b'C H A P T E R 23T H E E N D O W M E N T O F U RA N I U MPennsylvania and became part of the Now the TMI operators wanted to know The connection between INEL and TMIeffort to secure the plant in a cold shut- the shape and condition of the fuel continued in many forms. INEL teamsdown position. 8 inside their damaged pressure vessel. developed training and emergencyAfter the PBF had run simulations of the response techniques for TMI accidentBut the hard-slogging work of investi- TMI accident, INELscientists took the scenarios, many of which had beengation was just beginning. How could test bundle, still in its container vessel, learned because of the post-TMI inves-the place be cleaned up enough to start to Argonne-s tigation and the Semiscale tests. Later,We ts Neutron Radiographyanalyzing what had taken place inside (NRAD) reactor and made neutron radi- INEL scientists helped evaluate the con-the reactor? What exactly had happened ographs of the core. The images showed dition of the TMI fuel. INEL transporta-to the fuel elements inside the reactor a combination of melted fuel and a mass tion managers arranged the highlyvessel? Where had all the fission prod- of rubble collapsed at the bottom. complicated task of packaging the fuelucts gone after the fuel-rod cladding Beverly Cook was one of the INEL and other core debris for a trip to Idahohad burst or melted?engineers to take the news to TM .for further examination and temporaryIstorage. 11The PBF reactor at INELhad been We made slides of the images for a pre -designed to continue the tradition of sentation to the people in PennsylvaniaThe purpose in bringing the fuel to theS P E RT in testing the performance of and flew out there. They still had not INwas to determine what had takenE Lfuel elements during transients, or sud- seen the inside of the TMI vessel. Usingplace in the core during the accident.den bursts of power and heat. But it the PBF simulation, we told them whatWhat was below the rubble bed and itscould handle a far larger repertoire of their core would look like. We showed solidified sublayer? INELs p e c i alis stsimulated accident scenarios than could them zones of melted fuel and how theydesigned and built a 20,000-pound coreS PERT. By this time, the many varieties would lay over rubble at the bottom. bore machine in the thirty months after of imagined accidents had acquired They didnt believe it. They couldnt the accident and took it to TMI. A dapt e dhighly specific names and acronyms: believe that so much of their core had from a commercial drilling machine, itreactivity-initiated accidents (RIA), melted. But we knew that the uranium had to fit through an air lock and operatep o we-cooling-mismatch (PCM) acci- oxide in the fuel had interacted with r emy. The drill bits bit throughr oteldents, anticipated transients without other metals and caused more meltingceramic and metal to reach the interiorscram (ATWS), loss-of-coolant acci- than they thought. of the reactor vessel. After a hole wasdents (LOCA), and severe fuel damage drilled, a remotely operated television(SFD) accidents. During each accident Later, when the TMI core was opened camera inspected the interior of the core.simulation, sophisticated instruments up for the remote insertion of cameras,With these techniques the scientistsrecorded temperatures of fuel, of we watched the procedure as it unfold mapped the core, learned where the fiscladding, of coolant; the building pres- ed on a videotape. The camera went insion products were located, and devel-sure inside the fuel rods; the change in from the top and was gradually sent oped a plan to ship the materials safelyshape of fuel rods during the event. further and further into the vessel. No to Idaho for further examination andMonitors detected and timed the precise one had edited the remarks of the camtemporary storage. The last shipment of-movement of fission products as they era operators as they were doing this, TMI debris arrived in Idaho in 1990 andescaped from a fuel rod whose cladding and we heard them say in amazement,the fuel examination program continuedhad failed. As usual, PBF tests took Wheres the core? and other for several years. 1 2place only after a computer program had deletable expletives. They werent find -predicted the results of the test. Constant ing anything at all at the top of the vesAfter this real accident, which had-refinementand post-test examination sel, just foot after foot of empty space.involved a small leak caused by theof melted and mangled fuel rods in a hot When they finally got a look at it, the stuck pressure-relief valve, the focus ofcellbrought predictions and actual core lay pretty much exactly as we hadLOFT and Semiscale experiments shift-results into closer and closer agreement. 9 predicted. ed to investigating small leaks and a10225'