Current Activities of Neutron Imaging Facilities in KUR ... - Science Direct

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Physics Procedia 43 (2013) 42 – 47

The 7th International Topical Meeting on Neutron Radiography

Current activities of neutron imaging facilities in KUR (Kyoto University research reactor) Yuji Kawabata*, Yasushi Saito Research reactor Insitute, Kyoto University, Kumatori, Osaka 590-0494, Japan

Abstract

Kyoto University research Reactor (KUR) restarted in Spring 2010 with low enriched fuel (20%) after 4 years tentative interruption for fuel conversion. There are two facilities for neutron imaging: 1) B4 port at supermirror neutron guide tube (5x107 n/cm2/s at 5 MW, 1 cmx7.5 cm), 2) E2 port (3x105 n/cm2/s at 5 MW, 15 cm dia.). As we have large experimental space at the end of the guide tube and need small shielding because the neutron flux of KUR is not high, we have very large flexibility in the experimental set up. Thus, experiments in B4 should be specialized in the measurements which require large and/or unconventional equipments to accommodate special sample conditions. The E2 port with the low neutron flux is used for experiments which need very long or frequent machine times . 2013 The Authors. Published byaccess Elsevier Ltd. under CC © 2013 The©Authors. Published by Elsevier B.V. Open BY-NC-ND license. Selection and/or peer-review responsibility of ITMNR-7 Selection and/or peer-review under responsibiltyunder of ITMNR-7 Keywords: Type your keywords here, separated by semicolons ;

1. Introduction Kyoto University research Reactor (KUR) shown in Fig.1 is a light-water moderated tank-type reactor with the nominal thermal power of 5MW[1]. It has been operated constantly more than 40 years after its criticality in 1964 and full power (5MW) in 1968. The operation with highly enriched (93%) uranium fuels(U-Al) ended on 2006, and KUR started again with low-enriched (less than 20%) uranium fuels(U3Si2-Al) in 2010 after 4 years interruption for the fuel conversion. KUR has been served for the Japanese inter-university research program in physics, chemistry, biology, engineering, agriculture, medicine and so on. About 120 proposals are accepted per year under this program. The main experimental facilities are a Heavy water neutron irradiation facility for BNCT(Boron

*

Corresponding author. E-mail address: kawabata@rri.kyoto-u.ac.jp

1875-3892 © 2013 The Authors. Published by Elsevier B.V. Open access under CC BY-NC-ND license. Selection and/or peer-review under responsibilty of ITMNR-7 doi:10.1016/j.phpro.2013.03.005

Yuji Kawabata and Yasushi Saito / Physics Procedia 43 (2013) 42 – 47

Neutron Capture Therapy), pneumatic tubes for neutron activation analysis, a neutron radiography facility, material irradiation facilities with controlled temperature, a hydraulic conveyer for isotope production and high-dose material irradiation, a supermirror neutron guide tube for neutron imaging, and Ni-mirror neutron guide tubes for SANS and neutron reflectometry.

Fig. 1. KUR (Kyoto University research Reactor)[1]

2. Neutron Imaging Facilities in KUR As KUR is a middle class neutron source, the neutron flux is not high enough to attract researchers strongly. It is important to have distinguishing facilities which can make special experiments possible. From this point of view, KUR has a heavy water neutron irradiation facility for BNCT, material irradiation facilities with well controlled (340-773K) and very cold (10K) temperature. It also has the world's first supermirror neutron guide facility constructed in 1985[2]. There are two facilities for neutron imaging in KUR. 1)The B4 port at the end of a supermirror neutron guide tube (Neutron Flux = 5x107 n/cm2/s at 5 MW, Beam size = 1 cmx7.5 cm, L/D = 60(vertical) and 70(horizontal) , Neutron flux and L/D changes according to the sample position because of the guide structure.): As well known, neutrons can penetrate metals and are sensitive to water. Neutron imaging is a good tool for the two-phase flow research which requires to observe a water-vapor system through a metal container and heaters. Though this research field is quite important for the nuclear safety engineering, it requires high electric power and large experimental space to settle many experimental equipments. Usually, a high power electric system is not allowed in the reactor hall because of the risk of electric noise which the reactor safety system may have. So, we installed this high power two-phase experimental facility[3] far from KUR using a supermirror guide tube, and this electric power line was separated from that of the reactor. Thus we have a large experimental space at the end of the guide tube outside of the reactor building. The maximum electric power is DC 20V x 1200A. The max pressure of water loop is 2MPa. The temperature range is 20 - 150 oC and the flow rate is 0.028 - 2 l/min. The high power system and the water loop in B4 port are shown in Fig.2. Another important feature is a small shielding because the neutron flux of KUR is not high. The radiation shielding in B4 is shown in Fig.3. We have very large flexibility in the experimental set up which is difficult to proceed in a high flux facility with a hard and rigid shielding. Thus, experiments in B4 port should be specialized in the measurements which require large and/or special equipments to accomodate the special sample condition: for instance, two phase flow (high electric power), superfluid flow of water (high pressure and temperature), aerospace propellant (hydrazine which is explosive and toxic), and explosive fracture of concrete (fire).

