America’s fatal nuclear accident you’ve never heard of

On January 3, 1961, an explosion at the Nuclear Reactor Testing Station in Idaho Falls killed three operators. From the article:

"America’s fatal nuclear accident you’ve never heard of
Dale M. Brumfield

Around 9:10 p.m. on January 3, 1961, first responders rushed to the site of the Stationary Low-Power Nuclear Reactor Number One (or SL-1) forty miles west of Idaho Falls, Idaho after a routine automatic fire alarm went off. As they approached, they noticed a cloud of vapor surrounding the cylindrical 48-ft tall silo-like building, but with air temperatures hovering at -6˚F, that was not considered unusual.
Their indifference turned to alarm, however, once inside the reactor building stairwell, when their radiation detectors spiked to near-fatal levels. At 10:45 p.m., and clad in full protective radiation suits, rescue personnel made it into the central core building and were aghast to find the SL-1 control core in shambles. Radiation levels were so high they were only permitted to enter the badly damaged control room for one or two minutes at a time to retrieve Army Specialist John Byrnes, who was dead, and Richard McKinley, who was still alive but so contaminated his body was emitting 500 roentgens (r) of radiation per hour — a fatal dose. He died within minutes of being removed.

The third operator, a 25-year-old Navy Seabee and Electricians Mate Richard Legg, could not immediately be found. Rescue personnel at first assumed he made it out of the control area prior to whatever the hell happened there. But after almost twenty minutes of searching, one of the responders happened to look up at the ceiling just over the remains of the mutilated control rod core — and was horrified at what he saw.

In 1954 the cold war-obsessed US Army began evaluating the use of low-power nuclear reactors in the Arctic wilderness of Canada and northern Greenland as part of the DEW (Distant Early Warning system) radar stations whose sole purposes were to watch for Soviet invasion. These power units were intended to be stationary, as well as low-power for electrical and heating generation, hence the SL designation.

In 1957 Chicago’s Argonne Laboratories designed and constructed a prototype reactor, and around October 1958 it was fully operational on the National Reactor Testing Station, a sprawling half-million-acre complex in the prairies of southern Idaho 40 miles west of Idaho Falls. A company called Combustion Engineering was selected as the operating contractor

A total of sixty Army and Navy personnel, including Legg, Byrnes and McKinley, were hired and trained as operators on the SL-1, which was shaped somewhat like a missile silo. At the top of the reactor was a circular working area, where the control rods could be raised and lowered in the operational processes. The reactor itself, as well as its water-cooling apparatus, were located beneath the working area down to ground level.

The core was initially designed with 40 fuel elements, controlled by five 32”-long cross-shaped rods, each constructed of 1.5mm-thick cadmium, coated with 2.0mm of aluminum. The reactor used 93.2% highly enriched uranium fuel, and operated at 300 PSI with naturally circulating ordinary (or “light”) water as a coolant.

On December 21, 1960, the reactor was shut down for end-of-the-year maintenance and recalibration, and the primary crew left for the Christmas break, leaving Legg, Byrnes and McKinley to complete the prescribed routine maintenance procedures in their absence.

Work was tedious and uneventful for the three technicians in the middle of a frozen nowhere until midnight on January 3, 1961, when the reactor was configured and primed for only 3 megawatts of power, meaning only 40 (of 59) possible fuel assemblies and five (of nine) control rods were in place. While this was significantly less power than the reactor was capable, this configuration contravened the “one stuck rod” rule, meaning that it would still be possible to shut down the reactor even with one rod stuck in the “completely out” position — a potentially hazardous condition.

This indicated one of the several design flaws in the SL-1 that would later haunt them.

At 9:01 p.m., procedures required that the central control rod, which regulated the rate of the fission reaction by absorbing excess neutrons released by the U-235 atoms, be manually withdrawn only 4.2 inches to reattach it to the drive mechanism. But post-incident calculations showed that for reasons not immediately understood, Byrnes lifted the rods far past that height, to almost 20 inches. At that height, the reactor went critical, and in four milliseconds the reactor spiked to 20 gigawatts — over 6,300 times its safe operating capacity.

While speculation was that the control rods could have possibly stuck, another design flaw that may have forced Byrnes to “jog” the mechanism to release them, it is known that in those four milliseconds enough heat was spontaneously generated in the water left in the reactor to instantly vaporize it. This, in turn, created an extremely concentrated “water hammer” that shot to the top of the reactor vessel at 109 mph, smashing the top of the vessel in a massive detonation that caused not just the entire 26,000-lb housing to jump vertically over nine feet, but for massive control rods, shield plugs and other pieces of the assembly to be blasted upwards with enough force to embed them into the steel and concrete ceiling 13 feet overhead.

It was quickly determined by the first responders that Byrnes and McKinley both had been struck in the back by high-pressure water and steam and thrown into a shield block, based on the location of their bodies.

