Optimizing the implementation of the target motion sampling temperature treatment technique: How fast can it get?

Tuomas Viitanen, Jaakko Leppänen

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    1 Citation (Scopus)

    Abstract

    This article discusses the optimization of the target motion sampling (TMS) temperature treatment method, previously implemented in the Monte Carlo reactor physics code Serpent 2. The TMS method was introduced in [1] and first practical results were presented at the PHYSOR 2012 conference [2]. The method is a stochastic method for taking the effect of thermal motion into account on-the-fly in a Monte Carlo neutron transport calculation. It is based on sampling the target velocities at collision sites and then utilizing the 0 K cross sections at target-at-rest frame for reaction sampling. The fact that the total cross section becomes a distributed quantity is handled using rejection sampling techniques. The original implementation of the TMS requires 2.0 times more CPU time in a PWR pin-cell case than a conventional Monte Carlo calculation relying on pre-broadened effective cross sections. In a HTGR case examined in this paper the overhead factor is as high as 3.6. By first changing from a multi-group to a continuous-energy implementation and then fine-tuning a parameter affecting the conservativity of the majorant cross section, it is possible to decrease the overhead factors to 1.4 and 2.3, respectively. Preliminary calculations are also made using a new and yet incomplete optimization method in which the temperature of the basis cross section is increased above 0 K. It seems that with the new approach it may be possible to decrease the factors even as low as 1.06 and 1.33, respectively, but its functionality has not yet been proven. Therefore, these performance measures should be considered preliminary.
    Original languageEnglish
    Title of host publicationProceedings
    Subtitle of host publicationInternational Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013
    Pages950-961
    Publication statusPublished - 2013
    MoE publication typeNot Eligible
    EventInternational Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2013 - Sun Valley, ID, United States
    Duration: 5 May 20139 May 2013

    Conference

    ConferenceInternational Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2013
    Abbreviated titleM&C 2013
    CountryUnited States
    CitySun Valley, ID
    Period5/05/139/05/13

    Fingerprint

    Sampling
    Temperature
    Program processors
    Neutrons
    Physics
    Tuning

    Keywords

    • doppler
    • Monte Carlo
    • neutron tracking
    • on-the-fly
    • tempereature

    Cite this

    Viitanen, T., & Leppänen, J. (2013). Optimizing the implementation of the target motion sampling temperature treatment technique: How fast can it get? In Proceedings: International Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013 (pp. 950-961)
    Viitanen, Tuomas ; Leppänen, Jaakko. / Optimizing the implementation of the target motion sampling temperature treatment technique : How fast can it get?. Proceedings: International Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013. 2013. pp. 950-961
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    Viitanen, T & Leppänen, J 2013, Optimizing the implementation of the target motion sampling temperature treatment technique: How fast can it get? in Proceedings: International Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013. pp. 950-961, International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2013, Sun Valley, ID, United States, 5/05/13.

    Optimizing the implementation of the target motion sampling temperature treatment technique : How fast can it get? / Viitanen, Tuomas; Leppänen, Jaakko.

    Proceedings: International Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013. 2013. p. 950-961.

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

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    T1 - Optimizing the implementation of the target motion sampling temperature treatment technique

    T2 - How fast can it get?

    AU - Viitanen, Tuomas

    AU - Leppänen, Jaakko

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    N2 - This article discusses the optimization of the target motion sampling (TMS) temperature treatment method, previously implemented in the Monte Carlo reactor physics code Serpent 2. The TMS method was introduced in [1] and first practical results were presented at the PHYSOR 2012 conference [2]. The method is a stochastic method for taking the effect of thermal motion into account on-the-fly in a Monte Carlo neutron transport calculation. It is based on sampling the target velocities at collision sites and then utilizing the 0 K cross sections at target-at-rest frame for reaction sampling. The fact that the total cross section becomes a distributed quantity is handled using rejection sampling techniques. The original implementation of the TMS requires 2.0 times more CPU time in a PWR pin-cell case than a conventional Monte Carlo calculation relying on pre-broadened effective cross sections. In a HTGR case examined in this paper the overhead factor is as high as 3.6. By first changing from a multi-group to a continuous-energy implementation and then fine-tuning a parameter affecting the conservativity of the majorant cross section, it is possible to decrease the overhead factors to 1.4 and 2.3, respectively. Preliminary calculations are also made using a new and yet incomplete optimization method in which the temperature of the basis cross section is increased above 0 K. It seems that with the new approach it may be possible to decrease the factors even as low as 1.06 and 1.33, respectively, but its functionality has not yet been proven. Therefore, these performance measures should be considered preliminary.

    AB - This article discusses the optimization of the target motion sampling (TMS) temperature treatment method, previously implemented in the Monte Carlo reactor physics code Serpent 2. The TMS method was introduced in [1] and first practical results were presented at the PHYSOR 2012 conference [2]. The method is a stochastic method for taking the effect of thermal motion into account on-the-fly in a Monte Carlo neutron transport calculation. It is based on sampling the target velocities at collision sites and then utilizing the 0 K cross sections at target-at-rest frame for reaction sampling. The fact that the total cross section becomes a distributed quantity is handled using rejection sampling techniques. The original implementation of the TMS requires 2.0 times more CPU time in a PWR pin-cell case than a conventional Monte Carlo calculation relying on pre-broadened effective cross sections. In a HTGR case examined in this paper the overhead factor is as high as 3.6. By first changing from a multi-group to a continuous-energy implementation and then fine-tuning a parameter affecting the conservativity of the majorant cross section, it is possible to decrease the overhead factors to 1.4 and 2.3, respectively. Preliminary calculations are also made using a new and yet incomplete optimization method in which the temperature of the basis cross section is increased above 0 K. It seems that with the new approach it may be possible to decrease the factors even as low as 1.06 and 1.33, respectively, but its functionality has not yet been proven. Therefore, these performance measures should be considered preliminary.

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    KW - Monte Carlo

    KW - neutron tracking

    KW - on-the-fly

    KW - tempereature

    M3 - Conference article in proceedings

    SN - 978-162748643-9

    SP - 950

    EP - 961

    BT - Proceedings

    ER -

    Viitanen T, Leppänen J. Optimizing the implementation of the target motion sampling temperature treatment technique: How fast can it get? In Proceedings: International Conference on Mathematics and Computational Methods Applied to Nuclear Science & Engineering, M&C 2013. 2013. p. 950-961