An ion source of original concept, named "BPD Ion Source" is described, in which the source plasma is produced by an electron beam-plasma discharge. A hydrogen ion beam of 120 mA can be continuously extracted from the plasma in the direction of the electron beam at an extraction voltage of 30 kV through a single circular aperture of 8 mm dia. located at the bottom of the discharge chamber. The current density has reached 239 mA/cm². The hot electrons contained in the source plasma facilitate the extraction of this intense ion beam. The normalized emittance of this source was observed to be 9.4 × 10^-7 m-rad with 100 mA beam extraction. The abundance ratio of the beam ion species and other characteristics are described and a discussion is presented on the possibility of scaling up for purposes of practical application.

View full abstract

The purpose of this paper is to elaborate a closed-loop digital control system to regulate a reactor during commanded changes of power level, making use of the optimal control and trajectories derived in the previous paper. Simple application of this optimal control scheme alone would not permit satisfactory control of the reactor, on account of various external disturbances that would affect the control in actual practice. This dif-ficulty has been overcome by linearizing the system equations around the optimal control and trajectories derived as above, and thereto applying modern control theory.
The feedback control system is first examined for a case where all requisite state variables are accessible. Then for the case where not all state variables are thus acces-sible, a method is devised for estimating the inaccessible variables. The estimates are obtained by detecting the accessible state variables a given number of times during each control stage, using the generalized inverse.
A closed-loop system is constituted by incorporating this method of estimation into the feedback circuit. The resulting system is shown to provide amply satisfactory per-formance in terms of response time and the accuracy.

View full abstract

An advanced method has been developed to analyze the heterogeneity effect of a multi-region plate lattice system accurately enough with the coarse group constants. This treatment is characterized by the modification brought to effective admixture cross sec-tions and correction on elastic removal cross sections. The mutual interference among different plates are taken into account in determining the admixture cross sections. The effective cross sections thus obtained agree well with the results obtained by ultra fine spectrum codes. The elastic removal cross sections of light nuclides are corrected near the sodium resonance by means of a simple analytical expression for the flux depression. With this correction remarkable improvement was observed in the flux heterogeneity. In solving the multi-group transport equation for flux heterogeneity, the fission source iter-ation was found to be dispensable under most conditions.

View full abstract

The problem inherent in the laser flash method is the involvement of comparatively large errors occasioned by the non-uniform radial distribution of the intensity of radiant heat emitted by the laser.
This error due to non-uniform heating is evaluated in this paper from the theoretical analysis made of a case where radiant heat with parabolic intensity distribution impinges pulsewise on one surface of a disk. The result indicates that much of the existing data reported in literature from measurements by laser flash are not very reliable, and that serious error in determining thermal properties can only be avoided by imposing severe limitations on the dimensions of the specimen, or else the results obtained from pulsewise and non-uniform heating of the specimen are subject to correction to account for the non-uniform heat distribution.

View full abstract

For incorporation in the process of Pu purification with TBP, a modified method is proposed for the effective reduction stripping of Pu without the use of reducing salt, whose function is replaced by excess nitrous acid in the extraction feed. The nitrous acid acts as "redox reagent" for Pu(IV) in the stripping bank and in the extraction feed. The practical applicability of this process was experimentally proved by both batchwise extraction and flowsheet studies with miniature mixer-settlers.
The addition of 0.1 mol/l of nitrous acid to the extraction feed caused about half of the nitrous acid initially added to be loaded on the TBP and be carried toward the stripping bank. Over 99.9% of Pu including 40% of Pu(III), is stripped under the con-ditions of 0.3 N HNO₃, 0.008 N HNO₂, and with a flow ratio of 1.4 (aq./org.).
Basic studies related to the above flowsheet were also made on the extraction of nitrous acid with TBP and the reduction of Pu(IV) with nitrous acid. The redox poten-tials were also calculated.

View full abstract

Plutonium samples (330 μg) of various isotopic compositions were measured with a high-resolution Ge (Li) detector. The γ-rays counted are the 43.5 keV of ²³⁸Pu, the 38.7, 51.6 and 129.3 keV of ²⁹⁹Pu, the 45.2 keV of ²⁴⁰Pu, and the 148.6 keV of ²⁴¹Pu. To estimate the relative photopeak efficiencies of the γ-rays, an empirical curve was derived from measurements of the three γ-rays of ²³⁹Pu adopted as internal standard. Data treatment is described in detail as well as the method of correction to account for the activities of ²³⁷U and ²⁴¹Am inherently accumulating in the plutonium sample. The branching ratios of the γ-rays of plutonium were also evaluated by comparing the γ-ray spectrometric results with mass-spectrometric data.

View full abstract