key: cord-0612247-y6ap2ywm
authors: Chadwick, M. B.
title: Foreword: Manhattan Project Nuclear Science&Technology Developments at Los Alamos
date: 2021-03-09
journal: nan
DOI: nan
sha: c252dfd7035649b5c101c91bd2d7ba69cf5bb426
doc_id: 612247
cord_uid: y6ap2ywm

A collection of articles reviewing Trinity on its 75th anniversary.

Our universities' science and engineering luminaries, together with their best graduate students, came together at various Manhattan Project locations across the country under intense pressure and worked at a frenetic wartime pace to successfully develop a workable atomic bomb. This gathering of scientific and technical excellence was a unique event in our history, and their collective effort led to a remarkable outpouring of scientific creativity in nuclear and material sciences and in hydrodynamics and neutronics computations, and led to the creation of what would become today's US DOE national laboratories. The historic effort was facilitated in large part by Oppenheimer's superb (and, at the time, unproven) leadership. The Manhattan Project, together with the MIT Radiation Laboratory's wartime work on radar and E.O. Lawrence's accelerator research, represents the beginnings of big science, bringing thousands of researchers together to solve problems, a model that has since proved so effective for the scientific community in the field of particle physics, sequencing of the human genome, and the discovery of gravitational waves.

To recognize the Trinity anniversary, this special issue of Nuclear Technology focuses on aspects of the science and engineering breakthroughs made during the Manhattan Project at Los Alamos (then called Project Y), 1943-1945. Both technical papers and technical history papers are included. Their goal is to clarify the nature of the breakthroughs made, correct previous misunderstandings in the open literature, illuminate fascinating aspects of the underlying research, and illustrate how science from 75 years ago has proven foundational for the peaceful use of nuclear energy and today's nuclear technology. These papers benefit from the authors' access to extensive material in our Los Alamos National Security Research Center (NSRC) archives, much of which has not been available to broader audiences.

The idea of this special issue grew out of a seminar series that I hosted at Los Alamos in the summer of 2020. Afterward, I challenged our staff to write up their work as technical papers to be published in an internal Los Alamos classified research journal. The invitation was extended to colleagues at the Lawrence Livermore National Laboratory, Sandia National Laboratories, and the Atomic Weapons Establishment (AWE) at Aldermaston in the UK (appropriate given the large British contribution to the Manhattan Project). The authors overcame substantial challenges in completing the papers during the COVID-19 pandemic, not least of which was the limited access to our onsite archives. Despite this, our project led to the fascinating suite of papers presented here. Subsequent discussions with the American Nuclear Society resulted in the decision to make this scholarship available to a broader readership by publishing the unclassified papers in this special issue of Nuclear Technology with open access.

Below, I summarize some of the key insights to be found in this collection of papers.

Nuclear science and technology. Ref. 5 documents the neutron cross sections measured with increasing accuracy during the Manhattan Project. Accurate neutron cross sections were needed to determine critical masses and, therefore, the quantities of 235 U and 239 Pu required from Oak Ridge and Hanford. In short order, four university accelerators were disassembled and reassembled at Los Alamos, and methods were established to make measurements on extremely small samples owing to the initial lack of availability of enriched 235 U and plutonium. In just two years, advances in experimental methods led to measured nuclear data that are surprisingly close to today's best values in our Evaluated Nuclear Data Files (ENDF). Many of the key original papers and numerical values have now been archived through a collaboration with the International Atomic Energy Agency (IAEA) and Brookhaven National Laboratory in the internationally available Experimental Nuclear Reaction Data (EX-FOR) database. Also, an early, little-known British paper is transcribed 5 : Bretscher's 1940 description of the usefulness of plutonium, written around the time that the element was discovered.

Papers on the first fast critical assemblies (Hutchinson et al. 6 ) and pulsed and solution assembly experiments (Kimpland et al. 7 ) provide details about how critical masses were determined and how they influenced subsequent research across the world on nuclear criticality and criticality safety. The Los Alamos "water boiler" assembly was the world's third reactor to become operational (in 1944, after Chicago's CP-1 and Oak Ridge's X-10 piles), the first to use a solution, and the first to use enriched uranium fuel. During the Manhattan Project, bare critical masses were not measured directly-there was insufficient time or material; instead, the wartime measurements focused on reflected assemblies and subcriti-cal measurements from which bare critical masses could be estimated with extrapolative calculations. Sood et al. 8 describe the evolution of neutronics calculational capabilities from early neutron diffusion work to subsequent refinements by Serber and Wilson (a British researcher) and the postwar innovations of S n deterministic and Monte Carlo neutron-transport simulations.

Andrews, Andrews, and Mason 9 describe the Canadian work at the Montreal Laboratory and Chalk River and the essential role Canada played in supplying nuclear materials for the Manhattan Project. The authors also tell of the contributions of the talented Canadians who came to work on the Manhattan Project in the US. The Montreal Laboratory's work was focused on neutronic criticality theory and heavy-water-moderated reactor experimentation--research that proved to be important for postwar CANDU reactor development.

