Operation Greenhouse, Scientific Director's Report of Atomic Weapon Tests at Eniwetok, 1951, Annex 1.6 Blast Measurements Part VI-Ground Shock Measurement, Section 2-Crater Survey (Ex) (Deleted)

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Scientific Director’s Report of Atomic Weapon Tests at Eniwetok, 1951 Annex 1.6 Blast Measurements Part VI-Ground Shock Measurement Los Alamos Scientific Laboratory Los Alamos. New Mexico This is an extracted version of WT409 OPERATION GREENHOUSE, Annex 1.6, Part VI, Approved for public release: distribution is unlimited. Extracted version prepared for DEFENSE NUCLEAR AGENCY

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REPORT DOCUMENTATION PAGE a. REPORT SECURITY CLASSIFICATION !b. DECLASSIFICATION I DOWNGRADING SCHEDULE Approved for publfc release; distribution ia. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7r. NAME OF MONITORING ORGANIZATION Los Alamos Scientific Lab. (rr applicable) Defense Atomic Support Agency 8b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT lDENTlFlCATlON NUMBER k. ADDRESS (City, State, and ZIP Ccdej 10. SOURCE OF FUNDING NUMBERS PROGRAM PROJECT TASK ELEMENT NO. NO. NO. 1 mLE mwe Serw ~a~fica~o@OPERATIONGREENHOUSE, SCIENTIFIC DIRECTOR'S REPORT OF ATOMIC dEAPON TESTS AT ENIWETOK, 1951, ANNEX 1.6 - Blast Measurements, Part VI - Ground-shock Yeasurements.Section 2 - Crater Survey, Extracted Version ‘3a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year, Month, DayJ rovide an unclassified version for unlimited distributlon. The work was performed by the lefenseNuclear Aaencv in support of the DOD Nuclear Test Personnel Review Prowam_ 17. COSATI CODES 16. SUBJECT TERMS (Continue on reverse if necessay ad idcntdy by block number) FIELD GROUP SUB-GROUP Greenhouse Blast Effects 19. ABSTRACT (Continue on reverse if necessary ad identify by block numbed _ The purpose of this report was to study the general characteristicsof the craters formed from nuclear explosions in connection with Operation Greenhouse to formulate general rules as to their site and shape. On the basis of the results, it was concluded that (1) craters on Eniwetok Atoll may be roughly described as conical sections and scaling relationships for the depth, radius, and volume are given as functions of yield; (2) crater formations are significantlyaffected not only by local ~011s but probably by the major geological structure of the 0zoll; and (3) the completely different -phenomenologyinvolved in nuclear explosions in comparison with TNT denies any justification for attempting to scale to correlate the results of TNT with nuclear explosions short of the detailed considerationsof the very different early hydrodynamfc history of each explosion. 20. DISTRIOUTION I AVAILAEILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION QUNCLASSIFIEDNNLIMITED 0 SAME AS RPT. 0 OTIC USERS UNCLASSIFIED DO FORM 1473,84MAR 63 APR edltlon may Be used uml exnaustea. All other editlonr are obsolete. SECURITY CLASSIFICATION OF THIS PAGE

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Classified material has been removed in order to make the information available on an unclassified, open publication basis, to any interested parties. The effort to declassify this report has been accomplished specifically to support the Department of Defense Nuclear Test Personnel Review (NTPR) Program. The objective is to facilitate studies of the low levels of radiation received by some individuals during the atmospheric nuclear test program by making as much information as possible available to all interested parties. The material which has been deleted is either currently classified as Restricted Data or Formerly Restricted Data under the provisions of the Atomic Energy Act of 1954 (as amended), or is National Security Information,or has been determined to be critical military information which could reveal system or equipment vulnerabilities and is, therefore, not appropriate for open The Defense Nuclear Agency (DNA) believes that though all classified material has been deleted, the report accurately portrays the contents of the original. DNA also believes that the deleted material is of little or no significance to studies into the amounts, or types, of radiation received by any individuals during the atmospheric nuclear test program.

