That Time Scientists Ran Experiments on Whether Pinching Someone in the Butt Could Cause a Nuclear Meltdown

Following
World War II, the United States military expended great efforts to
harness the power of the atom. Military planners were enamored with
the promise of cheap, long-term power offered by a nuclear reactor,
and efforts were in full swing in the 1950’s to develop nuclear
reactors to support the military.

Before satellites were available to monitor for impending
attack, radar stations were placed in locations that were thought
most likely routes for Soviet nuclear missiles. The Distance Early
Warning (DEW) line was a line of radar outposts across the arctic
in Alaska and Canada, where radar operators would watch 24 hours a
day, 7 days a week for incoming ballistic missiles. These outposts
were maintained by regularly flying fuel and supplies in to the
outposts to generate electricity and heat. Perhaps it goes without
saying that this was very expensive, and the U.S. military was very
interested in a cheaper alternative, and so looked to nuclear
reactors. A series of reactors were envisioned, some mobile (to be
identified as M-type reactors), some stationary (designated as
S-type), at a variety of power levels (L for low, M for medium, H
for high).

One of the first of these reactors to be developed was the SL-1
reactor (S for stationary, L for low-power, and 1 because it was
the first of this type). The intended purpose of this particular
reactor was to provide heat and electricity to radar monitoring
stations along the DEW line. The reactors were designed to take
advantage of local materials for shielding where possible, and were
also designed such that the pieces when disassembled could be
easily transported to the location where they would be set up and
operated. This meant that the large concrete structures used to
safely contain modern reactor vessels would have been too heavy and
costly to build, and so a simple steel building was erected to
protect the reactor components from the elements. The hope was that
soldiers with a minimal amount of training would be able to operate
and maintain these reactors with a minimum amount of support,
enabling them to be operational for up to three years without
refueling.

The SL-1 reactor design was flawed in many ways. As an example,
thin boron sheets were attached to the outside of the control rod
blades to provide better control of the fission process in the
reactor. In the core of the reactor, Boron is converted into Carbon
14, and this tended to cause the boron sheets to deform and
eventually flake off, causing the control rods to stick and hang up
periodically in the reactor core. Another more fundamental design
flaw was the ability for the reactor to achieve criticality with
the actuation of only one of the control rods. Criticality in a
reactor is the condition where it supports a sustained nuclear
fission reaction and can generate power. On the SL-1 reactor, if
the central control rod were withdrawn, criticality could be
achieved, even with the other control rods fully inserted. As a
result of this reactor accident, modern reactors are required to be
designed in such a way that the withdrawal of any single control
rod cannot cause the reactor to become critical.

The SL-1 reactor went critical (i.e. caused sustained nuclear
fission for the first time) in August of 1958, and was then used to
produce power, and to train reactor operators. Soldiers who wished
to become reactor operators were given 9 months of initial training
in Fort Belvoir, Virginia, before heading to the desert in eastern
Idaho for an additional 6 weeks of classroom training, before
training with a senior reactor operator crew operating the SL-1
reactor. The reactor was operated by a crew of 2-3 people, and
maintenance was typically conducted by the same two to three-man
reactor crew, in keeping with the goal of the reactor development
program to have a reactor that could be operated and maintained
with minimal support in a remote area. During the day shift in
Idaho, a health physicist was typically also on hand to monitor the
radiation exposure of the crew.

On December 23, 1960 the SL-1 reactor was shut down in
preparation for the Christmas holiday, after which crews began to
conduct scheduled maintenance to prepare the reactor to resume
normal operation. On January 3rd, 1961 the night shift took over
the maintenance operations on the reactor from the day shift. This
included two Army men, John A. “Jack” Byrnes, the Senior Reactor
Operator, and Richard L. McKinley, a trainee, and a Navy man,
Richard C. “Dick” Legg, the Assistant Operator and shift
supervisor.

For the most part, the men on the shift were competent and
unremarkable among the other trainee reactor operators in their
class. Several interesting things emerged after the accident in
relation to the men involved, however. Jack Byrnes, for example,
worked part time at a gas station, filling cars with gas, topping
up tires and cleaning windows. While Byrnes didn’t invent the
side-hustle, this has to be one of the more interesting pairings of
all time, Nuclear Reactor Operator by day, Pump Jockey by night.
Byrnes was also having some sort of marital trouble, and it is
known that Byrnes wife called the reactor building a few times the
night of the accident, although whether this played into the events
on the night of the accident is unknown, as is the substance of
their discussion.

After the accident, it also came to light that Dick Legg was
known as a prankster. Among his many pranks, he reportedly once
turned off a fan used to cool specific reactor instruments, causing
the system to alarm. After nearly sending everyone on the shift
into a panic, Legg coolly reached around the back of the control
panel and switched the fan back on. These were the men preparing
the reactor for operation the night of January 3rd, 1961.

Part of the maintenance conducted during the shut-down of the
reactor required that the control rods be disconnected from the
control rod drive mechanisms. Under normal operations, these
mechanisms would lift and lower the control rods to increase or
decrease the power output of the nuclear reactor core, which would
in turn cause more or less steam to be generated. This steam would
then power turbine generators for electrical power, and heat for
the reactor building. On the night of January 3, 1961 the men were
working to reattach the control rods to the drive mechanisms. When
the central control rod was disconnected, a C-clamp was attached at
the level of the floor above the reactor to support the weight of
the control rod while the control rod drive mechanism was
disconnected. To reconnect it, one man had to lift the roughly 85
lb control rod off the supporting C-clamp so another man could
remove the clamp. To enable the control rod to be lifted, a handle
was attached in the place of the control rod drive mechanism. At
9:01pm on the night of January 3rd, 1961 Jack Byrnes was lifting
the control rod. Dick Legg was crouching next to him, ready to
remove the C-clamp, and Richard McKinnley was standing a short
distance away, holding a Cutie Pie radiation instrument to monitor
radiation exposure levels.

The procedure called for the control rod to be lifted no more
than 2 inches to disconnect the clamp. Subsequent investigation has
shown that the control rod was lifted 20 inches or more out of the
core. This caused the power level in the reactor core to rise
extremely quickly (a condition referred to as “prompt
criticality”), and within fractions of a second much of the fuel
had melted, and a large amount of steam was formed. This steam
explosion then caused the large layer of cooler water above the
reactor core it to accelerate upwards and slam into the underside
of the reactor vessel head. The reactor vessel then jumped,
shearing all the piping and instrumentation connected to it,
dislodging shield blocks, and eventually hitting the ceiling of the
reactor building. All three men died as a result of the accident,
it is believed that Byrnes and Legg died immediately, and McKinnley
may have survived until shortly after he was recovered from the
reactor building, and is thought to have died in the ambulance
within hours of the accident, although this is not clear. At any
rate, he never regained consciousness. The three men were the only
witnesses to what actually caused the accident.