The Mark IV Bomb
Crash of the B-29 on Travis AFB, CA
August 5, 1950
The B-29 was loaded with a
fourth-generation O Mark IV atomic bomb, an implosion bomb similar to
the one dropped during World War II on Nagasaki.
Similar to "Fat Man"
dropped on Nagasaki which was a Mark III. Yield 1 to 31 kilotons.
(Bomb dropped on Hiroshima had a yield of 15 kilotons)
The Mark IV
atomic bomb (also referred to as Mark 4, Mark-IV, Mk 4 and Mk-4) weighed
10,800 pounds had a yield
of from 1-31 kilotons and
was in service from March 1949 until May 1953.
The Mark IV, was
manually "safed" by removal of a capsule containing the
fissionable material through a trap door in the sphere reachable from
the nose of the case.
was accomplished with the N-1 dolly originally procured from Boeing
Aircraft Company beginning in late 1947. The N-1 was a low bed roadable
dolly without a lifting mechanism. The B-29 was literally lifted up
(tilted), the Mark IV rolled in place and the B-29 lowered as the bomb
was guided into the bomb bay.
When the Travis
B-29 crashed, the capsule containing the fissionable material was not in
place. In fact, it wasn't even on the same plane.
It was standard
operating procedure at the time that when transporting "special
weapons" not to transport the fissionable capsule and the main
sphere containing the high explosives trigger together.
bomb did have depleted uranium in it, used as ballast. The high density
of depleted uranium meant very small amounts (in volume) could be used
while not taking up very much space, thus keeping the overall size of
the bomb to a minimum.
More on Depleted
is what is left over when most of the highly radioactive types
(isotopes) of uranium are removed for use as nuclear fuel or nuclear
weapons. The depleted uranium used in armor-piercing munitions and in
enhanced armor protection for some Abrams tanks is also used in civilian
industry, primarily for stabilizers in airplanes and boats.
Depleted uranium is a heavy metal that is also slightly radioactive. Heavy metals (uranium, lead, tungsten, etc.) have chemical toxicity properties that, in high doses, can cause adverse health effects.
Depleted uranium that remains outside the body
can not harm you.
A common misconception is that radiation is depleted uranium's
primary hazard. This is not the case under most exposure scenarios.
Depleted uranium is approximately 40 percent less radioactive than
natural uranium. Depleted uranium emits alpha and beta particles, and
gamma rays. Alpha particles, the primary radiation type produced by
depleted uranium, are blocked by skin, while beta particles are blocked
by the boots, most clothing, etc. While
gamma rays are a form of highly-penetrating energy , the amount of gamma
radiation emitted by depleted uranium is very low. Thus, depleted
uranium does not significantly add to the background radiation that we
encounter every day.
When fired, or after "cooking off" in fires or explosions,
the exposed depleted uranium poses an extremely low radiological threat
as long as it remains outside the body. Taken into the body via metal
fragments or dust-like particles, depleted uranium may pose a long-term
health hazard to personnel if the amount is large. However, the amount
which remains in the body depends on a number of factors, including the
amount inhaled or ingested, the particle size and the ability of the
particles to dissolve in body fluids.
Check out the ATSDR-PHA
Report to find out more about the survey conducted
of the crash site to determine any health hazards.