Port Chicago - 50 Years:
was it an atomic blast?
(EDITOR'S NOTE: In January 1990, the Napa Sentinel commenced a series of
concerning the explosion at Port Chicago in San Francisco Bay on July 17,
other articles were produced to support the theory that the explosion was
the years, the Sentinel has been challenged on one point of the articles: If
it was a
nuclear explosion what about the radiation? For several years our research
devoted itself to searching for records of other atomic explosions of the
era to determine
the levels of radiation association with those tests. This four part article
question of radiation at Port Chicago.)
DESCRIPTION OF THE BLAST
On the night of July 17, 1944, a huge explosion occurred aboard one of
merchant ships docked at the Port Chicago Magazine located on the Suisun
Bay, 11 miles
upstream from Vallejo. Clocks in the town of Port Chicago, over a mile away,
by the shock waves at 10:19 p.m. The enormity of the blast was shown by the
earthquake registered as far away as Bonner's Ferry, Nevada. The explosion's
fire ball, as
observed by pilots flying over the area, towered in the night sky to an
altitude of 8000
or 9,000 feet before being extinguished.
Observers reported a blinding flash "...that literally filled the
flame." It was followed "...by other flashes of less intensity,
and then a dull,
very odd orangish glow that seemed to hang in the sky for as long as ten or
minutes, then it all went black". Two ships, thousands of feet from
navigating the narrow Roe Island Channel, were reported by their crews as
being lifted up
from the surface of the water by the underwater shockwaves bouncing off the
Their first impressions were that they had run aground. One of these ships,
Redline tanker had the top of its superstructure completely ripped off by
the air blast.
Part of the deck was lifted. All doors were blown in. All tanks were
ruptured. All of the
ships bulkheads were blown in, one being forced completely out of the ship
opposite side. All of this was the result of air shockwaves.
The ship turned around and sank in shallow water, riddled with shrapnel.
Two 450 cargo
ships were berthed facing opposite directions on the finger pier at Port
Chicago: The Quinault
Victory, newly arrived and as yet not loaded, and the E. A.
low in the water with her cargo of munitions. The main explosion had
occurred aboard the E.
A. Bryan, which was completely vaporized. No identifiable part of it was
Different eyewitness reports from the crews of the ships in the channel
litanized the 450 foot, 7,000 ton Quinault Victory's final ordeal:
- Her bow end, from the foremost mast forward, was lifted high up into
- Pieces of docking were seen in the air with pilings attached.
- A funnel-shaped area was observed 200 feet in the air, on top of which
was the bow of
one of the ships with mast attached.
All that remained of the Quinault was sixty feet of keel with
attached, pushed 1,000 feet out into the channel.
Parts of the bodies of the Navy work battalion and their officers, as
well as those of
the ships Merchant Marine crews and Navy Armed Guards were found on
across the channel, almost a mile away, many blown there as human missiles
by the force of
the explosion. In addition there were many heavy pieces of railroad cars and
plating found on the island.
The crater on the river bottom was, at its deepest, 27 feet. At least 10
feet of this
was mud, which is more difficult to cavitate than soft rock. The crater was
700 feet long and three hundred feet wide. The explosion, which took place
below the water
line of the E.A. Bryan, occurred at an average depth of 15 feet below
With the flooding tide, the water was over 33 feet deep. Thus, the force of
the blast had
to remove an enormous amount of water before it could even get to the
bottom, and once it
did, it still removed 27 feet of soft rock and mud.
In culling over the various newspaper accounts and eyewitness reports of
Chicago explosion, no phenomena seems more ubiquitous than the white flash.
Journal description of July 21, 1944, is typical, though from the
perspective of 23
miles away: "Plainly visible here was the towering pillar of flame that
the southern sky. The hills of the Napa Valley were momentarily illuminated
sunlight." Scores of persons, convinced that an earthquake was
imminent, ran from
their homes in their night clothes. On land, to the south of the disaster,
of the Naval Base suffered damage beyond repair. All buildings in the town
Chicago, which 1was a mile to a mile and a half from the explosion, were
seriously. Ten per cent were damaged beyond repair. Fifty percent were
to being knocked off their foundations. The bridge crossing the Carquinez
rocked violently as described by passengers crossing the bridge on a bus.
All the downtown
store windows were shattered in Vallejo, 22 miles away.1 Mare Island
damage from the explosion, with some streets being littered with as much as
two inches of
The explosion which vaporized the Liberty Ship E. A. Bryan and
blew to bits all
but a small section of the keel of the other ship, the Quinault
Victory. It also
killed 320 men and destroyed the Port Chicago base, a critical munitions
supplying the Pacific War. Today, we know Port Chicago as the Concord Naval
Station, a sprawling 5500 acre Navy complex extending over the hills from
the Suisun Bay
into Clayton Valley, near Concord.
