[back to index]


Radiation field parameters for pressure vessel monitoring
in VVER-440 using the NRI LR-0 experimental reactor (~1990)

 1. Name of Experiment:
    Radiation field parameters for pressure vessel monitoring in VVER-440
    using the NRI LR-0 experimental reactor (~1990)

 2. Purpose and Phenomena Tested:
    The benchmarks have been realised to support the reactor pressure vessel
    (PV) dosimetry qualification. The fast neutron spectra in monitoring and 
    critical locations of VVER-440 have been measured.
 3. Description of the Source and Experimental Configuration
    A mock-up simulating symmetry sector of about 1/6 of VVER-440 reactor 
    was assembled in LR-0 experimental reactor in Nuclear Research Institute
    (NRI) Rez near Prague. The mock-up represents full scale simulation in
    radial direction from the core boundary to the biological shield. The
    core, core blanket, basket and barrel simulators were located inside the
    LR-0 tank, and the PV and biological shield outside the tank. 
    A steel displacing tank (an air gap) simulated the water density
    reduction  corresponding to the VVER-440 operational NPP. The mock-up is
    axially shortened (50 %) due to 1.25 m active length of the LR-0 fuel pins.
    The LR-0 experimental reactor is a critical assembly (without
    cooling); maximum allowed power is 5 kW for 1 hour or 10**8 / cm2 / sec
    maximum thermal neutron flux density. The fuel is fresh (without
    burn-up) and the source distribution can be calculated by appropriate 
    pin-by-pin codes (e.g. MOBY DICK, which is standardised for VVER in 
    the Czech Rep., or by Monte Carlo codes). The core boundary power
    distribution simulates the equilibrium after 5 fuel cycles in a VVER-440
    power reactor.

 4. Measurement System and Uncertainties
    The fast neutron spectra in the energy range from about 0.1 MeV up to 
    10MeV approximately were measured with the proton recoil spectrometer in
    the central plane along the mock-up axis in the monitoring and crucial
    points of the PV (at the barrel - in the displacer, before and behind 
    the PV simulator and in 1/3 of its thickness). The spectrometer
    consists of stilbene scintillator and a set of spherical hydrogen
    filled proportional counters with different pressures of the hydrogen. 
    A table of typical uncertainties(energy resolution, counting statistics)
    in different energy regions is presented in reference [1]. The energy  
    resolution varies in the mentioned energy interval from 6 to 10 %, the 
    (typical) statistical uncertainties were in the interval 2 - 20 %. 
    To support core calculations, several hundreds of fuel pins were 
    scanned to measure radial power distribution.
 5. Description of Results and Analysis
    The neutron spectra in crucial points were measured by two independent
    groups from the Czech Republic (Skoda Plzen and NRI Rez) and two rounds 
    of mock-up measurements were done. The measured spectra were (except
    where errors were found) identical within the experimental 
    uncertainties. The spectrometers were compared also in reference fields.
    The Skoda results are presented because of their completeness and 
    consistency, the uncertainty information is included [1, 3]. The 
    measured proton recoil spectra were unfolded using a differential method
    described in [2].
    Because the measurement of absolute power in a critical assembly is 
    difficult, especially when the power is changed by several orders, the 
    space-energy distribution is presented in relative units (i.e. the 
    spectra in measuring points).

 6. Special Features
    Engineering model with geometry and material composition corresponding
    to the power station. The benchmark was realised in two variants, with
    standard and reduced cores (i.e. with dummy steel element simulators at 
    the core boundary).

 7. Author/Organizer:
    Authors:    (see point 9 below) 14 authors from Nuclear Research 
                Institute Rez plc (NRI Rez) and 8 from Skoda, Plzen, 
                Czech Republic; 9 authors from Russian Research Centre 
                "Kurchatov Institute" (RRC KI), Moscow and 3 Gidropress,
                Podolsk, Russian Federation

    Organisers: NRI Rez and Skoda, Plzen, Czech Republic and
                RRC KI, Moscow and Gidropress, Podolsk, Russian Federation

    Compilers:  Osmera B. and Mikus J., NRI Rez and
                Zaritsky S., Gurevic M., RRC KI, Moscow

    The review needs to be carried out. Contributions are highly appreciated.
 8. Availability:

 9. References:
    [1] Osmera, B., Holman, M., Integral Experiments for Reactor Pressure 
        Vessel Neutron Exposure Evaluation, Proceedings of Nuclear Data for 
        Science and Technology, Juelich, Germany, 13 - 17 May, 1991, pp. 650

    [2] Holman, M., Marik, P., Franc, L., Scintillation Spectrometer with
        a Crystal of Stilbene, ZJE - 191, 1976, Skoda Works, Nuclear Power
        Construction Department, Information Centre, Plzen, Czech Republic 
        Holman, M., Neutron Spectrometry Using Scintillation Spectrometer and 
        Hydrogen - Filled Proportional Counters, ZJE-220, 1979, ibid.

