In 1955 I moved from New York with my wife and child to Los
Angeles. On November 15 of that year I
started working at a division of one of the aircraft companies, North American
Aviation, called Atomics International, often abbreviated as AI. The purpose of this new division was to
establish a foothold for the parent company in the new field of nuclear reactor
power. Nuclear power was touted at the
time as being “clean” power. Nuclear
power stations did not emit black soot, oxides of carbon and sulfur, and
radioactive material that occurs naturally in coal.
The company secured a number of contracts for developing
types of power reactor. Many of these
contracts dealt with portable power units for military use. These contracts developed information that
was classified. Another government
contract was for a prototype reactor in which the coolant was sodium rather
than water. Coolant is the fluid that
extracts heat from the fissioning fuel elements and delivers it to a rather
conventional power unit through a heat exchanger. The advantages of sodium rather than water
were based on the fact that sodium remains a liquid from its melting point at
C to above 1,000o
Since it could operate at such a high temperature, the power plant would
have a higher Carnot efficiency than one in which water was used to transfer
the heat. In addition to improved thermodynamic
efficiency, a sodium cooled reactor had no need for pressure containment. All parts of the reactor operated at
atmospheric pressure. Only the steam
produced in the final heat exchanger operated at high pressure.
The disadvantages of using sodium relate to the chemical and
physical properties of the element. It’s
chemically very reactive. Air, and
especially oxygen and water vapor, must be kept away from the liquid
sodium. In addition it has a negative
reactivity coefficient with respect to the generation of neutrons. It absorbs them and the reaction produces radioactive NA24
which decays to magnesium. Because it absorbs neutrons, any gap or
bubble in the sodium in close contact with the uranium fuel produces a slight
increase in the efficiency of producing neutrons. If a sodium cooled reactor suddenly lost all
its coolant, the reactor would start a power excursion as well as experiencing
an immediate rise in temperature of the fuel.
A different effect occurs with a water-cooled reactor. Water absorbs few neutrons and also is a good
moderator. Loss of water causes a power
reduction in such a reactor. Of course,
the fuel elements get very hot, just as in the case of a sodium reactor with
loss of coolant.
Atomics International built the Sodium Reactor Experiment
(SRE) at the Rocketdyne-AI Field Test Station in the Simi Hills between Los
Angeles and Simi Valley. The reactor
began operation to demonstrate its ability to support a power plant in about
1957. In 1959 the reactor had an
accident that resulted in damage to 13 of the 42 fuel elements. There are numerous reports written at the
time about various aspects of the accident.
These reports state:
Some of the fuel elements broke open and released
radioactive fission products.
These fission products were contained within the
sodium coolant. The sodium was so
radioactive that it couldn’t be disposed of.
It was used in the subsequent re-start of the reactor next year, in
There is a free surface to the sodium in the
reactor core. The space above the sodium
is normally filled with helium. The
helium is periodically vented to storage tanks and later vented. Fresh helium is introduced. After the accident the cover gas consisted of
helium and also two inert gases: xenon and krypton. These were transferred along with the helium
to the storage tanks and later vented.
These are radioactive gases.
Being gases without chemical activity, they rapidly dispersed and did
not contribute to any appreciable radioactive contamination of the site.
Measurements were made and reported regarding
the amount and kinds of radioactive fission products that were retained in the
sodium. The report I read was written by
Bob Hart, whom I knew when I worked at AI.
In July 1959 the reactor experienced a power
excursion. The operators shut the reactor
down. The coolant was drained. Equipment was used to open various plugs in
the top of the reactor vessel to enable a camera to take pictures of the fuel
elements. The fuel elements were then
removed. There was no damage observed to
coolant tubes, the moderator logs, moderator cans, or other fixed parts of the
reactor vessel. Frank Fillmore, whom I
knew, wrote a report about the power excursion.
He concluded that the excursion was the result of bubbles in the sodium coolant
that would produce the positive reactivity coefficient mentioned above.
Since there was no damage to the reactor vessel,
including all the tubes, it was decided to load the reactor with new fuel and
start it again. It resumed operation in
1960 and operated without any problems for another four years.
The cause of the accident was found to be a leak
of an organic fluid used to cool the motors of the sodium pumps through a
rotating seal into the sodium. The fluid
formed carbonaceous clumps, similar to the clumps formed in a frying pan when
food is badly scorched. The clumps
partly plugged some of the coolant tubes and allowed the fuel elements in those
tubes to overheat and be damaged.
From these reports that I have read, I conclude that the
accident to the SRE did not rise to the level at which one would say that there
was a “melt-down.” That term has been
applied to certain other reactor accidents, particularly at Three Mile Island
in Pennsylvania and a Chernobyl in Ukraine.
In those cases the reactor was cooled with water and the water boiled
off and left the core with no coolant.
As a result, there was enough heat not only to damage the fuel elements
but also the coolant tubes that they were in.
The result was a twisted mass of partly melted tubing, extensive release
to the environment of radioactive fission products, and a mess that could only
be dealt with by burying it. None of
this happened to the SRE.
In spite of what I’ve just written, there is a persistent
belief among some people that there was a melt-down, a large release of
radioactive material, and consequent increase in people living within a few
miles of the site experiencing cancers.
Since the presumed melt-own is not reported in any official or responsible
document, this belief is supported by a presumption that the government and the
contractors involved (AI, Department of Energy, Defense Department) are “covering
up” the truth.
I have a problem. How
do I go about convincing any of these melt-down believers that there was no
melt-down and no cover-up?
A few minutes ago I read an alarming e-mail from a member of Move-On.org. Republicans in the House are putting together legislation that would effectively scuttle President Obama's plans to achieve a diplomatic solution to the problem with Iran. The law would impose conditions on any settlement that Iran would not accept. These Republicans would prefer a war with Iran rather than a negotiated settlement.
If this proposed law were enacted by the House, even if the Senate did not concur, it would amount to a vote of no confidence in the President. It would indicate to the Iranian government that the Americans are not serious about achieving an agreement by negotiation and instead want an imposed settlement. Our experience with the present regime in Iran indicates that they would simply abandon all negotiations and continue their work toward building their own nuclear weapon.
The American public is tired of war. Our recent wars have mostly not been successful. We fought in Viet Nam to prevent that country from becoming ruled by communists. We failed. We fought a short war with Iraq over Kuwait and oil. I guess we had some limited success with that. We fought wars in Afghanistan and Iraq and did not achieve our stated objectives in either case. How can we imagine that we would be successful in Iran?
Realistically the Republican move in the House is not so much a desire to derail any hope of a peaceful settlement with Iran but rather a way of discrediting a President that most Republicans hate with passion. It's a violation of an ancient rule in American politics: Partisan politics stops at the water's edge. The Republicans are set on breaking that rule.