Unrestricted area

Unrestricted area is an area in which an individual could receive from an external source a maximum dose of 2 mrem (20 pSv)/h, and access to the area is neither limited nor controlled by the licensee. 

Caution Radioactive Material or Danger Radioactive Material This sign is posted in areas or rooms in which ten times the quantity or more of any licensed material specified in Appendix C of 10CFR20 are used or stored. All containers with quantities of licensed materials exceeding those specified in Appendix C of 10CFR20 should be labeled with this sign. These labels must be removed or defaced prior to disposal of the container in the unrestricted areas. 

Maximum permissible concentration In air released to unrestricted areas... 

Those portions of 10CFR20 specifying permissible occupational dose levels and levels of radiation and activity concentrations in unrestricted areas are consistent with all of the selection bases and, therefore, are included as top-level regulatory criteria. 

Section 20.106 - Radioactivity in effluents to unrestricted areas Limits specified in Appendix B, Table II. 

One last type of radioactive material for which special storage criteria would be needed is in the relatively rare instances where neutron radiation sources would be used. Neutron radiation would be found primarily in reactor facilities, but neutron sources are also used in moisture density probes in a number of research areas. If the source were to be taken from the instrument, the shielding would need to consist of a layer of plastic or paraffin, 5 to 20 cm thick, either impregnated with boron or surrounded by cadmium. Some gamma shielding also might be required in an unrestricted area, vvhich could be provided by lead or in some cases by concrete blocks. 

Public dose is an exposure of a member of the public to radiation or to the release of radioactive material, or to another source, either in a licensee s controlled area or in unrestricted areas. This does not include background radiation or any kind of medically related exposures. 

The licensee must conduct operations in such a way as to ensure (1) that the total effective dose to individual members of the public from the licensed operation does not exceed 100 mrem (1 mSv) in 1 year, exclusive of the dose contribution from the licensee s disposal of radioactive materials into sanitary sewerage, and (2) the dose in any unrestricted area from external sources does not exceed 2 mrem in any 1 hour. 

A licensee must control and maintain constant surveillance of licensed materials that are in a controlled or unrestricted area and that are not in storage. 

Losses of significant amounts of radioactive materials must be reported to the NRC both by telephone and by a written report. If the amount that is not accounted foris equal to orgreater than 1000 times the quantity specified in Appendix C to 10 CFR Part 20, and it appears that an exposure could affect persons in unrestricted areas, the loss shall be reported by telephone as soon it is known to the licensee. Within 30 days after lost, stolen, or missing material is discovered, the NRC must be notified by telephone of any amount greater than 10 times the quantity specified in Appendix C that is still missing at that time. Most facilities will make their report to the NRC Operations Center. 

If licensed materials are stored in an unrestricted area, the materials must be securely locked topreventtheirremovalfromthe area. Many materials used in the life sciences mustbe kept either in refrigerators or freezers, which should be purchased with locks or equipped with padlocks afterward. If the radioactive materials in an unrestricted area are not in storage, they must be under the constant surveillance and immediate control of the licensee. 

It has already been noted that materials in unrestricted areas must be kept in secure storage when the user is not present. This requirement for security is applicable whenever the facility... 

It is rare for radioactive material to be taken deliberately one of the most common loss mechanisms is loss as trash, as already discussed. If it is a reportable incident,the NRC mustbe informed immediately by telephone or by a written report filed within 30 days of the specifics as to what was lost and the circumstances concerning the disappearance ofthe material. They wUl wish to know, to the best of the licensee s knowledge, what happened to the material and the possible risks to individuals in unrestricted areas. The steps taken to recover the material will need to be in the report and probably most important, the steps the facility intends to take to... 

A s noted above, a level of removable alpha contamination between nondetectable and about 0.3 nanoCi (10 Bq) per 100 cm is considered acceptable by many different groups for an unrestricted area. In restricted areas some organizations still do not accept any stray alpha contamination, except in the immediate work area, such as the inside ofa hood. However, a level of about 0.8 nanoCi or 30 Bq per 100 cm is considered acceptable by others. 

For beta and gamma contamination, otherwise unspecified, levels of 0.1 to 1 nanoCi per 100 cm are considered acceptable by various organizations for unrestricted areas. Forrestricted areas, these organizations usually make the acceptable levels ten times higher, i.e.,... 

OSHA requires the designation of restricted areas to protect individuals from radiation exposure. The term unrestricted area refers to any area access not controlled by the employer for purposes of protection of individuals from exposure to radiation. No employer can possess, use, or transport radioactive material within a restricted area that causes individuals to experience airborne radioactive material exposure in excess of limits specified in Table 1, Appendix B to 10 CFR 20. When monitoring exposure, make no allowance for the use of protective clothing or equipment, or particle size. 

The external and internal doses are then summed to evaluate compliance with the radiation dose limits. Table 25.1 lists these limits. For the general public, there is an additional dose limit for unrestricted areas that requires that the dose received in any 1 h must be <0.002 rem. This limit is not a dose "rate" but a limit. The 0.002 rem could be reached in 1 min, a "rate" of 0.120 rem/h, but if no other dose is received in the remainder of the hour, then the limit has not been exceeded. This requirement is worded... 

Unrestricted area means any area access to which is not controlled by the employer for purposes of protection of individuals from exposure to radiation or radioactive materials. 

Nuclear Regulatory Conmission Standards for Protection Against Radiation (10 CFR 20) 1 These regulations apply to activities licensed by the Nuclear Regulatory Commission and specify radiation dose standards for individuals in restricted and unrestricted areas. (See Table 2 for emission concentration limits.) Relevant and appropriate standards for the emission of specific radionuclides. Managing remediation activities in a manner to ensure emission standards are not exceeded. Monitoring remediation activities in a manner to verify emission standards are not exceeded. 1 2 3 4 o i 1— 0 5. VO SC X9 vO (P O - ... 

State regulations specifying radiation dose standards for permissible levels of radiation in unrestricted areas. Table II of Appendix A itemizes the allowable concentrations in air above natural background. The values in Table II are the same as the values in Table II, appendix B, Nuclear Regulatory Commission Standards (10 CFR 20). 

The total effective dose equivalent to any individual member of the public cannot exceed 0.1 rem in a year, exclusive of the contribution from the license s disposal of waste. The dose in any unrestricted area shall not exceed 2 mrem in any... 

Because of this very great hazard, NRC regulations for radioiodines in the work environment are especially stringent. For example, the limits for I in air are 5 X lO microcuries per cubic meter for restricted (work) areas, and 8 X 10 5 microcuries per cubic meter for unrestricted areas. The following special techniques and procedures are recommended to help control exposure to radiations from radioiodine. 

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