UCRL-ID-124784 Nuclear Excavation (Letter to- R. E. Miller, AEC) G. H. Higgins January 13,1970 This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermom National Laboratory under Contract W-7405-ENG-48.
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'f LAWRENCE RADIATION LABORATORY ",O. BOX 808,VERMORE. CALIFORNIA 94550 January 13, 1970 TELEPHONE ( 4 1 5 ) 447-1100 TELEX 34-6407 AEC LRL LVMR TWX 910-386-8339 AEC LRL LVMR Mr. Robert E. Miller, Nanager Nevada Operations Office U. S. Atomic Energy Commission P. 0. Box 14700 Las Vegas, Nevada 89114 Dear Bob: /o -- 73 Several weeks ago you asked Harry Reynolds why nucl ear excavation experiments were necessary and important. I apologize f o r not having answered sooner, b u t i n view of the f a c t t h a t the Sturtevant schedule has been delayed, I trust the delay will not be too harmful. As you know, f o r the past e i g h t y e a r s i t has been a matter of U.S. policy t o develop nuclear excavation technology. T h i s policy has been consciously reviewed and confirmed by each o f the U.S. presidents, from the administration of Dwight Eisenhower down t o the present administration. I am going t o assume t h a t these reviews and the documents prepared i n support o f them (such as t h a t prepared by DPNE, t i t l e d "The Value and Need f o r Nuclear Excavation" of December 1969) and contained i n the hearings on the Non-Proliferation Treaty, the AEC Authorizing Legisl a t i o n, and the statements of the Inter-Oceanic Canal Commission, establish the j u s t i f i c a t i o n f o r nuclear excavation i n general. 1 believe you would agree t h a t the conscious and considered decision by the Chief Executive t o establish a goal was adequate j u s t i f i c a t i o n f o r us t o attempt t o reach the goal. For example, t o the best o f my knowledge, National Security Action Memorandum No. 152, (dated April 30, 1962, subject: Panama Canal Policy and Relations w i t h Panama) signed by President Kennedy, is s t i l l i n effect. In particular, this memo s t a t e s t h a t "The Chairman, Atomic Energy Commission, will establish w i t h i n the Plowshare Program a research goal t o determine w i t h i n approximately the next five years the f e a s i b i l i t y, costs and other factors involved i n nuclear methods of excavation," (referring, of course, t o t h e Trans-Isthmian Canal). I understand t h a t the five-year time period was a l t e r e d, verbally, when the c o n f l i c t between the Limited Test Ban Treaty and nuclear explosives development became apparent i n 1964-65, b u t t h a t the basic policy and goal has not been rescinded. The most recent confirmation is the statement t h a t Seaborg made (News Conference a t the White House w i t h Glen Seaborg, January 28, 1969) i n which he said, i n p a r t, 'The President 6
Letter t o R. Miller, NVOO _--._I-c I I - --x. COPK 70-2 page 2 -- --- expressed a great i n t e r e s t -- and he asked me particularly t o t e l l you this -- in the peaceful uses o f atomic energy. He particularly identified Plowshare... as an area i n which he had a special i n t e r e s t. " Later in the same news conference, in response t o a question about the canql, Seaborg stated "Yes, the President expressed great i n t e r e s t and hoped we would be able t o make a l l the t e s t s necessary t o make t h i s feasible" (referring t o the Isthmian Canal). However, as both you and I know, Undersecretary R'chardson i s a t t h i s moment, formally reviewing this administration's view toward excavation, and i t i s possible excavation technology will be dropped from the Plowshare Program. As long as i t i s a p a r t of policy, and u n t i l i t i s dropped, I see no real purpose t o secondguess the decision t o develop the technology. With the previous assumption, the question t o be answered i s "Why are nuclear excavation experiments needed now? -- not "Why i s nuclear excavation important?" T h i s is largely, i f not entirely, a technical matter. A t the risk of over-simplifying, I will attempt t o summarize the two key questions t h a t remain t o be answered i n order t o establish the f e a s i b i l i t y of large-scale excavation. Fact 1: Comparison of projected costs of nuclear excavation and conventional excavation show that nuclear excavation is only practical and economic when the individual explosive yields a r e i n the order of 100 kilotons and larger. That i s t o say, when the excavation depth is 200-300 f t or deeper, and the width is o f the order of a quarter mile and larger. Fact 2: Excavation experiments have, except f o r the Sedan experiment, been conducted w i t h yields less than 35 k t. Sedan, i n desert alluvium, does not give information relevant t o most o f the proposed excavation applications (see l i s t appended t o the d r a f t DPNE report of December 1969). Fact 3: Theoretical understanding o f cratering and calculations o f c r a t e r s are i n reasonable agreement a t the low yields. There is no data a t higher yields. Fact 4: The mechanisms f o r producing craters, spallation, gas acceleration and compaction are of different re1 ative importance a t h i g h yields than a t low yields, according t o the theory. I t i s not possible, as nearly as we can t e l l from measurements a t low yields, t o find out i f the theoretical treatment of the gas acceleration phase i s correct. To demonstrate the importance o f gas acceleration a t higher y i e l d s, we have calculated the size o f explosive i t would take t o produce a 748'deep excavation w i t h the gas acceleration phase as calculated and w i t h i t suppressed t o t h e same degree i t was i n the Danny Boy experiment. In the f i r s t case, the yield required was 1 Mt. While there are safety problems involved, there a r e places, particularly remote areas, where..it is possible t o safely detonate a 1 M t explosive.
