RE: Release Criteria - Fe55

["Redmond, Randy R. (RXQ) " <RXQ@Y12.doe.gov>]

I suggest determining the contribution of Fe-55 (I'm sure you have this

information) and then establishing a surrogate(s) (Co-60, Cs-137) that can

be measured by field techniques;  lower your release limit based on the

Fe-55 contribution.



Randy Redmond

BWXT Y-12 L.L.C.

Y-12 National Security Complex

Radiological Control Organization

Email:  rxq@Y12.doe.gov

Phone:  865-574-5640

Fax:  865-574-0117





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

> From:	Yann Donjoux [SMTP:Yann.Donjoux@cern.ch]

> Sent:	Wednesday, September 12, 2001 2:36 AM

> To:	radsafe@list.vanderbilt.edu

> Cc:	Hall, Donald C. Jr

> Subject:	Re: Release Criteria - Fe55

> 

> "Hall, Donald C. Jr" wrote:

> > 

> > We would like information on how other nuclear plant radiological

> protection

> > programs address "hard-to-detect" isotopes such as Fe-55 with regard to

> > release of personnel and materials from Radiologically Controlled Areas

> > (RCAs).

> 

> Dear Sir,

> 

> I would be very interested if you have any reports concerning your

> question, if you could forward any answers.

> I have been involved, in the past into Fe-55 measurement. The only non

> destructive method that we tested was X-Ray spectrometry using a Si PIN

> detector (called XR-100T, Amptek) to detect Fe-55 X-Ray (5.9 keV).

> Unfortunately, such kind of detector are not stable and can not be

> efficiency calibrated. We then used a comparative method, since most of

> the sample also have Mn-54 in it. We then make a comparison between area

> of Mn-54 X-Ray peak (5.4 keV) and Fe-55 X-Ray peak (5.9 keV). By a

> "standard" gamma spectrometry we determine the amount of Mn-54 and by

> calculation can obtain the quantity of Fe-55 (taking into account auto

> absorption, difference of efficiency of the XR-100T between Fe-55 &

> Mn-54 and so on...). We then tried to evaluate the success of this

> method, by intercomparison with a chemical process, but the chemical

> process has never been conducted to its final state and we now have more

> important things to carry on. Consequently, I cannot tell you if it's a

> good method or not. Anyway, in accelerator, the activation is not

> uniform, and you generally measure with this non-destructive method only

> the first micrometer (depth) of the material, which maybe not

> representative.

> 

> PS: interesting article: Applied radiation Isotopes, Vol 43, No 11, pp

> 1355-1362 (1992)

> [Int. J. Radiat. Appl. Instrum. Part A]

> 

> For information, France has no release criteria, and switzerland takes

> 30 Bq/g (free release) or 5 MBq.

> 

> Regards,

> -- 

>  _____________________________________________________________

> | Yann Donjoux   Division TIS / Radioprotection (RP) - E07900 |

> | CERN, Organisation européenne pour la Recherche Nucléaire   |

> | CH-1211 Geneve 23, Switzerland.                             |

> | Electronic mail      Yann.Donjoux@cern.ch                   |

> |_____________________________________________________________|

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