RE: Criticality accident

["Bolling, Jason E" <bollingje@ports.usec.com>]

According to the report (LA-13638), the last fatal accident occurred in the

United States on July 25, 1964 at the United Nuclear Fuels Recovery Plant at

Wood River Junction, Rhode Island.  This accident was interesting in that

the original excursion took place in a tank that was being stirred by a

motorized mixer.  After the operator fled the building, the plant

superintendent and shift supervisor responded to the scene and turned off

the mixer.  The resulting change in shape of the solution (from a turbulent

vortex to a calm cylinder) was sufficient to cause another critical

excursion that resulted in 60 to 100 rad dose to the two men.  Because the

criticality alarms were already sounding, the second burst almost happened

undetected.  It was only after their dose estimates were calculated that it

became apparent the second excursion had happened at all.



The original operator who caused the excursion died 49 hours later.



Another interesting fact from this report is that of all the various

criticality accidents, the one with the lowest uranium enrichment was an

accident in Russia in 1965 involving 6.5% uranium oxide slurry.  So,

basically, getting uranium enriched 3% to 5% (as in U.S. power reactors) to

achieve an accidental critical configuration appears to be somewhat

difficult.



Jason Bolling

Nuclear Criticality Safety

Portsmouth Gaseous Diffusion Plant



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

From: BERNARD L COHEN [mailto:blc+@PITT.EDU]

Sent: Monday, March 18, 2002 10:46 AM

To: RuthWeiner@AOL.COM

Cc: radsafe@list.vanderbilt.edu

Subject: Re: Criticality accident







On Mon, 18 Mar 2002, BERNARD L COHEN wrote:



>

> On Sat, 16 Mar 2002 RuthWeiner@AOL.COM wrote:

>

> >

> > There have been 22 such accidents since 1943, 21 of them in solution

(liquid)

> > media.

> >

> > There have been 9 fatalities altogether (I think I remember this number

> > correctly).

>

> 	--How long has it been since the last fatal accident. I was under

> the impression that all of these accidents happened before about 1965. If

> so, that is important because it indicates that the problems have been

> solved.



	--I thought the report was about accidents in U.S. That is what my

question above was about.



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