Voyage of the Devilfish

Delaney did not like the commands from the Conn, but he also believed in Navy Regulations, the Reactor Plant Manual and the Ten Commandments. In about that order. So, reluctantly, he gave the next orders: “Reactor operator, shift reactor main coolant pumps one, two, three and four to slow speed. Manual group scram the reactor and secure pumps one, two and three.” The reactor operator, an aggressive first-class petty officer named Manderson, acknowledged and flipped each reactor main coolant pump T-switch on the lower reactor control panel to the slow speed position, then pulled each switch upward. The indicating lights at the pumps changed from FAST to SLOW. Manderson stood and lifted a square Plexiglas cover over a rotary switch at the top of the reactor control panel: the switch was marked MANUAL SCRAM. Manderson looked over his shoulder at Delaney. Delaney nodded. Manderson rotated the switch. As the switch handle came to rest at the position marked GROUP SCRAM, a dozen things happened in the nuclear plant within fifty milliseconds. And as far as Delaney was concerned, all those things were bad. The reactor siren sounded, a wailing police-car siren in the maneuvering room. The control rod bottom lights lit for group one, the controlling rod group. The rod position digital counter began dialing group one’s indicated position down to zero.

The reactor power meter dropped from 15 percent, normal for all stop with slow pumps, to zero. Within seconds, main coolant average temperature dropped from 496 degrees Fahrenheit to 465 and continued to fall. The STARTUP RATE meter on the RPCP went from zero to minus 0.3 decades per minute as the power level crashed into the immediate range, enroute within minutes to the startup range. These were only the indications at the reactor plant control panel. Two compartments forward, inside the reactor compartment, the six control-rod drive mechanisms of group-one rods lost their magnetic latch voltage. As the electrical power was interrupted from the scram breakers tripping, the magnetic flux holding the rods engaged to the drive motors collapsed, and as the magnetic attraction disappeared, springs opened alligator assemblies, disconnecting the rods from the holding mechanisms. Massive vertical springs pushed the six control rods made of an obscure element named hafnium to the bottom of the reactor vessel. The hafnium had the odd property of acting as a black hole for the subatomic neutron particles that made the Devilfish’s screw turn. When the six rods hit the bottom of the core, most of the neutrons flying around in the center of the reactor were absorbed by the hafnium instead of by uranium atoms. As the uranium atoms stopped absorbing neutrons, the fission reactions came to a halt like popcorn removed from an oven, going from full frantic popping to sporadic pops at odd intervals. The fissions stopped. The uranium atoms, stuffed deeply into the fuel elements, stopped splitting, and so no longer added 200 megaelectron volts each of energy to the fuel element material. The end of the energy input was sensed immediately by the water coolant flowing in the fuel elements that no longer were superhot. The coolant stopped being heated by the fuel and arrived at the steam generators relatively cool at 465 degrees. Such coolant in the steam generators was useless in boiling the water from the condensers to turn it into steam. Low steam pressure in the steam generators starved the propulsion turbines and turbine generators in the engine room. For a moment, the blare of the alarms was accompanied by the sickening, shrieking howl of the two huge steam turbines aft as they wound down from 3600 RPM to a complete stop. To Delaney it was the sound of the Devilfish starting to die. The electrical operator opened the breakers to the turbine generators as the steam pressure went away. Now the ship was on battery power alone. The fans in the ventilation ducts spun down and stopped. The air stopped flowing. The room grew hot and stuffy as the air conditioning disappeared. For a few moments the residual heat of the plant was overcoming the arctic cold. Soon, however, the boat would be as cold as the arctic sea surrounding it.

“Cut out the reactor siren. Shut main steam one and two,” Delaney ordered. The alarm siren stopped, leaving maneuvering in an unreal quiet. Manderson rotated two more switches, and two eight-inch gate-valves shut in the main steam headers, eliminating hope of a fast restart of the reactor.