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Theory of Fielding - Set V - Implosion and Uranium Hydride

From: HB Laes
Date: 26 Sep 1999


Phenomena: "Hall was probably not only the first conveyor of the implosion principle to Moscow, but also the source of the concept of the uranium-hydride bomb." (Bombshell, page 127)

Discussion. A case can be made that the most interesting and important chapter of Bombshell is Chapter 14, Passing the Implosion Principle. In addition to new sources of information and cogent analysis, the authors rightly zero-in on the intelligence value of the implosion secret. "This [implosion] was the germ of one of the seminal inventions of the twentieth century, and the idea was so counterintuitive that Soviet physicists might have taken a decade to come up with it on their own." Indeed, as the authors point out, the Russians did not have a word in their language for implosion, meaning an explosion inward.

The centerpiece of the author's story and the focus of this set's discussion is a comprehensive Report on atomic intelligence prepared for Lavrenti Beria by the NKGB, dated February 28, 1945. We couldn't agree more with the author's assessment of this document: "The Report would rank among the more remarkable intelligence feats of World War II." Readers can find the Beria Report in Special Tasks (Appendix Two, Document 7). The Report is stunning because it reveals the quality and contemporaneity of the information the Soviets had on both implosion and the physics of uranium-hydride. These were the absolutely front burner problems being worked on at Los Alamos in late 1944 and early 1945.

The authors lay down a couple of useful markers to facilitate the analysis, which we will just repeat and second for the sake of brevity. First of all, they show that the time between collection of documents in the field and distribution of intelligence product at the Center was on the order of 4 to 6 weeks. Conservatively, the scientific and project information that underpin the 28 February Beria Report had to have been obtained by Soviet field operatives no later than mid January 1945. Secondly, with respect to the only 3 known sources at Los Alamos - Fuchs, Hall, and Greenglass - two can be readily discounted; Greenglass patently didn't have the access, and Fuchs' first delivery to his courier after going to Los Alamos in July, 1944, was February 16, 1945 - too late for inclusion in the Beria Report.

The thesis of Chapter 14, then, is that Ted Hall (Mlad) provided the exceptional information on implosion and uranium-hydride contained in the 28 Feb document sent to Beria. That this is even plausible, given that Hall had volunteered to the NKVD less than 2 months previous, is sustained by credible evidence that in mid-December 1944 Saville Sax traveled to Albuquerque, New Mexico, rendezvoused with Ted Hall, and returned with a written report from Hall. Parenthetically, we see this trip as more of a Ted and Savy gig, carelessly abetted by Kurnakov, rather than a NY Residentura directed operation. We see Yatskov as unpleasantly surprised by such freelancing; hence the immediate ordering of "full background checks" on Hall, Sax and Bluma Sax. If there was a briefcase or suitcase, we suggest it was probably full of New Mexico/Albuquerque maps, tourist literature, etc.

Although the timing works, the description of what Hall handed over to Sax is problematical: (1) Page 114. "Sax carried back to New York a piece of paper far more important than a response on sulfur dioxide. It was only a page or two, something Hall had written by hand during one of his breaks from work in the Gadget Division." (2) Page 127. "What Hall gave to Sax in Albuquerque, this source said, was a short summary of the early results of the Ra-La implosion experiments. Hall's handwritten paper included a description "in the form of equations" of how an implosion was supposed to work. It also contained a capsule explanation of why this new technique for rapid assembly of the critical mass was seen on the Hill as promising."

The authors' case in Chapter 14 is built primarily around two CLUES pointing to Ted Hall. The first clue involves two documents, a 16 March 1945 technical appraisal authored by Igor Kurchatov (full text @ Bombshell archives) and a 31 March 1945 Venona Document, Moscow to NY, No. 298 ( The subject of Kurchatov's appraisal was "material" that "contained the scientific background for several crucial points" in the Beria Report. Two of these points were new to Kurchatov: the implosion concept and uranium-hydride as an "active substance." In his report, Kurchatov opened his analysis with the comment, "The material is of great interest." The 31 March Venona message was ostensibly the Center's first acknowledgement to NY on the information recently received from Fuchs and Hall. The last, short paragraph of this message makes the following reference to Mlad: "Mlad's report about work [4 groups unrecoverd]. [1 group unrecovered] great interest."

The authors find this duplicated phrasing a compelling nuance. They write, "Thus the phrase [great interest] in the cable referring to Mlad's report was almost certainly a paraphrase of Kurchatov's glowing review just two weeks earlier about the prospect of an implosion bomb." We too find the duplicated phrasing compelling, but we take a different road. Ted Hall was an important member of Bruno Rossi's Ra-La Method team, one of about ten work groups in the Gadget Division. The Ra-La method was the very creative idea of Robert Serber (Theoretical Division) to measure the compression force and symmetrical uniformity of implosion test shots. In no way were the Ra-La invention and the Ra-La team's methods technical 'no brainers.' On the contrary, they were no doubt of extreme interest and value to Soviet scientists. Hall would certainly have given a good account of his own work in his report. So our theory is that there exists another Kurchatov memo that addresses the Ra-La work and contains his stock phrase, "great interest," for signaling a well done; the Lubyanka drafter followed suit.

