Research Reactor JRR-3 Research Articles

A new convention for the epithermal neutron spectrum for improving accuracy of resonance integrals

A new convention for the epithermal neutron spectrum component is formulated in this work, aimed at improving the accuracy of resonance integrals determination. The (1 + β)/(βE + E1+α) form here proposed, is an approximating function of the epithermal neutron spectrum based upon calculations performed by the state-of-art Monte Carlo code MVP-3. Bias effects on determination of resonance integrals, due to the application of the well-known and used so far approximating functions, such as 1/E, 1/E1+α as well as the new form (1 + β)/(βE + E1+α) are compared, where E is the neutron energy, α a shape factor, and β a new shape factor introduced in this work. The other bias effect is also investigated, which is caused by neglecting the position dependence of a neutron spectrum inside an irradiation capsule. To get a demonstration of the bias effects due to these assumptions, upon the determination of a neutron spectrum from a quantitative point of view in a practical case, the thermal neutron-capture cross section and resonance integral of 135Cs measured at a research reactor JRR-3 are re-evaluated. A superior property of the proposed new mathematical expression is discussed. The experimental method is proposed to determine the new shape factor β by a combinational use of triple flux monitors (197Au, 59Co, and 94Zr), and its analytical methodology is formulated.

Hierarchical structure of microbial cellulose and marvelous water uptake, investigated by combining neutron scattering instruments at research reactor JRR-3, Tokai

We discuss microbial cellulose (MC) produced by Acetobacter Xylinum and its metabolism related to the bacterium body structure on a basis of knowledges obtained by the small-angle scattering method with combining different spectrometers. MC is a supra-molecule system impregnated with a huge amount of water about 99% by weigh. In the previous literature [Eur. Phys. J. E, 2008 and Macromol. Symp. 2009], we elucidated that 90% of total water is accumulated in non-crystalline bundle causing concentration fluctuations. In this paper, we develop our arguments by newly adding the knowledges on (i) the hierarchy in a bacterium body studied by SANS & USANS and (ii) the non-crystalline local structure in as-produced MC in a culture solution, confirmed by neutron diffraction with polarization analyses. As a control to emphasize the peculiarity of MC, we compare MC to a synthetic polymer gel of poly(N-isopropylacrylamide) (PNIPAAm) in a swollen state. Consequently, we conclude that a mechanism of excellent water absorption found for MC is attributed to capillarity related to hierarchically preserved non-crystalline domains, whereas tight hydration onto a monomer unit via a hydrogen bond is crucial to result in high water absorption for the PNIPAAm gel.

Multi-tube area detector developed for reactor small-angle neutron scattering spectrometer SANS-J-II

A newly developed multi-tube area detector for a small-angle neutron scattering (SANS) spectrometer (SANS-J-II) at the research reactor JRR-3 in Tokai, Japan, has been implementedviathe use of one-dimensional position-sensitive3He detectors (tubes). Ninety-six active tubes of 8 mm in diameter and 650 and 580 mm in length were filled with 15 atm (1.52 MPa) of3He and aligned vertically parallel in order to cover a sufficiently large area for small-angle scattering measurement. These tubes are enclosed in an air chamber together with neutron encode and GATENET modules (VME boards), which compose a standard data acquisition system for the spallation neutron source of the Japan Proton Accelerator Research Complex. This system facilitates the acquisition of time-of-flight neutron event data. The multi-tube detector is mounted on a truck moving in a vacuum chamber of the SANS spectrometer. After discriminating noise originating from γ-rays, and calibrating the positions and sensitivities of individual tubes, the resolution was determined (i.e.channel widths along parallel and vertical directions along a tube). The counting rate of one tube was determined to be 1.4 × 103counts per second with a counting loss of 1%. This implies that the new detector, composed of 96 tubes, can detect more than 105neutrons per second with a counting loss of 1%. To demonstrate its use, small-angle scattering originating from a diblock copolymer film with a highly oriented lamellar microdomain was observed. The data acquisition in event mode has a great advantage in time-resolved measurements that are synchronized with external stimuli imposed on a sample.

