Posted on by steve blank

I started working when I was 14 (I lied about my age) and counting four years in the Air Force I’ve worked in 12 jobs. I left each one of them when I was bored, ready to move on, got fired, or learned as much as I can.

There was only one job that I quit when I feared for my life.

Life Is Good

The Vietnam War had just ended and I was out of the Air Force back in college living in Ann Arbor Michigan. Colors other than olive green or camouflage slowly seeped back in my life as “Yes sir, and no sir” faded away. Unlike my previous attempt at college as a pre-med, four years working with electronics convinced me that perhaps I ought to study engineering.

Civilian life was good, the government was paying my tuition and I got a college work/study job in the University of Michigan physics department. After a few weeks, the Physics lab staff realized I knew something about repairing electronics (you try fixing a sodium-iodide scintillation detector without a manual.) I got asked, “Would you like to work at the nuclear reactor?” I thought they were joking. “The university has its own nuclear reactor?”

Oh man, something really new to learn. “Heck yes, sign me up.”

Nuclear Reactors on Campus

Starting in 1953 the U.S. built over a 150 research reactors. Much smaller than the ~500-1,500 megawatt nuclear reactors that generate electricity, by the late 1960s these 1 to 10 megawatt reactors were in 58 U.S. universities. In addition, 40 foreign countries got research reactors in exchange for a commitment to not develop nuclear weapons. (But these reactors used weapons grade Uranium-235 for their cores, and by the late 1970’s we realized it wasn’t a good idea to be shipping highly enriched uranium overseas.)

My first day in the reactor electronics lab I got a lecture from the health physics department. I was given a film-badge (a dosimeter to measure whole body radiation) and taught how to use the hand and foot monitors (to prevent radioactive contamination from spreading outside the containment dome.)

Scram

Lots of things could go wrong in a nuclear reactor – loss of cooling, power failure, jammed control rods, reactor power excursions, etc. While a reactor failure can’t create a nuclear explosion, if its core is uncovered long enough it can generate enough heat to melt itself, with all kind of nasty consequences (see Three Mile Island and Chernobyl.) To “scram” a reactor means an emergency shutdown by inserting neutron-absorbing control rods into the core. This stops the nuclear chain reaction. My job in the reactor electronics lab was to rebuild the reactor “scram system.”

The scram system had three parts: the mechanical part (the control rod drives and electromagnetic latches), the electronic part (comparators circuits and trip logic), and the sensors (to measure neutron flux, core temperature, pool water level, etc.)

The 20-year old electronics in our existing scram system were based on vacuum tubes and had the annoying habit of scramming the reactor every time a thunderstorm was nearby. And summertime in the Midwest has lots of thunderstorms. The Nuclear Regulatory Commission had approved a transistorized version of the electronics. My job was to build the approved design, retrofit it into the existing power supplies and integrate it with the existing mechanical systems and sensors.

But first I was going to see the reactor.

Cerenkov radiation

Over time I would get used to visiting the reactor, but the first visit was awe-inspiring. Entering the containment building through the air lock, my eyes took a few seconds to adjust to the dim light. The first thing I saw was a gigantic mural of the earth rising over the moon painted on the side of the dome. After another few seconds I realized that the mural was illuminated by an unearthly blue glow coming from what looked like a swimming pool below it. My eyes followed the source of the light down to to the pool and there I first saw the 2 MW nuclear reactor in the bottom of the swimming pool – and it was generating its own light. When I could tear my eyes from the pool I noticed that in the far end of the building was a glass wall separating a room bathed in red light, where the reactor operators sat at their console. The lab manager let me stand there for a while as I caught my breath. Hollywood couldn’t have set the scene better.

As we walked towards the pool I learned that the bright blue light was Cerenkov radiation from the reactor core (electrons moving faster than the speed of light in water polarizing the water molecules, which when they turned back to their ground state, emitted photons.) We briefly walked across a bridge that spanned the pool and stood directly over the core of the reactor. Wow. They were going to pay me for this?

Dose Roulette

Over the next few weeks, as I began work on the scram system, I got to know the control room operators and others on the staff. Most of them were ex-Navy reactor technicians or officers. They had been around nukes for years and were bemused to find an ex Air Force guy among them.

One of their weekly rituals was to read the bulletin board for the results of the dosimeter readings. Since most of my time was spent outside the containment dome my radiation exposure numbers were always zero. But there was a bizarre culture of “you’re not a real man until you glow in the dark” among the ex-Navy crew. They would celebrate whoever got the highest dose of the week by making them buy the beer for the rest.

After spending the last four years around microwaves I had become attuned to things that you couldn’t see but could hurt you. In the Air Force I had watched my shop mates not quite understand that principle. On the flightline they would test whether a jamming pod was working by putting their hand on the antenna. If their hand felt warm they declared it was. When I tried to explain that the antenna wasn’t warm, but it was the microwaves cooking their hand, they didn’t believe me. There were no standards for microwave protection. (I always wondered if the Air Force would ever do a study of the incidence of cataracts among radar technicians.)

You Buy The Beer

In a few months I had the new scram system ready for debugging. This required connecting the new electronics to the neutron detectors in the pool that monitored the core. We timed this for the regular downtime when used fuel elements were swapped out and they had lowered the pool water level for easier installation. I remember standing on the bridge right over the reactor core watching as the reactor techs remotely connected up the cables to my electronics. I leaned over the bridge to get a better look. By now the reactor was so familiar that I didn’t think twice of where I was standing.

A week later as I was about to enter the dome, I heard someone congratulate me and ask when I was going to buy the beer. They were pointing to the Health/Safety printout on the wall. In one week I had managed to get close to my annual allowable radiation dose (~5 rems?).

In my mandatory talk with the the safety officer to figure out where I got exposed, I remembered hanging out over the core on the bridge. The heavy water in the pool was both a moderator and a radiation shield. With the pool level lowered I shouldn’t have been on the bridge. I had been in the wrong place at the wrong time.

“Don’t do it again” was his advice.

Career Choices

That week I finished up the installation and resigned from the lab. While the radiation dose I received was unlikely to effect my health, the cumulative effect of four years of microwaves and the potential for more unexpected “winning the dosimetery lottery” convinced me to consider alternate jobs in electronics.

In some sense my career in startups was steered by deciding to avoid future jobs with gamma rays or high-power microwaves.

But I sure learned a lot about nuclear reactors.

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Postscript: a year and a half after I left, the power reactor at Three Mile Island had a core meltdown. For years I would worry and wonder if I had wired my scram system correctly.

Lessons Learned

Things you can’t see can hurt you (microwaves, gamma rays, toxic bosses.)

No job is worth your health.

If it seems dangerous or stupid it probably is.

Rules and regulations won’t stop all possible mistakes.

No one but you will tell you it’s time to quit.

Filed under: Air Force, Technology |