Tales from the Nuclear Age:

 Copyright © 2010 Charles Glassmire


Jan. 31, 2010


           Private and government laboratories are often identified by an acronym composed of first letters of the facility name. Thus, Los Alamos Scientific Laboratory becomes “LASL”, Lawrence Radiation Lab “LRL” etc. In the early sixties, the General Electric Company operated a test reactor in California down the coast near a town called Pleasanton. It was located at Vallecitos, about seven miles from Livermore, in the rolling brown hills so

the Vallecitos Reactor Site

the Vallecitos Reactor Site

familiar to all Californians in winter. It was called the General Electric Test Reactor, hence GETR. On the same site was a General Electric boiling water reactor (GEBWR) which supplied electricity to the area up until the middle 1960’s.   

          The GETR had a rather unique capability then. It ran with highly enriched Uranium fuel, an enrichment much too dangerous for ordinary power reactors. This created a very high thermal neutron flux in the reactor core, higher than most any other research reactor in the US at that time. (Neutron flux is a number counting the number of neutrons crossing through an imaginary square centimeter of space inside the reactor core. It sort of tells you how many neutrons are flying around inside the reactor, how many Uranium 235 atoms are fissioning, and thus how much power the reactor is generating. The more flux, the more power and the higher the core temperature.)  It was an experimental testing reactor; consequently it was often used for high power density experimental irradiations requiring unusually high flux. The associated Radioactive Materials Laboratory provided hot cell capabilities to examine radioactively “hot” materials after irradiation. The staff there was a relatively creative bunch, and open minded enough to accept new devices and ideas for testing. This was long before the days when the nuclear industry became introverted and cautious. It was an exciting time.

          So if you were Westinghouse, and were building, say, a very high flux density Nuclear Rocket Engine Vehicle like NERVA, the GETR provided an excellent place to examine the effects of radiation on the nuclear fuel in the NERVA engine. Even if it was General Electric! The fact that GE and Westinghouse were the two major US competitors in the nuclear power reactor-selling business was irrelevant to us engineers. We were going to Mars.

          So it was that I, a very young engineer, was designated to travel from the Astronuclear Laboratory in Pittsburgh to California, along with the lead engineer ( my friend Dave), to irradiate some NERVA fuel and observe the results. I was really chosen because the married guys in our group didn’t want to spend several weeks away from their families, and since I was the single guy, I got elected. I was secretly happy though, since I had never been there, and California seemed a distant and exciting place to visit.

          Now when you irradiate a Uranium based fuel with lots of neutrons, a lot of fissions occur (the Uranium nucleus breaks into several pieces, liberating lots of energy in the process.)  During this energy release nothing gets burned; there is no Carbon emissions involved, so it’s a completely self contained green process. Use the heat to turn a turbine and voila, you are generating clean electricity! We are utilizing the binding energy of the Uranium nucleus, a very strong force which was created billions of years ago in a supernova sun which threw off the planet Earth, and all the Uranium it contains. So, incidentally, all the Uranium on earth is exactly the same age, and has decayed away at exactly the same rate. But back to my story.

          We were to ship small pieces of nuclear fuel to GETR for the test. But these samples got very hot when they were in a high-flux reactor. In fact, the fuel temperature would reach a white hot condition, about 4,100 degrees Fahrenheit. This was around the temperature the NERVA Engine operated, so we had to hold the fuel at that temperature for about 20 minutes for our test. This was quite a challenge. Most ordinary materials melted and vaporized when they got white hot. So we had to contain the stuff in a special capsule. It was the old conundrum about if you had a perfect acid which would dissolve anything in the world, what would you keep it in? Answer: Stainless Steel.  But this would melt at 4000 F, so we used a can inside a can system with circulating cooling water between the two cans. This removed the heat generated, and prevented melting nicely. Or so we calculated.

          Also, there was another complication. We had to know the temperatures inside the inner can. This meant putting in a device called a Thermocouple. This would measure the temperature and send it by wire out of the experiment. The wires had to pass out through the steel can, and thus had to be sealed water and air tight. But, you are asking, why didn’t the thermocouples melt inside that hot can? I had designed the thermocouples to be clad in an exotic metal called Tantalum. It had an extremely high melting point and 4000 F (in a vacuum) didn’t phase this metal. It was expensive though. They were each hand made and fabricated, so the thermocouples cost several thousand dollars each. AND there were six of them. Gasp. But we had to have the data or the test was useless.

          The question was how to seal the devices air tight when they passed through the steel can? Any oxygen left inside would quickly oxidize all the metals and destroy the capsule. Dave had thought about this and earlier had run a test in a vacuum furnace, using silver braze. It had worked beautifully, and afterward Dave had the test piece on his desk when he showed it to me. Around the tantalum was a lovely perfectly smooth meniscus of braze flowing nicely onto the steel. The seal tested air tight. No problem.

          But during the assembly of the test cans it proved impossible to braze the thermocouples to the stainless steel. The technicians destroyed thermocouples, one after another in a futile effort at assembly. After inquiring around, Dave was horrified when the metallurgists told him it was impossible to braze Tantalum to stainless steel!  He desperately tried his furnace test again, and this time the braze wouldn’t seal. It came out in little raggedy beads with holes in the steel can. We now had one hundred thousand dollars (in 1960’s money) of unassembled capsules sitting in the lab with no way to seal them and one very mortified test engineer…

 (to be continued…)


9 Responses to “GETR”

  1. Larry Hammond Says:

    Pretty Awesome story telling there Chuck!!

  2. Mark Says:

    Ideas highly fissionable material seat of pants / money = Science. Sweet. Must have been the greatest time ever.

  3. Ed McCormick Says:

    I like your periodic updates – it is never too late to learn new information.

    Keep in touch.

    Ed McCormick

  4. Paulo Says:


    Very nicely written story. I enjoyed it so much.

    I can sympathize with this young teenager. I hope he has a happy and fulfilling life doing whatever he likes.

  5. R D Smith Says:

    Thanks for the article – my father got his RO license at GETR and I have many found childhood memories of the plant and fishing at the lake.

    • Charles Glassmire Says:

      Thanks for the kind memories.

      I am one of the few who have the distinction of scramming the GETR reactor. Not a happy experience.

      Be well.

      Charles Glassmire

  6. retrosurf Says:

    “Not a happy experience.”

    Oh, those make the very best stories.

  7. John L. Turk Says:

    I have the distinction to be the one to force GE to close this reactor. I can be reached at I have a long a tawdry story to tell you, if interested.

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