The Role of the Research Reactor JRR-3 in Neutron Sciences

The Role of the Research Reactor JRR-3 in Neutron Sciences

High-resolution neutron structure analyses of porcine pancreatic elastase

Elastase is a serine protease classified in the chymotrypsin family, and is attractive target for studies of structure based drug design (SBDD). The structural information including hydrogen positions and hydration will help us to further elucidate the catalytic mechanism of serine protease. To obtain such structural information, we performed the neutron structure analyses of porcine pancreatic elastase (PPE) with and without its inhibitor using diffraction data obtained at a BIX-3 diffractometer in the research reactor JRR-3. The PPE structure in complex with a peptidic inhibitor, which was used to mimic the tetrahedral intermediate state, was determined to 1.65 Å resolution [1]. His57, Asp102, and Ser195 (chymotrypsin numbering) compose the "catalytic triad" conserved in the active site of serine protease. The complex structure determined by neutron crystallography shows that the hydrogen bond between His57 and Asp102 is essentially short but conventional hydrogen bond, not a low-barrier hydrogen bond. In addition, this neutron structure clearly shows that the oxygen of oxopropyl group of the inhibitor is present as an oxygen anion rather than a hydroxyl group, supporting the role of the oxyanion hole in stabilizing the intermediate in catalysis. The neutron structure of PPE without inhibitor determined to 1.9 Å resolution shows that a water molecule and hydroxyl group of Ser195 block to two backbone amides of Gly193 and Ser195, which form oxyanion hole, respectively. This structural information allows us to understand the role of resting state upon the catalytic reaction. Furthermore, the structural change of the active site residues including hydration structure obtained from the comparison between structures with and without inhibitor may help designing potent inhibitors by SBDD.

Neutron diffractometer covering protein crystals with large unit cell at J-PARC

The structural information of hydrogen atoms and hydration waters obtained by neutron protein crystallography is expected to contribute to elucidation of protein function and its improvement. However, many proteins, especially membrane proteins and protein complexes, have larger molecular weight and then unit cells of their crystals have larger volume, which is out of range of measurable unit cell volume for conventional diffractometers. Therefore, our group had designed the diffractometer which can cover such crystals with large unit cell volume (target lattice length: 250 Å). This diffractometer is dedicated for protein single crystals and has been proposed to be installed at J-PARC (Japan Proton Accelerator Research Complex). Larger unit cell volume causes a problem to separate spots closer to each other in spatial as well as time dimension in diffraction images. Therefore, our proposed diffractometer adopts longer camera distance (L2 = 800mm) and selects decoupled hydrogen moderator as neutron source which has shorter pulse width. Under the conditions that L1 is 33.5m, beam divergence 0.40and crystal edge size 2mm, this diffractometer is estimated to be able to resolves spots diffracted from crystals with a lattice length of 220 Å in each axis at d-space of 2.0 Å. In order to cover large neutron detecting area due to long camera distance, novel large-area detector (larger than 300mm × 300mm) with a spatial resolution of better than 2.5mm is under development. More than 40 these detectors plan to be installed, providing the total solid angle coverage of larger than 33%. For neutron guide, ellipsoidal supermirror is considered to be adopted to increase neutron flux at the sample position. The final gain factor of this diffractometer is estimated to be about 20 or larger as compared with BIX-3/4 diffractometers operated in the research reactor JRR-3 at JAEA (Japan Atomic Energy Agency) [1,2].

Development of a Dynamic CT System for Neutron Radiography and Consecutive Visualization of Three-Dimensional Water Behavior in a PEFC Stack

A dynamic CT system was developed for visualization of consecutive three-dimensional water behavior in a PEFC stack for neutron radiography. The system is composed of a neutron image intensifier and a C-MOS high speed video camera. An operating stack with three cells based on the Japan Automobile Research Institute standard was visualized using the neutron radiography system at a research reactor JRR-3 in Japan Atomic Energy Agency. The dynamic water behavior in channels in the operating PEFC stack was clearly visualized every 15 seconds by using the system. The water amount in each cell was evaluated by the CT reconstructed images. It was shown that a cell voltage decreased gradually when the water increased and increased rapidly when the water was evacuated. It was estimated that the power generation stopped when the channel of a cell was partly filled with the water because the air supply was blocked to a cell in the stack.

A combined method of small-angle neutron scattering and neutron radiography to visualize water in an operating fuel cell over a wide length scale from nano to millimeter

In order to visualize water generated in an operating polymer electrolyte fuel cell (PEFC), a neutron radiography (NR) apparatus, composed of a scintillator, optical mirrors and a CCD camera, was installed at a sample position of the focusing and polarized neutron small-angle scattering (SANS) spectrometer (SANS-J-II) at research reactor JRR-3 at Japan Atomic Energy Agency, Tokai, Japan. By combining SANS and NR, we aim to cover a wide length scale from nanometer to millimeter. The new method succeeded in detecting a spatial distribution of the water generated in individual cell elements; NR detected the water in a gas diffusion layer and a flow field, whereas SANS quantitatively determines the water content in a membrane electrode assembly (MEA).

