United States Nuclear Regulatory Commission - Protecting People and the Environment

Health Physics Position on Posting of High Radiation Areas

HPPOS-242 PDR-9111220087

See the memorandum from L. J. Cunningham to J. H. Joyner (and others) dated August 8, 1991. An area containing fields that would require classification as a locked high radiation area was enclosed by a licensee using an inaccessible wire cage which is sometimes referred to as a cocoon. Although staff practice has been that the cocoon need not be posted, it is a good safety practice to identify the area as hazardous by putting up a sign saying “CONTACT HEALTH PHYSICS BEFORE ENTRY” or other appropriate warning. The health physics position was written in the context of 10 CFR 20.201 and 20.203, but it also applies to the "new" 10 CFR Part 20, Sections 20.1003 and 20.1902.

A licensee in Region V enclosed an area containing radiation sources in a wire cage (or cocoon) that extended from the floor to the ceiling with no gate or access point. The sources of radiation were some valves and associated piping that produced a radiation field of up to 1.5 R/hr at 18 inches from their surfaces. Such fields would require that the area be controlled as a locked high radiation area. However, instead of locking the whole area, which was a room, the licensee constructed a wire cage around the source. The cage was of such a size that the radiation fields outside the cage were consistent with the postings for the room. No postings were attached to the cage.

According to 10 CFR 20.203 (c), “Each high radiation area shall be conspicuously posted with a sign or signs bearing the radiation caution symbol ....” The requirement does not indicate whether the posting is designed only for access control purposes, or also to identify the area itself, regardless of immediate intent to enter it. [Note: 10 CFR 20.1902 (b) states: “The licensee shall post each high radiation area with a conspicuous sign or signs bearing the radiation symbol ....”] 10 CFR 20.202 (b) (3) defines a high radiation area as “any area, accessible to personnel, in which there exists radiation ....” Therefore, an area that is not accessible would not be classified by staff as a high radiation area requiring posting. Since the cocoon is constructed to be inaccessible, the staff practice has been that it need not be posted. However, the cocoon may be made accessible by breaking the barrier, such as, for example, by cutting a hole in the wire cage. Once opened and "accessible", the area becomes a high radiation area requiring posting.

Note: 10 CFR 20.1003 defines a high radiation area as “an area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.”]

Although staff practice has been that posting the cocoon does not involve the posting requirement of 10 CFR 20.203 (c) [or 10 CFR 20.1902 (b)], identification of hazardous areas, such as putting up a sign saying “CONTACT HEALTH PHYSICS BEFORE ENTRY,” is good safety practice. Records that identify the nature of the hazard in the cocoon may be lost or may not be readily available to persons who may have to enter the area, especially in an emergency.

Although a cocoon does not have an access point such as a door, a major leak, fire, or similar contingency may make it necessary to break the cocoon and enter. The absence of postings in such situations could present a hazard to personnel making the entry. In addition, once the cocoon has been broken and the area has been made accessible, the licensee would be in violation unless proper postings had been made before opening the cocoon.

Regardless of the policy adopted for areas enclosed in a cocoon, that policy must be included in the radiation worker training material to satisfy the requirement of 10 CFR 19.12, “Instructions to Workers.” This health physics position was developed by NRR's Radiation Protection Branch and has been coordinated with all NRC Regional Offices and NMSS. The Office of the General Counsel has no legal objections.

Regulatory references: 10 CFR 19.12, 10 CFR 20.202, 10 CFR

20.203, 10 CFR 20.1003, 10 CFR 20.1902

Subject codes: 1.2, 4.1, 4.7

Applicability: Reactors

Page Last Reviewed/Updated Thursday, March 29, 2012