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Three
Mile Island: The Inside Story
The Importance of the Sonar Survey
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Figure
9.1. This montage makes evident the large impact
that the core topography survey, and the topographic
model presenting its results, had on conceptions
of the real state of affairs within the reactor
vessel.
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This importance of the INEEL core topography survey was recognized
in several publications in 1985 and 1986, but later reviews made
only passing reference to it (ref. 12, ch. 5) or omitted it entirely
(ref. 21). Among the factors contributing to this rapid forgetting
of the impact of the sonar survey was an over-valuation of—and
over-investment in—video inspections of the interior of the
reactor vessel. And this was because, in the estimation of the authors
of the comprehensive technical history of the TMI cleanup, “Even
when accurate predictions of core conditions could be made, engineers
and management were reluctant to accept the bad news until it was
seen on a video screen. A picture equaled far more than a thousand
words.” (Ref. 12, ch. 5, p. 1, which, ironically, itself contributes
to this erasure of the sonar survey’s significance.)
The INEEL core topography team recognized this not-til-we’ve-seen-it-with-our-own-eyes
bias arising in good part from the not-wanting-to-know-what-we-don’t-want-to-be-so
mentality of the reactor’s manufacturer and the utility’s
management. And it was in part for that reason that they put so
much effort into providing such striking means for visualizing their
results. But the large impact of their sonar survey had rather the
effect of leading to still larger investments in video in order
to see what was so.
Thus although the sonar survey in the summer of 1983 had provided
a precise and detailed topography of the cavity at minimal cost—minimal
not merely in dollars, but also in personnel-hours of radiation
exposure and in hours of cleanup time lost—in April 1984 its
results were confirmed by a specially designed video camera and
camera manipulation system providing broadcast-quality images and
position and orientation data (ref. 5, p. 144). And that was just
the beginning. Once the head (top) of the reactor vessel was unbolted
and lifted off, still more elaborately complex and expensive video-guided
sample retrievals were undertaken—and described with enthusiasm
(ref. 21, p. 575):
“. . . it was necessary to develop the tools, procedures,
techniques, and proficiencies that would enable a five-member
crew to perform as a single individual. The task required a camera
operator to continuously position and reposition underwater cameras
to provide clear video images of the sampling activities, an operator
to position underwater lights to provide the best possible lighting
for the camera, an operator to position and operate a heavy-duty
cutting tool mounted on a long pole, and an operator to manipulate
and position a long-handled grasping tool used to hold the fuel
rod sample during cutting. The fifth member of the team was the
engineer/task supervisor who supervised the sample activity and
coordinated the movements and positioning of the tools by directing
the actions of the other team members. Extensive mock-up training
and practice were necessary to produce the team proficiency that
proved to be essential to the success of the sampling task.”
Under the spell of such extravagant efforts, the historic importance
of so quick and cheap an investigation as the ultrasonic survey
was bound to be forgotten.
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