Journal of Nuclear Science and Technology

Dependence of Effective Resonance Integrals on Moderator Slowing Down Properties

M. H. McKAY

1964 Volume 1 Issue 8 Pages 279-283
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.279

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Effective resonance integrals calculated by means of the usual approximations do not have the dependence on moderator slowing down properties which is shown by "exact" calculations.
In this paper a modified effective resonance integral is defined in such a way as to fit the exponential form of the resonance escape probability. Application of a generalised "intermediate-resonance" approximation to this modified effective resonance integral shows a dependence on the slowing down properties of the moderating nuclei in good agreement with "exact" calculations.

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Relocation of Fission Products and Pu in Irradiated UO₂ Pellet

Noboru OI, Tadao OHNO, Keiji NAITO

1964 Volume 1 Issue 8 Pages 284-289
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.284

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Distribution of fission products (¹⁴⁴Ce, ¹⁰⁶Ru, ¹³⁷Cs, ⁹⁵Zr-⁹⁵Nb and 85Kr) and Pu were examined in UO₂ pellets which were irradiated at high temperature (-3, 000 ?? ). Two capsules, each containing six natural uranium UO₂ pellets were irradiated in GETR at 0.05 and 0.10% burnup respectively. The UO₂ pellets were completely fused into a single rod, and a big void was formed along the length of the rod as a result of the high temperature. Analysis was made by direct γ-scanning along the length and across sections of the rods, as well as by samples scraped off from the rods. Pu and Ru were found to be distributed fairly regularly, while Cs was markedly concentrated at both ends of the rod where the temperature was lower than the middle part. Zr-Nb was found to be concentrated in the inner portions which were the hottest parts. About 2% of the ⁸⁵Kr remained in a sample of 0.05% burnup, though only a trace amount in that of 0.1% burnup. Distribution of γ-activity along the length of the rods was quite irregular, having wide depleted sections, which might be explained from the exposure to high temperature.

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Temperature Coefficient of Neutron Multiplication Factor

Kazuhiko INOUE

1964 Volume 1 Issue 8 Pages 290-297
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.290

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A method for calculating the temperature coefficient of the neutron multiplication factor in an infinite homogeneous medium is investigated for the purpose of discussion of the temperature coefficient for thermal reactors. Two kinds of expression for the temperature coefficient of the neutron multiplication factor are derived and given in terms of solutions of the integral equations which describe neutron balance in a stationary homogeneous system. The results of numerical calculations performed with the exact formula derived are compared with those based on the Maxwellian distribution model. The present method is recommended for accurate calculation, particularly in the case of strong non-1/v cross sections. For the case of weak non-1/v cross sections, the Maxwellian distribution approximation suffices for obtaining fairly good results.

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Surface Diffusion Phenomena in Gaseous Diffusion, (II)

Separation of Binary Gas-mixtures

Kunio HIGASHI, Hiroo ITO, Jun OISHI

1964 Volume 1 Issue 8 Pages 298-304
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.298

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The effect of surface diffusion flow on the separation by gaseous diffusion is discussed.
Previously the authors proposed a new model for surface diffusion mechanism and derived therefrom an expression of surface diffusion coefficient. Applying this expression it will be possible to predict the degree of separation in gaseous diffusion accompanied by surface diffusion flow. This is verified from theoretical and experimental results for the separation of a mixture of n-butane and propane. It is notable that the heavier component, n-butane is enriched in the lower pressure side, contrary to the well-known separation effect of Knudsen which predicts that the lighter component should always be enriched on the lower pressure side. It is also confirmed from experimental results on the enrichment of 15N on natural nitrogen gas that Knudsen's formula is perfectly applicable to analysis of the separation of unadsorbable gas-mixtures.

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Beta-Spectroscopy of Low Level Samples by a Coincidence Type Scintillation Spectrometer

Eiichi TANAKA, Toshiyuki HIRAMOTO, Takashi MARUYAMA

1964 Volume 1 Issue 8 Pages 305-310
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.305

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A coincidence type β-ray scintillation spectrometer of simple construction and its performance are described. This instrument is suitable for measuring extremely low β-activity in samples. The background of the detector is, in principle, lower than of a conventional low background G-M counter of anti-coincidence type. The instrument makes it possible to determine maximum β-ray energies and to identify nuclides with activity as low as 1 dpm. The minimum detectable activity considered from the view point of nuclide identification is also discussed.

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Silicon Surface Barrier Detector

Seiichiro GOTOH, Zinzaburo TAKAGI

1964 Volume 1 Issue 8 Pages 311-315
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.311

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A method has been established for producing silicon surface barrier detectors having an energy resolution of 0.7% for 5.3 MeV a particles, and which are stable for long periods of time. The fabricated detector has been proved to possess a depletion layer as thick as 200μ and a surface layer with energy loss less than 15keV for 5.3MeV a particles. The stability of the detector was also tested and it was found to be stable for at least 2-3 months.

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A Guide to Release-Rate of Iodine-131 from Stack in Normal Operation of Reactor

Toshinori IIJIMA, Ichiro MIYANAGA

1964 Volume 1 Issue 8 Pages 316-321
Published: 1964
Released on J-STAGE: February 28, 2008

DOIhttps://doi.org/10.3327/jnst.1.316

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For estimation of release-rate of 131I, are discussed both the effect of individual variations by age in the general population and the additional effect of ingestion of foods contaminated in the neighborhood of a reactor-site. The limiting release-rate from the 55-meter stack of the Japan Power Demonstration Reactor (JPDR) is then estimated.
The release-rate should be determined in consideration of children of ages one and two since in these subjects the positive effect from increase in breathing-rate exceeds the negative effect due to increase in thyroid-mass. The effect from ingestion with green vegetables would become comparable to that from inhalation with air, when the deposition-velocity is 2cm/sec and the intake-rate is about 100 g/day. The limiting release-rate from the JPDR is about 4mc/hr under meteorologically neutral conditions with mean wind-speed of 2.5m/sec, which is the most predominant condition at the Tokai site.

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Errata Vol.1, No.7 (October)

1964 Volume 1 Issue 8 Pages 321
Published: 1964
Released on J-STAGE: April 21, 2008

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