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The large-scale modification of the JRR-3 was carried out for the years 1985–1990 to meet the demands for higher performance and greater utilization. After the modification, the fuel was converted to the high-density silicide fuel for upgrading the fuel cycle performance in 1999. The exchange of the thermal neutron guide tube to the super-mirror tube has been advancing since 1998 for upgrading thermal neutron beams. In the JRR-4, the conversion to the LEU silicide fuel, the renewal of some reactor systems, and the installation of a medical irradiation facility, etc. were carried out for the years 1996–1998. The JRR-3 will be utilized over the future as a complementary neutron source with the high-intense spallation neutron source, which is being constructed in the Japan Atomic Energy Research Institute. The JRR-4 will contribute continuously to the advancement of the medical technology.

For test and research reactors, the core conversion to low-enriched uranium fuel is required from the viewpoint of non-proliferation of nuclear weapon material. Improvements of core performance are also required in order to respond to recent advanced utilization needs. In order to meet both requirements, a high-performance fuel element of high uranium density with Cd wires as burnable absorbers was adopted for JMTR core conversion to low-enriched uranium fuel.From the result of examination of an adaptability of a few group constants generated by a conventional transport-theory calculation with an isotropic scattering approximation to a few group diffusion-theory core calculation for design of the JMTR high-performance fuel element, it was clear that the depletion of Cd wires was not able to be predicted accurately using group constants generated by the conventional method. Therefore, a new generation method of a few group constants in consideration of an incident neutron spectrum at Cd wire was developed. As the result, the most suitable high-performance fuel element for JMTR was designed successfully, and that allowed extension of operation duration without refueling to almost twice as long and offer of irradiation field with constant neutron flux.

The austenitic stainless steels of type 304 and type 316 and the precipitation hardened type 630 stainless steel were irradiated to doses ranging from 5 × 1024 to 1.2 × 1026 at 323 K in the Japan Materials Testing reactor (JMTR). Tensile and fracture toughness tests have been carried out at 293 K. Type 304 and 316 steels in the solution annealed condition hardened by irradiation to about 700 MPa. Fracture toughness values for these steels decreased with dose. Only a small hardening occurred after irradiation for cold worked type 304 and precipitation hardened type 630 steels. The effect of irradiation on the fracture surfaces was small.

TiNi and TiPd shape memory alloys (SMA) reveals good workability and shape memory properties and these SMAs seem to be one of hopeful functional materials in a severe irradiation field. The effects of irradiation induced residual strain on the deformation processes of TiNi and TiPd SMAs after neutron irradiation with fluences ( E > 1 MeV) up to 3.9 × 10 24 m −2 at Japan Materials Testing Reactor (JMTR) were investigated by the remote controlled X-ray diffraction measurement. Residual strains of TiNi SMAs took place over damage of 0.1 dpa and the strains were not completely removed by post-irradiation annealing at 473, 523 and 573 K. On the other hand, residual strains of TiPd SMAs scarcely occurred after irradiation, and furthermore, the TiPd SMA seems to be an irradiation-resistant material. This may be explained by a difference between the irradiation response of a parent phase and that of a martensitic phase to neutron irradiation. Deformation processes of SMAs are associated with stress fields generated by irradiation in a parent phase with B2 type ordered structure or in a martensitic phase with 2H and 9R type close-packed structures.

The effect of intravenous infusion of NCO-700, a new synthetic inhibitor of thiol protease, on infarct size and regional myocardial blood flow was studied in 36 anesthetized open-chest dogs. Dogs underwent either 1 hr or 3 hr of left anterior descending artery occlusion followed by reperfusion. Animals in the treated groups received a single bolus intravenous injection of NCO-700 (20mg/kg) before reperfusion followed by a 2-hour infusion of the same dose. Regional myocardial blood flow was determined serially by the hydrogen clearance method. At 12 hr after starting reperfusion, the zone at risk was defined by dye injection and the Zone of necrosis was subsequently determined by triphenyltetrazolium chloride staining of left ventricular slices. There were no major hemodynamic differences between control and treated groups. In the 1-hour occlusion groups, infarct size (as a percentage of the zone at risk) was markedly reduced in NCO-700 treated animals (n=10) compared with control animals (n=10) (9±3% vs 39±7%, p

Nine high grade gliomas (5 glioblastomas and 4 anaplastic astrocytomas) were treated with BSH-based intaoperative boron neutron capture therapy (IOBNCT). BSH (100 mg/kg body weight) was intravenously injected, followed by single fraction irradiation using the mixed thermal/epithermal beam of Japan Research Reactor 4. The blood boron level at the time of irradiation averaged 29.9 (18.8-39.5)microg/g. The peak thermal neutron flux as determined by post-irradiation measurements varied from 1.99 to 2.77x10(9) n cm(-2)s(-1). No serious BSH-related toxicity was observed in this series. The interim survival data in this study showed median survival times of 23.2 months for glioblastoma and 25.9 months for anaplastic astrocytoma, results which are consistent with the current conventional radiotherapy with/without boost radiation. Of the 4 residual tumors, 2 showed complete response (CR) and 2 showed partial response (PR) within 6 months following BNCT. No linear correlation was proved between the dose and the occurrence of early neurological events. The maximum boron dose of 11.7-12.2 Gy in the brain related to the occurrence of radiation necrosis. The clinical application of a mixed thermal/epithermal beam and JRR-4 facilities on BSH-based IOBNCT proved to be safe and effective in this series.

