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Re: Powernet: NRC revision of Skin Dose limit - How does it relate to NCRP recommendations?
What is the meaning of 'essentially equivalent to the former skin dose
limit'. 0.1 Sv over 10 cm2 would seem to be equivalent to twice the
former skin dose limit of 0.5 Sv over 1 cm2. Please correct me if
necessary. The factor of 2 is not trivial because of the threshold-type
dose response for deterministic effects. At 0.5 Sv over 1 cm2 the claim
that no clinically significant effects have ever been observed is probably
true. For 0.1 Sv over 10 cm2 it is not true - hence the NCRP
reservation in publication 130. The need to avoid unnecessary
regulatory burden seems to be the over-riding factor in not enforcing
the NCRP recommendations in toto, and this may indeed be justifiable.
But the possibility of the new hot particle dose limits giving rise to a
small incidence of ulcerations should not be forgotten. While this may
be acceptable in the USA it is unlikely to be acceptable in some other
parts of the world - such as the UK.
Best regards
Monty Charles
*****************
On 26 Jul 2002 at 8:17, Alan Roecklein wrote:
> 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
>
> -----------------------------------
> Reply to: powernet@hps1.org
> If Questions, contact Mike Russell, CHP at russelmj@songs.sce.com
>
>
Dr Monty Charles
Reader in Radiation Physics
Head of Radiation Biophysics Group
School of Physics & Astronomy
The University of Birmingham
Edgbaston
Birmingham
Tel 0121 414 3483
Fax 0121 414 4725
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