Preparing for ENDF/B-VIII

. Although the next major release of the ENDF/B library is not due until the 2017–2018 time frame, ENDF/B-VIII is already positioned to become the most important release of the library in some time. ENDF/B-VIII will be built around the Neutron Reaction Standards as well as the 1 H, 16 O, 56 Fe, 235 U, 238 U and 239 Pu evaluations developed as part of the Coordinated International Evaluation Library Organization (CIELO) pilot project. In this contribution, we summarize these improvements as well as the many other improvements to ENDF that have already been made or are scheduled to be made in the next year. Improvements already included in the ENDF/B-VIII beta releases: ﬂexible and physically LRF=7 resolved resonance 12 updated evaluations Thermal capture EGAF , Thermal Scattering Law evaluations from NCSU ( α and β phase SiO 2 , SiC, lucite, BeO, and polyethylene) and from the CAB-CNL collaboration (heavy and light water) (cid:127) Many new evaluations in the neutron sublibrary (n, 12 , 13 C, 40 Ar, 54 , 57 , 58 Fe, 58 , 59 , 60 , 61 , 62 , 64 Ni, 63 , 65 Cu, 73 As, Sn, m 1 Np) (cid:127) of Red Cullen’s EPICS2014 library, updating the photo-atomic, electron and atomic-relaxation sublibraries. Many are the year including new evaluations such as charged particle evaluations translated from LLNL’s ECPL. In addition to these major changes, ENDF/B-VIII will be the ﬁrst ofﬁcial library released simultaneously in the legacy ENDF-6 and the newly developed Generalized Nuclear Data (GND) formats.


Status of ENDF/B-VIII
ENDF/B is the United States' most important data library for nuclear applications and is used in nearly all particle transport codes. As a result, ENDF/B-VII.1 (the previous release, published in 2010), contained 423 evaluations in the neutron sublibrary and has been cited in literature 913 times as of September 2016 [1]. The last major release, ENDF/B-VII.0, was cited an astounding 1469 times [2]. With this history, the Cross Section Evaluation Working Group (CSEWG) is preparing another major release: ENDF/B-VIII. The core of this library are the CIELO evaluations [3] described below as well as the host of other improvements and additions also listed below.
We have made three ENDF/B-VIII beta releases before ND2016, the last in August 2016. With each release, the library has improved dramatically. We anticipate several more beta releases before the end of 2017.
The complete list of changes and additions are available at the NNDC GForge site (https://ndclx4.bnl. gov/gf/project/endf). The β2 release is available at https://ndclx4.bnl.gov/gf/project/endf/ scmsvn/?action=browse&path=%2Ftags%2FENDF-B-VIII.beta2%2F for the subversion repository and https://ndclx4.bnl.gov/gf/project/endf/frs/ for tarballs of the data. a e-mail: dbrown@bnl.gov In this contribution, we will highlight some of the major features in ENDF/B-VIII and direct readers to some of the other CSEWG contributions to this conference.

Neutron standards and CIELO evaluations
Every major release of the ENDF/B library coincides with new releases of the Neutron Standards evaluations and ENDF/B-VIII is no exception. The Neutron Standards Project is a long standing IAEA Nuclear Data Section Data Development Project to develop reference neutron cross sections. The new Neutron Standards evaluations will be detailed in A. Carlson contribution R181: "A new evaluation of the neutron data standards".
With the long-term success of the Standards project the CIELO pilot project was created in order to deliver standards-quality full evaluations to the data community for inclusion in regional libraries such as ENDF/B. Given the significant contribution of US based scientists to CIELO, it is no surprise that CSEWG has chosen to include CIELO evaluations in ENDF/B-VIII. The CIELO project is described in M. Chadwick's plenary talk (PL499) and different aspects of the CIELO project from CSEWG members are presented in a series of other contributions to this conference: S100: R. Capote "New fit of neutron thermal constants for 233,235 U, 239,241 Pu and 252 Cf: microscopic