The official theory of the explosion maintains that 1.5 kilotons of war
containing TNT and Torpex, placed on the pier and in the holds of the
Liberty ship E.A.
Bryan, were accidentally detonated all at once -"highorder".
disagreement between the government damage reports on the size of the blast.
Army/Navy Safety Board Report, Technical Paper #6 reports the yield of the
explosion as 2.13 kilotons, which is in excess of the conventional
aboard the E.A. Bryan. The Naval Court of Inquiry came to the
conclusion that the
accidental detonation was caused by several factors, including:
- War-induced oversized work load and pressure on the men.
- Incompetency of the officers at the base.
- The Base Commandant's promotion of competition among loading officers.
- Gross violation of safety precautions.
Various articles reported in the Sentinel by researcher Peter
Vogel and David
Caul, have outlined the entire history of the explosion,
of the dawn of
the nuclear age, of the prototype atomic bombs that existed and of
official reports concerning atomic testing, Los Alamos and Port Chicago. We
readers to those various articles for background as well as Mr. Vogels
Scholar article, "The Las Wave From Port Chicago," and will
not repeat that
material in this series.
The first concept of an atomic bomb was that it would be necessary to
place it on a
naval vessel and send it into the port of the enemy. In 1944, no strategic
airfield was available that could be used for delivery of an atomic bomb. At
the time of
the Port Chicago explosion the United States involvement in the Pacific war
focused on maritime battles and the need for a "port buster" was
of the highest
importance. Scientists at Los Alamos had an exquisite interest in
determining the lethal
or sinking ranges of all types of surface vessels and submerged submarines
bombs detonated under water. This concern is very prominent in the first
edition of The
Effects of Nuclear Weapons, 1950. There were two striking advantages in
atomic bombs in the water as port-busters:
- A bomb which was detonated under water could be a ton lighter because
it would not
require a heavy tamper. This lightness would enable it to be carried by
- A water detonation would not subject the crew of the drop plane to
radiation and heat
because the water would act as a shield.
Accordingly, the bomb would not have to be dropped from 30,000 feet, a
which was not available in the summer of 1944. The Enola Gay, by
Thomas and Witts
documents the timetable of the development of high altitude bombing
techniques. As far
back as 1943, the High Military Policy Committee, the board of directors of
Project, had chosen the Japanese fleet concentrations in the harbor at Truk
as the first target for the atomic bomb. Declassified documents from the
District History, Project Y, from the U.S. Department of Commerce, have been
The National Technical Information Service, LAMS-2532, Vol. I, December
1961, page 8:13,
refers to the "...results of certain underwater tests (performed in
been directed toward achieving the goal of using a nuclear weapon against
fleet concentration at Truk, in Micronesia." Port Chicago would have
been a perfect
"blast gauge" for a port-buster type atomic bomb.
The height of the fireball, the Wilson condensation ring, and the damage
counties of California, all point to something more insidious than
1.5 kilotons of ammunition to go off all at once. Evidence for the theory
- declassified letters and memoranda with incriminating wording,
- scientists from the Los Alamos Laboratory arriving at the site
- the hidden facts about the test of a bomb called Mark II,
- the white flash and other circumstantial evidence. Some of the counter
the nuclear theory is:
- lack of radiation reports at Port Chicago, and
- the alleged impossibility of supply of enough fuel for even a small
bomb in July 1944.
The possibility that the explosion was nuclear but accidentally
detonated while being
transshipped through Port Chicago on one of the cargo vessels has also been
what classified memos said
By David Caul and Susan Todd
(Part Two of a Four Part Series)
Copyright, Napa Sentinel July 15, 1994
Through the Freedom of Information process, dozens of suspicious letters
the Port Chicago explosion have surfaced. A memorandum from Captain William
S. Parsons to
Major General Groves, director of the Army's activities related to the
is particularly interesting. Captain Parsons was the deputy director of Los
Laboratory in 1944 and conducted the lab's study of the Port Chicago
Parsons-Groves memorandum dated 25 September 1944 was his third preliminary
report on the
Port Chicago explosion.
The memorandum read: "I believe that it is necessary at this time
to examine the
scope of the responsibilities and duties which are imposed by a directive to
manufacture and furnish, with the prospect of successful delivery during
this war, a
weapon of entirely new characteristics.
"I divide this mission into three separate parts, which have in
common the fact
that failure or lateness of any one will surely bar the weapon from the war.
