You need JavaScript to view this

Cavity pressure history of contained nuclear explosions

Abstract

Knowledge of pressure in cavities created by contained nuclear explosions is useful for estimating the possibility of venting radioactive debris to the atmosphere. Measurements of cavity pressure, or temperature, would be helpful in evaluating the correctness of present code predictions of underground explosions. In instrumenting and interpreting such measurements it is necessary to have good theoretical estimates of cavity pressures. In this paper cavity pressure is estimated at the time when cavity growth is complete. Its subsequent decrease due to heat loss from the cavity to the surrounding media is also predicted. The starting pressure (the pressure at the end of cavity growth) is obtained by adiabatic expansion to the final cavity size of the vaporized rock gas sphere created by the explosion. Estimates of cavity size can be obtained by stress propagation computer codes, such as SOC and TENSOR. However, such estimates require considerable time and effort. In this paper, cavity size is estimated using a scheme involving simple hand calculations. The prediction is complicated by uncertainties in the knowledge of silica water system chemistry and a lack of information concerning possible blowoff of wall material during cavity growth. If wall material blows off, it can significantly change the  More>>
Authors:
Chapin, C E [1] 
  1. Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)
Publication Date:
May 01, 1970
Product Type:
Conference
Report Number:
CONF-700101(vol.1); INIS-XA-N-228
Resource Relation:
Conference: Symposium on engineering with nuclear explosives, Las Vegas, NV (United States), 14-16 Jan 1970; Other Information: 30 refs, 16 figs; PBD: May 1970; Related Information: In: Symposium on engineering with nuclear explosives. Proceedings. Vol. 1, 871 pages.
Subject:
42 ENGINEERING; CALCULATION METHODS; CAVITIES; GASES; HEAT TRANSFER; NUCLEAR EXPLOSIONS; PRESSURE MEASUREMENT; ROCKS; SIZE; TEMPERATURE DEPENDENCE; UNDERGROUND EXPLOSIONS; VAPOR CONDENSATION
OSTI ID:
20555827
Research Organizations:
American Nuclear Society, Hinsdale, IL (United States); United States Atomic Energy Commission (United States)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
TRN: XA04N0763010801
Availability:
Available from INIS in electronic form
Submitting Site:
INIS
Size:
page(s) 463-480
Announcement Date:
Feb 20, 2005

Citation Formats

Chapin, C E. Cavity pressure history of contained nuclear explosions. IAEA: N. p., 1970. Web.
Chapin, C E. Cavity pressure history of contained nuclear explosions. IAEA.
Chapin, C E. 1970. "Cavity pressure history of contained nuclear explosions." IAEA.
@misc{etde_20555827,
title = {Cavity pressure history of contained nuclear explosions}
author = {Chapin, C E}
abstractNote = {Knowledge of pressure in cavities created by contained nuclear explosions is useful for estimating the possibility of venting radioactive debris to the atmosphere. Measurements of cavity pressure, or temperature, would be helpful in evaluating the correctness of present code predictions of underground explosions. In instrumenting and interpreting such measurements it is necessary to have good theoretical estimates of cavity pressures. In this paper cavity pressure is estimated at the time when cavity growth is complete. Its subsequent decrease due to heat loss from the cavity to the surrounding media is also predicted. The starting pressure (the pressure at the end of cavity growth) is obtained by adiabatic expansion to the final cavity size of the vaporized rock gas sphere created by the explosion. Estimates of cavity size can be obtained by stress propagation computer codes, such as SOC and TENSOR. However, such estimates require considerable time and effort. In this paper, cavity size is estimated using a scheme involving simple hand calculations. The prediction is complicated by uncertainties in the knowledge of silica water system chemistry and a lack of information concerning possible blowoff of wall material during cavity growth. If wall material blows off, it can significantly change the water content in the cavity, compared to the water content in the ambient media. After cavity growth is complete, the pressure will change because of heat loss to the surrounding media. Heat transfer by convection, radiation and conduction is considered, and its effect on the pressure is calculated. Analysis of cavity heat transfer is made difficult by the complex nature of processes which occur at the wall where melting, vaporization and condensation of the gaseous rock can all occur. Furthermore, the melted wall material could be removed by flowing or dripping to the cavity floor. It could also be removed by expansion of the steam contained in the melt (blowoff) and by thermal stress fractures at the melt-solid interface. There are three distinct heat transfer regimes, depending on the temperature of the cavity gas. When the cavity gas temperature is greater than the temperature at which wall material is removed by melting or blowoff, heat transfer occurs with mass removal. The water contained in the removed wall material is added to the cavity gas. As the cavity temperature decreases, due to the heat loss, a temperature will be reached where the gaseous rock condenses. Thereafter, the gas is composed entirely of steam. Heat transfer during condensation is the second heat transfer regime. Following condensation the cavity gas will continue to cool, and material will continue to be removed from the walls as before. However, when the cavity cools sufficiently, the wall material becomes extremely viscous. Further heat transfer takes place by conduction into the walls. The heat transfer rate will be considerably reduced when this occurs since rock is a rather poor conductor of heat. Heat transfer by conduction is the third heat transfer regime. A parametric study of pressure histories in contained underground nuclear explosions is made and the results of the calculations are compared with the limited experimental data available. (author)}
place = {IAEA}
year = {1970}
month = {May}
}