Letter to R. Miller, The yield required i n the second case - without gas acceleration i s about 35 M t, and while i t may be possible a t a few places i n the world t o detonate this large a single yield, most of the projects previcrusly examined would be infeasible because of ground shock or a i r b l a s t or-both. We believe the lower yield calculation t o be correct, b u t without experiments i n the yield range between 200 and 1,000 k t, there is no experimental verification. The commitment of this country to undertake excavation of "d sea-level canal, a harbor, a cut-through mountain pass, o r any large-scale excavation demonstration o r project requires an assumption about cratering efficiency a t high yield. I t should be obvious, however, t h a t waiting until the f i r s t step of the demonstration itself t o f i n d out whether the calculations a r e correct will, i n most cases, entail an unacceptable r i s k t o the potential user. I f the AEC o r the U. S. government cannot, i n good f a i t h, a s s e r t t h a t a useful excavation will r e s u l t from a project, very few ( i f any) users will consider nuclear excavation as an alternative t o more costly b u t proven conventional techniques. Besides cratering mechanisms there i s an additional important issue t o be determined. The radioactivities produced by the clean excavation explosive a r e d r a s t i c a l l y different from those produced by weapons. I t has only been possible t o make assessments of the biological impact of nuclear excavation by using data from the Cabriolet and Schooner experiments. Assessment of exposure from inhalation, through food-stuffs and from external radiation i s also critical i n determining f e a s i b i l i t y of particular applications. Assessment o f the safety of the planned experiments is based on "worst case" assumptions. These "worst case" assumptions frequently involve three o r four orders of magnitude of accumulated conservatism. Without f i e l d experiments, these same ultra-conservative, res t r i c t i v e practices will be continued. The consequence of these continued practices w i l l be elimination of most i f not a l l demonstration and application projects. The importance of this problem can probably best be demonstrated w i t h one simple observation. The radioactive source from Sturtevant is somewhat l e s s than the aggregate source was from Buggy. Yet, uncertainties regarding the behavior of radioactivity a t h i g h yields necessitates a public information and evacuation plan which is, a t the l e a s t, very troublesome. You will recall we executed Buggy w i t h hardly a ripple i n ' p u b l i c o r private sectors and no technical safety problems. T h e minimum key experiments t o complete an adequate assessment of these two aspects of nuclear excavation are, i n my personal opinion, Sturtevant, Yawl and Galley. If Sturtevant worked exactly as calculated and every experimental program was 90 or 100%successful, Yawl might be bypassed without serious loss. Galley, w i t h five o r more 100-300 k t charges detonated simultaneously, would s t i l l be required because of probable differences i n both cratering mechanisms and radioactivity distribution between 1 k t (Buggy experience) and 1,000 k t (useful level).
COPK 70-2 l e t t e r t o R. Miller, NVOO - Page 4 I hope t h i s l e t t e r answers your question regarding the need for nuclear excavation experiments and conveys t o you a deep concern about t h e potential dilema that our government will face i f asked t o assess a r e a l nuclear excavation application without prior high-yield. cratering experiments. Sincerely yours < I.. -ic' Gary H. Higgins K-Division Leader GHH :ca D i s t r i b u t i o n : (8 copies, Series A) i i 1A: R. Miller, NVOO, Las Vegas 2A: M. May 3A: G. Werth 4A: H. Reynolds 5A: R. Batzel 6A: 6. Higgins 7,8A: f i l e