"...The fact of the war, and the fact that victory may be in sight
in 1944 in
Germany, and probably in 1945 in Japan, combine to force concurrent rapid
(the) . . .work."
Later, in the letter, Parsons addressed the proposal on the part of some
of the more
progressive scientists on the Manhattan Project to test the bomb in the
desert instead of
using it against the enemy. "This same exaggerated idea of the
possibilities of thousand-ton explosions had led to proposals in high and
quarters that if we are winning the war anyway, perhaps the best use of the
gadget is in a
staged field test in an American desert; to which could be invited such
as the United States desired to impress with our victory over the atom and
power to win victories over our future enemies.
"The kind of reasoning in the above paragraphs is also attractive
in that it
disposes of the two really difficult and disagreeable problems; (a) final
and manufacture, and (b) military delivery. To have our project culminate in
spectacularly expensive field test in the closing months of the war, or to
have it held
for such a demonstration after the war, is, in my opinion, one way to invite
and military fizzle, regardless of the scientific achievement. The principal
with such a demonstration is that it would not be held one thousand feet
Square, where the human and material destruction would be obvious, but in an
desert, where there would be no humans and only sample structures. From my
Port Chicago, I can give assurance that the reaction of observers to a
desert shot would
be one of intense disappointment. Even the crater would be
Why would Port Chicago be linked with a report on an atomic test?
concerned that the war might end without the use of the bomb. His first
priority was to
enter the bomb into the war, before it was too late. In this letter he
suggestion that the use of the bomb must be governed and justified by moral
considerations. It becomes obvious that Parsons wants the bomb to
demonstrate both the
material and the human casualty factors.
The human factor Port Chicago was carefully recorded by the damage
reports to Los
Alamos and to the National Defense Research Committee, which oversaw the
Project. Port Chicago would have been an ideal area by which to gauge the
A topographical map of the area in 1944 shows the ideal setup. Even the
were correct to blow the radioactive debris out over the channel and Honker
deserted marshlands. The nearest downwind populated areas was the tiny town
20 miles away, surrounded by farmland.
There is yet another letter in the paper trail leading back to a
explosion at Port Chicago. This letter was first made public in the Napa
in February 1994. James Conant, who was a member of the board of directors
Manhattan Project referred to a full-scale test of the weapon in a letter to
Groves. In the letter he indicated that the secret test occurred shortly
1944. The Port Chicago explosion took place on July 17, 1944. The explosion
to was a year before the Trinity test, which has officially been documented
as the first
The interesting part of Conant's report is that the results of the first
shortly before August 1944 exactly match the damage report Captain Parsons
wrote on Port
Chicago. The letter states that dwelling houses were damaged in the test.
The letter is
dated August 17, 1944, one month after the Port Chicago explosion. It is one
of the most
heavily sanitized, declassified documents on the subject. It is entitled
Visit to Los Alamos." In the name of national security, 50 years later,
left only a few sentences intact: "It is agreed that the Mark II should
be put on the
shelf for the present. If all other implosion methods fail, it could be
taken off the
shelf and developed for combat use in three to four months time."
letter continues: "It was agreed that for dwelling houses the area of
Class B damage
was about as follows for 1000 tons of TNT:
- 90 percent Class B damage = 0.5 miles radius .75 square mile area.
- 10 percent Class B damage 1.5 miles 7.5 square mile.
The emphasis is on the word was. He states the damage
This fits the description of the damage at Port Chicago. According to
letter, the Mark II was a working bomb as of July 1944 and it could have
been readied for
combat delivery in a few months.
Just where the atomic test Conant referred to was held is not stated in
The first page of the letter was censored out. Obviously Conant and Groves
had known all
along that the test had been held. But what was their motive for keeping it
Mark II is rarely talked about in the literature about nuclear weapons.
damage to Port Chicago cited by Captain Parson corresponds exactly to that
the Mark II by Conant:
90 percent Class B damage = 0.5 miles radius .75 square mile area. 10
percent Class B
damage 1.5 miles 7.5 square mile.
Research and Sentinel articles reveal that Los Alamos scientists
were on the scene at Port Chicago the morning after the explosion. These
early arrivals of
key Los Alamos and Manhattan Project officials to Port Chicago create some
Captain Parsons visited the site of the Port Chicago explosion twice. One of
purposes of his second visit was to interview air crews flying in the
vicinity of the base
at the time of the explosion. He was specifically concerned to determine the
height of the
The documentation has been extensive in previous Sentinel
articles. Now that
the foundation has been laid, the next two parts will explain the radiation
comparison to other nuclear tests of the era.
how it compares with other tests
By David Caul and Susan Todd
Copyright, Napa Sentinel, 1994
Third of a Four Part Series
Throughout the years, there have been several critics of the Port
explosion theory. Among the most noted were the late Russ Coughlan, general
manager of KGO
TV and his producer Bob Anderson. In their documentary entitled "The
Mystery of Port
Chicago", they discounted the nuclear theory based on what they believe
absence of flash burns among victims, temporary blindness and radiation
sickness, such as
reported from Hiroshima and Nagasaki.
