The effect of neutron heating on the burn characteristics of inertial confinement fusion pellets is investigated by applying the calculational method developed in an earlier paper (Part I). The basic equations are time-dependent transport equations for fusion neutrons and recoil ions, being written in terms of the modified Eulerian coordinates originally proposed by Wienke (1974). After incorporating these equations into the one-dimensional hydrodynamics code MEDUSA, burn simulations are made for isobaric D-T pellets models compressed to 1, 000 times the liquid density. It is found that in reactor-grade pellets, the inclusion of neutron heating decreases the fuel gain from the values obtained by neglecting the neutron heating. Calculations neglecting the energy transport by recoil ions overestimate the neutron energy deposition to plasma ions. The energy spectrum of neutrons emitted out of a typical D-T burning pellet is also shown. These neutrons contain fast components whose energies reach more than 20MeV.

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In the initial stage of reflood phase of PWR-LOCA, quasi-stable surface of water is established in a core. Spurious pressure spikes are often encountered when two-fluid model codes are used to analyze two-phase flow dynamics in the initial stage of reflood phase. These pressure spikes are not observed in experiments. Since these pressure spikes affect other variables such as void fraction, it is important to eliminate these pressure spikes to get physically reasonable results with two-fluid model codes. In the present study, it is quantitatively clarified that these pressure spikes result from numerical acceleration loss of liquid above the surface of water where liquid does not exist. Furthermore, a method is developed to mitigate the acceleration loss of liquid above the surface of water. It is confirmed that this method is effective to eliminate these pressure spikes without losing benefits of the present two-fluid model codes.

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In general, functional tests are required periodically to detect failures in standby equipment as a means of assuring their availability on demand. However, these functional tests may have an adverse impact on the system availability, because of their potential negative effects such as unavailability at the period of testing, increase of failure rate resulting from excessive wear due to testing. Therefore, in principle, there is an optimal test interval for each standby system. As it normally is difficult to determine analytically the optimal test interval for the real systems in the industry, we therefore introduce the Monte Carlo simulation method for this purpose. In this paper, a one-component system was chosen firstly to introduce the concept of test interval optimization as well as the feasibility of using Monte Carlo simulation. Secondly, a real system in the nuclear power plant, Standby-liquid-control system, was studied using Monte Carlo simulation technique. The promising results obtained confirm the concept and methodology used.

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This paper introduces the present status of the comprehensive material performance database for nuclear applications, which was named JAERI Material Performance Database (JMPD), and examples of its utilization. The JMPD has been developed since 1986 in JAERI with a view to utilizing various kinds of characteristic data of nuclear materials efficiently. Management system of relational database, PLANNER, was employed, and supporting systems for data retrieval and output were expanded. In order to improve user-friendliness of the retrieval system, the menu selection type procedures have been developed where knowledge of the system or the data structures are not required for end-users. As to utilization of the JMPD, two types of data analyses are mentioned as follows :
(1) A series of statistical analyses was performed in order to estimate the design values both of the yield strength (Sy) and the tensile strength (Su) for aluminum alloys which are widely used as structural materials for research reactors.
(2) Statistical analyses were accomplished by using the cyclic crack growth rate data for nuclear pressure vessel steels, and comparisons were made on variability and/or reproducibility of the data between obtained by JK-increasing and 1K-constant type tests.

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The sorption of ¹³⁷Cs by soil simulated from its main compositions of clay (Ca-saturated bentonite), organic matter (humic acid) and sand, as well as their relative contributions have been studied. All these sorbents revealed linear sorption isotherm under the initial concentration ranging from 10^-12 to 10^-10 mol/l of ¹³⁷Cs. Therefore, surface phenomena, adsorption and/or ion exchange, dominate the sorption of ¹³⁷Cs on soil.
In the experiments of mixed sorbents, humic acid was added to a mixture of bentonite and standard sand. It was found that distribution coefficient K_d decreased nonlinearly with the weight fraction of humic acid. The conclusion was that some sorption sites of bentonite were blocked by humic acid. A model using a block function with an exponential form was proposed as a means to explain the phenomena observed in this experiment. Such phenomena should be taken into account when assessing or selecting the disposal site of radwaste.

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The process of ion collection from a plasma produced between parallel plates by pulsed lasers was simulated with a two-dimensional numerical code. The trajectories and velocities of ions in the electric field are calculated using Newton's equation of motion. Assuming the Boltzmann relation for electrons, the electric field is calculated by solving numerically the Poisson equation. The numerical results for the time development of the ion collection are shown to be in good agreement with experimental results.

