ACR Electronics L-32 FIELD MARKER LIGHTING SYSTEM Informacje Techniczne Pobierz pdf (Strona 57)

(b) Orientation of the x-ray beam in the room,

(d) Size of the room and the equipment layout, and

(e) Degree of occupancy in the adjoining areas.

One cannot arbitrarily assume that a given thickness of

Lead will be appropriate on all barriers.

Existing records

of room barrier design and the

report of the

shielding evaluation should be reviewed.

Any one of the following conditions should cause a new

barrier evaluation to be Initiated.

(a) Records of previous room barrier certifi-

cation by a qualified expert as defined

by NCRP Report No. 49 cannot be found

(Reference #17)

(b) Previous room barrier certification is

incomplete.

that changes in equipment, its operation,

or the room barriers have not been made

since the last barrier certification.

If the facility is new, a complete survey of the

facility during and after the construction should be done.

This includes visual inspections of shielding integrity

during the construction of the room barriers, relative

measurements to detect any voids in the barrier with an

appropriate radioisotope prior to

installation

of the

radiographic equipment; and quantitative measurements of

stray radiation levels outside the room after installation

of the radiographic

equipment.

this case,

"quantitative" means the determination of exposure levels

per week outside the room using the installed equipment as

the source of radiation.

Actual readings must be scaled

to reflect the projected workload of the Installation. If

the facility's shieldinn has been modified, spot checks

should be made.

Actual procedures in the evaluation of protective

barriers have been

discussed in

Reference #18) and

NCRP Report No. 57,

recently by

K.J. Strauss

(Reference #19).

NCRP Report No. 49 (Reference #17) and

NCRP Report No. 35 (Reference #20) contain information on

the design of barriers for routine x-ray rooms and dental

x-ray rooms respectively.

IV-5. Instrumentation

The quantitative survey meter used to measure leakage

radiation,

scattered radiation within the room or

radiation levels outside the room barriers must be chosen

carefully.

An ionization chamber with a sensitive volume

of one liter coupled to an electrometer with integrating

capabilities is one

type

of instrument

suitable for

measuring weak radiation fields of short duration. The

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