[en] A method is introduced for determining streaming paths through a non-multiplying medium. The concepts of a ''response continuum'' and a pseudo-particle called a contribution are developed to describe the spatial channels through which response flows from a source to a detector. An example application of channel theory to complex shield analysis is cited

[en] During the period September 1974--February 1975, a detailed investigation was undertaken on the neutron streaming from reactor shielding observed on board the N.S. Mutsu. Tests were carried out with the reactor at partial power (83 KWth = 0.23% of full rating, under which condition the radiation distribution was measured in the space outside the primary and secondary shields, for the purpose of determining the cause of the abnormal radiation observed during the preceding low-power tests. The results derived from these measurements, as well as analytical calculations, indicated that the abnormal radiation resulted from neutrons leaking out through the gap that existed between the pressure vessel and the primary shield. Based on the foregoing results, a plan has been adopted for modifying the shielding arrangement, by adding new shielding to close the gap referred to above and further supplementing and modifying both the upper and lower parts of the reactor shielding structure

[en] A series of shielding mock-up experiments was performed at JRR-4, a swimming pool type reactor, of Japan Atomic Energy Research Institute (JAERI) to obtain the necessary experimental data and the sufficiently accurate method of calculation adopted for the modification of the Mutsu primary shield. Analyses for the experiments were carried out by using of the S/sub n/ codes, ANISN and TOWTRAN. The two dimensional calculations were performed with the P₁ - S₈ approximation. The neutron streaming through the annular gap between the pressure vessel and the primary shield has been confirmed to be estimated from the present method of calculation. The agreement between the calculated and the measured values is generally in about a factor of 2 to 4

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[en] Highlights of the recent progress in understanding the problem of high speed stream evolution with increasing heliocentric distance are reviewed. Crucial to this understanding are the measurements made in the inner solar system by Helios and the outer solar system by Pioneers 10 and 11. When coupled with observations at 1 AU these measurements allow a testing of current theoretical models of stream evolution. 21 references

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[en] A Albedo-Monte Carlo method, employing the Albedo concept, for the analysis of radiation streaming through rectangular concrete duct in nuclear facilities is proposed. The numerical results, in terms of dose attenuation factor, using fast neutron source are compared to experimental data and are in good overall agreement. The use of the Albedo-Monte Carlo method in 3 dimensional geometry can be a powerful technique for saving computer time and is suitable for a quick estimation and, especially in the calculation for preliminary design of shielding structure, is more pronounced than that of the other methods in the effective analysis of radiation streaming problems. (Author)

[en] A spatially variable coronal expansion, when coupled with solar rotation, leads to the formation of high speed solar wind streams which evolve considerably with increasing heliocentric distance. Initially the streams steepen for simple kinematic reasons, but this steepening is resisted by pressure forces, leading eventually to the formation of forward-reverse shock pairs in the distant heliosphere. The basic physical processes responsible for stream steepening and evolution are explored and model calculations are compared with actual spacecraft observations of the process. Solar wind stream evolution is relatively well understood both observationally and theoretically. Tools developed in achieving this understanding should be applicable to other astrophysical systems where a spatially or temporally variable outflow is associated with a rotating object

[en] The pressure vessel of Mutsu is enclosed by a primary shield consisting of a laminated iron-water shield padded with lead (lower primary shield), atop which is placed concrete shields (middle and upper primary shield). Between the primary shield and the pressure vessel, there is an air gap through which coolant piping of 23.1 cm outside diameter padded with thermal insulation penetrates from the pressure vessel into and through the concrete shield. The radiation from the reactor core streams into the air gap, and then into the coolant pipe. A mock-up experiment to examine the radiation attenuation along the coolant pipe penetration through the pressure vessel wall and concrete shield was performed in the JRR-4 swimming pool reactor. The radiation was measured along the air gap and along the coolant pipe. Neutron measurements were made in terms of the reaction rates of ⁵⁸Ni(n,p) ⁵⁸Co and ¹⁹⁷Au(n,γ)¹⁹⁸Au. Lithium fluoride thermoluminescence dosimeters were also used to obtain neutron flux and gamma-ray dose rates. For analyzing the experimental results, radiation transport calculations were performed by means of the S/sub n/ code TWOTRAN. The annular air gap around the pressure vessel was treated in two dimensions. The resulting angular flux was adapted to calculations covering the coolant pipe, through conversion of coordinates accompanied to bootstrap treatment. Comparisons made between calculated results and experimental data indicated that the preset data and design method are adequate for estimating the radiation leakage with satisfactory accuracy