Nuclear explosions produce temperatures on the order of millions of
centigrade, whereas conventional explosions generate heat on the order of
degrees. In addition, at the time of a nuclear detonation, intense
emanates from the fireball.
This article will present an explanation of how a nuclear explosion at
could have features which would prevent flash blindness and flash burns, and
how it was that the effects of the radiation exposure on the personnel at
would not have been as obvious as KGO indicated.
Given the many variables which surround nuclear explosions, such as
placement, potential yield, type of device, and topography, it is not always
judge in advance what will happen. Therefore, nuclear explosions can be very
and do not always duplicate each other.
The lack of flash burns and flash blindness or "eclipse
blindness" at Port
Chicago is consistent with the explosion being nuclear. All of the damage
reports cite the
center of gravity of the explosion as being 15 feet below the water line of
Bryan, and, therefore the explosion would have thrown up a large plume
of water. This
phenomenon, together with the fact that the bomb detonated within one of the
holds of the
7500 ton cargo ship, would have sharply attenuated or eliminated the thermal
emanating from the fireball within the first few seconds of the explosion.
This would have
happened in two ways:
- the steel of the ship and the water would have both absorbed the heat,
it, acting as a heat sink; and
- the ship and the water would have shielded the thermal radiation from
populated areas. Even clouds, smoke or fog can substantially decrease
radiation from a nuclear flash.
By the time the fire ball had vaporized the ship and risen above the
surface of the
water, and out of the plume, the spray and debris, the fireball would have
cooled to the
point that flash burns and blindness would not have occurred.
It is interesting to note that even at Hiroshima, where there was
nothing to block the
thermal radiation, the blink reflex and the recessed position of the eyes
prevent flash blindness, and the effect of thermal radiation on the eyes was
small. The so-called "eclipse blindness" associated with viewing a
explosion results when the intensity of the light uses up all of the eye's
visual purple in the retina; blindness then persists for a half an hour or
enough of the substance is produced in the eye to allow vision again. The
lack of flash
burns and flash blindness at Port Chicago is fairly easily explained by the
effect of the water and the ship. Even at Bikini, the underwater explosion
without eye protection for the men.
Anderson and Coughlan cite in their KGO documentary that the wreckage
conspicuously uncharred and unburned. This, they state, is yet another sign
explosion was non-nuclear. However, the Los Alamos damage report states that
thrown out by the blast were melted by heat. The Napa News Chronicle
"great hunks of hot metal" lying all around the vicinity after the
Similar reports are to be found inthe book No Share of Glory by
Robert Pearson. Tom
Shaw, a Napan who watched the complete progression of the explosion from an
mile away in the town of Port Chicago, told the Sentinel that he
red and white hot pieces of the ship's plating tumbling end over end
streaking toward him.
These reached him before the blast wave, and so were traveling in excess of
the speed of
sound. He was able to take it all in before he was knocked to the floor by
Anderson's and Coughlan's strongest argument against a nuclear thesis
rests on a test
they performed on pieces of shrapnel they found near the blast site.
the pieces of shrapnel from the blast to radiation tests." Coughlan and
concluded that the tests showed that the pieces could not have been in an
explosion. However, just finding any pieces of metal near the explosion 44
does not mean that they came from the ship in which the bomb had detonated.
could have come from the ship which did not contain the bomb, or from one of
or machinery on the pier. In that case, the test becomes less meaningful. In
metal to pick up radioactivity, it must have close proximity to the bomb.
of radioactivity diminishes with distance. Coughlan and Anderson have no way
determining where the pieces came from. Second, they don't say what test
they performed on
the pieces. If they simply tested for radioactivity, then it is not
surprising that the
pieces showed none. The British Government detonated a 24 kiloton plutonium
bomb at Monte
Bello, Australia in October of 1952. The bomb was placed on a Frigate in
shallow water and
detonated. None of the isolated steel fragments of metal that had been
thrown out from the
Frigate on to the surrounding islands showed any sign of radioactivity
ten years. At Port Chicago, Coughlan and Anderson found no signs of
radioactivity in the
metal after 44 years, yet they concluded the explosion could not have been
shielding and absorption effect by the ship and the plume would also have
diminished the nuclear radiation (i.e., gamma, neutron and x-ray), as well
as the thermal
radiation. This still leaves open the possibility of residual radiation
being left in the
area, and we will cover that aspect shortly.
