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Fwd: Re: Powernet: NRC revision of Skin Dose limit - How doesit relate to NCRP recommendations?





In FR Notice of Final Rulemaking (67FR16289;April 5,2002),the NRC  discussed the NCRP recommendations published in NCRP 130 and Statement No.9. The NRC staff said  that the recommended observational level for a DRP exposure of 10 rem (0.1 Sv) is well below the new limit of 50 rem (0.5 Sv) averaged over 10 cm2. It is essentially equivalent to the former skin dose limit, at which no clinically significant effects have ever been reported. The NCRP  stated in Report No. 130 that based on extensive research at BNL and elsewhere, at the new limit few if any effects are expected to be observed, and those effects would be transient in nature. NCRP further stated that if effects are observed from a DRP exposure, the result is an easily treated medical condition involving an extraordinarily small stochastic risk.

For these reasons, and to avoid unnecessary regulatory burden, the staff did not incorporate the NCRP recommendation for medical observation into the new rule. The staff did note in the FR Notice that the NCRP reports addressed this and other "good practices" that might be useful in controlling skin doses.



>>> m.w.charles@bham.ac.uk 07/18/02 06:29AM >>>

Recently Alan Roeklein kindly circulated the NRC summary regarding the 

skin dose limit in 10 CFR part20.  This essentially increases the averaging 

area from 1 cm2 to 10 cm2 but keeps the dose limit of 0.5 Sv fixed. The 

summary follows closely the NCRP statement 9 (March 30, 2001) - although 

this is surprisingly not mentioned in the statement.  However, the NRC 

summary does not include an important part of the NCRP recommendation - 

in the event of the skin dose exceeding 0.1 Gy averaged over an area of 10 

cm2 the area should be observed for 4-6 weeks.  At the new dose limit - 

which is effectively 5 Sv averaged over 1 cm2 - there is about a 50% 

probability of a skin lesion from a hot particle (NCRP 130).



Does anyone know why the NRC have not implemented the NCRP 

recommendations in full?  I believe that NRC deliberations are sometimes 

recorded and publicly available. If there is any recorded discussion on this 

topic please can anyone direct me to it?



Many thanks



Monty Charles

Dr Monty Charles, Reader in Radiation Physics

Head of Radiation Biophysics Group

School of Physics & Astronomy

University of Birmingham, Edgbaston

Birmingham B15 2TT, England

M.W.Charles@bham.ac.uk 

TEL +44  0121 414 3483

FAX +44  0121 414 4725



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If Questions, contact Mike Russell, CHP at russelmj@songs.sce.com



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