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Approved by: FREDERICK REINES Approved by: ALVIN C. GRAVES Director, Program 1 Scientific Director Los Alamoe Scientific Laboratory Los Alamor, New Mexico

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1.3.1 General Characteristics of a Nuclear Explosion at a 1.3.2 Geologic Structure of the Atoll at Eniwetok . . . 1.3.3 Hydrodynamic Variables at the Ground for a Tower Shot 1.3.4 Scaling of Crater9 for Nuclear Explosions CHAPTER 2 PROCEDURES AND TEST RESULTS . . 3.2 Size and Shape in Crater Scaling . . . CHAPTER 4 CONCLUSIONS AND RECOMMENDATIONS 1.1 Schematic Comparison of Nuclear Explosion and Small-charge 1.2 Reflected Pressure on the Ground vs Time for 50 Kt, 300-R Height of Burst, at Several Horizontal Distances Rh .......5 1.3 Ratio of Air Density in Reflected Region on the Ground to Density of Undisturbed Air vs Time for 50 Kt, 300-ft Height of Burst, at Several

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1.4 Materiat.Yeloeity II* in Reflected Region on the Ground VI Time for 50 Kt, 300-ft Height of Burst, at Several Horizontal Distances Rk 1.5 Temperature on the Ground vs Time for 50 Kt, 300-ft Height of CHAPTER 2 PROCEDURES AND TEST RESULTS 2.1 Contour of Crater, Greenhouse Dog Shot . . . 2.2 Contour of Crater, Greenhouse Easy Shot . . . 2.3 Present Topography, Greenhouse George Crater . 2.4 Topograph, Ivy Mike Crater, 2 Weeks After Shot Time 3.1 Profiles of Greenhouse Dog Crater .... 3.2 Profiles of Greenhouse Easy Crater ,... 3.4 Profiles of Ivy Mike Crater ..... 3.5 Mean Crater Radius as a Function of Yield . .

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The purpose of this test was to study the general characteristics of the craters formed from nuclear explosions in connection with Operation Greenhouse at Eniwetok and, if possible, to formulate general rules as to their size and The crater shape, especially at Eniwetok, may well be a dynamic rather than a static problem, as will become apparent in the discussion of results. In general, this report is restricted to the description and study of the craters at a late stage when they were in relatively stable configuration. Data are not available on, nor does the report consider in detail, the intermediate configurations of the craters. This test was performed at the instigation and request of Frederick Reines, Director of Program 1 for Operation Greenhouse. In his directive, reproduced in Appendix A, detailed plans were given for the array of stakes, as well as for surveys to be made before and after Dog and Easy shots. Edward J. Zadina, then of J-Division, Los Alamos Scientific Laboratory (LASL), was in charge of the project until he left J-Division in the spring of 1952, at which time the responsibility for the report was assigned to the present Data for the crater survey were received in the late summer and fall of 1952. The preparation of the report has been delayed, however, in part by preoccupation with other operations. In the meantime, the crater survey for Mike shot of Operation Ivy became available and has been incorporated as part of this report. The author would have liked to make more detailed analyses and study of the results, which the subject deserves. However, some worth-while conclusions appear justified from a cursory study; this, together with his impending transfer from LASL, makes it worth while to publish the report in its present form. 1.3.1 General Characteristics of a Nuclear Explosion at a Soil-Air Interface Some general characteristics of the phenomena involved in a nuclear explosion at an interface between soil and air is contained in Report LA-1529.l This was based in turn on a detailed study for the nuclear explosion in soil in preparation for Jangle Underground shot. A principal result of both these studies is the vastly greater material and shock velocities in air relative to those in soil during the extremely high pressure phases of a nuclear explosion. This results in a very small energy transfer to the soil, and in relatively broad and shallow cratefs. In LA-1529 methods are suggested and carried out for calculating the peak pressure as a functibn of distance beneath Ground Zero. The craters from nuclear explosions are expected to be markedly different in size and shape from those of TNT, and no attempt is made here to scale craters between TNT and nuclear explosions. Figure 1.1 is reproduced from LA-1529 and shows the relative shape,of the shock configuration for both nuclear explosions and TNT. Although the figures are intended to be qualitative, they are not exaggerated; the pronounced difference in shape of the ground shock is occasioned by the very different relative velocities between soil and air at the very high pressures

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associated with the beginning of nuclear explo- gard to the equation of state, the material vesions, in comparison with corresponding rela- _ locity, u, is given by tive velocities at the lower pressures associ- I Fig. 1.1 Schematic Comparison of Nuclear Explosion and Small-charge Explosion. Note the broad shallow character of the nuclear shock in soil, as shown above, with the relatively deep shock from TNT, shown below. The small energy transfer on nuclear explo- where P = absolute pressure behind the shock sions follows from the high density and incom- PO = ambient pressure ahead of the shock pressibility of soil relative to air at comparable 1 V = specific volume behind the shock pressures. The time rate of work per unit area VO = ambient specific volume ahead of the of shock front in any substance is proportional t shock to the product where % = the rate of work per unit area and P = the absolute pressure behind the It follows then that the rates of doing work by the shock in soil and the shock in air are reUsing only conservation of mass and momentum at the same pressure level in both media. The in the Rankine-Hugoniot equations, without re- incompressibility of soil means that the quan-

