Information about UF6 Releases

[Tom McClelland <mccleltw@aramco.com.sa>]

Although tornadoes do strange things and have erratic effects, the release 
scenario proposed below is what I've come to call 'self-editing', i.e., the 
effect is overwhelmed by the cause.  In this case the danger associated 
with a tornado, and the tremendous dispersion associated with tornado 
winds, would make the release of UF6/HF/UO2 one of the least of the 
immediate worries.

As far as delayed release effects are concerned, from 'throwing' a cylinder 
someplace and having it rupture,  one *very* important thing to remember is 
that the UF6 is a solid under normal ambient conditions and isn't going to 
'leap' out of its storage/shipping container. Large releases should occur 
only when UF6 is heated to liquid, then it is under pressure and a release 
reacts with atmospheric moisture and oxygen to form a negatively-buoyant, 
but reactive, plume of HF, UOx compounds, and some UF6 in the 'center' of 
the plume.

There is a *lot* of information about UF6 releases that were analyzed 15 to 
20 years ago under the requirements of DoE Manual Chapter 0524.  People 
with the appropriate clearances, especially at Oak Ridge, Paducah, and 
Portsmouth, should have access to these reports.  Some of the original 
dispersion calculations were done by the Risk Assessment group at Battellle 
Columbus and should contain plenty of valuable information.  Furthermore, 
someone should have a [DoE] report about a liquid release from a cylinder 
at Portsmouth sometime in the late '70s.

On a related matter, when the risk assessments were being done, 
toxicological data were gathered for inhalation of various forms and 
enrichments of uranium.  Roughly, the guidelines were that below 9% to 10% 
U235 enrichment the long-term effects were due to heavy metal poisoning; 
above that concentration the committed dose became the limiting factor.

As a final note, some of the recent conversations about fluorine and 
gaseous diffusion would have been classified 25 years ago [and I don't seem 
any older, it's just that most of my friends are in their 50s and 60s].

If I can be of further vague assistance, email privately.

Regards,

Tom McClelland
Obviously, these thoughts are my own peculiar mix and are not held or 
approved by anyone I know or work for.

----------
From: 	Susan Gawarecki[SMTP:loc@icx.net]
Reply To: 	radsafe@romulus.ehs.uiuc.edu
Sent: 	Wednesday, January 27, 1999 11:36 PM
To: 	Multiple recipients of list
Subject: 	UF6

I've been following the discussion of the hazards associated with UF6
with interest.  There are approximately 4700 cylinders of the substance
stored outside in yards at the K-25 site (or East Tennessee Technology
Park, ETTP) in Oak Ridge (many more are kept at Paducah and
Portsmouth).  DOE contends this is a resource, rather than a waste, and
plans to store it well into the next century in the current form, with
regular inspection and maintenance of the cylinders.  Many stakeholders
contend that continued storage of this material is incompatible with the
current process of "reindustrializing" the K-25 site, that is having
commercial ventures lease space for a variety of manufacturing or
service activities.

Interestingly, three sites that exceeded the primary dose limit for
gamma levels and are potentially accessible to the public, according to
Tenn. Dept. of Environment & Conservation DOE Oversight Division, are
all near the UF6 cylinder storage yards at ETTP.

While rational people agree that minor leaks are self-healing and that
this scenario of surveillance and maintenance will allow safe storage
for many years, we feel that little attention has been paid to the
potential for catastrophic release from severe weather.  You may have
heard about the recent tornados which destroyed downtown Clarksville,
Tenn., and damaged a suburb of Jackson, Tenn.  Several years ago, a
tornado touched down at the entrance to the Y-12 Plant in Oak Ridge,
rolling an empty tank (not UF6) off its support and tearing down
high-tension electric lines along the valley to the NE.  If we were so
unlucky to have a tornado touch down at K-25, I doubt that the cylinders
could withstand the stresses (there would be other releases from
destruction of contaminated buildings, but let's ignore those for the
sake of simplifying the scenario).

It's likely that the resulting cloud of HF would pose an immediate local
danger, but the dispersion of depleted uranium would also be a concern
to the community. Has anyone modeled (or speculated) on this scenario?

While on-site conversion of the UF6 to a stable oxide form seems to be
the preferred alternative by the community, funding constraints may
force transportation to Paducah, KY, or Portsmouth, OH, for conversion.
The structural integrity of the cylinders and the method of handling and
overpacking them become more significant concerns in that case.

I would be interested in your professional opinions.

Regards,
Susan Gawarecki
--
==================================================
Susan L. Gawarecki, Ph.D., Executive Director
Oak Ridge Reservation Local Oversight Committee, Inc.
136 South Illinois Avenue, Suite 208
Oak Ridge, Tennessee  37830
Phone (423) 483-1333; Fax (423) 482-6572; E-mail loc@icx.net
VISIT OUR UPDATED WEB SITE:  http://www.local-oversight.org
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