Re: One last comment on Irradiation -Reply

[Jose Lopez <JLOPEZ@MEDNET.SWMED.EDU>]

Franz:

There are many factors that are not being discussed about the safety of
irradiators and radiation incidents. Primarily we have to remember that a
large number of Pool-type (Class IV) irradiators throughout the world
have been around since the '70s and most of them are of the AECL
(Atomic Energy of Canada Ltd.)design (Now Nordion) . Furthermore, they
typically operate seven days a week, 24 hours a day, and stop only for
the scheduled routine maintenance. 

The accident in El Salvador in 1989?, was in an AECL designed
irradiator. A product cardboard box interfered with the movement of the
source rack. AECL had experienced that problem in the late 70's in
Sherman, TX and to correct the situation they modified the design putting
a very thin aluminum sheet as a shroud to protect the source rack. AECL
notified all the AECL irradiators in the late 70's and requested them to 
make that simple modification. The irradiator in EL Salvador chose not to
implement such changes, and in 1989? they got bit.

The Pool-type irradiators are generally over-designed with safety
features  there are radiation detectors into and out of any exit, interlocks
for everything, survey meters attached by chain to the only key to the
door, etc. etc. etc.

Most accidents that have occurred have had to do with defeated
interlocks, survey meters that were out of batteries or otherwise not
working, and foremost with human error. I have read that the operator of
the Irradiator in El Salvador declared that he thought that if he  turned out
the lights inside the cell, the radiation would cease!. He did, and when he
went in with defeated interlocks and  without a working survey meter
and with a failed radiation alarm at the door, he saw the glow of the
source rack. BTW, that irradiator had the initial sources that were
installed in the 70's ;  they never re-sourced. The activity had decayed to
less than 100,000 Ci Co-60.

I heard a story that the AECL crew flew to El Salvador to assist, but
when they landed, there were bullets flying all around in the airport and
they never deplaned, just flew right out. I guess, bullets are just as
effective as gamma rays in doing damage!

The USNRC has a NUREG document that was published around 1989
that has a detailed summary of incidents involving irradiators.
There is the one in Israel, or the one in Singapore where a product box
caught on fire, and after many attempts to remedy the situation,
management decided to let it extinghish itself out. The sources remained
intact.

These incidents, may seem outrageous, but in reality if you take into
consideration the thousands, probably millions of irradiation-hours
logged, and the relative low number of casualties, then the process is
relatively very safe.

Usual disclaimer,  need it or not!
 Happy Holidays

Jose Lopez, Ph.D., P.E.
Radiation Safety Officer
Univ. of Texas Southwestern Medical Center at Dallas
(214) 648-3952

Stephane, 

Unfortunately these stories might sound incredible, but they are not just
stories. Many accidents have occurred with radioactive sources, though
most of them involved sources for radiography and medical treatment.
But even in irradiation facilities people have died from radiation. You
never hear about such accidents in the news media, though they are not
kept secret and are well known. It seems to be more important to the
mass media to discuss potential risks involving a large number of
persons than actual accidents involving only one or a few persons who
died. 

If I remember correctly the IAEA has only recently published a book on
accidents in irradiation facilities and the lessons learned. If you or fellow
radsafers are interested in that book I could find out - but please respond
to my private e-mail address.

Joyeux Noel!

Franz
Schoenhofer
Habichergasse 31/7
A-1160 WIEN
AUSTRIA/EUROPE
Tel./Fax:	+43-1-4955308
Tel.:		+43-664-3380333 e-mail:		schoenho@via.at