But what happened to Legg?

The first automatic alarm (that did not differentiate a pressure surge from excessive temperatures — yet another flaw) had been received at the Atomic Energy fire station and security headquarters eight miles away at 9:01 p.m. and fire engines arrived at the SL-1 building at 9:10. Firemen equipped with Scott air packs and radiation meters went through the buildings in search of the three operators, but were repulsed from the reactor building by very high radiation readings of 25 r per hour, the maximum limit of their meters. At other positions inside the administration building they encountered pockets of radiation ranging from 10 r to 500 r per hour — lethal dosages that could kill them all.

Alarmed at what they were finding, the rescue personnel issued a Class I Disaster over the National Reactor Testing Station (NRTS) radio network at 10:25 p.m.

At 10:35, Combustion Engineering Supervisors fully equipped in protective gear entered the 500 r contaminated control room for only two minutes at a time. There they saw McKinley on the floor, still alive, bleeding and trying to move. But since their time was up, they had to leave him.

Within seconds two more supervisors entered, placed McKinley on a stretcher and carried him out. He was carried in a lead-lined panel truck several miles away but at 11:14 he was declared dead and brought back to the facility. At that time it was discovered that his head and hands were emitting 500 r of radiation per hour, and decontamination procedures failed to reduce it.

At 10:38, three more supervisors entered the control room looking for Legg. It wasn’t until one man looked up that he discovered the awful truth. At the time of the so-called “excursion,” or explosion, Legg had apparently been standing on top of the reactor, and the force of the explosion discharged one of the heavy shield plugs (resembling a giant spark plug) out of the housing through his chest, propelling his body straight up into the ceiling, leaving the poor man impaled, dead and dangling thirteen feet in the air.

He had to be left there until a recovery protocol could be established.

The next day, January 4, Byrnes’ body was recovered out of an area where radiation levels registered 750 r per hour — a level that could cause death within hours. The personnel had to be extensively briefed, rehearsed and attired in protective clothing, then worked as two-man teams for only one minute at a time to get the body out. Byrnes’ highly contaminated body was then taken to a chemical processing plant that had been equipped to receive him.

Coincidentally, on this same day the Idaho Falls Lions Club held a meeting in the Roundup Room of the Rogerson Hotel and heard a speaker present the dangers of nuclear fallout. They then watched a Federal Emergency Management Agency film, “Walt Builds a Fallout Shelter.”

It wasn’t until January 8 that a procedure to remove Legg’s body from the ceiling was initiated. A 5’x20’ net was positioned under him by a crane boom, and working 65 seconds at a time, rotating rescue personnel had to remove his body off the 40-inch plug and lower it into the net. Legg’s body was finally removed from the building at 2:37 a.m. on January 9.

A post-mortem examination showed that his body had not decayed during the six days he was suspended from the ceiling, as the heavy radiation had effectively sterilized him.

Parts of all three men, including their hands, were so radioactive that after they were autopsied, they were considered too dangerous to transport by public highway to a radioactive waste burial site only 16 miles away, so they had to be moved with other radioactive residue of the accident to a site several hundred yards northeast of where SL-1 was formerly located.

Investigators troubleshooting the explosion formulated several hypotheses of what caused it. Sticking fuel rods was a problem with other SL-1 reactors, but never during start-up. They concluded that one of the rods had stuck in its channel when Byrnes tried to lift it, and that shifting it back and forth to unstick it inadvertently lifted them all too high too fast — a fatal design flaw.

Another theory that seems far less likely is that the accident was a murder-suicide, instigated by Byrnes against Legg. Apparently, there was tension between the men because of Legg’s recent promotion, and even a rumor started that Byrne’s wife had called him the day of the accident, asking for a divorce. There is little fact to back up these assertions, and it appears to be just rumor.

At the conclusion of the investigation, the entire reactor and structure was cut up with torches and buried. The site is surrounded by a fence and extensive warnings.

Tami Thacker, a former nuclear safety analyst at the Idaho National Laboratory and nuclear safety consultant, wrote in an undated report that “When you consider the faulty welds … the increasingly sticking rods during the last month of operation, the ambitious testing at relatively high reactor powers in order to test the new condenser which would have accelerated the degradation of materials, it becomes clear that management decisions caused the sticking control rod which, in my mind, undoubtedly caused the accident.”

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Idaho State Journal, 1–6–1961
Richard C. Legg is buried in Kingston, Michigan. Richard L. McKinley is buried in Arlington National Cemetery in Washington DC, and John A. Byrnes is buried in Whitesboro, New York. Because of their bodies’ high radioactivity, all are buried in lead-lined coffins embedded in several cubic yards of concrete. Their graves cannot be moved without approval of the Atomic Energy Commission."