2G LTAS NSM 4G 1G C2 C2-1 5G 9C C1 HER ULS RESA 6G T2 SANS-U 8T C1-1 C1-3 T2-1 C1-2 PONTA 7R 5G T1 T2-2 > BIX- @ TAS-2 T2-3 T2-4
TOPAN TNRF 6G 7R Guide Hall PGA T1-4-1 LCE T1-4-1A HQR KSD KPD [NDC] T1-4-2 Reactor Hall T1-1 T1-2 T1-3 T1-4-3
0 10m
FIG.5. Layout of neutron beam experimental instrument at JRR-3M.
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No.1 Pool
Core Tank P.E.+Boron Lead
Irradiation Room
Core
Bismuth
D2O Tank Cd Shutter
FIG.6. Cross sectional view of neutron beam facility for BNCT at JRR-4.
3. CURRENT STATUS OF UTILIZATION
In JRR-3M, the main utilization fields are neutron scattering experiments. Status of utilization fields in 1998 is shown in Fig.7. Neutron scattering experiments occupied 61 % of the total use . One- third of the total use are irradiation experiments fields. In neutron scattering experiment, solid state physics is a major field and soft material such as polymer and biology account for about a quarter, chemistry, neutron optics and fundamental physics are minor fields. As for the other neutron beam experiments, neutron radiography, prompt gamma ray analysis and development of super-mirrors are listed with 12% occupation. Figure 8 shows the trend for the total number of users who worked in the field of beam experiments(person-day) categorized by affiliation. The number of users in 1998 is decreasing, because the JRR-3M experienced three unscheduled shutdowns by trouble of a CNS facility. In 1998 the number of users outside JAERI was more than that inside JAERI. The number of outside users was increasing year by year increased. Most of outside JAERI users are researchers from universities, occupied about 60 % ; inside JAERI users occupied about 40% in 1998. Especially the total number of neutron beam users, who worked mainly in the field of neutron scattering has reached 17,000 person-day, and requested beam time has reached twice of available beam time in 1997. All proposals are reviewed once a year by JAERI and University-Group independently, and are determined weather each should receive beam time and how much time is to be allocated.
In JRR-4, the main utilization fields are capsule irradiation for activation analysis, RI production, material irradiation tests, silicon transmutation doping and so on. Figure 9 shows the trend for the total number of capsules irradiated in JRR-3M and JRR-4. And as other experiments, are reactor engineering experiments, prompt gamma ray analysis, education-traning of reactor engineers. Furthermore, as new utilization field, are BNCT. But an application to patient are not yet as of July this year.
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Neutron radiography 2,261 (3%) Prompt gamma-ray analysis 2,261 (3%) Silicon irradiation 2,261 (3%) Neutron scattering Supermirror experiments experiments 2,261 (3%)
47,483 (61%) Neutron activation 77,210 analysis 1035 (1%) time・item 9,180 (12%) Others 605 (1%)
Fuels and materials for
the reactor 9,863 (13%)
Radioisotope production
FIG.7. Status of utilization field of JRR-3M in 1998.
(person-day)
20000 Users outside JAERI
Users inside JAERI
15000
9022 8660 8485 10000 8392
4477 4752 5000 3390 7875 2027 6932 6051 346 5092 377 3199 3286 2507 2769 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 (Fiscal year)
FIG.8. The number of users who worked in the field of beam experiments categolized by Affiliation at JRR-3M.
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3000 JRR-4 JRR-3M
JRR-2 2500 767 936
2000
1500 735 1096 1704 1675 1311 1567 (number) capsules Irradiated 1000 1859 1214 373 490
500 475 378 582 583 91 337 365 231 229 148 100 0 1990 1991 1992 1993 1994 1995 1996 1997 1998 (Fiscal year)
FIG.9. The trend for the total number of capsules irradiated in JRR-2, JRR-3M and JRR-4.
4. REPLACEMENT OF CNS MODERATOR CELL
The cold neutron source(CNS) facilities of the JRR-3M have been operating without exchanging a moderator cell for ten years since a start-up the reactor in 1990. The moderator cell of CNS is thin wall container of the 0.8 mm thickness made of austenitic stainless steel. The fast neutron fluence of moderator cell is estimated to reach 2.0x1020 n/cm2 by the latter half in last fiscal year, and the cell was replaced by the new one with the same specification in consideration of embrittlement by neutron irradiation. The replacement was carried out last October to this march. After that, JRR-3M has been operated succesfully.
