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Using NJOY to Create MCNP ACE Files and Visualize Nuclear Data

Date:Monday September 08, 2025 through Friday September 12, 2025
Time:10:00 Monday to 12:00 Friday (US Mountain Time); only AM session on Friday
Place:Los Alamos, NM, USA
Maximum Enrollment:12
Minimum Enrollment:8
Prerequisites:Class attendees are expected to have some experience with the MCNP code.
Cost:$1800

Other key dates:

  • June 20, 2025, non-US citizen registration deadline.
  • August 11, 2025, class go / no-go determination and refundable withdrawal deadline.
  • August 25, 2025, late-registration deadline.

See Other Details below for more information on these dates.

Table of Contents

Summary

This class will introduce participants to the Evaluated Nuclear Data File (ENDF) format and the NJOY Nuclear Data Processing System that can be used to produce nuclear data application libraries from it.

Time will be available to discuss NJOY capabilities that are of interest to class participants.

The class will be based on version 6.2 or later on the MCNP code and the current version of the NJOY code, NJOY2016, available here.

Topics include:

  • Introduction to ENDF.
  • History of NJOY.
  • How to obtain the code package and update the source code to create a new executable.
  • Create input decks and examine the associated output from the basic components of NJOY required to produce MCNP continuous energy neutron ACE files and MCNP thermal scattering ACE files.
  • Create input decks for NJOY's PLOTR & VIEWR modules to visualize cross sections and their ratios, scattering angular distributions, & secondary spectra.
  • Run MCNP with newly processed data.
  • Create multigroup data files using NJOYs GROUPR module.
  • Convert incident neutron nuclear data files in the ENDF format into MCNP continuous energy (.c) ACE files.
  • Plotting nuclear data using NJOY.
  • Convert ENDF formatted thermal scattering law files into MCNP (.t) ACE files.
  • Utilize newly processed data in MCNP.
  • Processing nuclear data into multigroup data files.

    • Please address all correspondence regarding this class to the MCNP Registrar.

    Click to Register For This Class

    Next Steps after Registering

    Your registration is not complete until the following documents have been submitted to the MCNP Registrar. Everyone must:

    1. Submit proof of an MCNP license.
      • For those who received access to the MCNP code from RSICC, submit either:
        • RSICC Single-User Software License / Software Export Control Agreement (SECA) PDF (example, preferred), or
        • RSICC request history (example). An email with this history is automatically sent to you after authenticating with the RSICC Order History webpage and verifying contact information.
      • For those who received access to the MCNP code directly from LANL: submit the fully approved software-distribution form you received when access was granted.
    2. Submit a completed MCNP class request form.
      • A frequently asked question is "Why do I have to fill out this form when I just registered?" Unfortunately, the processes that need to be followed to admit students to MCNP classes require these two sets of data to be submitted, processed, and kept separately. We apologize for the inconvenience.

    In addition, all non-US citizens must:

    1. Submit image(s) of identification document(s) in the form of either:
      • Official government identification card (acceptable for online classes), or
      • Passport name/photo pages and any applicable visa(s) (required for in-person classes) or
      • US Permanent Resident card (i.e., the USCIS I-551 form also known as a "green card"), if applicable. Submit images of front and back.
    2. Submit detailed résumé or curriculum vitae with the following details (download an example Microsoft Word document):
      • Company/school name, location (city/country), position held, and dates of employment (start and end month/year).
      • The employment and education from the time of turning 18 years old must be accounted for with no gaps.
    3. Clearly indicate all citizenships when asked about citizenship. If born in a country not listed in 10 CFR 810, then evidence of non-citizenship and/or renunciation of birth-country citizenship must be provided.

    Before the class starts, all participants:

    • Must obtain and install the MCNP6 code.
      • The executable version is sufficient for class purposes. Directions to request the code from RSICC can be found here. Note that LANL employees follow a different process to acquire access to the MCNP code.
    • Must submit registration fee promptly upon notification.

    Payment Options

    The class fee includes a collection of files with all class slides (over 600), handouts, and other reference material.

    There are four payment options, with credit card being the preferred option. Details about each method follows.

    1. Credit card (preferred)
      • Visa, MasterCard, or Discover Card are accepted for payment.
      • Please pay at: https://about.lanl.gov/lanl-resources/payments-to-the-lab and select MCNP Training from the dropdown menu.
      • Payment Description: Class title and date. If another individual will be making payment on your behalf, please have them include your name in this field.
    2. Check
      • Please make out your check (US dollars only) payable to: Los Alamos National Laboratory/UT32
      • Make sure your name appears on accompanying documentation with the check.
      • Mail the check to:
        Cashiers
        Los Alamos National Laboratory
        P.O. Box 1663, MS P231 Los Alamos, NM 87544 USA
    3. Wire transfer
      • Please email the MCNP Registrar with a request for wire transfer bank information.
    4. Internal cost code (LANL employees must use this)
      • Please email the MCNP Registrar and provide a complete cost code and organizational code.

