SL-1: Aftermath

Tales from the Nuclear Age:

Copyright © 2010 by Charles Glassmire


July 31, 2010

SL-1: Aftermath

           Examination of metal parts from the bodies and other evidence soon determined that the SL-1 reactor had gone “prompt critical”. This sudden release of a burst of thermal neutrons had occurred within a tiny fraction of a second, actually estimated at about  4 milliseconds ( 4/1000 of a second). But it was to take almost two years of investigation by a team of physicists and engineers before the strange sequence of events and mechanics of what had happened that cold night were finally known.

          This reactor accident was unprecedented in the history of the nuclear industry. These were the first industrial casualties in the existence of the Atomic Energy Commission. The Commission Headquarters immediately appointed an investigations committee, and a separate technical advisory committee, all arriving by January 4. The Joint Committee on Atomic Energy sent one of its staff to be an independent investigator. Some Atomic Energy Labs sent their own personnel to help uncover the mystery. Military representatives arrived from al three services. Army volunteers came from a special Chemical Radiological Unit based at the Dugway Proving Grounds to assist and learn from the event. Radiation fields inside the containment building were still very high.

          Since all the personnel had been accounted for as beyond saving, the  new task was to determine if the reactor was stable, or capable of additional problems. The cause of the accident was still mysterious. Most of the water had been evaporated from the core by a burst of heat. It was now re-condensed several inches deep on the reactor building floor. Water is a neutron moderator. This means it slows down neutrons to a slow speed where they can fission a Uranium 235 nucleus. So the more water present in the core the higher the core reactivity and the more fission heat is generated. Examinations by a remote video camera, and supporting calculations soon showed the core was stable without the water moderator in place. This was a small bit of good news and also a credit to the reactor designers. The nations Press had arrived en masse.

          Aircraft radiation monitors reported the roof of the reactor building was intact, which was a small miracle in itself. This reactor was built before the days of industrial containment vessels. Now a days all American reactors are built inside a steel containment “cage”. This is a several inch thick steel bottle designed strong enough to trap any exhaust gases, explosions and other radiation events, so that nothing is released to the environment. New Containment vessels are now designed to even resist the impact of a jet airliner crash. But the SL-1 building was little more than a large circular housing around the reactor. It was amazing the structure had resisted the forces in play. The survey Aircraft reported that a cloud of Iodine 131 had escaped and floated downwind, but was quickly dispersed by the winds and decayed to harmless levels. No other escaped isotopes were detected in the surrounding desert and highways.

          But the fundamental mystery remained. What was the cause of this event? Inside, the SL-1 was a disastrous mess. Timed by Health Physics personnel, cleanup crews of volunteers wearing dosimeters dashed in, received their quarterly dose of radiation and retired from radiation work for three months. Holes were drilled into the bottom of the core to photograph the core elements. It was determined that some of the Uranium fuel had melted from the burst of intense heat. It was decided the entire reactor should be disassembled and examined piece by piece in Hot Cells. The Aircraft Nuclear Propulsion Project (ANP) had been recently shut down, and unemployed technicians from that project were able to utilize the giant Hot Cell remote exam rooms to study the pieces.

          After months of cleanup work, it came time to remove the core pressure vessel via a crane. Engineers worried about

SL-1 Core Pressure Vessel

disconnecting the array of piping which connected the core pressure vessel to the rest of the building. This would involve long hours of welding in a radiation environment. There was not a large supply of welders to take the dose. Then photography revealed that the piping and metal connections to the building were already severed! The pressure vessel was already free floating in position.

          The ceiling of the reactor room was examined closely, and deep gouge marks in the ceiling, nine feet above the core, matched the pattern of rods protruding out of the top of the pressure vessel itself. Thus the entire steel reactor pressure vessel containing the core had been exploded upward out of its position with great force, severing all piping connections, hitting the ceiling of the building and then falling back into its resting place!

          Scratches on the guide tube of the main control rod showed it had been quickly extracted by the technician working there, to a length of 23 inches out of the core instead of the required 4 inches. This was unprecedented, pushing the core into instant super critical condition. This had caused an instant burst of fission neutrons and released a hugh amount of fission heat. The core coolant water instantly flashed into steam, expanding and hitting the inside top of the pressure vessel with the large force of a water hammer. This impact had blown the pressure vessel upwards to impact the ceiling, severing all metal supports, piping and electrical connections, and killing the technician working there before falling back to rest. All within a small fraction of a second. Calculations later verified the accuracy of this scenario .

          There are some who say the control rods had a documented history of sticking when withdrawn, and the technician had jerked too hard on the rod. A cladding had been welded to the side of the rods, and as it aged it had changed dimension slightly, interfering with easy sliding of the rods in their holes. There are those who say that procedures had not been well documented by the operator, and the military crews had been inadequately trained. There are some who say a technicians companion had played a physical joke from behind him at a critical moment, causing a reflexive muscle jerk on the rod. And there are some who say that the rod was intentionally jerked up beyond its safety limits by a technician whose wife had deserted him and told him to never come home again. This then becomes a tale of the first suicide by nuclear reactor in the brief history of the nuclear age …

 (to be continued …)


2 Responses to “SL-1: Aftermath”

  1. Says:

    Awesome blog! Do you have any tips for aspiring
    writers? I’m hoping to start my own blog soon but I’m a little lost on everything.
    Would you suggest starting with a free platform like WordPress or go for a paid option?

    There are so many options out there that I’m completely overwhelmed .. Any tips? Kudos!

    • Charles Glassmire Says:

      Thank you for the kind words.

      I find the free wordpress to be an excellent host. Their editor is a little bit quirky but otherwise I’m very pleased.

      As for writing, the best advice I ever got was to write about something you know. Push it to the end of your knowledge but don’t go any further.

      Apply the seat of the pants to the seat of a chair and write whatever comes to your mind. Don’t worry about organizing – do that later after the ideas are in the computer. There are excellent editing tools after you get the main stuff down.

      Good luck. Keep reading!

      Charles Glassmire

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