how hot is clean?

[atomicarcheologist]

I was at the homefront this past weekend, mixing Cinco de Mayo and Mother's Day holidays when I ran across some old work buddies.  After some tequilas and catching up conversation, things turned to current affairs of the business.  We started discussing contamination levels, disposal practices, and some of the engineering tools now in place to deal with these things.  During the heat of the conversation, we could not agree on a limit of contamination (fixed) that could legally be left on interior surfaces of a building that is being delicensed.  I was appointed point man to put this subject to the readers of Nukeworker.com.  So, how much contamination can a licensee leave on their buildings' interior surfaces?

[PWHoppe]

Depends on who the licensee is. Are we talking the DOE or the NRC? Are we talking about EPA, State (various), and what sort of isotopes are we looking for; mfp, TRU, NORM, or other? The questions are almost endless. This can get into a really complex issue and one with no easy answer.

[RDTroja]

This can get into a really complex issue and one with no easy answer.

I couldn't agree more. The whole 'no detectable activity' mindset that the nuclear industry has adopted as a knee-jerk reaction to some mistakes that were made releasing contaminated materials is a prime symptom of the problem. As the science of detection improves and the limits get squeezed down, we are more frequently stuck with the 'by what standard' question. I dread the day when the MCA/GeLi is the release tool and the debate becomes 'how long a count is required to get the MDA low enough?', but I feel it coming if we don't get a good dose of sanity from somewhere.

[RDTroja]

Generally, (depends on the isotope) 5 k average, 15 k max.

Wow... if that is true, we should just leave everything we can't get out now in the buildings until they are delicensed and then they will be releasable... 

[JeffHawk]

Do a search for "MARSSIM" on the internet. This is the standard that we used to define what releasable means during the D&D work at Trojan.

[DDD]

You also have to consider inaccessable areas such as inbedded piping, If these areas are grouted you can get relief from the agencies to leave conciderably higher levels.

[alphadude]

You must look at the contributions- ground water, soil and structures as an integrated component. 25 mr/yr is a good limit. This must be divided up among the three components, if applicable, and there ya go.  Its always good to establish an ALARA limit like 10 mr/yr. 

Analysis of the Hard to Detects, then scale to Cs-137 or some nuclide you can readily detect and go from there. Pipe may be several thousand dpm/100cm2 before 1 mr/yr is reached, but that depends on the mix. Am-241 and the likes can lower your easy to detect limit. Dose based is always better than contamination based limits- Three Building Project was a good example of how much it cost...

[alphadude]

Yea seems to be some confusion, the LTP vs NRC license requirements are usually two different things. free release vs FSS  and so on. It all comes down to agreements. "clean" means no detectable in general. not really related to FSS, since we have Cs-137 and Sr-90 in the background and this must be integrated into the FSS when applicable.

[MrHazmat]

Hey DOT say's 22 dpm/cm2 Alpha , 220 dpm/cm2 Beta-Gamma , and 0.5 mRem/hr is clean 

[radgal]

That's for TRU. Depleted Uranium the numbers are different much higher,same is true but even more so for H3.  As others have stated above it depends on the isotope.

[SloGlo]

Hey DOT say's 22 dpm/cm2 Alpha , 220 dpm/cm2 Beta-Gamma , and 0.5 mRem/hr is clean 

dis iz what dot is sayeen these daze?  i thought it wazant crapped up until it waze, like, 22k or so, betagamma external to da package?

[atomicarcheologist]

This is beginning to sound like our conversation last weekend, albeit a whole lot more sober.
If you are allowed to leave 25 mr/yr, isn't that a lot more than 15Kdpm/100cm2 max per meter? 
Is imbedded piping involved?  Or is that a separate issue, ala groundwater/soil limits?

[Llama]

Most LTPs are written using the 25 mr/yr criterion. A Resrad is run using the resident farmer senerio to give you the DCGLs for the 25 mr/yr and then you are finished. Wrong! The state EPA and DEP looks at that and makes their determination. Some give and take goes on (mostly give) and a final criteria is decided on. Some states are going to a 10 mr/yr criteria and in some instances materials must meet a 1 mr/yr.

[alphadude]

back to the original question-are u looking for signs of pollution? or looking for some thumb rule to make things work?  pollution free or "clean" is "no detect."  and even thats based on methods used... (LLD, MDC etc)

all these numbers we see here, 5k 15k, 1mr/yr, dot limits, etc. are risk based limits. analytically thats not "clean." they may be acceptable which is different animal all together

[MrHazmat]

dis iz what dot is sayeen these daze?  i thought it wazant crapped up until it waze, like, 22k or so, betagamma external to da package?

