Measurement of the response-ratio of an ionization chamber filled with dry air to that filled with P-10 gas in the calibration of gas monitors.
We developed a new method to determine the response ratio of an ionization chamber (Ohkura ionization chamber: type I-4096 01/06) filled with dry air to that filled with P-10 gas. The response-ratio was obtained by comparing the output currents of the ionization chamber after introduction of radioactive gasses of identical activities contained in two small vessels. The obtained ratio was 0.690 ± 0.003, which agreed with the results obtained by other methods.
Activity measurement of 85Kr diluted by a large volume balloon technique.
The National Metrology Institute of Japan (NMIJ) participated in the CCRI(II) Key-comparison of (85)Kr activity measurement. The absolute internal gas-counting method was used, with a set of proportional counters of different length. The original (85)Kr gas was diluted by a factor of 2x10(5) in order to achieve the suitable activity concentration for the proportional counters. A new dilution method was introduced, based on a large-volume balloon and gravimetric determination of the dilution volume with small uncertainties.
Present status in the field of internal gas counting
Abstract The gas-counting equipment at the National Bureau of Standards has been recently modified and reconstructed. The preparation of various radioactivity gaseous standards will be described. In some cases purity is assured by a prior separation in the isotope separator.