Annealed Cover Plate Glass
An annealed cover plate glass is a glass plate that is
used in the manufacturing of radiation shielding windows to seal the
operator side (cold side) and radiation side (hot side) of the window
assembly. The glass manufacturing process allows the glass to cool
slowly from its poured condition, resulting in normal internal stresses,
as opposed to tempered glass, which is an added process that increases
external stresses to the glass surfaces and strengthens the glass plate.
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Band Frame
A band frame is a steel weldment that fits around
the edge of a glass slab. The glass slab/band frame assembly is inserted
into the window housing. This design feature is used as a safety
precaution to minimize glass breakage when handling glass slabs and
assembling windows, and to minimize the risk of dielectric discharge
when performing maintenance on windows that have been irradiated.
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Barrier Shield or Alpha Shield Assembly
A barrier shield or alpha shield assembly consists
of a steel frame, gaskets and a plate of glass assembled together to
form a radiation resistant see-through barrier. The assembly is designed
to be mechanically fastened to the hot side of the wall embedment liner
to provide a gas tight containment barrier from the radioactive
contamination within the hot cell.
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Browning
Browning is the discoloration and darkening of a piece
of glass to a brownish color due to excessive radiation.
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Central Viewing Area
The central viewing area of a glass slab or glass
plate is that viewing area; circular or elliptical, of which the
diameter of axis is 80 percent of the maximum usable viewing window
dimensions.
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Checks
Checks are very small breakouts around the edge of
a glass plate, or glass slab that do not interfere with its’
performance.
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Clear View
The clear view area is the smallest viewing area of
all the glass components when viewing through a shielding window
assembly.
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Cold Side
The cold side is the surface on a
radiation-shielding window, that is the farthest from the radioactive
source, and is not contaminated. The operation side of the window.
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Cold Side Load
A cold side load window assembly is an assembly
that is inserted into a wall liner or removed from a wall liner from the
operator (cold side) of the window. This type of window is preferred
over a hot side load window that requires considerably more
decontamination work be performed within the hot cell before a window
assembly can be removed or replaced.. The big advantage is minimal down
time when changing out a shielding window.
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Cover Plate (Hot or Cold Side)
A cover plate is a glass plate positioned on the
hot and cold side of the window housing. The cover glass is often held
in place with a trim frame assembly, and seal gaskets. This assembly
achieves a seal, which isolates the inner glass slabs from the external
atmosphere, and also holds or contains the mineral oil or inert gas
within the window assembly.
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Density Inch
Density inch is a term used to describe the specific
gravity of a shielding material multiplied by the thickness of that
material in inches sometimes termed density thickness.
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Dielectric Discharge
A dielectric discharge is an instantaneous flow of
electrical current from an irradiated glass component to ground causing
sever damage to the glass, usually in the form of a dendritic fracture (Lichtenberg
Figure), or heavy cleavage. The discharge can occur spontaneously due to
a breakdown in the dielectric strength of the material, or it can be
initiated by pressure or by impact. When the discharge occurs, a bright
flash of light is emitted, and a load audible report is produced
(sounding like a shotgun blast). Energy of approximately 300,000 volts,
and 20,000 to 30,000 amps is not uncommon. Technicians performing work
on highly irradiated radiation shielding windows must take necessary
precautions to prevent dielectric discharge to themselves.
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Dose Rate
A dose rate is a quantity of radiation being
received over a given time.
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Dry Window
A dry window is a radiation shielding window that is
filled with lead glass components and purged with an inert gas. The
glass components within the shielding window assembly are normally
surface treated to minimize reflection, as opposed to using shielding
oil for this purpose in an oil filled window.
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Durometer
Durometer is a unit of hardness primarily used with the
description of gasket material. The higher durometer, the harder and
stiffer the material.
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Earthquake Blocks
Earthquake blocks are a set of fabricated
restraints which, when mechanically fastened into position, maintain the
positioning of the internal components of a shielding window (i.e. glass
slabs, band frames) in place should a seismic acceleration take place.
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Extraction Hole
And extraction hole is a drilled and tapped hole
used for inserting an eye bolt or threaded rod into for the purpose of
attaching window extraction or installation hardware to move the window
in or out of the wall liner.
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Extreme Viewing Angle
The extreme viewing angle is the maximum angle at which
a beam of light enters one side of a window and exits the other side.
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Hot Cell
A hot cell is an isolated shielded room that
provides a controlled environment for containing highly radioactive
material and equipment. The radiation levels within a hot cell are
typically in the order of several thousand roentgens per hour.
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Hot Side
The hot side is the surface on a radiation shielding
window, when installed, will be the closest to the radioactive or
radioactive contamination sources.
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Illuminate A
Illuminate A is the term applied to a panchromatic
light with a spectrum given by a gas-filled tungsten lamp operated at a
color temperature of 2848°
Kelvin as specified by C.I.E (International Commission on Illumination).
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Inclusions
Inclusions are small bubbles, stones, and seeds that
are visible in optical quality glass.
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Inert Gas
Inert gas is a type of commercial grade moisture
free gas, usually argon or nitrogen, that is subjected to the internal
window components to displace ambient air. Optical grade mineral oil
will absorb moisture in the ambient air, which will cause clouding of
the oil, and reduce visibility through the window. Likewise, the
moisture in ambient air within a dry window will deposit on the surfaces
of the glass slabs causing a film, which reduces visibility through the
window.
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Lead Packing
Lead packing material in the form of a packed lead wool
mesh or leaded material positioned inside a window housing band frame to
fill the voids between the edges of the glass slabs and the window
housing band frames. The packing is required to provide shielding
equivalent to the glass components within the window housing band
frames.
