Chernobyl Nuclear Accident Congressional Hearings Transcript

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and the designers about what was involved in those particular
products.
So, the short answer is, most of the plants that we presently
have today are in the design-as-you-go/regulate-as-you-go kind of
mode.
Senator Melcher. That would be like 90 out of 100?
Dr. Bunch. I don't think that is an unreasonable estimate, sir.
Senator Melcher. 90 out of 100. The Commission staff says that
there is practically a 50-50 chance of another TMI accident occurring.
Is this not interrelated with the same concern that the public
has, or the apprehension they have, with these plants, over the
design as you go aspect, as they are being constructed, and after
the design was figured out, what to regulate them—as you go—to
prevent any failure. Does not this therefore cause for alarm?
Dr. Bunch. My view is that the design of the plants on the part
of the designers, and the review of those plants on the part of the
regulators, did pay a good fair measure of attention to the fundamental
criteria under which those designs would be developed. A
fair measure of attention was given to making sure that the way
the plant was going to be laid out and engineered, was going to be
sound. The regulate-as-you-go part of it came when operating experience
came up, such as on water hammer, or materials failures, or
equipment wasn't behaving exactly the way that people had hoped
and intended, there needed to be accommodations and new ways of
dealing with those in design, and new ways of satisfying regulatory
solutions.
That particular way of dealing with after-the-fact experience has,
I think, caused some concern on the part of the public. It is on that
ground, I think, that what Mr. Denton was talking about, to get
past that and show that we have resolved those problems is going
to be very helpful.
Mr. Denton. Senator, I need to be sure I clarify one point. As a
result of those 18 or so probabilistic risk studies that were done,
many changes were made in the plants because they did identify
think the most
vulnerabilities and areas that contributed to risks I
recent commission tabulation, where they go back and look at the
plants as they exist today, and are being operated, the same calculation
gives an industry average severe core damage frequency of
about 6 chances in 100,000.
So, I think today if you ask the Commission about the 45 percent,
the answer you will get is 12 percent. It sounds like it is pencil
sharpening, but what it really is is that the vulnerabilities identified
in the earlier studies have been corrected, and therefore, as
those improvements are made in the plants, the probability of an
accident gets lower and lower.
The Commission is in favor of standard plants. There is an effort
going on with EPRI, the Electric Power Research Institute, in
which we would get the complete design before we issued any license.
The plant would be designed with a safety goal in mind, so
that that would be a part of the design. That has not been required
as part of our system up to now.
Senator Melcher. Mr. Denton, you mentioned drug and alcohol
programs for the people in the plants. What is the percentage of