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Page Title: Access Controls and Shielding from Radioactive Hazards - Continued
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3. a control device that energizes a conspicuous visual or audible alarm signal so that
the individual entering the High or Very High Radiation Area and the supervisor of the
activity (e.g., in a control room) are made aware of the entry;
4. entryways that are locked when not accessed and over which positive control can be
maintained when accessed;
5. continuous direct or electronic surveillance that is capable of preventing unauthorized
6. a control device that automatically generates audible and visual alarm signals to alert
personnel in the area before use or operation of the radiation source in sufficient time
to permit evacuation of the area or activation of a secondary control device that pre-
vents use or operation of the source;
7. for Very High Radiation Areas, additional measures as necessary to prevent access to
the area when dose rates are above the lower limit for a Very High Radiation Area.
Consideration should be given, in the selection of controls, to the allowance of space for
the controls, the necessity for administrative oversight of the controls, the need for periodic
inspection of the controls, and the ease with which a control may be bypassed. No control
should be installed such that it would prevent rapid evacuation of personnel.
b. Shielding
Shielding design should be based on the appropriate design objectives given in
10 CFR 835. The choice of design, arrangement, and material for shielding should be optimized
considering the following factors at a minimum: efficacy of dose rate reduction, potential corro-
sive or galvanic effects, the advantages of homogeneity vs the advantages of layers, weight, the
need for mobility of the shield, radiation heating potential, temperature resistance, and activation
potential. Occupancy considerations should be considered, including purpose of access(es),
required frequency of access, stay times, and number of workers requiring access.
The design of concrete radiation shields should be in accordance with the requirements of
ANS 6.4. The quality factors given in 10 CFR 835 should be used for determining the dose
equivalent of the various types of radiation for dose rate calculations in conjunction with the
appropriate methodology of ANSI/ANS-6.1.1-1977; alternatively, ANSI/ANS-6.1.1-1991 may be
used, where justified, with quality factors corresponding to its methodology (e.g., as given in
NCRP 116).
The shielding design for fusion facilities should consider the anticipated high-energy neu-
tron spectrum; appropriate high-density shielding should be provided as necessary for these
neutrons and made compatible with shielding for neutrons of lower energies and for gammas.

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