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tity 1 - (V/V,) is not far different from zero, whereas for strong shocks in air the same quantity is not far different from 1. The density of air relative to soil is ln the order of 10e3. At Enlwetok, the*W;rtm table comes within a few feet of the surface, the interstices of soil are water-filled, and the incompressibility of water further favors the propagation of shocks in air over the shock in ground. The greater area of the air shock is indicated in Fig. 1.1, which follows from similar considerations involving the shock velocity, and this area enhances the transfer of energy to the air by another factor of approximately 2. In LA-1529 it was shown that, over a substantial range of pressures, the relative rate of work of the ground shock to the air shock was around 0.001; something less than 0.1 per cent of the energy of the bomb is transferred to the soil and hence available for crater formation. The situation is somewhat different in very porous soils, such as at Nevada Test Site. There the soil may contain 40 per cent air by volume, so the quantity 1 - (V/V,) is not small, but a number more like 6/10. In this case, the relative rate of work in soil to air is still proportional to the square root of the density ratios and is more like a factor of only 100 to 1 in favor of alr over soil. In the paper on nuclear explosions in soil, it was predicted that slightly less than 1 per cent of the energy could be transferred to the soil and hence available for crater formation at Nevada Of course, crater formation is not likely to be a uniform or reproducible process in any real soil because of marked inhomogeneity in compressibility as well as in density, which is due in turn to pockets of air or water, rock formations, or differences in particle sizes. At the outset, the most one can hope for is a general description which suits the average condition. Local variations in crater size by factors of 2 seem entirely reasonable. 1.3.2 Geologic Structure of the Atoll at Crater formation at Eniwetok is further beset overlying 4000 ft are mostly loose, unconsolidated sands or coral but interspersed with large pockets of water and presumably local stringers or networks of coral formation. The relatively loose material is contained on the ocean side by a sheath of coral rock of varying thickness which is expected to have numerous weak spots because of joints and fissures characteristic of coral formations. The excess density of this inner material over that of water represents enormous potential energy by virtue of its elevation above the ocean floor. The Atoll is considered to be in a metastable state but is presently contained by the structural strength of the coral rock, by rock formations within the sands, and by internal friction in the sand formation. The theory of dilation has been applied ~JJthis geologic structure. The passage of the &ound shock may break up the coral sheath and rock formation to an unknown extent and disturb the matrix of sand particles. The theory suggests that the sand formation will momentarily behave as a dense liquid after passage of the shock and flow plastically; the excess hydrostatic pressure ting the sand material to flow to lower depths. If this structural failure occurred at a sufficient depth, the potential energy released could be?. come comparable to the energy in the destructive oceanwide tsunami, and, by virtue of this trigger mechanism, this energy would greatly exceed the small amount of energy transferred to the soil from the nuclear explosion. The purpose of LA-1529 was in good part to show that a large-scale geologic failure of the Atoll could not be reasonably expected. On the other hand, the theory and the geologic structure suggest the possibility that holes or pockets may occur in or near the crater, which would be more representative of the geologic structure than of the nuclear explosion. Near a structural weakness material could flow through fissures in the ruptured wall, both because of the shock pressures and because of gravity. 1.3.3 Hydrodynamic Variables at the Ground for a Tower Shot by difficulties involving the geologic structure of Some estimates of the magnitude of the hydrothe Atoll itself, which was shown by geologic dynamic variables in the air shock with their investigations under the direction of H. K. Ste- distribution in space are contained in a study by phenson of LASL and Roger Revelle of the the author and are reported in the Greenhouse Scripps Institution of Oceanography. Handbook of Nuclear Explosions2 This provides The Atoil rests on a consolidated basalt floor rough theoretical estimates for the air preswhich 1s about 4000 ft below sea level. The sures near Ground Zero of Greenhouse Easy

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shot. No experimental data are available in the region of the calculation, but ball and crusher gauge measurements by the Naval Ordnance region of these calculations appear to be in reasonable agreement with them. Very crude agreement with the theory was also afforded by the structural failure of the snap samplers on Greenhouse. These samplers had been designed according to the specifications in the theoretical study and, on Greenhouse Easy shot, successfully withstood the blast, whereas on Greenhouse George shot, where the reflected pressures were some ten times greater, the snap samplers were partlally demolished. The values of pressure, density, and material velocity and their time variation in the region of regular reflection beneath the tower were calculated for a 50&t bomb detonated on a 300-ft tower. Using a …