Technical Assistance Request, Use of Portable Shields for a High Dose Rate Afterloader Facility at Washington Hospital Center, Washington, D.C.
See the memorandum from J. E. Glenn to R. R. Bellamy dated June 25, 1992.
This NMSS memo responds to a technical assistance request from Region I, dated March 26, 1992, concerning Washington Hospital Center's request to relocate their high dose rate afterloader to a new location and use portable lead shadow shields to obtain compliance with the dose limits of 10 CFR 20.1301 for members of the public. The request was reviewed and the following guidance is given.
Although NRC's Policy and Guidance Directive, FC 86-4, for licensing high dose rate afterloaders presumes the necessary room shielding is obtained by the use of appropriate fixed wall, floor, and ceiling materials, it does not explicitly require it. However, portable shield should not be permitted as a permanent means of providing shielding for high dose rate afterloading facilities. This requirement is consistent with the recommendations contained in the most recent draft of the AAPM Task Group on Remote Afterloading Systems.
Washington Hospital Center may be allowed to use the portable shields on a temporary or emergency basis to insure patient care is not impacted. If portable shield are used, a positive method of ensuring the shield (s) are correctly positioned for each treatment must be provided, and "per patient" surveys must be performed for each treatment to insure that exposure rates in unrestricted areas comply with 10 CFR 20. The licensee would be expected to commit to the installation of appropriate permanent shielding within a reasonable period of time. The hospital must be made aware that the use of a cantilevered shield for limiting the exposure to the adjacent uncontrolled area above the treatment room may raise additional safety concerns about patient injury from improper design, maintenance, or mishandling during positioning of the shield.
After review of the technical assistance request, the licensee apparently omitted any description of the area security for the treatment room. Such a description is required by V (c) of FC 86-4. Since the licensee is proposing to locate the high dose rate afterloader with an existing superficial treatment machine, it is essential that they implement and describe a means of assuring that only one of the two radiation producing devices can be operated at a time. Also, the proposed shadow shield for the door and window would appear to obscure observation of the patient during treatment. If this is the case, the licensee must provide an alternate means of viewing the patient during treatment.
Regulatory references: 10 CFR 20.1301, 10 CFR 20.1302
Subject codes: 4.4, 5.3, 7.1, 12.8
Applicability: Byproduct Material