Dissent about Nuclear Safety
originally titled: To Dissent or not to
Dissent
I
Alison Turner is a department manager at a large commercial
nuclear generating plant. She is also a member of the Plant
Nuclear Safety Review Committee (PNSRC). The committee's
responsibilities include reviewing and approving design
changes, procedural changes, and submittals to the Nuclear
Regulatory Commission (NRC). Today Alison finds herself in a
difficult situation. PNSRC is meeting to decide what to do
about a heat exchanger problem. Routine testing on the previous
morning revealed degraded cooling water flow and high
differential pressure in one of the containment spray heat
exchangers of one of the two generating units. This unit has
just returned to service after two months of repairs. Test
results on the second heat exchanger were similar.
Although the other generating unit has been in continuous
service, testing reveals that its two heat exchangers are
operating at less than full capacity. The most likely cause of
the problem is sand blockage on the lake water side of the four
heat exchangers. After extensive analysis by engineers in the
Mechanical Engineering and Nuclear Safety & Licensing
Departments, it has been concluded that the cooling water flow
falls slightly below the minimum requirement set by the
technical specifications under which the plant is licensed.
Nevertheless, based on Mechanical Engineering's analysis,
Nuclear Safety & Licensing has prepared a Justification for
Continued Operation (JCO) for submission to NRC. PNSRC is now
meeting to decide whether to approve the JCO and forward it to
NRC.
As Alison reviews the JCO she is uncomfortable with one
assumption made in the analysis. The analysis assumes that the
heat exchangers still have 95% of their original heat transfer
capability. It is concluded that this would be satisfactory.
However, in anticipating possible accidents, Single Failure
Criteria require the plant to assume the loss of one heat
exchanger. Alison wonders if, under those conditions, the heat
transfer problem would be manageable. The JCO does not discuss
what might happen under that contingency. Seven members of
PNSRC are present, enough for a quorum. Alison is the least
senior member present. From the outset of the meeting,
committee chair Rich Robinson has made it clear that it is
important to act quickly, since any shutdown will cost the
company, and ultimately the rate payers, a lot of money in
additional fuel costs. "Repairs," he says, "might take a couple
of weeks. If we don't approve this, we may be facing a
multi-million dollar proposition. Fortunately, the JCO seems
fine. What do you think?" Brad Louks and Joe Carpello
immediately concur. Rich then says, "Well, if no one sees any
problems here, let's go with it." There is a moment of silence.
Should Alison express her reservations?
II
Alison Turner expresses her reservations. Brad Louks
replies, "We're talking about containment heat exchangers. It's
an Accident Mitigation System, and it's never had to be used
here--or at any other commercial nuclear plant that we know of,
for that matter. In fact, lots of plants don't even have
containment spray systems." "Right," adds Joe Carpello, "we're
ahead of the game on this one. I don't see any problem here.
Nothing's totally risk free, but we've always been leaders in
safety. Let's not get carried away with 'possibilities'." "I
don't think Alison meant to have us get carried away with
anything," Mark Reynolds interjects. "She's just wondering if
the JCO should address the question of how things would look if
we lost one of the heat exchangers. How much time would it take
the Nuclear Safety and Licensing Department to make a
calculation for us--another 3 hours? It's only 1:30pm, you
know." "What's the point, Mark?" asks Joe. "Our track record is
excellent, and the system is optional. It's not as though we're
taking any extraordinary risks."
Nothing further is said, and Rich Robinson calls for the
vote. Though not a committee requirement, PNSRC has always
acted unanimously. It often rejects, sometimes approves, but
always unanimously. As the call goes around the room, each
member approves. The last member called on to vote is Alison.
She still has serious reservations about approving the JCO
without the Nuclear Safety and Licensing Department making
further calculations. How should she vote?
III
Suppose Alison casts a negative vote and subsequent
calculations show that her worries were unfounded -- in the
event of an accident, a single heat exchanger would be adequate
to manage any likely heat transfer problems. Would it follow
that it was wrong for her to cast a dissenting vote? [Recall
that a single dissenting vote would not defeat approval. It
would only set a precedent of proceeding without
unanimity.]