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2)E2 port (Neutron flux = 3x105 n/cm2/s at 5 MW, Beam size = 15 cm dia., L/D=100, Cd ratio = 400) in the reactor hall: A cooled CCD based neutron imaging device with a CT system has been installed in E2 port by Riken[4]. It has a 6LiF-ZnS based scintillator with thickness of 100 micrometer. As the neutron flux is low, the number of users is small. It means that it has high flexibility in machine time. It is used for experiments which need very long or frequent machine times.

Fig. 2. High power supply system(left) and water loop (right) for two phase flow research using neutron radiography in B4 port

Fig. 3. Radiation shielding in B4 port

3. Current Neutron Imaging Activities The research subjects of neutron imaging in the KURRI progress report 2010 and 2011 are as follows.


[Facility development and engineering] 1) Project for improving the utilization activity o n KUR and HL in KURRI under strategic promotion program for basic nuclear research[5], 2) Neutron imaging of industrial components and simulation using VCAD system[4], 3) Catalytic decomposition characteristics of satellite propulsion thrusters using neutron radiography technology at Kyoto University research reactor institute(KUR)[6]. 4) Three Dimensional High-Resolution Neutron Computed Tomography at KUR[7], 5) Development of Prompt Gamma-ray analysis apparatus for a combination with neutron radiography[8] . [Two phase flow research] 7) Studies on boiling two-phase flow by neutron radiography for safety consideration of a nuclear reactor[9], 8) Visualization of two-phase flow in a polymer electrolyte fuel cell [10], 10) In-situ observation of mixing behavior in a flow-type reactor for supercritical hydrothermal synthesis using neutron radiography[11], 11) Neutron radiography on tubular flow reactor for supercritical hydrothermal synthesis of nanoparticles[12], 6) Quantitative measurement of liquid-film movement under forced convective boiling condition by using neutron radiography[13], 7) Quantitative evaluation of void wave propagation in oscillatory flow by using neutron radiography[14]. [Concrete research] 8) Experimetal research on the hydraulic behavior of high strength concrete under hight temperature[15], 9) Continuous measurement of water in cement during hardening for more than 20 days. [Others] 10) Application of neutron imaging for botanical research. 4. Concluding remarks The Science Council of Japan officially announced the "Japanese Master Plan of Large Research Projects" [16] for the first time on March 2010. It includes 43 projects for all fields of science. The project which Research Reactor Institute, Kyoto University, has proposed is selected as one of the "Large Scale Research Projects" in this plan. The title is "Promotion of Leading Research toward Effective Utilization of Multidisciplinary Nuclear Science and Technology". The summary of this project is "Efficient utilization of nuclear power and radiation provides solutions to maintain, sustain and even to improve development of human society. With collaborative use of important research resources (as for example, reactors and accelerators), this program's objective is to establish a center of excellence to grow and to promote multidisciplinary nuclear science and technology." Neutron imaging using a research reactor is recognized as an important research field in this proposal. We are also making a future plan including a pulsed neutron source with moderate scale which has a pulsed neutron imaging facility.

