Chernobyl Nuclear Accident Congressional Hearings Transcript

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nobyl. An American-Ukrainian Medical Center is an effective way
to provide for the integration of complex long-term research, medical
care, and public information projects. It is also a highly visible
contribution that will demonstrate the creativity of the U.S. and its
role in a highly sensitive area.
Furthermore, a helping hand from America is the most effective
way to promote our own democracy. The fate of the emerging democracy
in Ukraine will have profound implications, and the aid
provided thus far has been primarily nongovernmental. The American-Ukrainian
community has created linkages and now probably
will be seeking from our Government leadership and support.
Thank you.
Senator Graham. Thank you very much. Doctor.
Mr. Edward Purvis, Senior Engineer of Los Alamos Technical Associates.
STATEMENT OF EDWARD E. PURVIS, III, SENIOR ENGINEER, LOS
ALAMOS TECHNICAL ASSOCIATES, INC.
Mr. Purvis. Mr. Chairman, thank you.
I was assisted in the preparation of this testimony by Dr. Marvin
Goldman, who is the leader on the U.S. side of the joint working
group on the health effects of Chernobyl. His statement is included
in the submittal for the record. I will allude to information from it,
but I will concentrate on discussing the technical details about the
physical situation at Chernobyl, in particular the sarcophagus in
the nearby area. I appreciate the opportunity to review this.
To understand the current situation, it would help to best review
exactly what happened. The accident resulted from some design
flaws and some major operational problems. These led to a reactivity
excursion, which was a very large, rapid increase in power. The
actual part that really led to the results that you see lasted about
two-tenths of a second, and the power level went up to where it
generated in that burst about 32 gigajoules of energy. That's an
awful lot. It resulted in a very small fraction of the fuel in the reactor
going up to a temperature of about 13,000 degrees Fahrenheit
before the expansion of this now gaseous mass could disrupt it.
That was the major part of the damaging energy release.
What you now have is gaseous fuel putting a shock wave on the
fuel fragments, which took the graphite and the fuel—some of it
was very fine particles, some of it was larger fragments, some of it
was intact—and threw it onto the roof and into the yard. A lot of it
w£is left in what is now the sarcophagus. It was very, very hot. The
gases condensed, formed aerosols, and so forth. The hot fuel in contact
with the graphite caused burning, which resulted in radioisotopes
being released and going very high up into the atmosphere,
where they were dispersed over a very large area.
The exact amount of some isotopes, like radioactive iodine, that
were released and that were dispersed to the environment and
where it went will never be known. The reason is radioactive
iodine has a very short half-life, and there was no instrumentation
available to detect this. That data is lost. This is very important
with respect to what they were referring to on the thyroid gland
and the children in particular. Other isotopes, such as cesium, can