“A CSEWG Retrospective” 35th Anniversary Cross Section Evaluation Working Group November 5, 2001 National Nuclear Data Center Brookhaven National Laboratory Table of Contents Monday, November 5, 2001 Berkner Hall, Room B Time Title Author Page # 1:30 Introduction Charles Dunford 1 1:40 A Short History of Nuclear Data and Its Evaluation Norman Holden 3 2:00 A Worm's-Eye View of Pre-SEWG Cecil Lubitz* 2:10 Cross Section Evaluation Working Group History Sol Pearlstein 17 2:30 Memories of CSEWG: 1966 - 1968 Harry Alter 27 2:40 Some CSEWG Recollections Charles Dunford 29 3:00 Break 3:30 Cross Section Evaluation Working Group Physics Sol Pearlstein 41 3:50 Channel Spin in ENDF Cecil Lubitz* 4:10 The ENDF Standards Allan Carlson 47 4:25 The Covariance Files of ENDF/B Doug Muir 63 4:50 Progression of ENDF/B-VI: 1990 to 2001 Phil Young 71 5:15 Conclusion Appendix A: Summary of CSEWG Members, Committees, Meetings A-1 *Paper not included in this document Introduction This publication has been prepared to record some of the history of the Cross Section Evaluation Working Group (CSEWG). CSEWG is responsible for creating the evaluated nuclear data file (ENDF/B) which is widely used by scientists and engineers who are involved in the development and maintenance of applied nuclear technologies. This organization has become the model for the development of nuclear data libraries throughout the world. The data format (ENDF) has been adopted as the international standard. On November 5, 2001, a symposium was held at Brookhaven National Laboratory to celebrate the 50th meeting of the CSEWG organization and the 35th anniversary of its first meeting in November 1966. The papers presented in this volume were prepared by present and former CSEWG members for presentation at the November 2001 symposium. All but two of the presentations are included. I have included an appendix to list all of the CSEWG members and their affiliations, which has been compiled from the minutes of each of the CSEWG meetings. Minutes exist for all meetings except the 4th meeting held in January 1968. The list includes 348 individuals from 71 organizations. The dates for each of the 50 CSEWG meetings are listed. The committee structure and chairmen of all committees and subcommittees are also included in the appendix. This volume is dedicated to three individuals whose foresight and talents made CSEWG possible and successful. They are Henry Honeck who lead the effort to develop the ENDF format and the CSEWG system, Ira Zartman, the Atomic Energy Commission program manager who provided the programmatic direction and support, and Sol Pearlstein who led the development of the CESWG organization and the ENDF/B evaluated nuclear data library. Charles Dunford Brookhaven National Laboratory November 12, 2002 1 2 Prepared for the 51st Meeting of the USDOE Cross Section Evaluation Working Group at BNL November 5-7, 2001 A Short History of Nuclear Data and Its Evaluation Norman E. Holden* Brookhaven National Laboratory Upton, New York 11973-5000 ABSTRACT This paper reviews both neutron and non-neutron nuclear data over the past century, especially those data of relevance to the USDOE (formerly the USAEC) Cross Section Evaluation Working Group, CSEWG. Among the topics whose history will be examined are neutron cross sections, charged particle cross sections, neutron resonance integrals and neutron fission product yields. Other topics discussed include isotopic composition of the elements, nuclear spins and parities, radioactive half-lives, nuclear magnetic dipole moments and electrical quadrupole moments, alpha particle energies and intensitites, beta-ray energies and intensities and gamma-ray energies and intensities. The status of automation of these parameters into data files will briefly be discussed. INTRODUCTION In 1966, the Division of Reactor Development and Technology (DRDT) of the United States Atomic Energy Commission (USAEC) was concerned about the problems involved in the evaluation and processing of nuclear data for reactor calculations. The DRDT’s plan for the development of the necessary methods for the processing of the data and for obtaining data for immediate use in reactor calculations involved a long range goal of developing automated methods for processing nuclear data, as well as a short range goal of providing reactor designers with a reference set of data that they could use for their current projects. For the short term goal of obtaining a reference set of nuclear data, the DRDT sponsored the Cross Section Evaluation Working Group (CSEWG), a co-operative evaluation effort aimed at providing reactor designers with a good set of evaluated nuclear data. The proposed long range goal was to be addressed by CSEWG over time. Although the initial effort focused on neutron cross section data primarily, over time, CSEWG added other categories of nuclear data to their automated files of information. *This research was carried out under the auspices of