A general theory of third order moments-related reactor noise pulse experiments is presented. Detailed computation of a two-intervals moment of counts for a zero power one velocity point reactor with delayed neutrons is performed. The neutronic process is analyzed up to third order covariances via an extension of the usual mobility and diffusion matrices' approach. For this purpose, a stochastic diffusion matrix and a third order stochastic diffusion tensor are introduced. Detection effects are taken into account through a non-homogeneous Poisson distribution. No a priori approximation for the probability generating function of counts is assumed.

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An optimal dynamicai control of a linear reactor as a distributed parameter system is abtained numerically along with an anaiytical expression of the integral equation that should be satisfied by the optimal control. The function space methcd is employed to derive the equation, and it is known from the numericaJ experience that only the fundamental of expanding modes is enough to describe the integral kernel of the equation.Space-dependence is colected in the forcing term of the equation. The reactor core model is of two groups of neutrons in steady state and one group of precursors. Two performance functionals are tried. Both are quadratic but one is of the precursor history and the control, whereas, another is of the neutron flux density and the control. The latter formulation partly dissolves the weighting problem in the quadratic perfcrmance fufictional.

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Applicability of previously proposed void fraction correlation was studied on the boiling steam-water flows in tube. The correlation was found to be applicable to the data of Sekoguchi (d = 13.55 mm) and Bartolomei (d=25 mm), i.e. the value of parameter K in the correlation equals to unity. The average value of K for pipes of smaller diameter (d=6.1, 7.7 mm) was 0.57 for both adiabatic and diabatic steam-water flows. These values of K are not dependent on flow regime, heat flux and superficial water velocity within the investigated ranges. A criterion was established with a dimensionless group E₀λ which determines the K-value as : K=1.0 for E₀λ ?? 2 × 10^-6 and K=0.57 for E₀λ<2× 10^-6.
A comparison between the predicted values by this method and experimental values at pressures from atmospheric to 80 kg/cm² abs., heat fluxes 01.5 × 10⁶ kcal/m²-hr, pipe diameters 576.2 mm and gas-water volumetric flow ratios 0.0610⁴, showed that the present correlation is adequate within ±15% of deviation.

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A non-Markoffian Langevin equation
d/dth(t)=-∫^t_t0B(t-t')f(t')dt'+Z(t-t₀)g(t₀)+F(t)
for the fluctuations of known state-variables, f(t), is proposed. The non-Markoffian effect and the new stochastic term Z(t-t₀)g(t₀) are due to "hidden" state-variables g(t). The random force F(t) meets the requirement of the causality condition, but the random force given by R(t)=Z(t-t₀)g(t₀)+F(t) does not. A new relation between the fluctuation R(t) and the dissipation B(t) is found. The effect of external noise sources is formulated to demonstrate that the present formalism is useful for finding out hidden statevariables.

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The order of accuracy of finite-element type approximations, when applied to partial differential equations, depends generally on the smoothness of the exact solution, measured by means of Sobolev norms. The properties of the one-speed neutron density in multi-layer slab geometry are considered from this point of view. It is shown in particular that the neutron density admits finite Sobolev-integrals of order less than unity only. The integrability results are applied to derive asymptotic error estimates for piecewise polynomial variational approximations. The inclusion of proper singular functions in a polynomial trial space is shown to speed up the convergence.

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Various kinds of cold worked Al-Li alloys were irradiated in JRR-2 and the change in microstructure with post-irradiation annealing was examined in an electron microscope.In 30% cold worked specimen, bubbles are preferentially distributed on sub-boundaries.The grain interior contains only a small amount of bubbles. On the contrary, in 2% cold worked specimen, in which distinct sub-boundaries are rarely formed, most of bubbles are distributed within the grains. Bubbles aligned on a dislocation are frequently observed.
These experimental results are explained as follows. In heavily cold worked specimen, moving dislocations collect most of He atoms or their clusters in the course of subboundary formation after irradiation. In slightly cold worked specimen, dislocation density is insufficient to perform this process and He atoms or their clusters precipitate either upon dislocations or within the grains.

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In uranium enriching cascades, the enrichment obtained on the product can be enhanced by introducing reflux from the product end to the feed stage. The effect of the reflux is analyzed on the basis of the solutions obtained of stagewise discrete flow equations. The degree of enhancement achieved on the enrichment is represented by the ratio of enrichments between the cases with and without reflux. If the enrichment is much smaller than unity, the ratio is constant throughout the cascade, and the value increases monotonously with the reflux rate, reaching its highest value when the reflux is total, to equal the ratio between the enrichment prevailing in the feed flow and that in the waste flow when devoid of reflux.
Comparisons based on a model gas centrifuge cascade are made between three alternative expedients envisaged for enhancing the enrichment-(a) cascade feed flow control, (b) feed stage cut control, and (c) reflux rate control. Of these three expedients, (b) is found to bring about the highest enrichment with the least sacrifice of the separative work.

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Upon examining the effect of the presence of fission fragments (FF) on the formation by radiolysis of ethylamine and n-butane in ethane-ammonia system, no difference was discerned in the G-value, observed in the range of 114 kg/cm², between radiation containing FF and others devoid of FF-mixed radiations from reactor and ⁶⁰Co γ-rays. This result would indicate that the predominant reaction in the core of FF track is proton transfer from positive ions to ammonia, as in the case of γ-radiolysis. Rising total pressure of the system was found to bring about a decrease in G(C₂H₅NH₂) and an increase in G(n-C₄H₁₀). This behavior of the G-values indicates ionic formation of ethylamine by the reaction ;
C₂H₅⁺+NH₃→C₂H₅NH₃→^e-C₂H₅NH₂+H.

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Solution-treated type 304 stainless-steel specimens were bombarded with 200 keV C⁺ ions at a rate of 4.1 × 10^-3 displacements per atom (dpa) per second, to determine the dependence of void swelling on the irradiation temperature and dose, using specimens irradiated either with or without pre-injection of He (30 appm). The voids were measured by means of transmission electron microscopy. For observing temperature dependence, the irradiation dose was fixed at 41 dpa, to cover the range of irradiation temperature 425800°C. The peak swelling temperature was found to occur at 675°C in specimens pre-injected with He, and at 625°C, an He-free specimens ; and at these points the swelling reached 18 and 14%, respectively. Besides this faculty of He atoms to push upwards the peak swelling temperature, a notable effect produced by the presence of He in the specimen was the very marked extension upward of the limit beyond which swelling ceased to occur, and in the intermediate range of 700800°C, quite significant swelling was observed in He-injected specimens, when the He-free material had already ceased swelling. The dose dependence was examined up to 205 dpa with the irradiation temperature fixed at 625°C. At low doses, the presence of He was observed to enhance swelling, but above 40 dpa, the influence of He on swelling could no longer be observed. The swelling data generally showed good agreement with results from neutron and other ion irradiation experiments.

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In order to clarity the order of enhancement by fog formation in sodium evaporation under argon atmosphere, the previously reported experimental data were compared with the values predicted with heat and mass transfer analogy and the theory proposed by Hills et al. As a result, the following conclusions can be drawn as:
(1) In the range of sodium temperature 300500°C, the evaporation rates are one to three times as large as those predicted by heat and mass transfer analogy and three to eight times as small as those predicted with the theory by Hills et al.
(2) In the results by Horst and Sutherland et al., the evaporation rates are smaller than those predicted by heat and mass transfer analogy. This may depend on the geometrical difference between the heat transfer and the evaporation systems.

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