A series of reactor physics experiments have been carried out at the FCA to examine the availability of the nuclear data and computational method currently employed to evaluate the nuclear characteristics of the High Conversion Light Water Reactor. Experimental results of the effective and infinite multiplication factors k_eff and k_∞ are compared with the calculated ones for three zone-type FCA-HCLWR cores fueled with enriched uranium. The calculated k_eff and k_∞ values with use of the SRAC system and the cross section set based on the JENDL-2 data file show a good agreement with the measured ones. The calculated-to-experimental (C/E) values for k_eff and k_∞ do not depend on the cell parameters such as the fuel enrichment, the moderator voidage state and the moderator-to-fuel volume ratio, and these values are similar with each other There is also no inconsistency between the C/E values for k_eff and k_∞ : The average C/E values are 0 989 and 0 988 for k_eff and k_∞ respectively

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The axial enrichment and gadolinia distributions of BWR (boiling water reactor) fuel are optimized under control rod programming. The objective of the problem is to minimize the average enrichment required to reach a planned EOC (end-of-cycle) with criticality condition and axial power peaking constraint.
A method of approximation programming is employed as the basis for the solution method. Resulting linear programming problem at each iteration step is solved by means of goal programming algorithm. The method is applied to the initial fuel for a typical BWR/5 represented by an axial one-dimensional core model
Two-region analysis leads to the conclusion that the core bottom should be depleted during the cycle so that the power shifts to the core top at EOC. The enrichment and gadolinia distributions are determined to maximize EOC power peaking within a limit. The optimal solution of a 24-region fuel with a power peaking limit of 1.4 saves 10.6% in uranium ore compared with a uniform fuel depleted with a Haling power shape. Half the saving comes from an optimal natural uranium blanket implementation.

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The α-track method with a solid state nuclear track detector was used for the measurement of tritium production rates (TPR). Cellulose nitrate track detectors (Kodak LR-115) with Li-containing radiators were placed in a simulated fusion blanket of a Li₂O slab assembly with a Be layer and irradiated by D-T neutrons. After chemical etching, the etched-through tracks in the detectors were counted. Lithium metal was the most suitable radiator to distinguish tracks formed by α-particles of the Li(n, α)T reaction from the background. The experimental results agreed well with the calculations. This shows that the indirect α-track method is reliable in estimating TPR distribution.

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Gamma-ray induced losses of pure silica core and GeO₂ added core single mode optical fibers (Si-SMF and Ge-SMF) at 1.30 μm were investigated. Kinetic study on recovery curves of their γ-ray induced losses, showed that the induced loss could be divided approximately into two terms : one is dependent mainly on total dose and the other is dependent on dose rate, which has a tendency toward saturation when increasing total dose and was also represented by 3 components with different relaxation times The former term which is dependent mainly on the total dose was found to be due to IR tail absorption caused by irradiation and to be associated with the Si-E' center for the Si-SMF and the Ge (1) and Ge (2) centers for the Ge-SMF, respectively.

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The influence of '3-heat treatment in temperatures 1, 0001, 200°C on the microstructure and mechanical anisotropy of Zircaloy-4 fuel cladding was investigated.
Morphology of second phase particles and a-grain were markedly changed by the heat treatment. However, they were not much varied by the treatment conditions because of the constant cooling rate of 25°C/s. Heat treated Zircaloy tubes exhibited texture changes but the preferred orientation of grains was still remained.
With increasing heat treatment temperatures, the 0.2% yield strength decreased but the hoop strength was not changed due to the texture effect and α-plate width. The texture parameter, f values of Zircaloy tubes were influenced by the heat treatment conditions. In particular, a linear relationship between the 0.2% yield strength and the f value in longitudinal direction was derived.

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The γ-ray flux densities at the ground surface emitted from radon daughters in the overhead air have been calculated by means of the Monte Carlo method to investigate the effect of those on environmental γ-rays and to make a comparison with measured values It has been made clear that radon daughters distributed in an atmospheric hemisphere of the 500 m radius cause a variation in the γ-ray flux density at the detector near ground surface The amount of this variation has been calculated to be more than 10% of the background level Using the results obtained, γ-ray flux densities corresponding to any arbitrary vertical distribution of atmospheric radon daughters can be calculated easily.

