Calculating contained firing facility (CFF) explosive firing zones
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
The University awarded a contract for the design of the Contained Firing Facility (CFF) to Parsons Infrastructure & Technology, Inc. of Pasadena, California. The Laboratory specified that the firing chamber be able to withstand repeated firings of 60 Kg of explosive located in the center of the chamber, 4 feet above the floor, and repeated firings of 35 Kg of explosive at the same height and located anywhere within 2 feet of the edge of a region on the floor called the anvil. Other requirements were that the chamber be able to accommodate the penetrations of the existing bullnose of the Bunker 801 flash X-ray machine and the roof of the underground camera room. For the sole purpose of calculating the explosive firing zones, it is assumed that the above requirements will be met by the completed facility. These requirements and provisions for blast resistant doors formed the essential basis for the design. The design efforts resulted in a steel-reinforced concrete structure measuring (on the inside) 55 x 51 feet by 30 feet high. The walls and ceiling are to be approximately 6 feet thick. Because the 60 Kg charge is not located in the geometric center of the volume and a 35 Kg charge could be located anywhere in a prescribed area, there will be different dynamic pressures and impulses on the various walls, floor, and ceiling depending upon the weights and locations of the charges. Parsons used the TM5- 1300 methods to calculate the loadings on the various firing chamber surfaces for the design criteria explosive weights and locations. At LLNL the same methods were then used to determine the firing zones for other weights and elevations that would give the same or lesser loadings. Although very laborious, a hand calculation of the various variables is possible and an example is given in Appendix C. A code called "SHOCK" is available to perform these calculations rapidly and a version runs on a personal computer. Parsons used the SHOCK code extensively as well as several single and multiple degree of freedom codes which were provided by the U.S. Corps of Engineers. In addition, Parsons based their analysis/design on procedures stipulated in the publication DOE/TIC- 11268, A Manual for the Prediction of Blast and Fragment Loadings on Structures. Loadings on structures in Reference 2 and in calculations performed with the SHOCK code are based on weights of explosives in pounds of TNT equivalent. The equivalency of an explosive (for its blast effects on structures) is calculated by the ratio of its heat to detonation to that of TNT. We intend to use C-4 for testing the response of the firing chamber. Various values of the ratio for C-4 are available, Reference 2 lists numbers leading to a ratio of 1.15, while 1.13 is the ratio calculated from numbers given in the LLNL Explosives Handbook, (Reference 3). Parsons used a ratio value of 1.3 for generic high explosive to TNT equivalency. For design purposes, Reference 2 recommends a 20% increase in explosive weight. Parsons adopted this recommendation. For calculational purposes, 60 Kg of generic high explosive was taken to be equivalent to 206.3 pounds of TNT. Explosive firing zone maps are given for six elevations. The SHOCK code calculations for the 206.3 Lb. charge of TNT are given for the floor and roof of the firing chamber to illustrate the technique and because this charge results in the highest loading on the respective surfaces. This is followed by calculations for the 120.3 Lb. charge giving the maximum pressures on the East and West walls (no builnose accounted for). One of a series of code calculations is given to illustrate the reduced area feature of the code. In this case, a virtual blast door on the inside of the chamber wall is being considered. The two remaining plots are the calculated peak average pressures and impulses on the virtual door from charges of various weights as they are moved along a bisecting normal line to the door.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP)
- DOE Contract Number:
- W-7405-Eng-48
- OSTI ID:
- 8208
- Report Number(s):
- UCRL-ID-132204-Rev-1; 39DP01000; ON: DE00008208
- Country of Publication:
- United States
- Language:
- English
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Calculating Contained Firing Facility (CFF) explosive firing zone
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