Non-CIELO evaluations
Clearly ENDF/B-VIII is more than the Standards and CIELO evaluations. In the three beta releases so far CSEWG has added/updated many evaluations to the  Fig. 1. In addition, primary gammas from EGAF were added to 6,7 Li, 11 B, 23 Na, 27 Al, 28 Si, and 35,37 Cl. As neutrons are moderated to lower energies, scattering eventually can not be described by neutrons interacting with single nuclei. Instead neutrons scatter off macroscopic collections of nuclei so one uses the thermal neutron scattering sublibrary. A. Hawari's group at North Carolina State University has been especially prolific at developing thermal neutron scattering evaluations, having evaluated polyethylene, lucite, BeO (OinBeO and BeinBeO), SiC (SiinSiC and CinSiC), and α and β phases of SiO 2 , as discussed in Hawari's contribution I069. Plots of the polyethylene evaluation are shown in Fig. 2. Additionally, a collaboration between Canadian National Laboratory and Centro Atómico Bariloche (Argentina) has developed evaluations for light and heavy water as described in contribution I060 by J.I. Marquez Damian.
CSEWG has adopted the electro/photo-atomic and atomic-relaxation data from D.E. Cullen's EPICS2014 library [7] and added beta branchings to 24 isotopes in the decay sublibrary.

Theoretical and methodological developments
The push to develop standards level evaluations for CIELO has led CSEWG to adapt and improve models used in evaluations and the evaluation methodology. Contribution S503 from T. Kawano describes an inter-comparison of Hauser-Feshbach model codes aimed at better actinide evaluations. In addition to this comparison, there have been efforts to include the Englebrecht-Weidenmueller transformation [8] in reaction models and to tighten the connections between Hauser Feshbach and R-matrix approaches: I329: T. Kawano: "Advances in nuclear reaction calculations by incorporating information from nuclear mean-field theories" R183: D. Brown: "An analytic approach to probability tables for the unresolved resonance region". In addition to the improvements to the fast region modeling, there have been advances in R-matrix codes: S354: M. Pigni "Early Applications of the R-matrix SAMMY Code for Charged-particle Induced Reactions" R259: Limited inclusion of integral data into evaluation process Vladimir Sobes "Application Of The SAMINT Methodology To The New Cross-Section Evaluations of 63 Cu and 65 Cu".  [5]. In the upper right hand panel, we compare the total scattering, inelastic scattering and the incoherent elastic scattering cross sections. In the lower left panel, we show the total scattering cross section compared the data taken from EXFOR [4]. In the lower right panel, we show the incoherent elastic cross section compared to the data from EXFOR [4]. This figure taken from Ref. [6].

Testing and quality assurance
The improvements and additions to ENDF/B are only useful if there a rigorous quality assurance program to ensure the correctness and usability of the data. CSEWG has traditionally adopted a Phase I/II system where Phase I testing ensures the basic format and physics correctness of evaluations and Phase II testing involves testing the new evaluations in integral benchmarks. Nowadays, the entire Phase I testing has been automated using the ADVANCE continuous integration system. ADVANCE runs each evaluation through a battery of tests and through the PREPRO, NJOY and FUDGE processing codes to ensure that users can process the data (see the screenshot in Fig. 3). ADVANCE has recently been adapted to include a new version of the INTER code (see the screenshot in Fig. 4) and we are in the process of adding automated benchmarking to assist at Phase II testing. Complete ADVANCE build reports are available at http://www.nndc.bnl.gov/endf/b7.dev/qa/index. html.
After the testing in ADVANCE, the ENDF files undergo rigorous Phase II testing. In this conference, several contributions describe the results of integral benchmark testing of ENDF/B-VIII beta releases:

About CSEWG
The ENDF/B library is the main product of the Cross Section Evaluation Working Group (CSEWG). CSEWG is a long running yet very informal collaboration now in its 50 th year. CSEWG encourages collaboration with experimentalists, theorists, evaluators, data testers and data testers worldwide as evidenced by the graphic in Fig. 5.