the US Department of Energy, Contract Number DE-AC02-98CH10886 3 This paper will review the status of the evaluation of nuclear data beginning with the time that radioactivity was first discovered and nuclear data first became available in the late nineteenth century. It will conclude with the time that CSEWG began operation and held its first meeting at the Brookhaven National Laboratory’s (BNL’s) Cross Section Evaluation Center on June 9th and 10th, 1966. An overal general history of various categories of nuclear data will be followed by a review of the evaluations of specific types of data. PRE-HISTORY Our history of nuclear data begins at the end of the nineteenth century with the discovery of uranium rays (radioactivity) in February 1896 by Henri Becquerel1. The early part of that century saw the proposal of the atomic theory of matter and the concepts of atomic weights of the elements by John Dalton2. Later in the century, Lothar Meyer and Dmitri Mendeleev studied the physical and chemical properties of the chemical elements, respectively, and by using these properties, they arranged the atomic weights of the then known chemical elements in a periodic fashion, the so-called Periodic Table3. Toward the end of the nineteenth century, Issac Newton’s laws explained the behavior of both objects in motion and of gravity. From the work of James Clerk Maxwell and Heinrich Hertz, it was known that light, electricity and magnetism are interrelated and they were explained by a few simple equations. Everything was thought to be under control. Physicists thought that they had matters in hand. The first American Nobel Prize winner, Albert A. Michelson, in an 1894 speech at the University of Chicago, lamented that “the most important fundamental laws and facts of physical science have all been discovered. These are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote. Our future discoveries must be looked for in the sixth place of decimals.” Within three years of this speech, x-rays were discovered, the electron was discovered and radioactivity was discovered. THE NUCLEAR PROCESS BEGINS Nuclear data began with the discovery of so-called uranic rays by Becquerel and with the work of Marie and Pierre Curie, who tried to determine whether other substances besides uranium also emitted these rays (Marie Curie was the first to refer to this phenomenon as radioactivity4). The understanding of radioactivity was aided by the work of the New Zealand physicist, Ernest Rutherford, and the English chemist, Frederick Soddy on the atomic transformation law, for which Rutherford received the Nobel Prize in Chemistry. This award prompted Rutherford to quip that the quickest transformation he had ever witnessed was his change from physicist to chemist5. The radioactive decay rate was found to be proportional to the number of atoms which were undergoing decay. Mathematically, this led to an exponential form for the decay and to a characteristic decay constant (reciprocal life-time or half-life) associated with each radiation energy. 4 Although data was to be found in the early publications of the Curies and Rutherford, the first major review of these radioactive data was published in 1931 by the International Standards Radium Commission6 and contained tables of the lifetimes and the radiation energies of the natural radio isotopes. This report was published simultaneously in four other journals around the world; Phys. Zeitschr., J. Am. Chem. Soc., Phil. Mag. and J. Phys. Radium. In this age of radioactivity at the beginning of the century, many radioactive substances were being found with various atomic weight values. In 1911, Frederick Soddy used his displacement law for α-particle decay (reduce the atomic mass number by four and the atomic charge by two) and β transitions (no mass change and increase the charge by one) to show the chemical identity of meso-thorium (228Ra) and radium (226Ra)7. In 1913, he concluded that there were chemical elements with different radioactive properties and different atomic weights but with the same chemical properties, so they occupied the same position in the Periodic Table. He coined the word “isotope” (Greek for in the same place) to account for these radioactive species8. In 1897, the English physicist, J. J. Thomson, discovered the electron9. In 1912, he studied the rare gas neon by sending electrons through neon gas, creating neon ions, which he accelerated toward his detector (a photographic plate10). Using electric and magnetic fields operating at right angles to each other to deflect these ions, Thomson found darkening at two separate locations on the photographic plate, corresponding to positions for the 20Ne ion and for the 22Ne ion. Relative intensity of darkening on the photographic plate was 90% and 10%, respectively, for the two ion beams. Given that the atomic weight is equal to the average mass of the element, this could now account for neon’s non-integral atomic weight value of 20.2.