Living Polymerization Induced Macro- and Microdomain Investigated by Focusing Ultra-small-angle Neutron Scattering

By utilizing a biconcave refractive neutron lens (MgF2) 5-inch size & high resolution position sensitive area photomultiplier with scintillator (ZnS), we constructed a focusing ultra-small-angle neutron scattering (USANS) spectrometer (SANS-J-II) at research reactor JRR3, Tokai, Japan. SANS-J-II can successfully reach to qmin=0.0003 Å−1, where q (=4πsin(θ)/λ) is the magnitude of scattering vector given by wavelength λ and scattering angle 2θ, and simultaneously cover conventional small-angle neutron scattering (SANS) region to q=0.004 Å−1. Focusing USANS, thus realized, plays an important role to investigate the time-evolution of hierarchically ordered structures in the living radical polymerization solution, preparing poly(methyl methacrylate)-block-polystyrene (PMMA-b-PS). In the reaction process to synthesize a PS block chain from the end of PMMA block chain, we found the interplay between macro- and microphase separation. SANS at q>0.001 Å−1 determined time-evolving microdomain structures; as the polymerization proceeds, (i) first by order-disorder transition, a lamellar microdomain appears and (ii) second by order-order transitions, the morphologies of microdomains change to PMMA cylinder and successively to PMMA sphere. USANS at q<0.001 Å−1, exhibiting power law scattering (∼q−α) due to macrophase separation between PMMA-b-PS and PS homopolymer (appeared as by product). The exponent α varies from 4 to 2, reflecting a grain boundary of macrodomain rich-in PMMA-b-PS; when a lamellar microdomain appears, Porod law gives α=4, whereas when cylinder and sphere appear, α=2, due to inhomogeniety of the microdomain spatial distribution of the microdomains.

Focusing and polarized neutron small-angle scattering spectrometer (SANS-J-II). The challenge of observation over length scales from an ångström to a micrometre

SANS-J (a pinhole small-angle neutron scattering spectrometer at research reactor JRR3, Tokai, Japan) was reconstructed as a focusing and polarized neutron small-angle scattering spectrometer (SANS-J-II). By employing focusing lenses of a biconcave MgF2 crystal or of a sextupole permanent magnet and a high-resolution photomultiplier, the minimum accessible magnitude of the scattering vector qmin was improved from 3 × 10−3 Å−1 to an ultra-small-angle scattering (USAS) of 3 × 10−4 Å−1. Compared with a Bonse–Hart double-crystal method, the advantages of focusing USAS are the efficient detection of anisotropic USAS with an area detector, an improvement in q resolution Δq/q at conventional magnitudes of the scattering vector q ~ 10−3 Å−1 and a gain in neutron flux in the conventional q region of q ~ 10−3 Å−1.

The Challenge of Observation on Livings Things by Employing an Ultra Small-Angle Neutron Scattering Method

To address the question as to how small-angle scattering is effectively applied to the cell, i.e., ahierarchically ordered system comprising multi-components of macro and small molecules, the size ofwhich ranges from 100 μm to several μm, we reconstructed SANS-J (pinhole small-angle neutronscattering spectrometer at research reactor JRR3, Tokai) to focusing & polarized neutron small-anglespectrometer (SANS-J-II), by employing focusing neutron lenses and high resolution photomultiplier.Consequently, an accessible minimum wave number qmin was improved from 3×10-3 A-1 to mediumultra-small angle scattering of 3×10-4 A-1. The focusing USANS method, thus developed, is crucialto fill the gap in wave number q between those covered by a double crystal method and by a conventionalpin-hole method.

Tandem analyzer crystals system doubles counting rate for Bonse–Hart ultra-small-angle neutron-scattering spectrometer

A new tandem analyzer crystals system was introduced on Bonse–Hart ultra-small-angle neutron-scattering spectrometer at research reactor JRR-3, Tokai, Japan. Conventional Bonse–Hart setup consumes a considerable time to measure a scattering profile of whole q range (2×10 −4 nm −1< q<7×10 −2 nm −1, where q denotes magnitude of scattering vector) due to the step scan system, in which the scattered neutrons from the sample and having different q are measured step by step. To overcome this difficulty two analyzer channel-cut silicon perfect crystals were settled in tandem and each of them diffracted the scattering of different q. In consequence, a simultaneous detection at two different q positions was realized and the measurement time was reduced to half.

