Answer to Question #320 Submitted to "Ask the Experts"

Q

I've heard from several sources that the limits in RG 1.86 (and the current DOE Order 5400.5) are based on instrument sensitivity. Is this true? If so, is there any move afoot to revisit the 5400.5 limits?

A

You have touched on a long and somewhat controversial subject. Let's consider the first part of your question. The current release limits specified in the Department of Energy's Order 5400.5 are almost identical to those previously published in the Atomic Energy Commission's Regulatory Guide 1.86 in 1974. These are often referred to as "table value" release criteria. I was not present when these values were issued, however I have also been told by good sources that detection sensitivity—in a gross manner—was a consideration. If one reviews the table, however, you find that some of the radionuclides cannot be measured reliably at the limits specified using modern instrumentation—much less using those popularly used in 1974. It can therefore be assumed that detection was not the only parameter. There is more political consideration facing the change of these values than there is technical since it is difficult to change something that has been used for such a long time. Nonetheless, current protocols for release of facilities and land for uncontrolled use are in fact moving in a different direction. All government agencies are currently either recommending or allowing the use of site-specific, dose-based release standards for this purpose. Operational aspects, however, dealing with worker protection still require the use of "table" values for safety and contamination control. In summary, the release of sites and facilities (property) for public use is moving towards model-derived dose (or risk) based limits. It is also likely that a similar trend could emerge for the release of consumer and industrial products to the public. Operational health protection and contamination control limits are still specified as prescribed table values and seem unlikely to change any time soon. Robert Coleman Oak Ridge National Laboratory