Lecture 13

Underground Test Procedure

  1. Underground tests required careful preparation and monitoring. Hole depth and diameter are dictated by anticipated yield.
    1. Depth range:     600 – 2200 feet
    2. Diameter range:  48 – 120 inches.
  2. Containment of radioactivity in the hole is required; a geological survey is necessary prior to the test.    The hole is stemmed after the device is positioned.
  3. An underground cavity forms after the explosion. The cavity drops, forming a chimney. If the strength of the chimney is exceeded by the weight of overburden, the chimney collapses, forming a crater.

The Baker Test 


Baker Test Explosion.  Image courtesy of US Govt. Defense Threat Reduction Agency.
Click to enlarge.

  1. These were the first "weapons effects" tests ever conducted - tests designed specifically to study how nuclear explosions affect other things - rather than tests of the behavior of a weapon design (as was Trinity). The purpose of the tests was to examine the effects of nuclear explosions on naval vessels, planes, and animals.
  2. The closest ship to surface zero was the USS Saratoga. Eight ships were sunk or capsized, eight more were severely damaged. Sunk vessels were the USS Saratoga, USS Arkansas, the Nagato, LSM-60, the submarines USS Apogon and USS Pilotfish, the concrete dry dock ARDC-13, and the barge YO-160.
  3. Damage to the Atoll - The population had been removed, and numerous tests followed until the early sixties.  Now, the entire island is contaminated with radioactivity and the population is still not allowed to return:  In 2001, the US government granted $563,315,500 in reparations to the Bikinians.

 SEDAN Preparations

  1. SEDAN was a 1962 test to investigate “peaceful applications such as large scale construction efforts (Harbor building, Mountain removal, etc.)."
  2. It was an underground test.  In underground tests, most of the released energy goes into crater formation. Only a fraction of the energy goes into the blast, depending on explosion depth. The shape of the crater depends on the depth of explosion; new applications are bunker breaking small nuclear weapon developments.
  3. With SEDAN, the 104 kT thermonuclear device was buried 635 feet below ground level. The force of the detonation released seismic energy equivalent to an earthquake of 4.75 magnitude on the Richter Scale.  The blast moved 6.5 million cubic yards of earth and rock up to 290 feet in the air.  The resulting crater was 1280 feet across and 320 feet deep.
  4. Nuclear Bunker Busters
    1. Bunker busters need to contain most of the released energy underground to break structure by underground shock and energy release (no air venting).  Underground structures are difficult to break, even by surface nuclear explosions. Underground explosions cause ground motion and seismic shocks.
    2. 1 kT bomb 1 m underground would have same effect as 35 kT bomb 1 m above ground. Or, a 10 kt bomb 2 m underground would enhance explosion yield by a factor of 20.
    3. At low depths, most of the released energy is lost in the blast rather than converted into seismic energy.
    4. New dreams of the Pentagon to address the perceived threat from third world underground “terrorist” bunker systems.

Containment of a nuclear blast

  1. Natural limit of penetration (set by deformation and liquidization of the penetrating missile is about 20 m.
  2. The containment depth corresponds to explosive yield.  The present standard 300 kT earth-penetrating warhead would need to penetrate to 500 m (instead of 20 m) to fully contain the energy underground.  Even a 0.1 kT warhead needs a 40 m depth for containment. 

Bomb Test Characteristics

  1. The effects of Nuclear weapons
    1. Blast damage
    2. Thermal damage
    3. Radiation damage
    4. EM-pulse
    5. Scaling laws
    6. Protection and shielding.
  2. Distance effects
    1. Fall-out
    2. Atmospheric distribution.
  3. Effects on population
    1. Radiation effects
    2. Fallout conditions
    3. Short term medical consequences
    4. Long term medical consequences.
Citation: Mathews, G. (2008, May 30). Lecture 13. Retrieved November 22, 2014, from Notre Dame OpenCourseWare Web site: http://ocw.nd.edu/physics/nuclear-warfare/notes/lecture-13.
Copyright Spring 2008, by the Contributing Authors. This work is licensed under a Creative Commons License. Creative Commons License