RE: 10CFR20 mistake?

[david.nestle@EXELONCORP.COM]

I had to pull out my old dosimetry notes here, but I did find where we were

taught that Quality Factors, and thus dose equivalents, were not valid "for

accidents (above 15 rem)".  Given the difference in the dose and dose

equivalent values provided in the referenced sections (250 rads in

20.2202(a)(1)(iii); 50 rems in 20.2202(b)(1)(iii)), it may be that the NRC

is applying similar logic, but at a higher threshold.

______________________________________________________________

David R. Nestle, Health Physicist

Exelon Nuclear, Dresden Generating Station

T   815.942.2920 x3468

F   815.942.2920 x2563

www.exeloncorp.com



> -----Original Message-----

> From:	Jack Couch [SMTP:jgcouc@PLANETX.BLOOMU.EDU]

> Sent:	Thursday, April 05, 2001 1:47 PM

> To:	Sandy Perle

> Cc:	radsafe@list.vanderbilt.edu

> Subject:	Re: 10CFR20 mistake?

> 

> At 07:13 AM 4/5/01 -0700, Sandy Perle wrote:

> 

> ___Jack Couch___

> >> 20.2202 (a)(1)(iii) "A shallow-dose equivalent to the skin or

> extremities

> >> of 250 rads(2.5 Gy)..."

> >> Note the units used here for shallow-dose equivalent. It is the same in

> >> earlier editions of 10CFR20. In (b)(1)(iii) the units are in rems (Sv).

> 

> >> 

> >> Do you suppose there is a reason behind the difference in units, or is

> it

> >> just another governmental boo-boo? 

> >

> ___Sandy Perle___

> >This is not an ewrror. It;s simply a degree of the exposure and the 

> >definition, as defined below:

> >

> >§20.1004 Units of radiation dose.

> >(a) Definitions. As used in this part, the units of radiation dose 

> >are:

> >Gray (Gy) is the SI unit of absorbed dose. One gray is equal to an 

> >absorbed dose of 1 Joule/kilogram (100 rads).

> >Rad is the special unit of absorbed dose. One rad is equal to an 

> >absorbed dose of 100 ergs/gram or 0.01 joule/kilogram (0.01 gray).

> >Rem is the special unit of any of the quantities expressed as dose 

> >equivalent. The dose equivalent in rems is equal to the absorbed dose 

> >in rads multiplied by the quality factor (1 rem=0.01 sievert).

> >

> ___Jack Couch___

> Sandy, that's exactly my point. To reiterate, 20.2202 (a)(1)(iii)

> expresses

> (shallow) dose equivalent, not in SV and rem, but in Gy and rad. Later, in

> 20.2202 (b)(1)(iii) (shallow) dose equivalent is given correctly in Sv and

> rem.

> 

> regards,

> Jack

> 

> 

> 

> 

> 

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