    [3] Osmera, B., Reactor Dosimetry of WWER-440 Type Reactors, Nucleon, 
        3 - 4, 1993, p. 27, Nuclear Research Institute, 250 68 Rez, Czech Rep.

    [4] Osmera, B.,   Gurevich, M.,   Hort, M.,   Kam, F.B.K.,   Mikus, J.,
        Remec, I., Zaritsky, S., WWER-440 Pressure Vessel Dosimetry Benchmarks
        Evaluated Experimental Data, 1998 ANS Radiation Protection and Shielding
        Division Topical Conference - Technologies for the New Century, Nashville,
        Tennessee, April 19 - 24, Proceedings, p. I-419
    [5] Gurevich, M., Zaritsky, S., Osmera, B., Mikus, J., Kam, F.B.K., 
        Check and Visualisation of the Input Geometry Data Using the Geometrical
        Module of the Monte Carlo Code MCU: WWER-440 Pressure Vessel Dosimetry
        Benchmark, ibid., p. I-425

    [6] Zaritsky, S., Belousov, S., Brodkin, E., Egorov, A., Iljeva, K., Kam,
        F.B.K., Vessel Dosimetry Benchmarks : Calculation and Analysis, ibid., I-325

Results concerning the mock-ups investigations were presented in about 90 works, 
mostly published as Czech and Russian reports with restricted distribution.
    [7] B. Osmera, Benchmarking of Radiation Field Parameters, 
        Relevant for Pressure Vessel Monitoring. Review of Experimental Results in WWER-440 
        and WWER-1000 Benchmarks in LR-0 Experimental Reactor
        WWER-440 Benchmarks in LR-0 Experimental Reactor [UJV 12992-R (2008}]:
        - B. Osmera, S. Zaritsky, WWER-440 Mock-up Experiments in the LR-0 Reactor, 
        Mock-up No. 1 Description UJV-11811-R; RRC KI No. 36/23-2002 (2002)
        - B. Osmera, S. Zaritsky, WWER-440 Mock-up Experiments in the LR-0 Reactor, 
        Mock-up No. 2 Description UJV-11812-R; RRC KI No. 36/24-2002 (2002)
        - B. Osmera, S. Zaritsky, M. Holman, WWER-440 Mock-up Experiments in the LR-0 Reactor
        Experimental Data UJV-11813-R; RRC KI No. 36/25-2002 (2002)

10. Data and Format:
    The neutron spectra are presented in SAILOR group format including uncertainty in each group
    (one sigma, relative in %) [3].
    The spectra are normalised to the spectrum behind the PV where the integral flux above 1 MeV is equal 1.
    In order to compare the shapes of spectra to each one it is also presented in normalised 
    form - integral flux above 0.1 MeV is equal 1.

    Experimental space - energy indices consist of:
    - Experimental integral fluxes above 0.1, 0.5, 1,0, 2,0, 3.0, 5.0 MeV in measuring  points 
    (normalised to integral flux above 1 MeV behind the PV);
    - Experimental integral fluxes of spectra normalised in each point to integral flux above 0.1 MeV;
    - Experimental Attenuation Coefficients for integral fluxes. These data (spectra and spectral 
    indices) are presented in Tables [4].

    The measured relative core power distributions are presented in tables with coded coordinates of the pins 
    in cassettes or in the graphical form in the figures of the cassettes.

    Because of the complex design very close to that of the power reactor one many figures and coordinate 
    tables represent the mock-up geometry and composition starting with schematic arrangements and finishing with
    detailed description of all parts including arrangements for the measurements [5].

    The definition of the calculational tasks for comparison of calculations and experimental data 
    was examined in a series of calculations performed by different calculational groups [6].

    Filename                  Content
    ----------------------    ----------------
  1 vver440.htm               This information file
  2 VVER-440.pdf              Ref. [7]
  3 VVER-440.doc              Ref. UJV 12992-R (2008)

SINBAD Benchmark Generation Date: 12/2008
SINBAD Benchmark Last Update: 12/2008