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Variance Reduction with MCNP6

Date:Monday December 02, 2024 through Friday December 06, 2024
Time:10:00 Monday to 12:00 Friday (US Mountain Time)
Place:Los Alamos, NM, USA
Maximum Enrollment:12
Minimum Enrollment:8
Prerequisites:This is an intermediate- to advanced-level class intended for users who have some familiarity with MCNP6 and understanding of variance-reduction techniques such as that gained through attending the Introduction to MCNP6 class.

Other key dates:

  • September 13, 2024, non-US citizen registration deadline.
  • November 04, 2024, class go / no-go determination and refundable withdrawal deadline.
  • November 18, 2024, late-registration deadline.

See Other Details below for more information on these dates.


This class focuses on applying variance-reduction techniques in MCNP6 fixed-source calculations. Class examples provide experience running the MCNP6 code, understanding particle behavior through code output, and applying/tuning variance-reduction techniques.

The class includes lectures and hands-on computer use for a variety of variance reduction calculations. Time will be available to discuss individual questions and problems with the MCNP developers, and to pursue additional variance reduction topics.

The class will be based on version 6.2 or later on the MCNP code.

Topics include:

  • Brief review of particle transport, tallying, and statistics
  • Sampling, biasing, and statistical convergence
  • Understanding particle state with event logs
  • Implicit capture & weight rouletting review
  • Geometry-based importance splitting & rouletting review
  • Source biasing
  • Weight windows, and ways to generate them
  • Point detectors and DXTRAN
  • Forced collisions
  • Exponential transform
  • Please address all correspondence regarding this class to the MCNP Registrar.

    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 license 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:
        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 November 04, 2024) notifying them if a class is cancelled because of low enrollment.


    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 November 04, 2024), 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 November 18, 2024) 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 September 13, 2024. 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.


    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 August 2023 are listed here. The LANL badge office (and the MCNP classroom) are located in the

    Otowi building on Casa Grande Drive.
    The hours are currently 0700–1530 MDT and 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.


    Several of the hotels that serve Los Alamos are:


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