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17 March 2010

Answer to Question #4404 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Shielding

The following question was answered by an expert in the appropriate field:

In the CHP (certified health physicist) exam, part 1, last year they asked: What is the shielding height requirement, in the walls, of a medical x-ray facility? The answers were all even numbers, i.e., 6, 8, 10, and 12 feet. As I understand National Council on Radiation Protection and Measurements (NCRP) Report No. 49 this requirement is 7 feet. I feel that I am missing something and was hoping that you could tell me the correct answer to this question.

You are correct in that NCRP 49 recommends 7 feet as a minimum for any recommended shielding. Keeping in mind that the instructions on the CHP exam are to "choose the best answer," your answer should be 8', because 6 is not enough, 10 and 12 may not be practical for many installations, and commercially available lead-lined drywall is available in 8' lengths.

Ken "Duke" Lovins, CHP

Answer posted on 22 April 2005. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.