Hydrodynamics. Morgan and Archer 10 describe Los Alamos' Theoretical Division's Lagrangian hydrodynamic shock calculations, implemented on IBM punchedcard machines. Their paper presents the algorithmic advances made during the Manhattan Project by von Neumann that led to the late-1940s formulation of computational fluid dynamics by von Neumann and Richtmyer that is today the basis of simulations of everything from climate change to nuclear reactor design. But Morgan and Archer also illuminate the less appreciated, but very influential, roles of Peierls and Skyrme. The authors show that the first usage of "artificial viscosity," a concept central to computational hydrodynamics, appears to originate with Peierls in 1944. Skyrme is well known to nuclear and particle physicists, but few know of his shockphysics research. Indeed, it was the expertise in shock physics that was especially sought after by Oppenheimer and Bethe in the British Mission that brought two dozen British scientists to New Mexico in 1944. Other papers describe the history of the Los Alamos computing facility, focusing first on the "human computers" (Lewis 11 ) and then the IBM punched-card computations (Archer 12 ) needed for hydrodynamics and neutronics.

High explosives. The implosion design of the Fat Man atomic bomb relied on precision-engineered high explosives (HE) to symmetrically compress a solid ball of plutonium. Brown and Borovina 13 describe this HE work, its subsequent impact on broader shaped-charge technology, and its use in mining, oil recovery, and even SpaceX multistage rocket separation. AWE's Moore 14 describes pioneering British work on explosive shaped charges that influenced von Neumann, Neddermeyer, and Tuck's HE lens design. Indeed, it was new to me that both types of explosives used in the Trinity explosive lens system--"Comp B" (a mixture of RDX and TNT) and

Baratol--had their origins in earlier British defense research on HE formulation. Morgan's paper 15 describes the Jumbo steel vessel designed, if the Trinity test should have failed, to contain the Trinity gadget and conventional explosion and allow recovery of the precious plutonium. In the end, Jumbo was not used for Trinity, but the experience gained was valuable for later containmentvessel work and reactor engineering.

Plutonium materials & metallurgy. Martz, Freibert, and Clark 16 trace the exciting process through which the new element plutonium was discovered in 1940 at University of California-Berkeley. The first plutonium was characterized there and at the Chicago's Metallurgical Laboratory, before US research efforts were consolidated at Los Alamos in 1943. Particularly interesting is the early confusion caused by the widely varying density measurements and the subsequent discovery of the many complex phases of plutonium. This work collects the historical records and reconstructs the history of the rapidly advancing field of plutonium metallurgy and chemistry. The authors show that the idea of using gallium as an alloying agent to stabilize the malleable δ-phase of plutonium was first raised only a few months before the Trinity test, a reflection of the intense pace of the project. They also describe postwar work on the world's first fast reactor, Clementine, which operated in a canyon, no less, at Los Alamos. Another paper by Crockett and Freibert 17 describes the rapid wartime expansion of experimental and theoretical work on the equation of state (EOS). They describe the foundational EOS research needed to understand the hydrodynamic behavior of plutonium, uranium, and other materials. Los Alamos remains the DOE's center of excellence for plutonium research, signified in a joint effort with the NNSA and AWE by the sevenvolume Plutonium Handbook, 18 published by the ANS in 2019. The wartime plutonium work, unlike the other areas described above, did not benefit from earlier British research, except . . . Los Alamos's leading metallurgist, Cyril Stanley Smith, was a naturalized US citizen who had emigrated from England! Nuclear energy and yield. Hanson and Oldham 19 review the foundational radiochemistry methods developed to measure the yield of Trinity and how the techniques evolved in subsequent years. Mercer et al. 20 describe recent measurements of radionuclides in trinitite rock from Alamogordo. Their paper describes both traditional radiation-detection methods that are used in the training of IAEA inspectors at Los Alamos as well as the novel decay energy spectroscopy method.

In the years following the war, a yield of 21 kilotons (kt) for Trinity was announced by the DOE. This was higher than many of the Los Alamos scientists had orig-inally expected--the Fat Man "gadget" overperformed. Now, Selby et al.'s paper 21 shares our latest assessment that Trinity's yield was higher still, 24.8±2 kt. The new value comes from advances in precision mass spectrometry and related calculational methods that allow us to reanalyze the 75-year-old debris, measuring the stable nuclides into which the original radionuclides have decayed. Other papers examine early prompt assessments of Trinity's yield: Katz 22 seeks to understand how Fermi might have determined the yield when he observed the blast wave's impact on small pieces of falling paper; Baty and Ramsey 23 revisit G. I. Taylor's determination of the yield from the growth of the fireball. Using Lie group symmetry techniques, they rederive Taylor's two-fifths law relating a blast wave's position, time, and explosive energy.

