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Re: World must pay for Chernobyl

In a message dated 98-04-28 09:18:39 EDT,  S. Perle writes:

<< This whole incident and request is quite disturbing. There are three 
 important factors to consider:
 1. On the one hand, we see the arrogance of the demand itself, and, 
 the plea for additional funds to build newer technology. Granted, the 
 incident would never have occurred, if it weren't for the deliberate 
 mishandling of the incident. However, one must only look at TMI and 
 notice the same deliberate actions that led to an incident, that 
 luckily did not evolve to the same levels that Chernobyl did. >>

Without getting into the debate over what should be done to handle the present
situation at Chernobyl regarding cleanup, stabilization, replacement power, or
in dealing with contamination in the near or far-field, it is important to
make a technical point about why the Chernobyl accident occurred and had the
widespread consequences it did. Mishandling in the control the "incident" by
the plant operators had little to do with the accident's consequences. Within
a fraction of a second, the reactivity excursion led to a steam/chemical
explosion in the RMBK design which ruptured all the pressure tubes [thin
walled 6" heat transfer pipes] where they exited the top of the core,  and
blown away the reactor's concrete cover resulting in a discharge of Megacuries
of volatile core noble gases, halogens, and cesium into the near stratosphere.
At this point the "incident" was over except for trying to put out fires and
limit subsequent releases. [Note that if it wasn't for the biological shield
fortuitously directing the initial explosive gaseous release upward,
fatalities in the near field would have been substantial, due to doses from
noble gases exceeding fatal levels].

The main point is that due to the Chernobyl reactor's basic nucleonics design
flaw (i.e. it's positive coeffcient of reactivity) it was a "hot" or unstable
machine. Once it started to run away due to the control rods being withdrawn
too far during an ill-conceived and improperly controlled test, the system ran
away. A nuclear excursion occurred during a period of time that was too short
for any operator control. In a LWR when water boils away or voids form,
neutron flux to fuel decreases and the nuclear fission reaction slows down.
The opposite occured in the Chernobyl design. 

The mistake by the USSR was made in licensing and then building such a
reactor. It is a mistake to just blame the operators. Also, the fact that the
TMI accident had such minimal consequences was not "luck". Despite numerous
mistakes by TMI operators leading to a substantial core melt, etc., the
releases to the environment were minimal due to the design of the reactor, its
containment, and the physical processes that limit releases of radioactivity
to the environment from LWRs.

Stewart Farber, MSPH
Consulting Scientist
Public Health Sciences

email: radproject@usa.net    Phone: (401) 727-4947  Fax: (401) 727-2032