Decay heat in the blanket and shield of the Fusion Experimental Reactor (FER) was calculated using a newly developed radioactivation calculation code system THIDA-2. The decay heat at various time periods after shutdown were calculated. The decay heat level in the FER blanket was found to be at least one order of magnitude lower than in fission reactors at all time periods after shutdown. The necessity of following the transport of decay γ-rays in obtaining the detailed distribution of decay heat in the blanket was demonstrated. The validity of the γ-ray kerma factors used in the evaluation was also shown.

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A grooved moderator having grooves on the neutron emanating surface of the moderator has been proposed for the purpose of increasing the neutron intensity of the pulsed neutron source. Experimental studies on polyethylene grooved moderators are performed, and the effects of the groove, the optimum dimensions and the influence of the reflector on the optimum condition are examined with a view to enhancing the emanating thermal neutron intensity. The pulse shapes of emanating neutrons are also measured and the figures of merit of the grooved moderator are discussed.
The experimental results reveal that the optimum condition is determined by the balance of increase of intensity from the grooves and the decrease from the fins. The optimum dimensions for the moderator with a graphite reflector are as follows. The fin width is less than 1 cm, the fin length 810 cm and the fin area about 60% of the emanating surface. These values does not depend strongly on whether the moderator is covered by the reflector or not. This size of grooved moderator increases the emanating neutron intensity by about twice at the neutron energy of 25 meV, as compared with the rectangular shaped moderator of 5 cm thick, although it broadens the pulse width considerably. Analysis of the figures of merit suggests that although the grooved moderator is not useful for the usual neutron scattering experiments, it may be of value in experiments having a resolution which is not very sensitive to the pulse width.

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In the LMFBR, electromagnetic-flowmeters (EMFs) have been extensively used. A calibra-tion method for EMF using cross-correlation of its output voltage fluctuations has been pro-posed. This method, however, requires two pairs of electrodes, and it is desired to develop an alternative method without this requirement.
In the present paper, the process by which the turbulent behavior of a fluid in a pipe is transformed into the output voltage fluctuation is considered ; and the average frequency weighted by the square root of the autopower spectral density of the fluctuation is developed as a function of the flow rate. The average frequency is proportional to the product of the flow rate and the square root of the friction coefficient of the pipe. Consequently, the flow rate is determined by measuring the average frequency, once the proportional coefficient is obtained.
The experiment was conducted with a 12 in. diameter saddle coil type EMF in the primary cooling system of "JOYO" reactor. Though the experimental value of the propor-tional coefficient was somewhat deviated from the calculated one, it is concluded that the performance degradation of the EMF can be calibrated with an accuracy of 12% error.

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A through analysis of LOFT L2-3 is made with the THYDE-P code, which is based on the new non-equilibrium thermal-hydraulic model. The various assumptions and correlations in use for the present analysis are explained. In order to investigate DNB (departure from nucleate boiling), rewetting and quenching at the pool condition, several parameters are defined. The interfacial heat transfer coefficient between the gas and the liquid is assumed to have the same pressure dependence as of nucleate boiling. The overall trends of the experiment are well reproduced by the calculation. Much effort was found necessary, how-ever, to better understand DNB, rewetting and quenching at the pool condition, by taking into account the stored thermal energy and the stationariness of the temperature distribution in the fuel rod.

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The reaction between simulated high-level radioactive wastes (HLW) and CaO-stabilized zirconia with CaF₂ structure has been studied in the temperature range of 8001, 500 °C in air and in a mixture of 4%H₂+96%He. Under the heat treatment in air at temperatures between 1, 000 and 1, 400 °C, 4W/O simulated HLW was dissolved in the CaF₂ phase. The lattice parameter of the CaF₂ lattice increased with HLW content according to the equation a= 0.5134+0.00028x nm, where x is the HLW content in W/O. In the region of 420W/O HLW, two phases were present : the CaF₂ and scheelite type phases. The actinide and rare earth elements were dissolved in the CaF₂ lattice, of which lattice parameter varied with HLW content in the form a=0.5141+0.00014x nm. Under the heat treatment in a mixture of 4%H₂+96%He, three phases were formed in the sample containing the HLW. They were the CaF₂ phase, (Sr, Ca) ZrO₃ with orthorhombic structure and Mo metal. The actinide and rare earth elements were fixed in the CaF₂ lattice. The increase of the lattice parameter of the CaF₂ lattice was given by the expression a=0.5134+0.00022x nm.

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The phoswich detector is generally used for the detection of Pu and 241Am in lungs. But it's detection limit for Pu in lungs is insufficient for the purpose of radiation protection. Recently, the high-purity Ge detector for low energy photons became available. The validity of Ge detector for measuring the low energy photons from lungs was examined using Livermore phantom which validity was recently established. The two arrays, each of them consisted of four 2" Ge detectors, were assumed to be appropriate for covering the most efficient region of chest for X-rays from lungs. This arrangement was almost the same as that for two 5" phoswich detector system. From this study, Ge detector proved insufficient for detecting X-rays of Pu from lungs, but sufficient for γ-ray of ²⁴¹Am from lungs.

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The energy spectra of γ-rays in water, concrete, iron and lead are calculated by PALLAS-PL, SP-Br code for the plane perpendicular incidence. The calculation takes into account both annihilation and bremsstrahlung photons as well as Compton scattered ones as the secondary source.
Comparisons of energy spectra calculated by PALLAS were made with those of the moments method in water, iron and lead. In the PALLAS calculation the bremsstrahlung is neglected for the source energy of 6 MeV in iron because the influence of the bremsstrahlung on the energy spectrum is considered to increase for high energy photons. While for the case of inclusion of the bremsstrahlung source, a comparison of PALLAS calculations with experiments is made in transmitted dose through lead for a plane perpendicular 8-MeV source, resulting in good agreement.
Several examples of the calculated energy spectra in each material are presented at penetration distances of 0.5-, 1.0-, 2.0-, 4.0-, 7.0-, 10.0-, 20.0- and 40.0-mfp in 43 mfp depth for source energies of 0.115.0 MeV.

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