In August 1990, the Sentinel contacted Ernest Sternglass,
Radiology at the University of Pittsburgh specializing in Radiation Physics.
well-known for his work on nuclear fallout from bomb tests and nuclear power
its effects on the population, especially children. Dr. Sternglass original
1990 to the Port Chicago nuclear thesis was negative. He made a comparison
Chicago and the Bikini under-water test in 1946. He said that what happened
would have happened at Port Chicago, since in both cases the bomb would have
water. The radiation problem at the Bikini test was much worse than the
Trinity test, or
at Hiroshima or Nagasaki, were the bomb was detonated above the surface. At
immediately after the explosion, the radiation levels were very high in the
lagoon and on
the target vessels. There were reports of lingering radiation which was
difficult to clean
from the target ships. Eventually, elevated cancer rates were discovered
among the Bikini
veterans. (Editor's Note: Dr. Sternglass now feels that it is quite possible
Chicago could have been a nuclear explosion.)
Taking our cue from Dr. Sternglass, we can ask the following critical
question of the
Port Chicago nuclear thesis: If a nuclear device had exploded at Port
Chicago, and Port
Chicago would have been like Bikini, how could the rescue crews, operating
both in the
water and on land have been able to withstand the radiation that would have
area, especially so soon after the detonation?
Army units from Camp Stoneman, eight miles to the east, began arriving
at 2 a.m. (the
blast was at 10:19 p.m.). Port Chicago was never abandoned, although the
began to use the Army facilities at a Richmond dock as a temporary
It would seem from these facts that the Port Chicago explosion was
non-nuclear. But a
closer examination of the Bikini underwater explosion will show that the
harm to the men
at Bikini were not initially very obvious. The radiation effects were much
BIKINI EXPERIENCE AND COMPARISON
Nuclear explosions present radiation hazards to the public in two
- initial radiation's, which take the form of gamma, x-rays and neutrons
coming out of the
fireball during the first three seconds of the event; and
- delayed fallout, where radioactivity fission products and debris from
the mushroom cloud
descend to the earth.
The first type is over in three seconds, the second type lingers on.
Both can be
intense. Bombs which explode in the air such that the fireball doesn't touch
produce high initial radiation from the vicinity of the explosion, surface
zero, but the
delayed radiation for that area is negligible. Hiroshima and Nagasaki
no fallout from the bombs.11 The delayed fallout descends to the earth later
or miles away
downwind. Bombs which explode in the water tend to produce no initial
but can leave high levels of delayed fallout in the vicinity of the
explosion. This is
what happened at Bikini. The radiation left in the Bikini lagoon from the
was much greater than that which was left on the ground at the Trinity test
site in New
Mexico, Hiroshima, or Nagasaki, or the Bikini-Able aerial test.12 But the
water in which
the Bikini bomb was placed acted as a shield against the initial
In an air burst, as the fire ball cools, the radioactive residues of the
condense into extremely small particles which remain suspended in the
atmosphere for a
long time. ". . . in a low burst, the earth, dust and other debris from
surface are taken up into the fireball, and an increasing proposition of
other radioactivity) products of the nuclear explosion condense into
appreciable size.14 These large particles tend to fall out immediately,
contamination in the area of detonation. Additionally, proximity to water is
conducive to the deposition of large amounts of radiation near surface zero
coolness of the water prevents the fireball from rising to as great a height
as in the
case of an aerial detonation. Radioactive material then tends to fall back
more quickly to
the base of the explosion rather than to be blown away from the area,
falling out over a
period of time downwind. It is the delayed fallout that would have been a
problem at Port
Chicago, just as it was at Bikini, not the initial radiation from the
Some of the "victims" of the Bikini test, the target vessels
arrayed around the surface zero at various distances were drenched in
substances; there was intense radiation left in the waters of the lagoon.
After four days,
the authorities at Bikini conceded that the inspection parties were to spend
time aboard the doomed vessels because of the radiation. However, the
authorities told the
press and the men that this precaution was in accordance with a safety
factor of 1000.
They told the press and the men that they could take a thousand times that
and not be killed. They told them that this was a "peacetime"
standard, and that
during wartime the standard would be much less.
The planners of the Bikini test had been taken by surprise by the
The long-term radiological results of the test had been " . . . either
unforeseen, or had been placed in such conjectural terms that its relevance,
strategic considerations, was not understood". The Navy admitted that
". . .the
nature and extent of contamination of the targets was completely unexpected,
and no plans
had been organized for decontamination measures". Two or three days
explosion the Navy began to realize this. The Navy had known that there
would have been
high initial radiation in the area, but they hadn't counted on the delayed
contaminating the area in the vicinity of the lagoon.
