RE: MDA vs. Critical level for DOE Free Release surveys

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

Tom,



I refer to statistics as "sadistics" and I'm certainly not an expert at any

this.  I'll tell you what we do (DOE facility, NRC agreement state).



1.  We use the DOE 5400.5 surface contamination values (uranium 5000 dpm/100

cm2 total and 1000 dpm/100 cm2 removable); at times we also use the 15000

dpm/100 cm2 maximum depending on the value of the object.  Items are subject

to at least one decon to get the levels down - the ALARA statement in

5400.5.  The state accepts these values for free release.  Of course if its

metal, then we have to abide by the Richardson memo - no metal released if

its been in a contaminated area.  The 5400.5 values are consistent with Reg

Guide 1.86 values (even though some folks claim the 1.86 values are not for

free release).



2.  I'm not familiar with any reference or regulatory standard on whether to

use MDA or Lc; however, the EM-30 Performance Objective issued by DOE in the

early 90's basically said to pick one and justify it (for volumetric

release).  In my opinion (sadistically speaking) Lc is the correct value if

your objective is not to release any radioactive material (at whatever

confidence you choose).  Using Lc is impossible in the field due to varying

backgrounds, each instrument has a different efficiency, each tech uses a

different distance to the surface .. . .).



3.  See number 2.  The MDA value is what the instrument will detect with XX

% confidence (most people use 95%).  If you have an MDA of 100 dpm and a

sample is 100 dpm, then you'll have a distribution around your MDA - count

the sample with exactly 100 dpm in it twenty times and statistically 50% of

the time the value will be less than 100 dpm and 50% of the time the number

will be more than 100 dpm 50% of the time (sometimes you'll get exactly 100

dpm; sometimes, about 5% of the time using 95% confidence you'll get a value

less than the Lc).  Anyway, using the MDA to state that nothing is there is

not correct, that's where Lc comes in.  Check some of Brodsky's work and

NUREG 1400 contains some good info on MDAs and Lc.



Like I said, don't base anything on what I wrote - "sadistics."



Randy Redmond (32458)

Radiological Control Organization

BWXT Y-12 L.L.C.

Oak Ridge, TN

865-574-5640







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

> From:	Goff, Tom [SMTP:Tom.Goff@wipp.ws]

> Sent:	Tuesday, October 28, 2003 2:27 PM

> To:	''RadSafe Send Message'

> Subject:	MDA vs. Critical level for DOE Free Release surveys

> 

> > 	Title: 

> > 

> > 	We are discussing using a critical level for free release surveys.

> > Please provide answers to the following:

> > 	 

> > 	Are you using critical value or MDA for free release surveys of

> > materials from your site?

> > 

> > 	Does anyone have a reference/regulatory standard on whether to use

> > MDA or critical value for free release surveys?

> > 

> > 	Given that an MDA results in a 95% confidence in detecting

> > contamination at the MDA value, what is the corresponding confidence if

> > using the critical level?

> > 

> > 	I would welcome any other comments or thoughts on this.

> > 

> > 	Tom Goff

> > 	

> >

> --------------------------------------------------------------------------

> > ----------------------------------------------------------------

> > 	Let me know if you're ok with this.

> > 

> > 

> > 

> > 	Tom Goff

> > 	WIPP ALARA Coordinator

> > 	WIPP Integrated Waste Operations

> > 	(505) 234-8861

> > 	(fax)  234-8963

> > 	e-mail  Tom.Goff@WIPP.ws

> > 	page (505) 234-8850  (pager 479)

> > 	P.O. Box 2078

> > 	Carlsbad, NM 88221

> > 	Radiological Engineering: Anticipating Problems.....providing

> > solutions!!!

> > 

> 

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