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[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

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[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

[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

[en] Streamers are a generic mode of electric breakdown of large gas volumes. They play a role in the initial stages of sparks and lightning, in technical corona reactors and in high altitude sprite discharges above thunderclouds. Streamers are characterized by a self-generated field enhancement at the head of the growing discharge channel. We briefly review recent streamer experiments and sprite observations. Then we sketch our recent work on computations of growing and branching streamers, we discuss concepts and solutions of analytical model reductions and we review different branching concepts and outline a hierarchy of model reductions

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