Chernobyl Nuclear Accident Congressional Hearings Transcript

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firmed, but at least suspected that the thing that breached the confinement,
the suprastructure of the industrial building in which it
was located was a hydrogen explosion. Is that correct?
Mr. Denton. Let me answer the first question first. There was a
hydrogen explosion in the TMI containment. Those containments
were so big and so strong it did not threaten the integrity of the
building.
Our present view on the Chernobyl accident is that probably the
power surge which occurred ruptured some of those 1,700 pressure
tubes—one or more of those tubes—and exposed a very thin wall
enclosure of the core to direct reactor system pressure— 1,000
pounds per square inside pressure. It was probably the steam pressure
that caused the initial physical disruption of the core.
After that occurred, we think that the fuel overheated, the metal
water reaction produced hydrogen and hydrogen probably did seep
into several areas of the plant. It is thought that there was one or
more explosions of hydrogen. Then, that caused further core disruption
and that led to the graphite fire, and in effect, disrupted
the industrial type enclosure that was around this reactor.
I don't consider that plant as having the type of containment
building that we have in licensed plants in the United States.
The Chairman. Have we taken corrective action since TMI, dealing
with the potential for a hydrogen build-up?
Mr. Denton. Yes, sir. We have a rule that we adopted since TMI
requiring that plants be able to cope with the generation of hydrogen.
A great deal of research has been done at Idaho and other
places in that area, and some of it is still going on. But we have
provided all our plants a capability to withstand hydrogen, depending
on the circumstances.
We think our plants can all stand accidents beyond the design
basis, and some have the capability to withstand accidents that
would be greater, beyond the design.
The Chairman. When TMI occurred, we immediately turned to
research facilities in the United States to try to understand what
was happening, to interpret data that we were getting at TMI. We
turned to things like LOFT and PBF. Is that not correct?
Mr. Denton. Yes, sir; that is correct. We also, you recall, took
action to shut down similar, or plants of identical design following
TMI. I suspended the operation of the other B&W plants for some
time. I understand that in the Soviet Union, the other 15 or so
plants that are identical to this design are continuing to operate.
The Chairman. How were LOFT and PBF used at the time of
the TMI accident?
Mr. Denton. They were used two ways. We attempted to have
some conditions simulated right during the event. While I was at
TMI, we were in communication with the reactor laboratory, attempting
to use them to calculate what might happen next in the
TMI core. So there was some immediate use made of their capabilities.
Then after that, we had a large program to be sure we understood
the core, and Mr. Wade has mentioned a number of the tests
that were done.
I was at TMI just yesterday observing the preparations for loading
the first canister out of the core into the cast to be shipped to