We have our own 'nuance' judgments about the Kurchatov report and the Venona message. (1) Kurchatov consistently refers to "material" and "materials," both words suggesting quantity. How could Hall have addressed in a two page report all of the areas identified in the Beria and Kurchatov documents - implosion, uranium-hydride, beryllium insulation, "the system described," "the discharge (ballistic) method," "experiments to be staged," "bombs of somewhat smaller capacity," the Los Alamos lab, its ranges, etc.? We just have a hard time squaring this volume of intelligence plus the connotation of "material/s" with a two page, handwritten "report." (2) The Venona message treats Charlz' "materials" extensively but gives short shrift to Mlad's "report." Mlad's report almost seems relegated to an afterthought, not garnering a single technical pointer. Given the contention that the materials 'of'' Kurchatov's memo came from Hall, you would expect it to be otherwise. An explanation would be that Hall's report was interesting (valuable) but essentially confirmatory of other sources on implosion.

The authors' second clue is the fact that the meeting between Hall and Sax in Albuquerque fell within a unique sixty-day time frame when the Los Alamos lab "possessed enough ... uranium-hydride to make a critical mass." We readily accept their "triangulation" analysis; and the coincidence that the Hall/Sax meeting occurred during this important period is a very fair point. That circumstance, however, is just not enough to override our view that Hall's responsibilities on the Ra-La team were fundamentally experimental and divorced from the theoretical work on uranium-hydride. Also, with only a bachelor's degree one has to question whether Hall could have competently and comprehensively expounded on the hydride problem to the degree evidenced in the "materials." Finally we are influenced when the authors' write, "A half century later, Ted Hall didn't recall knowing anything about the uranium-hydride option, but at the time he probably did know of it." We don't see Ted Hall forgetting something as central to the Los Alamos effort as hydride (at that time), and something he consequently judged the Soviets needed to know in detail (hypothetically).

Let's further examine some of Kurchatov's 16 March comments on uranium-hydride: "Use uranium hydroxide 235 instead of uranium 235 as is mentioned in material is based on large possibility of absorbing of slow neutrons by uranium, which leads to reducing critical mass. Using hydrogen, however, leads to slowing development of the whole process and can prolong it to unacceptably large periods of time. Besides, because of small density of this substance it is necessary to increase critical mass. Thus its absolutely not obvious that use of uranium hydroxide instead of uranium can give that big (almost 20 times as much) advantage in mass which is mentioned in the materials." These were comments on theory, state of the art bomb theory at that.

To add perspective to our point that Ted Hall's Ra-La work does not evoke Kurchatov's comments (and hence the "materials"), compare Hans Bethe's description of Richard Feynman's work in the Theoretical Division: "[Feynman's] group was charged with the calculation of the behavior of uranium-hydride in a nuclear explosion. This had been suggested by Edward Teller because the hydride has a much lower critical mass than uranium metal. However the calculations gave an unsatisfactory result: Because the neutrons are very much slowed down by the hydrogen, the rate of neutron multiplication is low, and therefore the yield of such an explosion is also low."

Other comments by Kurchatov on the hydride issue are also interesting: "It seems exceptionally important to establish whether the system described was studied through calculation or by way of an experiment. If the latter, that would mean that the atomic bomb has already been executed and that uranium 235 has been separated in major quantities. The materials contain a remark that seems to suggest that. In describing the implosion method it is pointed out that no experiments have yet been carried out with active material, but they are to be staged within months." Comparing with Richard Rhodes', "At Los Alamos in late 1944 Otto Frisch, always resourceful at invention, proposed a daring program of experiments. Enriched uranium had begun arriving on the Hill from Oak Ridge. By compounding the metal with hydrogen-rich material to make uranium-hydride it had become possible to approach an assembly of critical mass responsive to fast as well as slow neutrons." Sounds to us like Kurchatov may have gotten a peek at Otto Frisch's Dragon experiment (so named by Feynman).

Our final point is very subjective, maybe a matter of interpretation, but one we find curious. On the hydride bomb issue, the authors' write, "How the early Soviet bomb designers managed to steer past the blind alley of the low-budget hydride bomb remains unknown." Well, if we can test your patience, please re-read Kurchatov's comments, quoted 3 paragraphs above. We don't know how others interpret this passage, but depending on how you read it, it may possibly answer the Albrights' question. Has Kurchatov done his own "calculations" to arrive at this opinion (calculations that took Feynman and a team to do) or is he recounting the scientific analysis in the materials at hand, which 'mention/suggest' that the hydride route might not be profitable? That research or finding at Los Alamos, as far as we can tell, satisfies the authors' "triangulation" condition. We would be interested in others' (especially Der Greif's) take on this.

Conclusion. As mentioned at the beginning we think Bombshell's Chapter 14 offers some unique insights into the pivotal period in Soviet espionage against the Manhattan Project. There is virtually no doubt of Bombshell's essential claim that Hall shared the bare secret of implosion. But in regards to our Theory of Fielding we gravitate to other candid reporting by the Albrights: "By early 1997, Hall said he had come to believe that Los Alamos probably did harbor yet another Soviet informant, a conviction based solely on the description of the extremely precise data the Russians say that they received....declaring with much emphasis that he did not "recognize himself" as having been in a position to supply the kind of precise bomb dimensions furnished to the Soviets." (Page 155)

Sources. Bombshell, Joseph Albright and Marcia Kunstel; The Making of the Atomic Bomb, Richard Rhodes (page 610); Most of the Good Stuff (Feynman in Los Alamos and Cornell), Hans A. Bethe (page 33)

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