NAC459.345. Precautionary procedures: Control of access to very high radiation area with sealed radioactive sources used to irradiate materials.

     1. Except as otherwise provided in this section, each area in which there may exist radiation levels in excess of 500 rads in 1 hour at 1 meter from a sealed radioactive source that is used to irradiate materials must meet the following requirements:

     (a) Each entrance must be equipped with entry control devices which:

          (1) Function automatically to prevent any person from inadvertently entering a very high radiation area;

          (2) Permit deliberate entry into the area only after the control device is actuated and causes the radiation level within the area, from the source of radiation, to be reduced below that at which it would be possible for a person to receive a deep-dose equivalent in excess of 0.1 rem in 1 hour; and

          (3) Prevent operation of the source of radiation if it would produce radiation levels in the area that could result in a deep-dose equivalent to a person in excess of 0.1 rem in 1 hour.

     (b) Additional control devices must be provided so that, upon failure of the entry control devices to function as required pursuant to paragraph (a):

          (1) The radiation level within the area, from the source of radiation, is reduced below the level at which it would be possible for a person to receive a deep-dose equivalent in excess of 0.1 rem in 1 hour; and

          (2) Conspicuous visible and audible alarms are generated to make any person who is attempting to enter the area aware of the hazard and to make at least one other authorized person, who is physically present, familiar with the activity and prepared to render or summon assistance, aware of the failure of the entry control devices.

     (c) The licensee shall provide control devices that ensure that, upon the failure or removal of physical radiation barriers other than the shielded storage container of the sealed source:

          (1) The radiation level from the source is reduced below the level at which it would be possible for a person to receive a deep-dose equivalent in excess of 0.1 rem in 1 hour; and

          (2) Conspicuous visible and audible alarms are generated to make potentially affected persons aware of the hazard and to make the licensee, or at least one other person who is familiar with the activity and prepared to render or summon assistance, aware of the failure or removal of the physical barrier.

     (d) When the shield for stored sealed sources is a liquid, the licensee shall provide a means to monitor the integrity of the shield and to signal, automatically, loss of adequate shielding.

     (e) Physical radiation barriers that comprise permanent structural components and have no reasonable probability of failure or removal in ordinary circumstances are not required to meet the requirements of paragraph (c) or (d).

     (f) Each area must be equipped with devices that will automatically generate conspicuous visible and audible alarms to alert persons in the area before the source of radiation can be put into operation and in time for any persons in the area to operate a clearly identified control device, which must be installed in the area and which is able to prevent the source of radiation from being put into operation.

     (g) Each area must be controlled by the use of such administrative procedures and such devices as are necessary to ensure that the area is cleared of persons before each use of the source of radiation.

     (h) Each area must be checked by a radiation measurement to ensure that, before any person enters the area after any use of the source of radiation, the radiation level from the source of radiation in the area is below the level at which it would be possible for a person to receive a deep-dose equivalent in excess of 0.1 rem in 1 hour.

     (i) The entry control devices required pursuant to paragraph (a) must be tested for proper functioning in the following manner:

          (1) Testing must be conducted before the initial operation of the source of radiation on any day, unless operations were continued uninterrupted from the previous day;

          (2) Testing must be conducted before the resumption of operation of the source of radiation after any unintentional interruption; and

          (3) The licensee shall submit and adhere to a schedule for periodic tests of the entry control devices and warning systems.

     (j) The licensee shall not conduct operations, other than those necessary to place the source of radiation in safe condition or to effect repairs on control devices, unless control devices are functioning properly.

     (k) Entry and exit portals that are used in transporting materials to and from the area and that are not intended for use by persons to enter or exit the area, must be controlled by such devices and administrative procedures as are necessary to protect and warn against inadvertent entry by any person through these portals. Exit portals which are for irradiated materials must be equipped to detect and signal the presence of any loose radioactive material that is carried toward such a portal and automatically to prevent loose radioactive material from being carried out of the area.

     2. Licensees or applicants for licenses who are subject to the provisions of subsection 1 and will use the source of radiation in a variety of positions or in locations which make it impracticable to comply with the requirements of subsection 1, may apply to the Division for approval of alternative safety measures. Alternative safety measures must provide persons with protection that is at least equivalent to the protection specified in subsection 1. At least one of the alternative measures must include an inter-lock control device that is designed to prevent entry based on a measurement of the radiation and that ensures the absence of high radiation levels before a person can gain access to the area where such sources of radiation are used.

     3. The entry control devices required by subsections 1 and 2 must be established in such a manner that no person will be prevented from leaving the area.

     4. As used in this section, sealed radioactive source means any by-product, source or special nuclear material that is used in sealed sources in irradiators that are not self-shielded.

     (Added to NAC by Bd. of Health, eff. 1-18-94)