RE: 1988 Irradiator Incident

["Jim Hardeman" <Jim#032#Hardeman@mail.dnr.state.ga.us>]

Otto -

Larry's right on target ... even as to the size of the sources (I usually say they're about the diameter of a soda can and about 4 times as tall ... that gives people a pretty good visual). Activity was around 50 kCi each ... we think that only around 10-20 Ci of Cs-137 actually made it out of a single source (out of the 252 in the pool at the time of the accident).

Legally, I can't agree with Larry as to the root cause of the incident, as (to my knowledge) defective manufacture has been neither proved nor disproved. There was a multi-million dollar lawsuit filed by the private owner of the irradiator against the source manufacturer (which happened to be DOE ... these were Waste Encapsulation and Storage Facility (WESF) capsules manufactured at Hanford) but the lawsuit was dismissed. DOE began to conduct destructive testing ... but I never heard a definitive answer. Larry's supposition was one of many put forward ... but there were many ... both "outside-in" (i.e. a failed weld, perhaps in part due to environmental conditions of use, allowed water to get into the capsule) and "inside-out" (i.e. impurities in the chloride failed the capsule from the inside, allowing the chloride to leak) failure mechanisms postulated ... but DOE has never said WHY the capsule failed. THAT's the multi-million dollar question.

BUT ... getting back to the issue at hand ... cobalt irradiators will not be subject to the same sort of capsule failure that occured in Georgia. Cobalt, unlike cesium chloride, is not very soluble in water. PLUS, to my knowledge, most of the commercial food irradiation going on right now is the "cold pasteurization" stuff using electron beams ... not even using cobalt.

Jim Hardeman
Jim_Hardeman@mail.dnr.state.ga.us 

>>> LGrimm@ADMIN.UCLA.EDU 7/10/2000 10:01:49 >>>
Otto:

As Jim Hardeman pointed out, the irradiator used Cs-137 as the source,
however it was designed NOT for food irradiation, but for medical products
sterilization.  As I am sure that you are aware, the use of Cs-137 (Co-60
being more common) for large scale irradiation is somewhat unusual.  I have
not heard of it being used in food irradiation.   

The Georgia irradiator leak was apparently the result of the following.  The
Cesium was in a chloride form, then double encapsulated in the stainless
steel tube which was about 2 foot long and 3 inch in diameter.  Apparently
the problem was that one Cs-137 tube was not properly manufactured.  It was
deduced that a little moisture was left in the chloride, and internal steam
pressure in the tube caused it to crack.  Being a salt, hydroscopic and in a
pool of water...      

It is nigh on impossible for a Co-60 source, as used in food irradiation, to
leak like a Cs-137 salt.  Therefore, the activists are mixing apples and
oranges as usual. 

PS: don't quote me on the sizes of the tubes.  I am going from memory and
pictures of the sources from a sister irradiator I helped to install in
Colorado.

Larry Grimm
	UCLA EH&S/ Radiation Safety Division
*	lgrimm@admin.ucla.edu   Phone:310/206-0712   Fax: 310/206-9051
*	On Campus: 501 Westwood Plaza, 4th Floor, MS 951605
*	Off Campus: UCLA Radiation Safety Div, 501 Westwood Plaza 4th Fl,
Box 951605, Los Angeles, CA 90095-1605
*	If this email is not RSD business, the opinions are mine, not
UCLA's.
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