The limits I posted are in cm2 not 100cm2, so actually it's 22000 and 2200 dpm/100cm2

[Phurst]

The limits I posted are in cm2 not 100cm2, so actually it's 22000 and 2200 dpm/100cm2

Perhaps you meant 2200 and 220 - know as Return to Service (RTS). DOT's way of saying clean. We recently asked them about it because it conflicts with NRC (None detectable). They reconfirmed that RTS is acceptable to send back to Mom and Pops Crib and pacifier shop.

[MrHazmat]

Perhaps you meant 2200 and 220 - know as Return to Service (RTS). DOT's way of saying clean. We recently asked them about it because it conflicts with NRC (None detectable). They reconfirmed that RTS is acceptable to send back to Mom and Pops Crib abd pacifier shop.

49CFR 173.443
(c) Except as provided in paragraph (d) of this section, each
transport vehicle used for transporting Class 7 (radioactive) materials
as an exclusive use shipment that utilizes the provisions of paragraph
(b) of this section must be surveyed with appropriate radiation
detection instruments after each use. A vehicle may not be returned to
service until the radiation dose rate at each accessible surface is
0.005 mSv per hour (0.5 mrem per hour) or less, and there is no
significant removable (non-fixed) radioactive surface contamination as
specified in paragraph (a) of this section.
    (d) Paragraphs (b) and (c) of this section do not apply to any
closed transport vehicle used solely for the transportation by highway
or rail of Class 7 (radioactive) material packages with contamination
levels that do not exceed 10 times the levels prescribed in paragraph(a)

(a) The level of non-fixed (removable) radioactive contamination on
the external surfaces of each package offered for transport must be kept
as low as reasonable achievable. The level of non-fixed radioactive
contamination may not exceed the limits set forth in Table 9 and must be
determined by either:
    (1) Wiping an area of 300 cm\2\ of the surface concerned with an
absorbent material, using moderate pressure, and measuring the activity
on the wiping material. Sufficient measurements must be taken in the
most appropriate locations to yield a representative assessment of the
non-fixed contamination levels. The amount of radioactivity measured on
any single wiping material, divided by the surface area wiped and
divided by the efficiency of the wipe procedure (the fraction of
removable contamination transferred from the surface to the absorbent
material), may not exceed the limits set forth in Table 9 at any time
during transport. For this purpose the actual wipe efficiency may be
used, or the wipe efficiency may be assumed to be 0.10; or
    (2) Alternatively, the level of non-fixed radioactive contamination
may be determined by using other methods of equal or greater efficiency.
    Table 9 is as follows:

    Table 9--Non-Fixed External Radioactive Contamination Limits for
                                Packages
------------------------------------------------------------------------
                                                  Maximum permissible
                                                         limits
                 Contaminant                  --------------------------
                                                Bq/cm2  uCi/cm2  dpm/cm2
------------------------------------------------------------------------
1. Beta and gamma emitters and low toxicity          4     10-4      220
 alpha emitters..................... .........
2. All other alpha emitting radionuclides....      0.4     10-5       22
------------------------------------------------------------------------
If you follow this completely you come up with 2200 and 220,(10% Eff.) but if the limit is 220/cm2 and you have 100 cm2 you would actually have 22000 dpm/100cm2. Not easy to understand if you are not use to dealing with Lawyer written regulations.

[Phurst]

49CFR 173.443
(c) Except as provided in paragraph (d) of this section, each
transport vehicle used for transporting Class 7 (radioactive) materials
as an exclusive use shipment that utilizes the provisions of paragraph
(b) of this section must be surveyed with appropriate radiation
detection instruments after each use. A vehicle may not be returned to
service until the radiation dose rate at each accessible surface is
0.005 mSv per hour (0.5 mrem per hour) or less, and there is no
significant removable (non-fixed) radioactive surface contamination as
specified in paragraph (a) of this section.
    (d) Paragraphs (b) and (c) of this section do not apply to any
closed transport vehicle used solely for the transportation by highway
or rail of Class 7 (radioactive) material packages with contamination
levels that do not exceed 10 times the levels prescribed in paragraph(a)

(a) The level of non-fixed (removable) radioactive contamination on
the external surfaces of each package offered for transport must be kept
as low as reasonable achievable. The level of non-fixed radioactive
contamination may not exceed the limits set forth in Table 9 and must be
determined by either:
    (1) Wiping an area of 300 cm\2\ of the surface concerned with an
absorbent material, using moderate pressure, and measuring the activity
on the wiping material. Sufficient measurements must be taken in the
most appropriate locations to yield a representative assessment of the
non-fixed contamination levels. The amount of radioactivity measured on
any single wiping material, divided by the surface area wiped and
divided by the efficiency of the wipe procedure (the fraction of
removable contamination transferred from the surface to the absorbent
material), may not exceed the limits set forth in Table 9 at any time
during transport. For this purpose the actual wipe efficiency may be
used, or the wipe efficiency may be assumed to be 0.10; or
    (2) Alternatively, the level of non-fixed radioactive contamination
may be determined by using other methods of equal or greater efficiency.
    Table 9 is as follows:

