Submarine K-19 (part 2)

Tales from the Nuclear Age

Copyright © 2011 by Charles Glassmire

 

Mar. 8, 2011

Submarine K-19 (part 2)

 

          The Soviet Union’s nuclear submarine K-19 was newly commissioned on April 30th 1960, followed by a year of sea trials. Finally she is at sea on her first duty assignment; the boat is ordered to stage a mock missile attack upon the Motherland. It is July 4th 1961 in the North Atlantic, and she is running deep to avoid detection.

          Lt. Yuri Povstyev is a 28 year old officer in charge of the ships propulsion systems. He is ending his shift in the reactor station when a final check of the starboard reactor coolant pressure gauge shows a vibrating needle on the main reactor loop. This is the major fluid source which cools the reactor core; this coolant is in direct contact with core fuel rods and contains high levels of radioactive fission products. He watches in amazement as the needle slowly vibrates backwards towards zero. With a growing sense of terror, he realizes the cause must be a leak in the loop and/or failure of the main coolant pumps – a potentially catastrophic development!

Suddenly, Captain Nikolai Zateyev receives a frantic message from the reactor room. At the same moment an emergency klaxon alerts the crew to a threatening condition there. Coolant flow for the starboard reactor has fallen to zero! He knows that without cooling, fission heat will quickly build up in the reactor nuclear core and could cause a core meltdown or a (non-nuclear) thermal explosion. Should such occur, his ship is in danger of sinking with her entire crew of 104 aboard.

Engineers in the nuclear power industry have long had an acronym for this dreaded condition. It is known as a “LOCA”, or “Loss of Coolant Accident”. It is one of the most feared of all accidents possible to occur in a power reactor, wherein the primary loop coolant flow is lost and the out of control core sits rapidly overheating. (NOTE: we are not talking about a nuclear bomb-like explosion. The LOCA accident could result in thermal explosions, and/or release of lots of radioactive fission products into the environment.) In commercial power reactors, the primary coolant loop involves very high coolant pressures, hugh quantities of coolant flow of contaminated (usually) water, and large diameter metal piping with numerous high quality welds holding the whole thing together quite firmly. It is a tribute to the industry that such systems are running continuously without accident ( except, of course,  for Three Mile Island, which we will discuss later.)

Because the LOCA could have catastrophic consequences, all power reactors in the U.S. are designed with a backup coolant system, which kicks in automatically if primary pressure is lost. K-19 did not have such a backup cooling system for either of its two reactors. Captain Zateyev pled, time and again during construction of K-19, for installation of such a backup system, but his entreaties fell upon deaf ears. The Soviet hierarchy was is a great hurry to show up the Americans.

The core temperature is rapidly rising now. Captain Zateyev orders both reactors to SCRAM, and now the boat drifts without power 300 feet below the surface of the North Atlantic. The SCRAM is a process whereby the reactor control rods are inserted rapidly into the core. They are made of neutron absorbing material (such as Boron) and quickly absorb the thermal fission neutrons (this happens within about four seconds in most reactor designs.) This effectively shuts down the fission process in the reactor, except for one thing.

In the core there are other neutrons being generated by the decay of the radioactive products which have built up during reactor life. These isotopes are still releasing neutrons into the core and, rule-of-thumb, still generate heat at about 7% of the full reactor power, depending on the isotope mix. This heat is called “decay heat”. So, as he watches in horror, the core temperature of the K-19 reactor continues to rise.

The term SCRAM is an interesting one. During the days of the first reactor designed by Enrico Fermi in 1942, under the bleachers at Stagg Field in Chicago, no one knew whether the theory would result in a stable “pile” of Uranium bricks. On the first day of start up of the reactor (Dec. 2, 1942), one fellow was standing on a balcony above the pile with a bucket of Cadmium water. He was to dump the bucket onto the top of the pile to absorb neutrons if the reaction ran out of control. In addition, Fermi put a scientist named Norman Hilberry on top of the pile with an axe. In the event of an emergency, Hilberry’s job was to cut a manila rope holding the central control rod above the pile. This would allow the control rod to drop into the center of the core and shut down the reactor, assuming their calculations were correct. Hilberry never was required to do his job that day, but from that day on, he became known as the “Safety Control Rod Axe Man” or SCRAM for short. This term for emergency shut-down has become universal in the nuclear industry.

Captain Zateyev was now faced with a command decision. Reactor temperature was out of control. If something was not done they were all doomed. His crew contained skilled metalworkers and welders. In a desperate gamble, he decides the core might be cooled by welding a connection from the boats water supply directly into the reactor core coolant loop. Pumping ships water into the core might cool it down to safe levels. The only problem was some men would have to work in a very high radiation field directly against the core to effect the modification. The dose rate was so high in the reactor room that the Captain knew these men could not survive such an exposure. The temperature of the reactor core was now approaching 1,470° F, which was close to the melting temperature of the Uranium fuel rods in the center of the core …

 

(to be continued …)

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3 Responses to “Submarine K-19 (part 2)”

  1. David Lambert Says:

    Could this be what might be happening this minute in Japan?

    • Charles Glassmire Says:

      David;

      Yes indeed – very similar problems with core cooling in Japan. They have arrived at the same desperate solution. Unfortunately, sea water will ruin the reactor internals and it won’t be usable again.

      Very astute of you to make the connection.

      Glad you are enjoying the blog. Tell your friends.

      (over 500 folks are reading each new installment!)

      Chuck Glassmire Tales from the Nuclear Age

  2. Heide Parreño Says:

    Very informative! Thanks for doing the research.

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