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18 March 2010

Answer to Question #255 Submitted to "Ask the Experts"

Category: Policy, Guidelines, and Regulations — Decommissioning and Disposal

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

Where might I locate European standards that provide the minimum levels of radioactivity that are to be detected by a 100 cm² probe used for monitoring medical radiation areas?

The minimum levels of radioactivity are not clearly defined for use in the United Kingdom. In practice, many hospitals work to 30 Bq/cm² for low toxicity nuclides while industry tends to work to 0.4 for alpha and 4 for beta emitters in the workplace and a factor of 10 down for free release materials from site clearance. Following is a translation of the German regulations:

Radionuclide	Workplace surfaces and the outer surfaces of protective clothing in controlled areas	Objects, clothing in occupationally monitored areas	Objects, clothing outside occupationally monitored areas
Alpha emitters for which an exemption level of 5kBq is specified	5	0.5	0.05
Beta emitters and electron capture nuclides with an exemption level of 5MBq*	500	50	5
Other radionuclides	50	5	0.5

Also applies to ¹⁴C, ³³P, ³⁵S, ⁴⁵Ca, ⁵⁵Fe, ⁶³Ni, ⁴⁸V, ¹⁴⁷Pm.
All in Bq/cm² averaged over 100 cm.
Does not include fixed activity which is not available for uptake.

Peter Burgess
National Radiological Protection Board United Kingdom

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