Two types of charcoal-impregnated filter paper CP-20A and CP-20B manufactured by Toyo Filter Paper Co., Ltd., Tokyo were tested for their collection performance on airborne iodine generated during ¹³¹l production at the lsotope Test Production Plant, which is successively filtered through traps in the cell and through two installed air cleaning systems. In order to observe the effect brought upon the collecting efficiency by differences in charcoal granule size, the CP-20A and -20B were impregnated with activated charcoal granules of about 2μ and about 70μ in the average diameter. This paper describes the experimental results and discussions on the dependence of collecting efficiency on (1) the nature of the airborne iodine, (2) the relative humidity of the sampling air, (3) the sampling period, and (4) the face velocity. In general, better performance for collecting airborne iodine was shown by the CP-20B as compared with the CP-20A.

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Tests on the performance of the JEFR safety rod drive mechanism were conducted with water flow simulating the specified sodium environment. Results obtained during 400 cyclic endurance tests show that the scram period of the safety rod passing through the core from scram initiation to 600mm displacement is 525 msec during the initial stages of test and 560 msec during final.
To provide a means of predicting and analyzing the scram characteristics, a computer code was derived from the results of these tests. This report describes the code, and presents an analysis performed there with on the scram characteristics of the safety rod drive mechanism, and on the effects of acceleration spring and coolant flow rate on the scram period The main points are as follows:
(1) The scram period is 6% shorter in sodium environment than in water due to the difference in density.
(2) A spring force of 2-3 times the gravity of the safety rod is effective in shortening the scram period.
(3) When the coolant velocity is designed to be much smaller than the mean velocity of the safety rod passing through the core, coolant flow rate would not influence the scram period to any extent.

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The current status of radioactivity standardization is reviewed from the standpoints of both preparation and use of radioactivity standard samples. The first part of the article concerns absolute and relative methods used for radioactivity calibration. Considering the primary importance of the 4πβ-γ coincidence method among a variety of the techniques, a detailed description is made of this useful method and its related techniques. The other methods also are surveyed briefly.
The second part deales with various associated techniques and practical considerations such as handling of radioactive solutions, detection and elimination of radioactive impurities.

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This report summarizes the computer codes for radiation shielding calculations available today in Japan. These computer codes have been applied to various calculations of shielding design and shielding analyses for neutrons and gammas. The codes are listed in the form of a table, classified according to calculational methods, such as kernel, removal-diffusion, diffusion theory, Monte Carlo, numerical integration of the transport equation, invariant imbedding, multiple scattering and ray analysis.

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