ON GAS AND HYDRAULIC TIGHTNESS OF LINAC ACCELERATING SECTIONS

A technique for calculating the required impenetrability of brazing linac accelerating sections cooled by water and for control of their hydraulic tightness based on the total helium leakage rate is given. Three types of cooling systems: a water stream in tubes soldered on the outer surface of the sections, a water stream along the outer surface and along the internal cooling channels in sections are considered. It is shown that the contact of accelerating sections surface with cooling water requires increasing the tightness of their soldering at least by 66 times. As an example, requirements for hydraulic and air tightness of accelerating sections for the developed accelerator LU-10 NSC KIPT are given.

Testing of the gaskets at liquid nitrogen and ambient temperature

The paper presents the results of the leakage measurements of bolted flanged joints operating at temperature of liquid nitrogen (77K) and ambient temperature. Three types of static gasket were tested. The results were presented in the form of a helium leakage rate as a function of its pressure. The measured data was discussed and compared with the leakage results obtained at the ambient temperature.

Contact Width Analysis of Corrugated Metal Gasket Based on Surface Roughness

Contact width is important design parameter for optimizing design of new metal gasket. The contact width was found have relationship with helium leak quantity. Increasing axial force, the contact width will increase and helium leakage will decrease. This study we conducted the surface roughness evaluation of 25A-size metal gasket before and after use. The results denote the real contact width after contact with flange having different surface roughness. The real contact width for the flange having smoother surface roughness is wider than the rougher one.

Study on Helium Leak Detecting for Post Irradiation Fuel Rods

In this paper, many methods on testing for post irradiation fuel rods were introduced, especially the method which used helium mass spectrometer leak detector. Helium detection device including pressure helium device, sniffer probe of helium detection device and vacuum chase leaks of helium detection device were designed. First, the device which tested and verified during the mockup experiment had been verified effectively. Then, a series of helium detection experiments were carried out for post irradiation fuel rods in hot cell. The experiments which was divided into three stages; before cutting, leak detection was carried out with sniffer probe of helium and vacuum chase leaks of helium, the background approach to leak rate, which indicated that there was no leakage or helium had been completely escape. When cutting, greater pressure change caused by helium which released from fuel rods, The result showed that there was no leakage. After cutting, in the following helium detection experiment, the background still approach to leak rate, which also indicated that there was no leakage. All the experiments indicated that helium leakage device were effective in great extent, in short, helium leakage device and method were good useful for leakage detection in hot cell, helium leak detecting for post irradiation fuel rods became true.