Uranium hydride bomb
Encyclopedia
The uranium hydride bomb was a variant design of the atomic bomb, that was first suggested by Robert Oppenheimer
in 1939 and advocated and tested by Edward Teller
. It used deuterium
, an isotope of hydrogen
, as a neutron moderator
in a U235-deuterium compound. The chain reaction
is a slow nuclear fission
(see neutron temperature
). Bomb efficiency is very adversely affected by the cooling of neutrons since it delays the reaction.
Two uranium hydride bombs are known to have been tested, the Ruth and Ray test explosions in Operation Upshot-Knothole
. The tests produced a yield comparable to 200 tons of TNT each; both tests were considered to be fizzles
. All other nuclear weapons programs have relied on fast neutrons in their weapons designs.
(UH3) or plutonium hydride
moderates (slows) the neutrons, thereby increasing the nuclear cross section
for neutron absorption. The result would be a lower required critical mass
, thereby reducing the amount of pure U235 or plutonium
needed for an explosion. The result was that the slower neutrons delayed the reaction time too much, and reduced the efficiency of the weapon. It increased the time between subsequent neutron generation events necessary for rapid explosion. It creates a problem in the containment of the explosion; the inertia
that is used to confine implosion type bombs will not be able to confine the reaction. The end result may be a fizzle instead of a bang. The predicted energy yield would be 1000 tons TNT equivalent.
, in 1943, uranium hydride was investigated as a promising bomb material; it was abandoned by early 1944 as it turned out such design would be inefficient. After World War II
, Los Alamos physicists were skeptical of uranium hydride in weapons. Edward Teller
remained interested, however, and he and Ernest Lawrence
experimented with the devices in the early 1950s at UCRL (later Lawrence Livermore National Laboratory
).
Two test devices were exploded in 1953 as part Operation Upshot-Knothole. The aim of the University of California Radiation Laboratory design was to produce an explosion powerful enough to ignite a thermonuclear weapon, with the minimal amount of fissile material. The core
consisted of uranium hydride, with hydrogen, or in the case of Ray, deuterium acting as the neutron moderator. The predicted yield
was 1.5 to 3 ktTNT for Ruth and 0.5–1 ktTNT for Ray. The bombs failed to have the predicted explosive power in practice.
Ruth, which used ordinary hydrogen-1, was the first device entirely designed at Livermore; it was fired on March 31, 1953 at 05:00 local time (13:00 GMT) at Mercury, Nevada
. The explosive device, Hydride I, weighed 7400 lb (3,356.6 kg) and was 56 inches (142.2 cm) in diameter and 66 inches (167.6 cm) long. The predicted yield was 1.5 to 3.0 kilotons, but the actual yield was only 200 tons. Wally Decker, a young Laboratory engineer, characterized the sound the shot made as "pop." The lower 200 ft (61 m) of the 300 feet (91.4 m) testing tower remained intact, although the upper third was destroyed.
A second device, Ray, used deuterium. It was fired on a 100 feet (30.5 m) tower on April 11, 1953. Although Ray managed to level the tower, the yield was similarly disappointing: again 200 tons, as opposed to the predicted 0.5–1 ktTNT.
Robert Oppenheimer
Julius Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. Along with Enrico Fermi, he is often called the "father of the atomic bomb" for his role in the Manhattan Project, the World War II project that developed the first...
in 1939 and advocated and tested by Edward Teller
Edward Teller
Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...
. It used deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
, an isotope of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
in a U235-deuterium compound. The chain reaction
Chain reaction
A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events....
is a slow nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
(see neutron temperature
Neutron temperature
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature. The neutron energy distribution is...
). Bomb efficiency is very adversely affected by the cooling of neutrons since it delays the reaction.
Two uranium hydride bombs are known to have been tested, the Ruth and Ray test explosions in Operation Upshot-Knothole
Operation Upshot-Knothole
Operation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site.Over twenty-one thousand soldiers took part in the ground exercise Desert Rock V in conjunction with the Grable shot...
. The tests produced a yield comparable to 200 tons of TNT each; both tests were considered to be fizzles
Fizzle (nuclear test)
In nuclear weapons, a fizzle occurs when the testing of a nuclear bomb fails to meet its expected yield. The reason for the failure can be linked to improper bomb design, poor construction, or lack of expertise. All countries that have had a nuclear weapons testing program have experienced fizzles...
