[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Self Shielded Irradiators

You wrote: 
Dear Kent, 
        Our University has such a self-shielded irradiator and like you I 
have had to dream up worst case scenarios and write contingency plans for 
it. The unit I am thinking of in this case has several hundred curies of 
Co-60 and small samples are fed into close proximity to the source on a 
piston operated system. When the irradiator was inspected a few years ago, 
the first comment that was made was about security. It shows how naive I 
was them, because my reaction was "the things weighs 5 tonnes, no-one is 
going to steal it" That was not the security he was talking about. If the 
piston delivery system wasn't adequately secured then an explosive device 
could be pushed into the source and I was left wondering how a bomb 
disposal squad would deal with such an event and also how I would assess 
what my contingency plans would be. Although the unit it locked, anyone 
with a respectable set of bolt cutters could gain access and cause a 
considerable amount of mischieve. Like Kent I would be interested in what 
contingency plans radsafers have for such, hopefully, extremely rare  
                                         David Hornsey 
 * David J. Hornsey, Radiation Safety.* 
 * South Building,                    * 
 * University of Bath                 *              
 * Claverton Down,                    *  
 * Bath BA2 7AY. UK.                  * 
 *                                    * 
 * tel:01225 826540                   * 
 * fax:01225 826779                   *   
 * e-mail: d.j.hornsey@bath.ac.uk     * 
Maybe I'm missing something, here, but why is this unique?  I have 2
about this thread: 
(1) There are all sorts of such scenarios that hp's have to deal with: 
involving unsealed radioactive material, transportation accidents involving 
multiple type A packages - there was a recent event involving a truck
a load of new reactor fuel, radiography malfunctions, contaminated injuries, 
and theft or intentional misuses situations. 
(2) In many of these situations, the radioactive material is a secondary 
concern.  Bombs and fires often kill people, radiation rarely results in 
anything more than a hypothetical risk and a potential regulatory snafu.   
A good reference point for determining the magnitude of a potential concern
10 CFR 30, Appendix C.  Per 10 CFR 30.32(i)(1) , a license appplication to 
possess quantities greater than those of Appendix C, must have either:  "(i) 
An evaluation showing that the maximum dose to a person offsite due to a 
release of radioactive materials would not exceed 1 rem effective dose 
equivalent of 5 rems to the thyroid; or (ii) an emergency plan for
to a release of radioactive material." 
Most self-shielded irradiators are Cs-137 or Co-60.  The Appendix C values
these radionuclides are 3000 Ci and 5000 Ci, respectively. Most instrument 
calibration devices are only a small fraction of this value. If you have a 
device with a larger quantity, it should definitely not be sitting in the 
corner of someone's lab. 
While we need contingency plans, we must not lose site of the fact that 
personnel safety, not man-millirems, is what's important. 
The opinions expressed are strictly mine. 
It's not about dose, it's about trust. 
Bill Lipton