The Lady Godiva device was an unshielded, pulsed nuclear reactor originally situated at the Los Alamos National Laboratory (LANL), New Mexico, U.S. It was one of a number of criticality devices within Technical Area 18 (TA-18). Specifically, it was used to produce bursts of neutrons and gamma rays for irradiating test samples, and inspired development of Godiva-like reactors. Physicist Otto Frisch remembered the Los Alamos team called an earlier unshielded uranium-235 assembly in 1944 "Lady Godiva".
The radiation source within the Godiva device was a fissile metallic mass (usually highly enriched 235U), about 30 cm in diameter. This was located at the top of a two-metre-high metal tower. The burst of radiation was produced when a piston of fissile material was quickly inserted and extracted from a cavity within the larger fissile mass. During the time these two masses were combined, they formed a critical mass and a nuclear chain reaction was briefly sustained.
Godiva's design was inspired from a self terminating property discovered when incorrectly experimenting with the Jemima device in 1952. Jemima operated by remotely lifting one stack of enriched uranium-235 disks up towards another, fixed, stack. On 18 April 1952, due to a miscalculation, Jemima was assembled with too many disks; this caused an excursion of 1.5 x 1016 fissions—an automatic scram—but no damage.
On 3 February 1954 and 12 February 1957, accidental criticality excursions occurred causing damage to the device, but fortunately only insignificant exposures to personnel. This original Godiva device, known as Lady Godiva, was irreparable after the second accident and was replaced by the Godiva II.
Godiva II was constructed inside a concrete building with 20-inch-thick (510 mm) walls and 8-inch-thick (200 mm) roof in a canyon a quarter-mile away from the control room.
Godiva's success in creating intense bursts spurred development of similar pulsed reactors, which also suffered accidental excursions, for example: 28 May 1965 at the 1965 White Sands Missile Range (parts were thrown 15 feet); and 6 September 1968 at the Aberdeen Proving Ground (middle melted, disks warped and bolts stretched).
In December 2002, the U.S. Department of Energy announced it was to move its TA-18 testing equipment including the Godiva burst machine from the LANL to the Device Assembly Facility (DAF) at the Nevada Test Site (NTS).
- McLaughlin et al. pages 78, 80-83. "Jemima ... apparent self terminating property of this excursion stimulated study with Lady Godiva,46,47,48"
- Garcia page 1
- Frisch, Otto Robert (1980). What Little I Remember. Cambridge University Press. pp. 161–162. ISBN 9780521280105.
an unusual assembly ... no reflecting material ... For obvious reasons we called it the Lady Godiva assembly.
- McLaughlin et al. page 109, "93%"
- Engelke pages 3-4
- Zipprich, L.J.
- McLaughlin et al. page 86, "Unreflected uranium–molybdenum metal fast burst reactor"
- Kazi et al., "center third of the safety block was melted"
- U.S. Department of Energy page 1
- Morris J. Engelke; Bemis Jr., Edwin A.; Sayeg, J. A. (May 1961). "LA-2569 Neutron tissue dose rate survey for the Godiva II critical assembly" (pdf). Los Alamos Scientific Laboratory. Retrieved 2008-02-28.
- Garcia, Manual (8 August 2005). "Test Plan for Godiva Move from LANL TA-18 to NTS DAF" (pdf). Lawrence Livermore National Laboratory. Retrieved 2008-02-28. id=UCRL-TR-214269
- Kazi, A.H.; Dubyoski, H.G.; Dickinson, R.W (1969). "Preoperational Test Experience with the Army Pulse Radiation Facility Reactor" (pdf). Proc. of the National Topical Meeting on Fast Burst Reactors. Albuquerque, NM: United States Atomic Energy Commission. pp. 353–371. Retrieved 2008-02-28.
- McLaughlin et al. "A Review of Criticality Accidents / 2000 Revision / LA-13638" (PDF). Los Alamos National Laboratory. May 2000. Archived from the original (pdf) on 20 March 2009. Retrieved 2008-02-28.
- U.S. Department of Energy. "Criticality Experiments Facility" (pdf). National Nuclear Security Administration Nevada Site Office. 15 June 2005. Retrieved 2008-02-28.
- Zipprich, L.J. (1 April 1959). "Radiation effects testing at the Los Alamos Godiva II A facility". Retrieved 2008-02-28. OSTI ID: 4268715
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