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Electron Paramagnetic Resonance (EPR) and optical spectra of uranium(V) species were observed in both processes of photo- and electrolytic reduction of UO₂(NO₃)₂-2tributylphosphate (TBP) in 80%TBP-n-dodecane solution. The formation of U(V) species was detected by an optical spectrum (_max : 770, 970 and 1, 420 nm). EPR signal with the value of g-factor 2.3 and a linewidth of approximately 1, 100 Gs was observed during the electrolytic reduction. On the other hand, during the photoreduction the signal with the value of g-factor 1.94 was observed and there was found a superhyperfine structure with the intensity ratio of 1 : 2 : 1, that is caused by the superhyperfine coupling with nuclear spin, I=1/2, of the strongly coordinated 31P to the central uranium through oxygen atom. The superhyperfine coupling constant was estimated to be 27 Gs. Moreover, the signal with the value of g-factor 2.00 due to an organic radical was observed. The residue after the thermo-gravimetric analysis of UO₂(NO₃)₂-2TBP was identified as α-UP₂O₇ by the powder X-ray diffraction analysis, indicating the strong coordination of TBP to the central uranium atom.

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A high power CW (Continuous Wave) test electron linac was designed to develop a higher power linac to transmute radioactive wastes. The test linac is energized by two 1.2 MW CW L-band klystrons to produce an electron beam with the energy of 10 MeV and current of 100 mA. The average beam power is 200 kW1 MW for the duty factor 20100%;.
In designing such a high power linac, authors selected a traveling-wave accelerator with TWRR (Traveling Wave Resonant Ring). This is to enhance the threshold current of BBU (Beam Break-Up) and to get high accelerator efficiency that results from the low value of attenuation constant τ and high field multiplication factor M which are permitted only with T WRR.
A kind of efficient cooling structure is adopted to an accelerator structure in order to disperse the generated heat by RF (Radio Frequency). The variational method is used to calculate the sizes and parameters of the disk-loaded accelerator structure employed. There is a discrepancy of the order of a few hundredth of one percent between the calculated sizes and the experimental ones. The M determined in the design agreed well with those measured in low and high power tests.

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A television imaging system for fast neutron radiography (FNR-TV) developed using the fast neutron source reactor YAYOI was applied to the baby-cyclotron based fast neutron source to get images of thick objects quickly. In the system the same technique as a current television imaging system of thermal neutron radiography was applied, while the luminescent converter was used to detect fast neutrons.
Using the CR39 track etch method it took about 7h to get an image, while the FNR-TV only 20 s enough for taking the same object. However the FNR-TV imaging result of the simulation model of a large explosive device for the space launch vehicle of H-2 type was not so good as the image taken with the CR39 track etch method. The reason was that the luminescence intensity of the FNR-TV converter was a quarter of that in the YAYOI.

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A prototype neutron area monitor with a silicon semiconductor detector has been developed which has the energy response of 1 cm dose equivalent recommended by the ICRP-26. Boron and proton radiators are coated on the surface of the silicon semiconductor detector. The detector is set at the center of a cylindrical polyethylene moderator. This moderator is covered by a porous cadmium board which serves as the thermal neutron absorber. Neutrons are detected as u-particles generated by the nuclear reaction ¹⁰B(n, α)⁷Li and as recoil protons generated by the interaction of fast neutrons with hydrogen.
The neutron energy response of the monitor was measured using thermal neutrons and monoenergetic fast neutrons generated by an accelerator. The response was consistent with the 1 cm dose equivalent response required for the monitor within ±34% in the range of 0.02515 MeV.

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Failure propensities of Zircaloy-4 cladding tube internally pressurized with Ar gas containing iodine and iodine plus each of other chemical species were examined at 360°C, to study the effect of corrosive fission products (FPs) on the integrity of spent nuclear fuel rods during dry storage, and also to assess the capability of preventing the spent fuel rod degradation.
The iodine stress corrosion cracking (SCC) of Zircaloy tube occurred in the long time/low stress exposure tests at stresses much lower than the conventional "threshold stress", with considerably large strains at failure. The addition of cesium to iodine perfectly suppressed the SCC. It is inferred from these results that the degradation of spent fuel rods induced by corrosive fission products is unlikely during dry storage. Even if iodine alone should take effect, a proper strain limit could prevent spent fuel rods from incurring iodine induced effects because of considerably large strains necessary for iodine SCC of Zircaloy tube at low stresses.

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