    Other Details

    Minimum Class Enrollment

    There is a minimum number of participants required for each class to be held. Registered class participants will receive an email no later than four weeks before the class start date (by August 11, 2025) notifying them if a class is cancelled because of low enrollment.

    Refunds

    If the class is cancelled because of low enrollment, participants may request a refund of any registration fees paid or may request that the fee already paid be credited towards their attendance at a future class.

    If you cannot attend the class for another reason and cancel your registration less than four weeks in advance (after August 11, 2025), we will be unable to refund any registration fee paid. However, the fee may be applied towards attendance at a future class. Alternatively, another person from your organization may attend in your place, depending on the citizenship of that individual. Contact the MCNP Registrar for further information.

    Last-minute Registrations

    Registrations received within two weeks prior to the start of a class (after August 25, 2025) may be accepted on a space-available basis and depending on the citizenship of the person registering.

    Non-US Citizens

    Registration requests for non-US citizens who are citizens of a country listed in US Regulation 10 CFR 810 are processed by the LANL Foreign Visits Office. This security approval processing is based on requirements issued from the US Department of Energy. The processing normally takes at least 60 days. You must register and provide all requested information by June 20, 2025. Although we can never guarantee that a security approval will be received, we will make every attempt to obtain an answer for your attendance request as soon as possible.

    Registration requests for non-US citizens who are citizens of or reside in a country not listed as a Generally Authorized Destination in US Regulation 10 CFR 810 cannot be processed by LANL and will be submitted directly to the Department of Energy.

    For a list of 10 CFR 810 countries, please go to the Electronic Code of Federal Regulations, 10 CFR 810.

    Pre-class Information

    Students who are fully registered and have confirmed payment for the class are ready to attend. This webpage lists the details needed to attend.

    However, prior to arrival the student must accomplish two critical steps with the computer he or she will use for the class:

    1. Install and test MCNP6.2 or MCNP6.3.
    2. Download the class materials (presentations, example input files, etc.).
      • A download link for a ZIP file containing class materials will be provided to registered and fully paid attendees the week, typically the Thursday, before the class.
      • The download is approximately 500 MB and should be fully extracted for use.

    Visiting Los Alamos

    The elevation of Los Alamos is approximately 7,500 ft (2,300 m). The air is thin and dry, so it is easy to become short of breath when ascending hills, stairs, etc. if not acclimated to this elevation. Remaining well hydrated is recommended.

    There is abundant wildlife in Los Alamos and throughout New Mexico. Please be particularly cautious while driving at night. Further, please be alert to the presence of bears, rattlesnakes, bobcats, mountain lions, and other potentially dangerous wildlife.

    Other information about visiting and enjoying Los Alamos is available through this website.

    Arriving

    Visitors to Los Alamos National Laboratory (LANL) usually fly into either Santa Fe Regional Airport (SAF) or Albuquerque International Airport (ABQ).

    Google Maps-based driving directions from each are:

    Other LANL-focused arrival information is available here.

    When arriving at Los Alamos National Laboratory, all vehicles pass through a vehicle access portal (VAP) where drivers will need to present current photo identification such as a state-issued driver's license or LANL-issued badge. Note that the VAPs on the Pajarito corridor require a LANL-issued badge.

    All visitors must obtain a badge as the first part of their visit. Identification requirements as of October 2024 are listed here. There are currently two LANL badge offices in Los Alamos. Before arriving, a badge office appointment will be made and the location that must be visited will be communicated. The two badge offices are:

    Badging questions can be answered by calling 505-667-6901.

    There are a variety of prohibited articles on LANL property that include: weapons such as pepper sprays, firearms, explosives, and knives with blade lengths greater than 2.5 inches (except for those used in food preparation), alcoholic beverages, illegal drugs and associated paraphernalia, drones or other unmanned aerial vehicles, and other items prohibited by local, state or federal law.

    In addition, while cameras are not prohibited, photography on LANL property is not permitted. This includes pictures and selfies taken with a cell phone or portable electronic device.

    Hotels

    Several of the hotels that serve Los Alamos are:

    Dining

    Dining information is available through the Los Alamos Chamber of Commerce with a downloadable summary here.