Shielding windows are designed to provide clear, undistorted in-cell viewing while providing radiation protection with shielding equivalent to the hot cell wall. Shielding window glass is formulated of various minerals to produce intended densities, colors, and other desirable characteristics. Because shielding glass has a high lead-oxide content, it is softer than regular window glass and more susceptible to scratching, chipping, staining, and corrosive substances.
The weight of a typical oil-filled shielding window assembly is approximately 10,000 lbs (4,500kg). Special handling equipment and techniques are required for installation or removal of a window assembly from a wall penetration.
Most shielding windows include glass cover plates on the inside and outside of the cell as protective barriers for the interior glass slabs. The glass slabs are usually contained in a steel structural housing, called a "tank." If an oil-filled window, the window housing or tank is filled with a high purity, clear mineral oil, specifically blended for resistance to deterioration from gamma radiation. If it is a dry window, the window housing and embedment liner cavity are pressurized with an inert gas purge to prelude the entrance of dust, moisture and oxygen into the window housing or liner cavity.
Measurements of window light transmission are made periodically to detect radiation-induced glass browning or oil cloudiness. If an oil-filled window, the tank oil is sampled and chemically analyzed to determine moisture content, hydrogen peroxide content, lead content, acidity and rate of deterioration caused by irradiation. If the oil sample indicates a chemical condition harmful to the glass, the oil is immediately changed to correct the problem. For dry windows, a window light transmission test is periodically made to verify 'browning' is not occurring. Other than cleaning the cover plates, there is no other minor maintenance operation, other than daily verifying the window purge is on and the rotometer indicates no gas leakage problems.
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Data and information contained in the tutorial was written by Dale A. Tobias, Premier Technology, Inc. and Hienz E. Hoffman and William G. Wash, Schott Glass Technologies, Inc. and may be reproduced only with written consent.
For information, contact Lyle Freeman
Vice President of Business Development
(208) 782-9129 lfreeman@ptius.net
