Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent

Tuomas Viitanen, Jaakko Leppänen

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

    Abstract

    The structural integrity of reactor pressure vessels (RPVs) can be studied by preparing test specimens from the RPV material, irradiating the specimens in the surveillance position or positions at the reactor periphery and measuring the material properties of the irradiated samples. To match the measurements of the test specimens to the state of the reactor pressure vessel at a certain moment of time, the neutron exposure of the irradiated test specimens as well as the reactor pressure vessel need to be determined. The exposure, more precisely the neutron fluence, is usually calculated using either deterministic or Monte Carlo calculation codes. Accuracy of the computational estimates can be increased by means of neutron dosimetry, i.e. by normalizing or adjusting the computational results to match the measured activation of neutron dosimeters. For this reason, also the surveillance specimens of Loviisa-1 and Loviisa-2 VVER-440 units are always irradiated together with several neutron dosimeters: The axial profile in the neutron fluence is monitored using Fe/Ni dosimeter discs, in addition to which the fluence spectrum is measured using separate wire dosimeters. In the current work, the measured activities from neutron dosimeters irradiated in the surveillance position of Loviisa-1 unit are used to validate Monte Carlo reactor physics code Serpent for calculations at the reactor periphery, for example surveillance position or RPV. The neutron source in the Serpent calculation is generated based on a full-core power distribution from simulator code HEXBU-3D, and Serpent is only used to calculate the neutron transport from the source points in the reactor core to detector locations. Since the neutron flux decreases by orders of magnitude between the reactor core and the locations of interest, the convergence of the Monte Carlo transport solution needs to be accelerated using new weight-window based variance reduction techniques of Serpent 2.1.27.
    Original languageEnglish
    Title of host publication26th Symposium of AER on VVER Reactor Physics and Reactor Safety
    Subtitle of host publicationBook of Abstracts
    Pages181-188
    Publication statusPublished - 2016
    MoE publication typeB3 Non-refereed article in conference proceedings
    Event26th Symposium of AER on VVER Reactor Physics and Reactor Safety - Helsinki, Finland
    Duration: 10 Oct 201614 Oct 2016

    Conference

    Conference26th Symposium of AER on VVER Reactor Physics and Reactor Safety
    CountryFinland
    CityHelsinki
    Period10/10/1614/10/16

    Fingerprint

    surveillance
    dosimeters
    pressure vessels
    activation
    reactors
    neutrons
    reactor cores
    fluence
    reactor physics
    normalizing
    neutron sources
    flux (rate)
    integrity
    point sources
    simulators
    adjusting
    wire
    moments
    detectors
    estimates

    Keywords

    • neutron dosimeter activation
    • VVER-440
    • WWER-440
    • Serpent
    • Loviisa
    • Monte Carlo
    • variance reduction technique

    Cite this

    Viitanen, T., & Leppänen, J. (2016). Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent. In 26th Symposium of AER on VVER Reactor Physics and Reactor Safety : Book of Abstracts (pp. 181-188)
    Viitanen, Tuomas ; Leppänen, Jaakko. / Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent. 26th Symposium of AER on VVER Reactor Physics and Reactor Safety : Book of Abstracts. 2016. pp. 181-188
    @inproceedings{8f65f0f1c6ab408aad6ac29ae8be9843,
    title = "Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent",
    abstract = "The structural integrity of reactor pressure vessels (RPVs) can be studied by preparing test specimens from the RPV material, irradiating the specimens in the surveillance position or positions at the reactor periphery and measuring the material properties of the irradiated samples. To match the measurements of the test specimens to the state of the reactor pressure vessel at a certain moment of time, the neutron exposure of the irradiated test specimens as well as the reactor pressure vessel need to be determined. The exposure, more precisely the neutron fluence, is usually calculated using either deterministic or Monte Carlo calculation codes. Accuracy of the computational estimates can be increased by means of neutron dosimetry, i.e. by normalizing or adjusting the computational results to match the measured activation of neutron dosimeters. For this reason, also the surveillance specimens of Loviisa-1 and Loviisa-2 VVER-440 units are always irradiated together with several neutron dosimeters: The axial profile in the neutron fluence is monitored using Fe/Ni dosimeter discs, in addition to which the fluence spectrum is measured using separate wire dosimeters. In the current work, the measured activities from neutron dosimeters irradiated in the surveillance position of Loviisa-1 unit are used to validate Monte Carlo reactor physics code Serpent for calculations at the reactor periphery, for example surveillance position or RPV. The neutron source in the Serpent calculation is generated based on a full-core power distribution from simulator code HEXBU-3D, and Serpent is only used to calculate the neutron transport from the source points in the reactor core to detector locations. Since the neutron flux decreases by orders of magnitude between the reactor core and the locations of interest, the convergence of the Monte Carlo transport solution needs to be accelerated using new weight-window based variance reduction techniques of Serpent 2.1.27.",
    keywords = "neutron dosimeter activation, VVER-440, WWER-440, Serpent, Loviisa, Monte Carlo, variance reduction technique",
    author = "Tuomas Viitanen and Jaakko Lepp{\"a}nen",
    year = "2016",
    language = "English",
    isbn = "978-963-7351-26-6",
    pages = "181--188",
    booktitle = "26th Symposium of AER on VVER Reactor Physics and Reactor Safety",

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    Viitanen, T & Leppänen, J 2016, Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent. in 26th Symposium of AER on VVER Reactor Physics and Reactor Safety : Book of Abstracts. pp. 181-188, 26th Symposium of AER on VVER Reactor Physics and Reactor Safety, Helsinki, Finland, 10/10/16.

    Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent. / Viitanen, Tuomas; Leppänen, Jaakko.

    26th Symposium of AER on VVER Reactor Physics and Reactor Safety : Book of Abstracts. 2016. p. 181-188.

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific

    TY - GEN

    T1 - Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent

    AU - Viitanen, Tuomas

    AU - Leppänen, Jaakko

    PY - 2016

    Y1 - 2016

    N2 - The structural integrity of reactor pressure vessels (RPVs) can be studied by preparing test specimens from the RPV material, irradiating the specimens in the surveillance position or positions at the reactor periphery and measuring the material properties of the irradiated samples. To match the measurements of the test specimens to the state of the reactor pressure vessel at a certain moment of time, the neutron exposure of the irradiated test specimens as well as the reactor pressure vessel need to be determined. The exposure, more precisely the neutron fluence, is usually calculated using either deterministic or Monte Carlo calculation codes. Accuracy of the computational estimates can be increased by means of neutron dosimetry, i.e. by normalizing or adjusting the computational results to match the measured activation of neutron dosimeters. For this reason, also the surveillance specimens of Loviisa-1 and Loviisa-2 VVER-440 units are always irradiated together with several neutron dosimeters: The axial profile in the neutron fluence is monitored using Fe/Ni dosimeter discs, in addition to which the fluence spectrum is measured using separate wire dosimeters. In the current work, the measured activities from neutron dosimeters irradiated in the surveillance position of Loviisa-1 unit are used to validate Monte Carlo reactor physics code Serpent for calculations at the reactor periphery, for example surveillance position or RPV. The neutron source in the Serpent calculation is generated based on a full-core power distribution from simulator code HEXBU-3D, and Serpent is only used to calculate the neutron transport from the source points in the reactor core to detector locations. Since the neutron flux decreases by orders of magnitude between the reactor core and the locations of interest, the convergence of the Monte Carlo transport solution needs to be accelerated using new weight-window based variance reduction techniques of Serpent 2.1.27.

    AB - The structural integrity of reactor pressure vessels (RPVs) can be studied by preparing test specimens from the RPV material, irradiating the specimens in the surveillance position or positions at the reactor periphery and measuring the material properties of the irradiated samples. To match the measurements of the test specimens to the state of the reactor pressure vessel at a certain moment of time, the neutron exposure of the irradiated test specimens as well as the reactor pressure vessel need to be determined. The exposure, more precisely the neutron fluence, is usually calculated using either deterministic or Monte Carlo calculation codes. Accuracy of the computational estimates can be increased by means of neutron dosimetry, i.e. by normalizing or adjusting the computational results to match the measured activation of neutron dosimeters. For this reason, also the surveillance specimens of Loviisa-1 and Loviisa-2 VVER-440 units are always irradiated together with several neutron dosimeters: The axial profile in the neutron fluence is monitored using Fe/Ni dosimeter discs, in addition to which the fluence spectrum is measured using separate wire dosimeters. In the current work, the measured activities from neutron dosimeters irradiated in the surveillance position of Loviisa-1 unit are used to validate Monte Carlo reactor physics code Serpent for calculations at the reactor periphery, for example surveillance position or RPV. The neutron source in the Serpent calculation is generated based on a full-core power distribution from simulator code HEXBU-3D, and Serpent is only used to calculate the neutron transport from the source points in the reactor core to detector locations. Since the neutron flux decreases by orders of magnitude between the reactor core and the locations of interest, the convergence of the Monte Carlo transport solution needs to be accelerated using new weight-window based variance reduction techniques of Serpent 2.1.27.

    KW - neutron dosimeter activation

    KW - VVER-440

    KW - WWER-440

    KW - Serpent

    KW - Loviisa

    KW - Monte Carlo

    KW - variance reduction technique

    M3 - Conference article in proceedings

    SN - 978-963-7351-26-6

    SP - 181

    EP - 188

    BT - 26th Symposium of AER on VVER Reactor Physics and Reactor Safety

    ER -

    Viitanen T, Leppänen J. Calculating neutron dosimeter activation in VVER-440 surveillance chains with Serpent. In 26th Symposium of AER on VVER Reactor Physics and Reactor Safety : Book of Abstracts. 2016. p. 181-188