These are used as a barrier against harmful radiation and atomic particles across openings for access to hot cells, and against similar radioactive-isotope handling arrangements and radiation chambers of high-energy x-ray machines or accelerators.
Usually, they must protect not only personnel but also instruments even more sensitive to radiation than people.
Shielding doors usually are much thicker and heavier than ordinary doors, because density is an important factor in barring radiation. Generally, these specialpurpose doors are made of steel plates, steel-sheathed lead, or concrete. To reduce thickness, concrete doors may be made of medium-heavy (240 lb / ft2) or heavy (300 lb / ft3) concrete, often made with iron-ore aggregate.
The heavy doors usually are operated hydraulically or by electric motor. Provision must be made, however, for manual operation if the mechanism should break down.
Common types of shielding doors include hinged, plug, and overlap. The hinged type is similar to a bank vault swinging door. The plug type, flush with the walls when closed, may roll on floor-mounted tracks or hang from rails. Overlap doors, surface-mounted, also may roll or hang from rails. In addition, vertical-lift doors sometimes are used.
BUILDERS HARDWARE
Hardware is a general term covering a wide variety of fastenings and devices for operating or controlling the operation of movable building components, such as??doors and windows. By common usage, the term builders hardware generally covers only finishing hardware, but some rough hardware is discussed in this section.
In point of cost, the finishing hardware for a building represents a relatively small part of the finished structure. But the judicious selection of suitable items of hardware for all the many conditions encountered in construction and use of any building can mean a great deal over the years in lessened installation and maintenance costs and general satisfaction.
To make the best selection of hardware requires some knowledge of the various alternates available and the operating features afforded by each type. In this section, pertinent points relating to selecting, ordering, and installing some of the more commonly used builders hardware items are discussed briefly.