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In order to study the migration behavior of non-cationic species of ⁶⁰Co, the aqueous solution of ⁶⁰CoCl₂ from which cationic ⁶⁰Co was eliminated by using cation exchange resin was introduced continuously into sandy soil layers at a relatively fast water flow It was found from the experimental results that the migration of non-cationic species of ⁶⁰Co was independent of that of cationic species. The reaction of non-cationic species of ⁶⁰Co between sandy soil and pore water could be described by the first-order reversible equation and the prediction of the migration using the reversible equation was effective to the case of pulse injection of non-cationic species of ⁶⁰Co. Therefore, when the movement of underground water is fast, the use of the reversible equation is effective to predict the migration behavior of non-cationic species of ⁶⁰Co

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An ultrasonic testing equipment for use in in-service inspection of nuclear power plant piping has been developed, which comprises an angle-beam electromagnetic acoustic transducer mounted on a vehicle for scanning the piping surface to be inspected. The transducer functions without direct contact with the piping surface through couplant, and the vehicle does not require a guide track installed on the piping surface, being equipped with magnetic wheels that adhere to the piping material, permitting it to travel along the circumferential weld joint of a carbon steel pipe. The equipment thus dispenses with the laborious manual work involved in preparing the piping for inspection, such as removal of protective coating, surface polishing and installation of guide track and thereby considerably reduces the duration of inspection. The functioning principle and structural features of the transducer and vehicle are described, together with the results of trial operation of a prototype unit, which proved a 1 mm deep notch cut on a test piece of 25 mm thick carbon steel plate to be locatable with an accuracy of ±2 mm.

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Dryout experiments have been conducted in a 5 × 5 rod bundle under high-pressure, low-flow and mixed inlet conditions which are of importance in the core thermal-hydraulic behavior during a loss-of-coolant accident (LOCA) of a nuclear reactor. The experimental conditions cover ranges of pressure from 3 to 12 MPa, mass flux from 20 to 410 kg/m².s and inlet quality from 0 4 to 0 9 The dryout data have been compared with several empirical critical heat flux (CHF) correlations that are commonly used to predict CHF behavior and with an equation derived on basis of a simple assumption. The Biasi correlation overpredicts considerably the CHF ; in some cases, it overpredicts the CHF by a factor of 10 or 100. The Bowring correlation underpredicts the CHF to approximately 1/2. The Katto correlation performs relatively well in correlating the present dryout data. An equation derived on basis of a simple assumption that dryout occurs due to complete vaporization of liquid in a subchannel performs best among the correlations examined in predicting the present dryout data

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In the latest paper of D₂O electrolysis fusion by Fleischmann & Pons⁽¹⁾ (F-P experiment, in the following), they reported that the observed enthalpy generation showed 10⁶⁷ times more frequent fusion-reaction rates than those of the known fusion channels, i.e., D(d, n)³He and D(d, p)T for which they observed consistent results between the neutron and the tritium generation, and concluded surprisingly that an "unknown fusion process" took place. What did really happen in their experiment ?
The author has studied the problem from a theoretical point of view in the last few weeks, and has reached the conclusion that the D-cat. cascade fusion channel, i.e., the following (i)→(ii) reaction cascade would open to be the predominant reaction channel in a highly deuterium-condensed Pd electrode. We may call this D-cat. type since deuteron exists at both the initial and the final state,
(i) D+ D→⁴He^*
(ii) ⁴He^*+D→⁶Li^*→⁴He+D+23.8 MeV.
Calculated results of fusion rates and neutron yield are consistent with the F-P experiment, and can explain the key results of the F-P experiment.
In the present note, key results of theoretical estimations are described. A detailed report will be submitted to a journal (a preliminary report describing the detail is available⁽²⁾).

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