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Lifting Eye Hole
A lifting eye hole is a drilled and tapped hole for
attaching an eye bolt, or pad eye to a component, which can then be
lifted.
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Light Transmission
Light transmission is the percent of light
transmitted through a material. An overall light transmission is usually
specified through the total glass component assembly in a radiation
shielding window assembly.
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Master-Slave Manipulators
A master-slave manipulator is a device used to
handle radioactive contaminated items or nuclear material in a hot cell.
The uncontaminated or “clean” portion of the manipulator is called
the “master” and the contaminated portion of the manipulator or
follower is called the “slave”. Some master-slave manipulators are
mounted through the wall of the hot cell and other types pass through
the ceiling. The various extensions and fingers of the slave components
duplicate inside the hot cell, the manipulations of the arms and fingers
of the operator at the cold side face of the cell.
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Mev
Mev is an abbreviation for “Million electron
volts”.
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mR
(Millirem) 1 x 10–3rem.
It is a unit of measure of human radiation exposure. Roentgen Equivalent
Man. 1000 mR equals 1 Rem.
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Non-Browning Glass
Non-browning glass is a glass type that has been
doped with small percentage of cerium oxide to stabilize the glass from
discoloration due to radiation exposure.
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Nanometer
A nanometer equals one billionth (1 x 10-9)
of a meter. The term is used to measure light wavelength.
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Normal View Angle
The normal view angle is the angle of view the
operator can see into a hot cell, when looking through the shielding
window at the operators’ eye level when his eye is a distance of 12
inches from the cold side cover.
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Oil Expansion Tank
An oil expansion tank is a stainless steel tank
attached to the cold side of the hot cell wall, a maximum of 24 inches
above the oil filled window that allows for volumetric changes of the
oil and inert gas within the window due to temperature or atmospheric
changes. The oil supply in the window is connected to the expansion
tank.
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Oil Fill/Drain Valve
Oil fill and drain valves are plumbing ports
located on the cold side of the window. These ports have adaptable
fittings to facilitate the draining and filling of shielding oil for
maintenance purposes.
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Oil Window
An oil window is a lead glass radiation shielding
window filled with an optical grade mineral oil.
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Panchromatic Light
A panchromatic light is a light that is sensitive to
all colors.
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R
Roentgen is a unit of radiation exposure equal to
the quantity of ionizing radiation that will produce one electrostatic
unit of electricity in one cubic centimeter of dry air at zero degrees
centigrade and standard atmospheric pressure (limited to x-ray and gamma
only).
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Rad
It is
the unit of energy absorbed from ionizing radiation, equal to 100 ergs
per gram or 0.01 joule per kilogram of irradiated material (in any
material).
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Radiation Resistant Gasket
A radiation resistant gasket is a tough radiation
resistant elastomer designed to withstand high levels of radiation.
Selection should be based on application compatible with the environment
and the shielding window components. General acceptance requires a
gasket be radiation tested to 1 x 109 R without significant
radiation degradation. The general working temperature range in air is
50° to 200°F.
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Radiation Shielding Window
A radiation shielding window is a device used to
view into a hot cell to work with radioactive materials, and to shield
the operator while performing the work. A shielding window is generally
constructed of a steel housing filled with optical lead glass with
leaded packing material to
secure the glass, to view into the hot cell. Most shielding windows have
cover plates and trim frames on both viewing ends to seal the window
cavity. The shielding windows can be either dry windows, or oil filled
windows.
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Shielding Oil
Shielding oil is an optical grade mineral oil used
to fill the voids between the glass slabs in an oil filled lead glass
shielding window assembly. The oil also has gamma and neutron shielding
ability. The mineral oil within the window cavity couples the glass
surfaces, and eliminates surface reflection of the individual glass
components, increases the index of refraction, increases the light
transmission, acts as a dielectric against dielectric discharge, and
aides in identifying degraded gaskets.
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Shine
Shine is the straight line path of radioactive
particles/waves.
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Short Finish
Short finish is the small microscopic pits, normally
found in the outer edges or corners on the surface of a polished plate
or slab of glass. The pits do not affect the optical visibility through
the glass.
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Source
Source is the radionuclide(s) of concern inside the
hot cell. The source emits radiation energy, which requires shielding to
protect working personnel.
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Striae
Striae are transparent lines appearing as though a
tread of glass has been incorporated into the slab or plate of glass.
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Streaming
Streaming is a theoretical straight-line path of a
radioactive particle/wave.
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Tempered Glass
Tempered glass is glass that has been modified by
heating and quenching in a manner such that the external surface
stresses are increased, resulting in an overall toughness of the glass.
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Trim Frame
A trim frame is a steel frame with a drilled hole
pattern. Its function is to mechanically fasten a cover plate to the hot
or cold side of the window housing or hot side of an embedment liner
using bolts and gaskets. The assembly achieves a seal, maintaining
containment of the atmosphere within the window cavity or embedment line.
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WG
WG is the abbreviation for the word “water
gauge”. It is the pressure differential, equal to the pressure exerted
by a column of water of the specified height.
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Wall Liner Embedment
A wall liner embedment is a steel weldment or
casting structure, which is usually embedded in the hot cell wall and is
not easily removed. The radiation shielding window fits into the wall
liner. The window can be installed or removed from the liner rather
easily.
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Window Housing
A window housing is the outer steel structure of
the shielding window, which contains the window components such as glass
slabs, band frames, leaded packing material and trim frame assemblies.
This fits into the wall embedment liner.
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