Knowledge of the effects of radiation was scant. "No one yet
greatest danger of atomic warfare, lingering radioactivity..." At first
resorted to old-fashioned methods, crews of men were set to scrubbing down
contaminated ships without any special protection, using "lye, foamite,
and soap spread with liberal amounts of Navy profanity. Men were ordered to
night on some of the "hot" target ships. Radioactive material was
all over the
decks, and the men tracked it around and got it on their clothing, hands and
of the officers thought that the risks could be ignored. It is true
that there were no reports of radiation sickness at Port Chicago, however,
there were no
official reports of radiation sickness at Bikini either, and this was an
test. The Bikini tests had showcase-extravaganza status, and monopolized the
the world's media for weeks. Port Chicago was unannounced.
Only some of the later written accounts of the Bikini test describe
as suffering illness from radiation. These reports took years to reach the
first book about Bikini, one which focuses on the radiation problem, asserts
there was no radiation sickness or injury there either.
The Veterans Administration was able for years to deny any connection
among Navy personnel and Bikini exposure. As of 1981, the VA had turned down
percent of all radiation-based claims for atomic veterans", including
the Bikini vets arguing that it was impossible to determine whether
the maladies in
question would have occurred regardless of radiation exposure. And this was
so even though
everyone knew that the men had participated in an atomic bomb test.
From the beginning, the cat was out of the bag at Bikini. But, how easy
would it have
been to correctly diagnose the radiation sickness and other more subtle
with this knowledge? If the men had been told, for example, that the
explosion at Bikini
was from conventional munitions on a ship, they would have looked for other
their maladies. And even though they knew they were exposed to the effects
of an atomic
bomb, it took years for the first claims to be put in.
Port Chicago: Epilog -
By David Caul and Susan Todd
Copyright, Napa Sentinel, 1994
In the second article of this series we quoted declassified letters
Peter Vogel. The letters were written by one of the top people in the
and referred to a secret detonation of a low-yield atomic bomb in July 1944,
the Mark II. The letters were dated shortly after the Port Chicago
explosion. Neither the
government nor any publication, except the Napa Sentinel, has officially
either the detonation, or the letters which describe it, and there is strong
the detonation referred to in the letters was actually Port Chicago.
The design of the Mark II is an anomaly in the history of U.S. nuclear
development. It was a crude, first attempt at making an atomic bomb which
operated on the
principle of implosion. Understanding how that crude Mark II bomb worked
will help us to
see an important difference between the Port Chicago radiation situation and
The bomb consisted of a sub-critical hollow tube of uranium contained in
cylinder of molded explosive material. When the cylindrical explosives were
hollow tube of uranium was crushed into a critical mass, and fission took
According to Peter Vogel, the uranium in the hollow cylinder was
enriched to less than
30 percent U-235, the rest being U-238. The Hiroshima bomb, which detonated
was enriched up to 80 percent. The Mark II's low fuel enrichment made it
from the uranium bomb which was dropped on Japan. However, there was another
difference: It used a moderator, like a nuclear reactor, and this is the
secret of how it
was able to operate on such poorly enriched uranium.
What fissions in an atom bomb or a nuclear reactor is uranium U-235.
contains only .7 percent of this isotope, the rest being U-238, which cannot
except under very special circumstances. A process of "enrichment"
is used to
increase the percentage of U-235, and it is very slow and costly; this was
Nuclear reactors are enriched up to 3 percent, but uranium bombs
generally contain up
to 80 percent. Reactors can run on such lean enrichment diets because their
is placed in a moderator, such as hydrogen, paraffin or graphite.
There are two advantages in slowing down the neutrons. First, slow
neutrons have the
highest probability of producing fission of the U-235 fuel. Second, uranium
which is not
highly enriched, containing larger amounts of U-238, absorbs or
many of the neutrons needed for fission. This capturing process hinders the
process. It takes neutrons out of circulation. When a neutron enters a U-238
U-238 is changed into plutonium through a series of transmutations.
However, U-238 can only capture neutrons traveling at the intermediate
slowing down the flow of neutrons through the use of a moderator, the
neutrons can still
produce fission because they are free from capture by the U-238.
U-238 is a contaminate which poisons the atomic reaction by preventing
way to deal with the problem is called "enrichment", removing the
U-238 from the
fuel leaving U-235. The fuel of the Hiroshima bomb, Little Boy, under this
slow and costly
process. Another way is to remove as much U-238 as is practical, and use
slow neutrons so
that the U-238 which remains is no longer a poison to the reaction. This is
what the Mark
II design did.
