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Information Notice No. 83-59: Dose Assignment for Workers in Non-Uniform Radiation Fields
SSINS No.: 6835 IN 83-59 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 September 15, 1983 Information Notice No. 83-59: DOSE ASSIGNMENT FOR WORKERS IN NON-UNIFORM RADIATION FIELDS Addressees: All nuclear power reactor facilities holding an operating license (OL) or construction permit (CP), research and test reactors, fuel cycle facilities, and all material licensees. Purpose: This information notice provides guidance to licenses on proper dose assignment to workers in non-uniform radiation fields. Licensees are expected to review the information provided for applicability to their facilities. No specific action or response is required. Description of Circumstances: Several power reactor licensees recently asked the NRC for guidance regarding proper assignment of extremity and whole body doses to workers involved in a specific steam generator (SG) maintenance activity. In an effort to reduce SG corrosion rates, licensees are increasing the frequency of sludge lancing--the removal of tubesheet chemical sludge by high pressure water jets ("hydrolasing"). Although improved, remote, dose-saving, ALARA techniques are becoming more available, workers still are required to manually insert an arm (only one at a time) through an SG handhole to assemble/disassemble and position sludge lancing equipment. Once the equipment is positioned, the actual sludge lancing operations can be performed essentially remotely, without exposing the worker to the high SG radiation fields. With the arm inserted, the head and trunk of the body are in a 1/2-1 R/hr radiation field, the upper arm is in a 3 R/hr radiation field, and the forearm and hand are in a 20-40 R/hr radiation field. During the course of work the arms are alternated and only one arm at a time is inserted into the SG. Licensees questioned whether each arm could receive the allowed quarterly dose, or thinking more conservatively, should the doses to the individual arms be additive. Additional guidance requested included defining the whole body areas of the arm. A further question concerned the applicability of the "skin of the whole body" dose limit to the hand and forearm (extremity) areas. 8308040051 . IN 83-59 September 15, 1983 Page 2 of 2 Guidance: Each arm can receive a dose up to the applicable regulatory limit. More generally, the dose received by each appendage may be separately determined and compared to the applicable regulatory limit when irradiation occurs in a non-uniform field; however, adequate surveys defining the radiation fields and a thorough dose evaluation must be performed to satisfy existing 10 CFR Part 20 requirements. Multiple dosimeters may be required to demonstrate compliance. Licensees are cautioned that increased personal monitoring vigilance for the remainder of the quarter may be required for affected workers. Records to satisfy the 20.401 requirements for surveys and monitoring results will necessarily become more complex. The NRC staff considers the "hand and forearm" to include the hand, the arm below the elbow, and the elbow. The whole body is defined in 20.101 to include gonads, active blood-forming organs, head and trunk, and lens of the eye; the staff considers the arm above the elbow as part of the whole body. Thus, for the situation described, monitoring should be provided for the lower arm area (extremity), the upper arm (part of the whole body), and the head and trunk of the whole body. If multiple dosimeters are used to monitor an area of interest (e.g., front and back of the trunk of the whole body), the dose for record keeping purposes is taken from the highest valid dosimeter reading. The limit to "skin of the whole body" (10 CFR Part 20) does not apply to the skin of the hand and forearm. Dose to the "hands and forearms" including the skin is limited to 18-3/4 rems in a quarter. Additional guidance on providing adequate personal monitoring is given in IE Information Notice No. 81-26, Part 3: Placement of Personnel Monitoring Devices for External Radiation Exposure (August 28, 1981) and its July 19, 1982 Supplement No. 1: Clarification of Placement of Personnel Monitoring Devices for External Radiation (see Attachments 1 and 2). If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office, or this office. Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement Technical Contact: J. E. Wigginton, IE (301) 492-4967 Attachments: 1. Information Notice No. 81-26, Part 3 2. Information Notice No. 81-26, Part 3, Supplement 1 3. List of Recently Issued IE Information Notices .
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