b'P ROVING THE P RINCIPLEThe control rods were not cylindricalin shape, as the name rod mighti m p l y. Rather they were cruciform,with four narrow fin-like projectionsthat moved up and down the length ofthe core in narrow sheaths. The fuelzone was nearly twenty-eight incheslong. Moving the rods three inches wassafe and not enough to invite a chaint on. reac i 10In recent weeks, the control rods hadseemed to stick slightly, perhapsbecause other items in the reactor corehad bowed, invading clearance spacesand putting pressure on the sheath,crowding the slender fins of the control INEEL 61-4rods. The three men, wearing their gray the ceiling, and thumped back into Scene at control station set up near junction ofcoveralls, were in the silo at 9 p.m., place, shearing all of its connections to Highway 20 and Fillmore Avenue.two of them directly over or very close the piping and instrumentation systems.to the top of the reactor, working with Iron pellets packed near the reactor asthe central control rod. At 9:01 some- thermal insulation and radiation shield- It would take nearly two years of tena-thing happened, the reactor went ing scattered all over the floor. The cious inquiry to make plain what hadprompt critical and blew up. water hammer expelled the control-rod happened in two seconds, and the longshield plugs, water, fragments of fuel, process of discovery began immediately.When the reactor went critical, it fission products, and other metal fromreleased so much heat energy in four the top of the reactor, leaving open At 9:01 p.m., the heat-sensitive firemilliseconds that it flashed the water holes. The violence of the explosion alarm above the SL-1 reactor radiossurrounding the fuel to steam. The killed all three of the men. 11 one long and two shortsthe code forsteam, being of lower density than liq- the SL-1 complexat the security cen-uid water and thus a less effective mod- Two of them died instantly, one thrown ter and the three NRTS fire stations.erator, quenched the nuclear reaction. sideways against a shielding block and Accident response procedures com-The decay heat built up rapidly. With the other straight upwards, where one mence. A security force notifies theno system operating to remove the heat, of the shield plugs pinned his body to duty officer and sets off for SL-1. Thetwenty percent of the fuel melted. The the ceiling. The head wounds of the firemen at Central, the closest to thesteam forced upwards the seven-foot third were fatal, but his pulse continued Army complex, grab a card detailingcolumn of still-liquid water above it. for another two hours. The blast blew the potential hazards at SL-1 andThe water rushed through the two feet shards of radioactive metal into their review it as the fire engine rolls. Theof air space. It slammed against the lid bodies, making them a danger to those duty officer tunes in to their conversa-of the pressure vessel at a velocity of who soon would try to rescue and tion. Nine minutes later, they arrive at160 feet per second and 10,000 pounds recover them. 12 the locked gate. Equipped with keys, aper square inch exactly as if it were a detail covered by prior planning, thepistona water hammer. The entire firemen unlock the gate. They observevessel jumped nine feet into the air, hit no fires, no apparent disturbance, and1 4 2'