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Fig. 4. Explosive fracture experiment of concrete using fire at B4 port in KUR[15]

References [1] http://www.rri.kyoto-u.ac.jp/en/LF/index.html [2] Akiyoshi T, Ebisawa T, Kawai T, Yoshida F, Ono M, Tasaki S, Mitani S, Kobayashi T, Okamoto S, Development of a Supermirror Neutron Guide Tube, J Nuclear Science and Techonology 1995;29[10]:939-946. [3] Saito Y, Sekimoto S Hino M, Kawabata Y, Development of Neutron Radiography Facility for Boiling Two-Phase Flow Experiment in Kyoto University Research Reactor, Nuclear Instruments and Methods in Physics Research 2011;A651:36-41 . [4] Yamagata Y, Hirota K, Morita S, Ju J, Ohtake Y, Yokota H, Sera T, Sunaga H, Kawabata Y, Hino M, Kitaguchi M, Sugiyama M, Neutron Imaging of Industrial Components and Simulation Using VCAD System, KURRI Progress Report (2010) 116. [5] Saito Y, Kawabata Y, "Project for Improving the Utilization Activity on KUR and HL in KURRI under Stragetic Promotion Program for Basic Nuclear Research (II)”, KURRI Progress Report (2010) 112. [6] Kagawa H, Satoh H, Murayama S, Kajiwara K, Nittoh K, Konagai C, Iwata Y, Kawabata Y, Catalytic Decomposition Characteristics of Satellite Propulsion Thruster Using Neutron Radiogaraphy Technology at Kyoto University Research Reactor(KUR), KURRI Progress Report (2010) 257. [7] Kagawa H, Nagata T, Masuoka T, Kajiwara K, Hata R, Mochiki K, Saito Y, Kawabata Y, Three Dimensional HighResolution Neutron Computed Tomography at Kyoto University Research Reactor Institute (KUR), KURRI Progress Report (2011) in print. [8] Sekimoto S, Hirose K, Takamiya K, Okumura R, Kawabata Y, Development of Prompt Gamma-ray Analysis Apparatus in KURRI, KURRI Progress Report (2010) 125. [9] Takenaka N, Asano H, Sugimoto K, Murakawa H, Kawabata Y, Saito Y, Studies on Boiling Two-phase Flow by Neutron Radiography, KURRI Progress Report (2010) 113. [10] Takenaka N, Asano H, Sugimoto K, Murakawa H, Kawabata Y, Saito Y, Visualization of two-phase flow in a polymer electrolyte fuel cell, KURRI Progress Report (2011) in print. [11] Tsukada T, Sugioka K, Takami S, Adschiri T, Sugimoto K, Takenaka N, Saito Y, Kawabata Y, In-Situ Observation of Mixing Behavior in a Flow-Type Reactor for supercritical Hydrothermal synthesis Using Neutron Radiography, KURRI Progress Report (2010) 114.


[12] Tsukada T, Sugioka K, Adachi J, Takami S, Adschiri T, Sugimoto K, Takenaka N, SaitoY, Kawabata Y, Neutron Radiography on Tubular Flow Reactor for Supercritical Hydrothermal Synthesis of Nanoparticles, KURRI Progress Report (2011) in print. [13] Nakamura S, Taniguchi S, Hirose T., Sakaura K, Ozawa M, Ami T, Matsumoto R, Umekawa H, Saito Y, Quantitative measurement of liquid-film movement under forced convective boiling condition by using neutron radiography, KURRI Progress Report (2010) 115. [14] Fujiyoshi S, Nakamura S, Sakakura K, Ozawa M, Ami T, Matsumoto R, Umekawa H, Saito Y, Quantitative Evaluation of Void Wave Propagation in Oscillatory Flow by using Neutron Radiography, KURRI Progress Report (2011) in print. [15] Kanematsu M, Emura G, Tamura M, Tuchiya N, Saito Y, Kawabata Y, Experimetal Research on the Hydraulic Behavior of High Strength Concrete under High Temperature, KURRI Progress Report (2011) in print. [16] http://www.scj.go.jp/ja/info/kohyo/pdf/kohyo-21-h135-1e.pdf

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