    Table 9--Non-Fixed External Radioactive Contamination Limits for
                                Packages
------------------------------------------------------------------------
                                                  Maximum permissible
                                                         limits
                 Contaminant                  --------------------------
                                                Bq/cm2  uCi/cm2  dpm/cm2
------------------------------------------------------------------------
1. Beta and gamma emitters and low toxicity          4     10-4      220
 alpha emitters..................... .........
2. All other alpha emitting radionuclides....      0.4     10-5       22
------------------------------------------------------------------------
If you follow this completely you come up with 2200 and 220,(10% Eff.) but if the limit is 220/cm2 and you have 100 cm2 you would actually have 22000 dpm/100cm2. Not easy to understand if you are not use to dealing with Lawyer written regulations.

You left out 173.443 (a) 1 where it gives the 10% efficiency

[MrHazmat]

It's there just out of order.

[atomicarcheologist]

Most LTPs are written using the 25 mr/yr criterion. A Resrad is run using the resident farmer senerio to give you the DCGLs for the 25 mr/yr and then you are finished. Wrong! The state EPA and DEP looks at that and makes their determination. Some give and take goes on (mostly give) and a final criteria is decided on. Some states are going to a 10 mr/yr criteria and in some instances materials must meet a 1 mr/yr.

How would you run a ResRad approach if you were not going to use the resident farmer scenario?  Perhaps the future use of the structure could be for an occupational or factory use only.  We could house lawyers or mill hunkies and that should change the numbers greatly, yes?

[Llama]

NUREGs have sugested a more realistic approach to the resident farmer. You can model it more realistically (i.e. if there are deed restrictions on the LTP). Therefore the modeling can reflect a truer future use of the land. The problem is to get a buy-in of all parties involved.


btw: MARSSIM I still have that cold brew awaiting you when you stop by

[RAD-GHOST]

AA,

You may be on to something with the Release Criteria based on Occupations!  I don't believe you could ever include lawyers in the D&D equation.  If you interjected lawyers into the calculation, " Worth vs Risk ", you would be Free Releasing the Commercial Plants at 100% Power!

Sorry, but I couldn't resist, RG! 

[atomicarcheologist]

AA,

You may be on to something with the Release Criteria based on Occupations!  I don't believe you could ever include lawyers in the D&D equation.  If you interjected lawyers into the calculation, " Worth vs Risk ", you would be Free Releasing the Commercial Plants at 100% Power!

Sorry, but I couldn't resist, RG! 

OK, thanks.  But to get back onto the topic, how much can one leave behind as clean with a delicense operation?  Could we assume that 100K/100 cm2 of Co60 would be OK?  Could we go to 150K if it was only U238?  What would the transuranics work out to?

[RDTroja]

OK, thanks.  But to get back onto the topic, how much can one leave behind as clean with a delicense operation?  Could we assume that 100K/100 cm2 of Co60 would be OK?  Could we go to 150K if it was only U238?  What would the transuranics work out to?

I have to admit total ignorance when it comes to D&D work, but if 100K/100cm² of Co60 is releasable anywhere, then what the hell are we worried about releasing items and areas that are over 1Kdpm/100cm² in the commercial end of the world? Or for that matter having release limits of 'No detectible activity' even considered if we are just going to release it all later at 100K?

That does not compute...

[raymcginnis]

At our site, the related questions that keep coming up are what is MDA and what is background.  We are politically driven on these two questions by protestors and community groups.  We have this big push from them to go to 10-6 levels, similar to chemical sites.  The problem is the natural radioactivity that has been here since the earth was created.  To get to 10-6 risk for uranium in soil, the labs would have to analyze the samples for 10 weeks to meet the MDA. 

If you have no community groups, then the answers given previously are correct.  For buildings, Mike was right.  Those are the most common limits.  For soil, you have to consider all the possibilities of land use and pick either the most likely, or if your politics drive it, the most conservative. 

When we use RESRAD for soil, we always go for "Family Farm" (most conservative) because of our politics.

We also use NDA for facilities and equipment when possible, but we have to state on our surveys what NDA is.  In general, we use ALARA as our goal.  For soil we use 15 mRem/yr as our limits in RESRAD, but we always try to get way below that.  MARSSIM explains all of these principals very well.  That is the path we are all on now, unless you are somehow grandfather claused out of MARSSIM.  Some NRC places may still be able to use 100 mRem/yr.  There is no standard for what is hot now.  It is all under debate.  There are NRC, DOE and DOD standards, but they all still disagree on this.  It is what you can negotiate with your regulator that sets your true limits.  That is determined by your local politics.  That is what I have found.  If you travel from place to place, your limits may change from place to place, depending on politics.

Nuff said.