Godiva device
The Lady Godiva device[1] was an unshielded, pulsed nuclear reactor[2] 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. It received its name from Otto Frisch, who called it "Lady Godiva" because it was 'naked and unshielded'.[3].
The radiation source within the Godiva device was a fissile metallic mass (usually highly enriched 235U)[4], 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 radioactive metal was quickly inserted and extracted from a cavity within the larger radioactive mass. During the time these two masses were combined, they formed a critical mass and a nuclear chain reaction was briefly sustained.[2]
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 1952-04-18, due to a miscalculation Jemima was assembled with too many disks which caused an excursion of 1.5 x 1016 fissions, an automatic scram, but no damage.[1]
Frisch himself received a larger than intended dose of radiation in 1944 when, leaning over the device for a couple of seconds, he noticed that the red lamps that flickered intermittently when neutrons were being emitted, were 'glowing continuously'. Frisch's body had reflected some neutrons back to the Lady Godiva device, causing the device to go critical, and it was only by quickly leaning back and away from the device and removing a couple of the uranium blocks that Frisch escaped harm, but 'if I had hesitated for another two seconds before removing the material ... the dose would have been fatal'. [5].
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.[1]
Godiva II
Godiva II was constructed inside a concrete building with 20 inch thick walls and 8 inch thick roof in a canyon a quarter mile away from the control room.[6]
In 1959 Los Alamos agreed to make Godiva II available to DOD contractors free of charge for 2 days each month, acknowledging its unique facility for radiation tests.[7]
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);[8] and 6 September 1968 at the Aberdeen Proving Ground (middle melted, disks warped and bolts stretched).[9]
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).[2][10]
Notes
- ^ a b c McLaughlin et al. pages 78, 80-83
- ^ a b c Garcia page 1
- ^ Diana Preston Before the Fall-Out - From Marie Curie to Hiroshima - Transworld - 2005 - ISBN 0-385-60438-6 p, 278
- ^ McLaughlin et al. page 109, "93%"
- ^ Diana Preston Before the Fall-Out - From Marie Curie to Hiroshima - Transworld - 2005 - ISBN 0-385-60438-6 p, 278
- ^ 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
References
- Morris J. Engelke (May 1961). "LA-2569 Neutron tissue dose rate survey for the Godiva II critical assembly" (pdf). Los Alamos Scientific Laboratory. Retrieved 2008-02-28.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - Garcia, Manual (2005-08-08). "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. (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.
{{cite conference}}: Unknown parameter|booktitle=ignored (|book-title=suggested) (help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - McLaughlin et al. "A Review of Criticality Accidents / 2000 Revision / LA-13638" (pdf). Los Alamos National Laboratory. May 2000. Retrieved 2008-02-28.
{{cite web}}: Check date values in:|date=(help)- LA-13638 covers United States, Russia, United Kingdom, and Japan, and is also available here and at this page, which also tries to track down documents referenced in the report.
- U.S. Department of Energy. "Criticality Experiments Facility" (pdf). National Nuclear Security Administration Nevada Site Office. 2005-06-15. Retrieved 2008-02-28.
- Zipprich, L.J. (1959-04-01). "Radiation effects testing at the Los Alamos Godiva II A facility". Retrieved 2008-02-28. OSTI ID: 4268715
External links
- Wimett, T. F. (1958). "Applications of Godiva II Neutron Pulses" (PDF). Proc. UN Intern. Conf. Peaceful Uses At. Energy, 2nd. Vol. 10. Geneva: United Nations, Geneva. pp. 449–460. Retrieved 2008-02-29.
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