Focusing and polarized neutron ultra-small-angle scattering spectrometer (SANS-J-II) at Research Reactor JRR3, Japan

By employing focusing lenses of sextupole permanent magnet and biconcave MgF 2 crystal, and high-resolution photomultiplier, SANS-J (pinhole small-angle neutron scattering spectrometer at research reactor JRR3, Tokai ) was reconstructed to focusing and polarized neutron ultra-small-angle scattering spectrometer (SANS-J-II). Consequently, an accessible minimum wave number q min was improved from 3×10 −3 Å −1 to 3×10 −4 Å −1. Furthermore, we added 3He sub-detectors with an analyzer super mirror at a sample position. With this setup, we perform polarization analysis at high q (>0.2 Å −1) in order to quantitatively discriminate spin incoherent scattering from hydrogen or to perform spin contrast variation, by a dynamic nuclear polarization method (>0.2 Å −1).

D108 中性子トモグラフィによる稠密バンドル内二相流の可視化と計測

Neutron tomography thermal-hydraulic measurement technique is originally developed based on the neutron radiography, computed tomography and two-phase flow measurement techniques. The purpose of the developing is to measure the void fraction distribution in the Reduced-Moderation Water Reactor which is a water-cooled breeder reactor designed by the JAERI as a future reactor. We have visualized and measured the void distribution of air/water two-phase flow and boiling flow in tight-lattice rod bundles. We used the research reactor JRR-3 as a neutron source. Three-dimensional data can be obtained in order to evaluate the numerical analysis codes. In this manuscript, the neutron tomography system, comparison between the reconstruction methods of computed tomography and examples of the measured two-phase flow data which was taken in the 7 rod bundle with a gap between rods of 1.0mm.

Achievement of world's best performance in Japanese LWR, through the successful development on fuels and materials

Research and development on fuel and cladding materials in the past 40 years, which led to the excellent performance of today's Japanese LWR are overviewed. Most of the programs for the development of LWR fuels and Zircaloy cladding tube have been conducted by the author, starting from the metal uranium fuel rod for the research reactor JRR-3, then going on to the domestic production of fuel for the power-demonstration reactor JPDR. LWR fuel fabrication has been successfully performed on these bases together with the research and development work on Zircaloy tube fabrication technology among metal industries. Fundamental works and co-operative studies among specialists from every related field have been effectively combined with the development works among industry, which contributed to the achievement of the world's top level fuel and thus to the excellent performance of 36 LWRs in Japan, today.

Core Thermohydraulic Design with 20% LEU Fuel for Upgraded Research Reactor JRR-3

Core Thermohydraulic Design with 20% LEU Fuel for Upgraded Research Reactor JRR-3

Core thermohydraulic design with 20% LEU fuel for upgraded research reactor JRR-3.

This paper presents the outline of the core thermohydraulic design and analysis of the research reactor JRR-3, which is to be upgraded to a 20 MWt pool-type, light water-cooled reactor with 20% low enriched uranium (LEU) plate-type fuel. For the condition of normal operation, the upgraded JRR-3 core is planned to be cooled by two cooling modes of forced-convection at high power and natural-convection at low power. The major feature of core thermohydraulics is that at the forced-convection cooling mode the core flow is a downflow, under which fuel plates are exposed to a severer condition than an upflow in cases of operational transients and accidents. The core thermohydraulic design was, therefore, done for the condition of normal operation so that fuel plates may have enough safety margins both against the onset of nucleate boiling (ONR) not to allow the nucleate boiling anywhere in the core and against the departure from nucleate boiling (DNB). The safety margins against ONB and DNB were evaluated. The ...

Experimental study of differences in DNB heat flux between upflow and downflow in vertical rectangular channel.

Experiments were carried out on DNB (Departure from Nucleate Boiling) heat flux for both upflow and downflow in a rectangular vertical channel simulating a subchannel in the fuel element of the research reactor JRR-3, which is scheduled to be upgraded at 20MWt with 20% low enriched uranium (LEU) fuel. The experiments were carried out for the conditions of pressure and velocity which are important for the safety design of the JRR-3. With the investigation of the data of the present experiment along with already existing data for both rectangular channels and other channels, a scheme of DNB heat flux correlations was obtained for upflow and downflow. With the all available data, the errors of the correlations adopted in this scheme were so evaluated as to utilize these results in the safety analysis of the JRR-3. This scheme includes a new correlation of DNB heat flux for upflow and the identification of a region of high coolant flow rate where no remarkable differences in the DNB heat flux are observed bet...