The moderator was created in the Mark II by compacting the uranium fuel
and forming it
into a plastic hydride. The hydrogen in the plastic slowed down the flow of
Layers of hydrogen containing paraffin were also used. This unique design
was a response
to a problem of the times: scarcity of higher enriched uranium. Much
enriched uranium was
needed to run the reactors which were breeding the plutonium at Hanford,
would fuel later bombs.
Because the Mark II design included a moderator and used fuel which was
less than 30 percent, it was somewhere in between a nuclear reactor and a
nuclear bomb. By
making as much of the fuel as possible go critical in a very short period of
time, it was
like a bomb. By using a moderator at the same time, it was like a reactor.
developments in enrichment made the Mark II obsolete. However, at the time,
the Mark II
provided a detour around the enrichment problem.
This ingenious device, however, was not at all efficient. The simple
explosives in the shape of a pipe was imperfect in squeezing the fuel into a
mass. Sections of the precious fuel squirted out the ends, escaped fission
wasted. The squeezing wasn't fast enough. Also, though slowing the neutrons
parasitic capture by the U-238, the fuel took too long to fission. Slowing
fission process is desirable in a nuclear reactor, speeding up the process
is desirable in
a bomb. Inspite of this, for the mark II the fuel tended to blow part before
most of it
could undergo fission. The neutrons took "...so long to act that only a
explosion would result." In a non-moderated bomb, all of the neutrons
within less than a millionth of a second. Anything less than a kiloton was
"feeble" by the bomb designers whose expectations ranged in the
In later bombs, such as Fat Man, a spherical configuration replaced the
bomb" design and the "perfect squeeze" of the fuel was
accomplished. Before that, however, the inefficient Mark II was the United
nuclear option. It was reliable, but its yield was less than a kiloton. The
putting on the shelf of the Mark II enabled Los Alamos to hedge their bets
on the untested
Little Boy, and the drawing board stage Fat Man.
After the Port Chicago explosion, James B. Conant, a critical figure in
development of a nuclear bomb, wrote a memorandum suggesting putting the
Mark II on the
shelf after a July 1944 test, a test never recorded in any public annals,
the date of the Port Chicago explosion. Conant wanted to commence work on
the Mark III.
The Mark II contained about five kilograms of fuel, and it used that
inefficiently. Much of the uranium did not undergo fission, and was squeezed
or blown out
of the critical mass and melted, avoiding fission. Even when a bomb is
"efficient", only one percent of the fuel actually fissions.
The workers, rescue personnel and survey teams at Port Chicago during
immediately following the explosion would have been exposed to a devil's
other chemical poisons from vaporizing ships which would have been as
unfissioned uranium. Since the Mark II's neutrons were moderated to below
there would have been very little transmutation of its U-238 into plutonium,
serious radiological hazard, especially if inhaled. Its design goes out of
specifically to prevent the production of plutonium. With only 30 percent
its fuel, it could not work any other way.
Large amounts of the dangerous plutonium were left at the Bikini site,
for a good share of the risk there. The danger from plutonium lies in the
tendency of the
element to concentrate in the bone where the continuous emission of alpha
cause significant injury. The Bikini bomb fuel consisted entirely of
plutonium. Fear of
plutonium contamination of the Bikini lagoon was strenuously advanced by Los
Alamos as a
reason to cancel the Baker test. Because of the way the Mark II worked, this
happen at Port Chicago.
Bikini was not the only underwater bomb test site where plutonium was
contribute to the radiation risk. On October 3, 1952, the British Government
tested a 25
kiloton plutonium bomb on the Monte Bello Islands, off the western coast of
bomb was placed in a forward hold of the frigate HMS Plym and detonated
style". Plutonium was found scattered over the area, and it was cited
as a serious
inhalation hazard in a report of the Royal Commission.
Approximately 70 percent of Mark II's fuel was U-238 which could not
If this unfissioned uranium had contaminated the area in the vicinity of the
would not have been a serious radiological hazard, but a chemical poison
which attacks the
kidneys. And more importantly, its radioactivity would not have been
apparent in the
summer of 1944. In 1943, the Nazis ordered the use of its entire uranium
metric tons, to substitute in its ammunition because of a shortage of
battlefields of Europe became littered with hundreds of tons of uranium
and bullets, a much larger quantity of uranium than the 10 pounds which
filtered down over the marshes and waterways adjacent to Port Chicago as a
result of the
explosion of the Mark II. Yet, Europe has never reported any problems
associated with the
expenditure of uranium by the Germans.