A medical irradiation facility for Boron Neutron Capture Therapy (BNCT) was installed at JRR-4 in June 1998.

A new medical irradiation facility has been installed in JRR-4. It was designed to permit selection of neutron energies from thermal neutron to epithermal range by changing the thickness of the heavy water layers. This facility then allows us to continue the thermal neutron irradiation protocol now performed in JRR-2, and to initiate the research and development of an epithermal neutron beam more suitable for deep brain tumor. Dosimetric measurements in the deep brain are not possible; therefore software simulation is being developed to estimate the dosimetry in these structures. The current status of the development of this new Computational Dosimetry System (JCDS) at JAERI will be described.

After the shutdown of the former JRR2, which had been used for boron neutron capture therapy (BNCT) in clinical cases, in summer 1998 a new neutron irradiation facility (JRR4) was installed as a medical reactor for BNCT at the Japan Atomic Energy Institute (JAERI), Tokai, Ibaraki. This JRR4 facility is a conversion of the former high-fuel uranium-loaded nuclear reactor to low-fuel uranium-loaded reactor. This facility is designed mainly for BNCT. There are medical facilities and equipment including an operating room and fully installed anesthetic apparatus to allow safe and effective intraoper-ative BNCT. An outline of this facility is presented in this chapter.

A collaborative determination of the major components of silver brazing filler metals (Ag–Cu–Zn–Cd, Ag–Cu–Zn–Ni, and Ag–Cu–Zn–Sn alloys) by inductively coupled plasma atomic emission spectrometry (ICP-AES) was conducted. The classical wet methods of gravimetry and titrimetry were also investigated for comparison, most of which are provided by Japanese Industrial Standards (JIS). Results of instrumental and classical analyses using a simple dissolution procedure with nitric acid showed excellent trueness and precision amongst all laboratories and for all alloys except those containing tin. The tin-containing alloy had to be dissolved, suppressing precipitation of the sparingly soluble hydrous tin(IV) oxide. Dissolution with mixtures of nitric and sulfuric acid gave the most satisfactory results without precipitation, thus enabling an accurate determination that favourably compared to the classical wet results. Finally we have evaluated the ICP-AES method and a hybrid method with gravimetry and ICP-AES according to the precision required, and found them to be suitable for standardization.

Right ventricular endomyocardial biopsies were performed in 34 patients with hypertrophic cardiomyopathy (HCM) and in 26 with dilated cardiomyopathy (DCM). The degree of myocardial interstitial fibrosis and that of myocardial fiber disarray were assessed from light-microscopic samples. Cell diameters were measured from the light-microscopic samples. For electron-microscopic investigation, a semiquantitative score system derived from Sekiguchi was used. The following results were obtained.1) Interstitial fibrosis was more prominent in DCM, while myocardial fiber disarray was more so in HCM.2) There was no correlation between myocardial cell diameter and ultrastructural alterations in HCM and DCM.3) In HCM, myocardial fiber disarray was correlated with ultrastructural alterations.4) In DCM, the left ventricular ejection fraction was negatively correlated with ultrastructural alterations.5) In HCM, there was no correration between interventricular septal thickness and myocardial cell diameter.

The clinical applicability and usefulness of diagnostic procedures in nuclear cardiology have been briefly reviewed, and personal experiences in this field were presented.

The phase transition of KH 3 (SeO 3 ) 2 , was studied by ultrasonic velocity measurements at 5 and 10 MHz together with X-ray diffraction measurement and pyroelectric examination. It was clarified that the crystal below the transition point ( T c ) is nonferroelectric and belongs to the centrosymmetric space group P2 1 / b . All of the elastic stiffnesses c i j were determined front the velocity data. The phase transition accompanies with a large phonon softening only in the c 44 mode. It was shown that the ferroelastic behavior above and below T c can well be explained by a phenomenological theory.

Myocardial T1-201 Washout rates (WORs) after exercise stress were measured in 15 normal subjects and 67 patients with coronary artery disease (CAD) or chest pain syndrome and the usefulness of WOR for the detection of CAD was studied.Myocardial tomograms were obtained both immediately after exercise and 3 hours later using a rotating gamma camera in 15 normal subjects and 67 patients. After low-pass filtering, images were reconstructed into short-axis, horizontal long-axis and vertical long-axis tomograms and visually interpreted. By using short-axis tomograms, left ventricle WORs were expressed as circumferential profile curves at the apex, center and base of the ventricle. Lower normal limits of the WOR were set at 2 SDs from the mean of the normal subjects. The combination of visual interpretation of SPECT with WOR increased the sensitivity of detection of CAD from 8.3% to 66.7% in patients with three-vessel CAD without losing specificity.WOR after exercise stress is believed to be a useful method of detecting multivessel CAD.