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RE: Pu contact dose rates



Franz,



I'll reply to RADSAFE as well, so that we can close this issue publicly.  I

apparently misunderstood your comments, so please accept my apology.  



I have perceived that there have often been suggestions on this list that

people are using it as a means of avoiding doing the work themselves.  While

this may happen sometimes (which would iritate me too), I don't believe that

to be the normal case.  Furthermore, DOE has been the object of many jokes,

and perhaps that has heightened my frustration level.  Since I was directly

named in your message, along with my association to DOE, I felt compelled to

respond, although perhaps it was in error.



As for the questions I originally asked, they are for real.  As I originally

mentioned, there have been many measurements and calculations published of

contact radiation dose rates for gammas, betas, and low-energy x-rays from

plutonium.  However, what I found is that since the alphas are easily

shielded by gloves and the dead layer of skin, the contact alpha dose rates

were apparently not as well documented, because they were not deemed as

important, since they were easily shielded (this is not to be confused with

internal doses, which are well documented, but addressed in a different

manner). The application that I am looking at is one of material damage

resulting from direct exposure to plutonium, either as contamination or as

solid material.  While the damage mechanisms from photons and neutrons have

been well studied, the surface damage from alphas are much less well known.

This is important when the material is being used as a sealing surface, such

as polymers used as valve seats.  DOE experienced a significant Pu-238

release and subsequent worker uptakes at one of our facilities a couple

years ago, partially due to failure of a valve seat, and I have the task of

recommending an approach for how we will deal with these applications in the

future.  I would be happy to forward you a copy of the accident

investigation report, as it may be of interest to you and others.



As it turns out, current research indicates that the damage mechanism is

much different for alphas than for penetrating radiations, and we are still

trying to evaluate the significance of that fact for our facilities.  I can

readily calculate the alpha dose rates (technically, what I am looking for

is the energy-deposition rate from alphas in various plastics), but I was

hoping to find a published method or results that I can compare my results

against, to provide a technical basis for a future DOE standard on this

issue.  (Note, this research is still in the pre-publication stage, so I'm

sorry that I cannot share all of it at this time.)



There is no scandal here, we do understand plutonium very well.  This is a

situation where DOE was bitten by a low probability event that has raised

some questions that were not previously recognized.



I hope this better explains what the original posting was all about, and

again, I apologize if I misunderstood your comments.



Doug Minnema, PhD, CHP

National Nuclear Security Administration, US DOE

<Douglas.Minnema@nnsa.doe.gov>





-----Original Message-----

From: Franz Schoenhofer [mailto:franz.schoenhofer@chello.at]

Sent: Monday, June 17, 2002 5:25 PM

To: Minnema, Douglas; radsafe@list.vanderbilt.edu

Subject: Re: Pu contact dose rates





Doug,



Since you posted to RADSAFE, I post to RADSAFE as well.



-----Ursprüngliche Nachricht-----

Von: Minnema, Douglas <Douglas.Minnema@nnsa.doe.gov>

An: radsafe@list.vanderbilt.edu <radsafe@list.vanderbilt.edu>

Datum: Montag, 17. Juni 2002 20:38

Betreff: RE: Pu contact dose rates





>Franz,

>

>At one time, as I recall, this list server was intended to allow us to ask

>questions of one another in a civilized manner.  I was not aware that this

>focus had changed.



If you reread my posting you probably will discover that the main part of my

contribution was, that I did not know, who was posting it. Emil Kerrembaev

posted a nice and humorous comment on my mail, which I really appreciated.

---------------------------------



I will be happy to post my full qualifications, if that

>is necessary in order for you to appreciate that this question has been

well

>researched before it was asked.  However, I did not, and still do not feel

>that to be necessary.



-----------------------------------------



What should this be good for?

---------------------------------------



>

>Yes, the DOE is the place for me.  Regardless of public opinion, it is

still

>the place where serious questions are raised, researched, and answered, and

>we still have a tremendous pride in our work.



--------------------------------------------------------------------------



Since I am non-American I can hardly be accused that I joined the common

attitude of bashing federal US agencies and departments. I do it in my own

country. Again, please do not tell me, that DOE and associated laboratories

or contractors never have looked into the question of doses from direct

contact with plutonium. I have no idea, how many people have worked during

the last almost 60 years with plutonium in DOE facilities, but I guess there

must have been at least tens of thousands. So please do not tell me and

other RADSAFErs, that no data are available about doses from direct contact

with Pu. If these considerations have not been done, I would regard this as

an incredible scandal.



In the course of the discussion about depleted uranium used in the Gulf war

and in Kosovo, enough knowledge should have been accumulated in order to be

able to draw conclusions for plutonium as well. The alpha-energies are much

to similar. And the DOE has no data available? You are kidding.









>

>Actually, Franz, you would be surprised at the number of questions that

>still exist in both DOE and the rest of the world, simply because

previously

>the answers were not deemed necessary for the work at hand.



If tens of thousands of people have worked with plutonium and even more on

uranium, nuclear fuel, reprocessing etc. then these answers were necessary

and please do not tell me, that these questions were not asked and not

answered.

----------------------------------------------------------------





Now, the nature

>of the work has changed, and the questions need to be re-asked.  Such is

the

>case here.



----------------------------------------------------------

Not only at your place. Six years ago I was at Mururoa and we were among

many other sample taking duties looking for hot particles. We isolated one

particle which according to gamma-spectrometry had a Pu-239 activity of more

than 1MBq. I handled it with my hands. Please could you inform me of how

many milliseconds of my life I lost?

------------------------------------------------------------------





But don't worry too much, because in this case some of our

>esteemed RADSAFE colleagues have already offered valuable assistance, and I

>have what I need.  To them I am very grateful.

----------------------------------------------------------------------------

---



I do not worry, because I regard the dose from direct contact with Pu-metal

to be ridiculously low, compared with the dose from Rn-222 in indoor air. If

you have reliable answers to your question, please share them with

RADSAFE!!!





This message seems to be typical. Whenever one dares to make a pointed

comment, people, who like in this case are not even be addressed, feel

vulnerated. Why? Is this a follow up of the NY-incident?



Regards,



Franz











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