5. UPGRADING OF THEREMAL NEUTRON GUIDE TUBES
Use of a supermirror guide tube instead of a natural nickel guide can increase neutron flux and transmits shorter wavelength neutrons through the guide. This performance promise to open up new possibilities for the experimenters for neutron scattering and other absorption experiments. In recent years, the constructions of supermirror guide have progressed at ORPHEE reactor and so on. At JRR- 3M, replacing program is progressing to obtain higher neutron flux and shorter wavelength neutrons. Replacing the thermal neutron guide tube (T-2) is the first project. Figure5 shows a horizontal view of the guide hall. It is planned that all element of the thermal guide tube (T-2) is replaced by a supermirror with an effective critical angle as same as twice of natural nickel. Other design parameters of the guide tube such as the radius of curvature and the cross section of the guide tube are not to change the layout of the existing instruments. Neutron transmission analysis have been conducted for design of the supermirror guide tube. Neutron trajectories were calculated using NEUGT code based on ray trace method which was developed to assess the design of the neutron guide tubes of JRR-3M. This code can not only calculate a neutron transmission and neutron spectra asumming the maxwellian spectra at a entrance of a guide tube, but also analysis the effect of abutment errors.
Figure10 shows calculated spectrum at the exit of T-2 guide tube as a function of reflectivity assuming the maxwellian spectra with 293 K at the entrance of guide tube. Total intensity at the end exit in the case with a reflectivity of o.95 is 5.6 times of the exiting nickel guide tube. Especially, intensity at 1.2 Angstrom is 10 times of the exiting one.
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0.45
0.40 Ni=2000
0.35 2Q-R=0.96 Intensity(Arb.) 0.30
0.25 0.20
0.15 0.10
0.05 0.00 012345 Wavelength ( )
Fig.10. Calculated neutron spectrum at the end of thermal guide(t-2) at JRR-3M.
6. DEVELOPMENT OF NEW INSTRUMENTS
6.1. Neutron Laue-Diffractometer for Crystallography in Biology
A diffractometer using nIP(neutron Imaging Plate) as a neutron detector has been constructed and is now under an ability test, as shown schematically in Fig. 11. An available neutrons are quasi- monochromated with a neutron velocity selector. The Laue diffraction patterns are recorded with nIPs. Combination technique of Laue method and nIP becomes possible to collect enough reflections to analyze structure of biological macromolecules precisely. Moreover the technique allows to reduce data recording times as against that of a conventional diffractometer with a gas-filled area detector.
6.2. Multiple Extreme Conditions System
Elastic and inelastic neutron scattering have provided useful information for the investigation of the condensed matters. The parameters of temperature (especially low temperature), magnetic field and pressure has generally been used as a physical variables for samples in such studies. However, so far only single or double of these parameters have been controled in neutron scattering experiments because of various technological difficulties.
An unique system was developed for controlling sample circumstances during the neutron scattering experiments. The system is able to generate simultaneously triple-extreme conditions of low temperature, high magnetic field and high pressure. Fig.12 shows a cut-away view of the system ; a conventional liquid-He cryostat with a superconducting magnet having an antisymmetric split-coils geometry for polarized-beam experiments and provides a vertical field up to 5T. The sample temperature range is about 1.7K to 200K. A high pressure cell was designed as a piston-cylinder type with the aim of generating pressure up to 2.5 GPa. All the cell parts were made of nonmagnetic materials(Al alloy, sintered-Alumina, etc.) with sufficient mechanical properties at low temperature.
6.3. Four-Circle Diffractometer
A single crystal diffractometer is being installed at T2-2 beam port by university group. This instrument works in the wave length of about 1 Angstrom to investigate the structure phase transition, structural disorder, hydrogen bonding in the field of condensed matter physics and so on.
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Sample
Velocity selector Collimator Slit
shield
NIP-shield NIP
Goniometor Beam shutter Collimator Slit Neutron Guide
FIG.11. Schematic view of a neutron Laue-diffractometer for crystallography in biology.
500
liquid-N2 reservoir variable-temperature insertion (VTI)
liquid-He liquid-He level sensor reservoir
1866 needle valve
high pressure cell superconducting magnet Neutron auxiliary heater
heater and heat exchanger temperature sensor
FIG.12. Cut-away view of multiple extreme condition system for neutron scattering.
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7. CONCLUDING REMARKS
At present, two research reactors are in operation in JAERI, and they are contributing to the basic researches and engineering R&Ds in both the nuclear energy fields and non-nuclear fields.
At JRR-3M, replacement of a CNS moderator cell was carried out this year to keep safe operation. Upgrading of existing nickel guide tubes with supermirror guide is also planned to increase the neutron intensity and open up new experimental opportunities. Futhermore, new instruments are being developed to meet the current demands for neutron beam experiments.
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