. All other nuclear weapons programs have relied on fast neutrons in their weapons designs.
Theory
The hydrogen in uranium hydrideUranium hydride
Uranium hydride, also called uranium trihydride is an inorganic compound, a hydride of uranium.-Properties:Uranium hydride is a highly toxic, brownish gray to brownish black pyrophoric powder or brittle solid. Its specific gravity at 20 °C is 10.95, much lower than that of uranium...
(UH3) or plutonium hydride
Plutonium hydride
Plutonium hydride is the chemical compound with the formula PuH2. It is one of two characterised hydrides of plutonium, the other is PuH3. PuH2 is non-stoichiometric with a composition range of PuH2 – PuH2.7. Additionally metastable stoichiometries with an excess of hydrogen can be formed. PuH2...
moderates (slows) the neutrons, thereby increasing the nuclear cross section
Nuclear cross section
The nuclear cross section of a nucleus is used to characterize the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction...
for neutron absorption. The result would be a lower required critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
, thereby reducing the amount of pure U235 or plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
needed for an explosion. The result was that the slower neutrons delayed the reaction time too much, and reduced the efficiency of the weapon. It increased the time between subsequent neutron generation events necessary for rapid explosion. It creates a problem in the containment of the explosion; the inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
that is used to confine implosion type bombs will not be able to confine the reaction. The end result may be a fizzle instead of a bang. The predicted energy yield would be 1000 tons TNT equivalent.
1953 tests
During early phases of Manhattan ProjectManhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...
, in 1943, uranium hydride was investigated as a promising bomb material; it was abandoned by early 1944 as it turned out such design would be inefficient. After World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, Los Alamos physicists were skeptical of uranium hydride in weapons. Edward Teller
Edward Teller
Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...
remained interested, however, and he and Ernest Lawrence
Ernest Lawrence
Ernest Orlando Lawrence was an American physicist and Nobel Laureate, known for his invention, utilization, and improvement of the cyclotron atom-smasher beginning in 1929, based on his studies of the works of Rolf Widerøe, and his later work in uranium-isotope separation for the Manhattan Project...
experimented with the devices in the early 1950s at UCRL (later Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory
The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...
).
Two test devices were exploded in 1953 as part Operation Upshot-Knothole. The aim of the University of California Radiation Laboratory design was to produce an explosion powerful enough to ignite a thermonuclear weapon, with the minimal amount of fissile material. The core
Nuclear reactor core
A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place.- Description :...
consisted of uranium hydride, with hydrogen, or in the case of Ray, deuterium acting as the neutron moderator. The predicted yield
Nuclear weapon yield
The explosive yield of a nuclear weapon is the amount of energy discharged when a nuclear weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene , either in kilotons or megatons , but sometimes also in terajoules...
was 1.5 to 3 ktTNT for Ruth and 0.5–1 ktTNT for Ray. The bombs failed to have the predicted explosive power in practice.
Ruth, which used ordinary hydrogen-1, was the first device entirely designed at Livermore; it was fired on March 31, 1953 at 05:00 local time (13:00 GMT) at Mercury, Nevada
Mercury, Nevada
Mercury, Nevada is a town in Nye County, Nevada, United States, 5 miles north of U.S. Route 95 at a point 65 miles further northwest of Las Vegas. It is situated within the Nevada Test Site and was constructed by the Atomic Energy Commission to house and service the staff of the test site. The...
. The explosive device, Hydride I, weighed 7400 lb (3,356.6 kg) and was 56 inches (142.2 cm) in diameter and 66 inches (167.6 cm) long. The predicted yield was 1.5 to 3.0 kilotons, but the actual yield was only 200 tons. Wally Decker, a young Laboratory engineer, characterized the sound the shot made as "pop." The lower 200 ft (61 m) of the 300 feet (91.4 m) testing tower remained intact, although the upper third was destroyed.
A second device, Ray, used deuterium. It was fired on a 100 feet (30.5 m) tower on April 11, 1953. Although Ray managed to level the tower, the yield was similarly disappointing: again 200 tons, as opposed to the predicted 0.5–1 ktTNT.