To make use of the newly developed heat exchanger, the Alfa plant had to move water rapidly through its many loops and baffles. This required a high-pressure pump which accounted for one hundred fifty pounds of the total system pressure — almost ten times what was considered safe in Western reactors. With the pump so powerful, the whole engine room complex, normally very noisy at high speed, was like a boiler factory, and the pump’s vibration was disturbing the performance of the monitor instruments. It was making the needles on his gauges waver, Petchukocov noted. He was right, and wrong. The pressure gauges were really wavering because of the thirty-pound overpressure waves pulsing through the system. The chief engineer did not recognize this for what it was. He had been on duty too many hours.
Within the reactor vessel, these pressure waves were approaching the frequency at which a piece of equipment resonated. Roughly halfway down the interior surface of the vessel was a titanium fitting, part of the backup cooling system. In the event of a coolant loss, and after a successful SCRAM, valves inside and outside the vessel would open, cooling the reactor either with a mixture of water and barium or, as a last measure, with seawater which could be vented in and out of the vessel — at the cost of ruining the entire reactor. This had been done once, and though it had been costly, the action of a junior engineer had prevented the loss of a Victor-class attack sub by catastrophic meltdown.
Today the inside valve was closed, along with the corresponding through-hull fitting. The valves were made of titanium because they had to function reliably after prolonged exposure to high temperature, and also because titanium was very corrosion-resistant — high-temperature water was murderously corrosive. What had not been fully considered was that the metal was also exposed to intense nuclear radiation, and this particular titanium alloy was not completely stable under extended neutron bombardment. The metal had become brittle over the years. The minute waves of hydraulic pressure were beating against the clapper in the valve. As the pump’s frequency of vibration changed it began to approach the frequency at which the clapper vibrated. This caused the clapper to snap harder and harder against its retaining ring. The metal at its edges began to crack.
A michman at the forward end of the compartment heard it first, a low buzz coming through the bulkhead. At first he thought it was feedback noise from the PA speaker, and he waited too long to check it. The clapper broke free and dropped out of the valve nozzle. It was not very large, only ten centimeters in diameter and five millimeters thick. This type of fitting is called a butterfly valve, and the clapper looked just like a butterfly, suspended and twirling in the water flow. If it had been made of stainless steel it would have been heavy enough to fall to the bottom of the vessel. But it was made of titanium, which was both stronger than steel and very much lighter. The coolant flow moved it up, towards the exhaust pipe.
The outward-moving water carried the clapper into the pipe, which had a fifteen-centimeter inside diameter. The pipe was made of stainless steel, two-meter sections welded together for easy replacement in the cramped quarters. The clapper was borne along rapidly towards the heat exchanger. Here the pipe took a forty-five-degree downward turn and the clapper jammed momentarily. This blocked half of the pipe’s channel, and before the surge of pressure could dislodge the clapper too many things happened. The moving water had its own momentum. On being blocked, it generated a back-pressure wave within the pipe. Total pressure jumped momentarily to thirty-four hundred pounds. This caused the pipe to flex a few millimeters. The increased pressure, lateral displacement of a weld joint, and cumulative effect of years of high-temperature erosion of the steel damaged the joint. A hole the size of a pencil point opened. The escaping water flashed instantly into steam, setting off alarms in the reactor compartment and neighboring spaces. It ate at the remainder of the weld, rapidly expanding die failure until reactor coolant was erupting as though from a horizontal fountain. One jet of steam demolished the adjacent reactor-control wiring conduits.
What had just begun was a catastrophic loss-of-coolant accident.
The reactor was fully depressurized within three seconds. Its many gallons of coolant exploded into steam, seeking release into the surrounding compartment. A dozen alarms sounded at once on the master control board, and in the blink of an eye Vladimir Petchukocov faced his ultimate nightmare. The engineer’s automatic trained reaction was to jam his finger on the SCRAM switch, but the steam in the reactor vessel had disabled the rod control system, and there wasn’t time to solve the problem. In an instant, Petchukocov knew that his ship was doomed. Next he opened the emergency coolant controls, admitting seawater into the reactor vessel. This automatically set off alarms throughout the hull.
In the control room forward, the captain grasped the nature of the emergency at once. The Politovskiy was running at one hundred fifty meters. He had to get her to the surface immediately, and he shouted orders to blow all ballast and make full rise on the diving planes.
The reactor emergency was regulated by physical laws. With no reactor coolant to absorb the heat of the uranium rods, the nuclear reaction actually stopped — there was no water to attenuate the neutron flux. This was no solution, however, since the residual decay heat was sufficient to melt everything in the compartment. The cold water admitted into the vessel drew off the heat but also slowed down too many neutrons, keeping them in the reactor core. This caused a runaway reaction that generated even more heat, more than any amount of coolant could control. What had started as a loss-of-coolant accident became something worse: a cold-water accident. It was now only a matter of minutes before the entire core melted, and the Politovskiy had that long to get to the surface.
Petchukocov stayed at his post in die engine room, doing what he could. His own life, he knew, was almost certainly lost. He had to give his captain time to surface the boat. There was a drill for this sort of emergency, and he barked orders to implement it. It only made things worse.
His duty electrician moved along the electrical control panels switching from main power to emergency, since residual steam power in the turboalternators would die in a few more seconds. In a moment the submarine’s power completely depended on standby batteries.
In the control room power was lost to the electrically controlled trim tabs on the trailing edge of the diving planes, which automatically switched back to electrohydraulic control. This powered not just the small trim tabs but the diving planes as well. The control assemblies moved instantly to a fifteen-degree up-angle — and she was still moving at thirty-nine knots. With all her ballast tanks now blasted free of water by compressed air, the submarine was very light, and she rose like a climbing aircraft. In seconds the astonished control room crew felt their boat rise to an up-angle that was forty-five degrees and getting worse. A moment later they were too busy trying to stand to come to grips with the problem. Now the Alfa was climbing almost vertically at thirty miles per hour. Every man and unsecured item aboard fell sternward.
In the motor control room aft, a crewman crashed against the main electrical switchboard, short-circuiting it with his body, and all power aboard was lost. A cook who had been inventorying survival gear in the torpedo room forward struggled into the escape trunk as he fought his way into an exposure suit. Even with only a year’s experience, he was quick to understand the meaning of the hooting alarms and unprecedented actions of his boat. He yanked the hatch shut and began to work the escape controls as he had been taught in submarine school.
The Politovskiy soared through the surface of the Atlantic like a broaching whale, corning three quarters of her length out of the water before crashing back.
The USS Pogy
“Conn, sonar.”
“Conn, aye, Captain speaking.”
“Skipper, you better hear this. Something just went crazy on Bait 2,” Fogy’s chief reported. Wood was in the sonar room in seconds, putting on earphones plugged into a tape recorder which had a two-minute offset. Commander Wood heard a whooshing sound. The engine noises stopped. A few seconds later there was an explosion of compressed air, and a staccato of hull popping noises as a submarine changed depth rapidly. “What’s going on?” Wood asked quickly.
The E. S. Politovskiy
In the Politovskiy’s reactor, the runaway fission reaction had virtually annihilated both the incoming seawater and the uranium fuel rods. Their debris settled on the after wall of the reactor vessel. In a minute there was a meter-wide puddle of radioactive slag, enough to form its own critical mass. The reaction continued unabated, this time directly attacking the tough stainless steel of the vessel. Nothing man made could long withstand five thousand degrees of direct heat. In ten seconds the vessel wall failed. The uranium mass dropped free, against the aft bulkhead.