During the Manhattan Project, Bethe and Feynman developed an analytic formula to predict the yield of a fission explosion from some elegant considerations. This work has had an enduring influence over the past 75 years; our classified research journal on Trinity has no fewer than five papers on different aspects of the formula--three from Los Alamos, one from Livermore, and one from AWE. A short paper by Lestone and Rosen (Livermore) 24 describes, for the first time, the formula and its relationship to earlier wartime British work by Frisch and Peierls and by Pryce and Dirac. (Wigner, who was Dirac's brother-in-law, said that "Feynman is a second Dirac, only this time human" 25 !).

Technical history. This special issue includes a number of technical history papers, including those mentioned above on the beginnings of computing. Another 26 discusses the origins of the nuclear-core design for the Trinity implosion and presents details of the invention patent by Christy and Peierls that is held in our NSRC archives, resolving longstanding disputes regarding who originated the idea (it was Christy). Moore gives 27 an introduction to Peierls' fascinating 1945 summary of the British contributions to the "Tube Alloys" project, the codename for the British work before it transferred to Los Alamos in 1943-1944. The author provides Peierls' summary in full--with Sir James Chadwick's marginal notes. Moore's useful introduction and footnotes shine light on the activities of the time and the progress by the British researchers toward establishing the feasibility of an atomic bomb.

Trinity and its impacts. I will end where we will begin. The first paper in our special issue is by Carr, 28 our Laboratory historian. He gives an overview of the Trinity test and its impact, explains why Oppenheimer chose the name, and provides additional context for the papers that follow. Carr also includes information from our NSRC archives related to the effects of the fallout from the test; also see the useful 2020 special issue in Health Physics 29 published by the National Cancer Institute (NCI). The NCI study was mandated by Congress and took seven years to complete, producing six impressive peer-reviewed articles.

Our goal for this collection of papers is that they reflect Robert Wilson's 1947 words in Los Alamos report LA-1009: "The work reported was for a specific military purpose. It will be gratifying to all those who participated in the work when it takes its more proper place as a contribution to the general structure of scientific knowledge." I can speak for all the authors when I say that we had fun writing these papers and that we learned many new things in the process, and I trust that this collection is indeed a contribution to both the history of science and to the advancement of science. It is clear how innovations in nuclear science and technology continue to benefit from cross-fertilization between national securitydriven and civilian programs. Furthermore, it is evident that foreign-born scientists have contributed substantially to US research advances. staff who played an exceptional role in writing numerous articles and in providing extensive valuable "internal" review feedback to our authors: Bill Archer and Craig Carmer (Los Alamos); Mordy Rosen (Livermore); Richard Moore and Peter Adsley (AWE); and Jonathan Katz (Washington University and Los Alamos). Furthermore, Critical Assembly, the excellent book on the Manhattan Project, written by Los Alamos historians in the early 1990s, 30 provided an important foundation for our research, and usefully identifies primary source archival material held in our National Security Research Center (NSRC). I am also grateful to Tom Kunkle who provided pointers to many valuable historical documents for our project. A paper that Kunkle is presently writing describes the German origins of implosion concepts, starting around 1940 and including the role of Guderley's 1942 hydrodynamics paper. Kunkle addresses the extent to which it was known or commissioned by Schumann for wartime German atomic energy research, and indeed whether any of this was known by US Manhattan Project researchers at the time as Lowell Wood has suggested 31 --stay tuned! This work was supported by the US Department of Energy through the Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the NNSA of the US DOE under Contract No. 89233218CNA000001.

The Science of Trinity

Trinity and the British Mission movie

The Treachery and Pursuit of the Most Dangerous Spy in History

Notes of the Interim Committee Meeting, Thursday

Nuclear Science Advances the Manhattan Project & Comparison to Today's ENDF Understanding

Criticality Experiments with Fast 25 and 49 Metal and Hydride Systems During the Manhattan Project

Critical Assemblies: Dragon Burst Assembly & Solution Assemblies

The History of Modern Monte Carlo for Neutronics

Canadian Contributions to the Manhattan Project and Early Nuclear Research

On the Origins of Lagrangian Hydrodynamic Methods

Trinity by the Numbers: The Computing Effort that Made Trinity Possible

The Los Alamos Computing Facility During the Manhattan Project

The Trinity High Explosive Implosion System: The Foundation for Precision Explosive Applications

Munroe Jets and the Trinity Gadget

The Origins of Blast Loaded Vessels

The Taming of Plutonium: Pu Metallurgy and the Manhattan Project

Equation of State: Manhattan Project Developments and Beyond

Weapons Radiochemistry: Trinity and Beyond

Gamma and Decay Energy Spectroscopy Measurements of Trinitite

A New Yield Assessment for the Trinity Nuclear Test, 75 Years Later

Fermi at Trinity

On the Symmetry of Blast Waves

Comparison between historic nuclear explosion yield formulas

The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom, Basic Books

Who Invented the Trinity Nuclear Test's Christy Gadget?: Patents and Evidence from the Archives

Outline of the Development of the British Tube Alloy Project

Thirty Minutes Before Dawn: The Story of Trinity

US National Cancer Institute: Cancer Risk Projection Study for the Trinity Nuclear Test-Community Summary

Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years