The Port Chicago explosion was very different from the Bikini test in
important respects. First, it occurred in shallow water. Both editions
The Effects of
Nuclear Weapons states that a shallow water nuclear detonation may not,
conditions, severely contaminate the area immediately in the vicinity of
surface zero. The
Effects of Nuclear Weapons states that a certain minimum depth is
necessary to produce
significant radiation in the vicinity of the point of detonation. A similar
held by Vannevar Bush, chairman of the Board of the Manhattan Project. The
Bikini bomb was
placed at 90 feet, the Port Chicago explosion occurred at 15 feet. In
addition to this,
military people did not regard it as a foregone conclusion that a shallow
detonation would contaminate a harbor area to the extent that troop
maneuvers would have
to be suspended.
In an article in the American Meteorological Society, as well as in The
Nuclear Weapons, the extreme humidity of the Bikini area is cited as a
to the contamination of the site of the explosion. Accordingly, high
humidity is a
necessary condition for severe contamination at the vicinity of surface zero
in the case
of an under water detonation. It is possible that all phenomena, exactly as
the Bikini test, would not occur if an atomic bomb were exploded under water
when a dry
air mass is present.
The main mechanism by which radiation from a nuclear explosion in water
is returned to
the place of detonation is something called the "base surge". The
base surge is
a highly radioactive mist which forms at the base of the water column, and
outwardly in a ring at a very high speeds. This mist contains lethal
radiation and tends
to deposit a relatively long-lived radioactive sludge on the surfaces of
objects in its
The manner of formation of the base surge is very important to the
issue. When the
fireball leaves the water, water is driven upward, following the fireball,
as the water
comes in to fill the void created by the million degree bubble. The speed of
vertically driven water is over a mile a second at first. It slows rapidly,
attain a height of 10,000 feet in less than a minute. At 10,000 feet the
water and all the
bomb residues, including the fission products, the mass of the ship, and
whatever has been
scavenged from the bottom, are vaporized.
In a short time the mixture cools and condenses back into liquid form.
Within 10 to 12
seconds the column begins to fall back into the water, much of it in the
form of an
aerosol. This aerosol or fog is highly radioactive as a result of the
form the nuclei of the droplets, are themselves radioactive. The intimate
takes place between the water and the radioactive solids is accomplished by
currents of the mushroom cloud at an altitude between 6000 to 10,000 feet.
aerosol slides down the sides of the column under the influence of gravity
at a very rapid
rate as a result of a phenomenon called "bulk subsidence". In bulk
the aerosol behaves like a homogeneous fluid. When it reaches the water, it
forms waves and is laterally transported away from the column, in all
spreading its poison along the surface of the water.
The phenomenon of bulk subsidence was not completely understood at the
time of the
Bikini test, and at first scientists thought that the column consisted only
Photographic evidence later showed that the column was largely an aerosol.
Due to the
research of P.A. Leighton of Stanford, it became known that these aerosol
suspension, fall under the influence of gravity at rates up to 10,000 times
such aerosol particles normally fall. This is the aerological mechanism
which delivers the
material almost immediately back to the base of the column and which created
radiological havoc at Bikini. The rate of fall of the aerosol is what is
possibility has been raised that if the air were dryer at the altitudes at
fission products and the water condense back into liquid and solid form
again, about 6000
feet, the base surge would not be formed. The water droplets would simply
the air, and there would exist no aerosol to be accelerated downward in
Leighton's bulk subsidence. What would exist then would be the slower
typical of an air burst distributing radioactivity over a large, downwind
Over Port Chicago the night of the explosion at 6000 to 8000 feet, the
humidity was less than 15 percent. This record was from Oakland, the nearest
station. The reading was taken about 2-1/2 hours before the explosion. This
was a very low
relative humidity. The Bikini test aerological data from several Navy and
observation ships were requested months ago by the Sentinel from the
Oceanographic and Atmospheric Administration. The Sentinel has been
these documents have been removed from their files and are unavailable.
Administration did send sample pilot balloon humidity data for other years
Island which they claim are typical for July, and these show high humidity
at 6000 feet,
approximately 75 percent.
If the base surge did not occur at Port Chicago as a result of the
shallowness of the
water and the dryness of the atmosphere, then this would have prevented much
delivery of the radiological "witches brew" back to the vicinity
detonation, including the long-lived and dangerous fission products of the
Documented evidence from the Manhattan Project and Los Alamos, four
investigation, the development and test of the Mark II in July 1944, the low
yield of the
Mark II, and the bomb placement in respect to the water level and weather
would conclude the explosion at Port Chicago was nuclear and could have been
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