This paper presents a master equation formulation of the fluctuations of neutron density in a nonlinear power reactor model system perturbed by colored multiplicative noise using the Van Kampen's master equation. The reactivity and power reactivity feedback coefficient are assumed to be stationary stochastic processes with short but finite correlation times.
Some statistical characteristics of the neutron density fluctuations, such as moment equations, stationary distribution and stationary moments, are derived and compared with the results calculated for the system with Gaussian white parametric noise. It is shown that in the limit of Gaussian white noise our results converge to those obtained by using the Stratonovich calculus. Some remarks on the divergence between the Stratonovich calculus and the Ito calculus are also given.

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It has been noted that precursory cooling plays an important role in quenching phenomena. In this work, a new model is presented by assuming that the heat transfer in precursory cooling is mainly due to film boiling, which persists in a finite length. Then the quench velocity and temperature profile are obtained based on the three-region model for one-dimensional axial heat conduction in a heated tube. We applied our model to several existing experimental results and obtained a correlation to predict the effective length of precursory cooling region. It turns out that the correlation takes an identical form for both falling-film rewetting and bottom flooding.

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Estimation of fuel channel inlet flow rate was performed, based upon the measurement of the void propagation time between two vertically placed neutron detectors in a BWR core. The procedure of estimation is as follows.
First, the time of void propagation between two vertically placed neutron detectors is measured by the cross correlation method. Next, starting from the initial estimation of the coolant inlet flow rate for four fuel channels surrounding the detectors and the pressure drop between upper and lower plenums, the thermal-hydraulic calculation is performed iteratively to obtain the final value of coolant inlet flow rate in agreement with the measured void propagation time.
The results show a good agreement with the fuel channel inlet flow value obtained by the theoretical calculation.

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Detailed fractographic and microstructural examinations were made on neutron irradiated and unirradiated zirconium specimens deformed to fracture at temperatures between liquid nitrogen (77 K) and room temperature (295 K), to study the effect of neutron irradiation on the fracture behavior of zirconium. The fracture surface and the microstructure of the necked portion of the specimen were observed by scanning and transmission electron micrography.
The data from tests in uniaxial tension to fracture, in combination with fractographic and microstructural observations, indicated that the operative mode of non-uniform deformation to fracture was principally slip, in the range from room temperature down to 200 K, while at temperatures below this range, twin as well as slip came to take part. The fractographic morphology was of ductile dimple mode at temperatures above 200 K and at 77 K in the case of irradiated specimens, but when unirradiated, a shear fracture of ductile cleavage pattern was observed throughout the range of test temperature covered in the study.
It is suggested that the mechanism producing the dimple mode that characterized the fractography of irradiated zirconium is associated with dislocation channeling structure, whereas the pseudo-cleavage pattern seen when unirradiated is related to the microscopic deformation band structure. No evidence could be obtained indicating that deformation twins directly brought about fracture.

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The precipitation behavior of thorium and uranium (VI) complex ions in several polybasic organic acid solutions with tripositive cobalt (III) or chromium (III) complex salts as the precipitant was studied.
Only the uranium (VI) precipitates [Co (NH₃)₆]₂[UO₂(C₄H₄O₅)₂]₃2H₂O and [Co (NH₃)₆]₂-[UO₂ edta]₃22H₂O were produced. Precipitation behavior is discussed on the basis of stability constant of complex ion and steric factor of the precipitates. The precipitates decompose to an oxide mixture of Co₃O₄ and U₃O₈ at about 400°C in the air through carbonate mixture of CoCO₃ and UO₂CO₃.

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In view of the physical relevance to the flow in the scoop chamber of a gas centrifuge, it is of importance to investigate the flow induced by the stationary cylinder located in a rotating gas field.
In the present study, simulating the scoop chamber of a gas centrifuge, a stationary cylinder was placed between co-rotating disks and the azimuthal velocity distributions behind it were measured by using a Pitot-static tube. From these experiments the following results were obtained. (1) When the stationary cylinder is placed in a rotating gas, the angular velocity of the gas starts to change at the outer edge of the cylinder and decreases as the rotation axis is approached. (2) In the wake flow behind the stationary cylinder, there exists a variation of the angular velocity with an angular period of 180°.

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