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INSTITUTUL DE CERCET Ă RI NUCLEARE PITE Ş TI. Calibration and references in neutron field measurements. Csaba ROTH. Calibration and references in neutron field measurements.

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INSTITUTUL DE CERCETĂRI NUCLEARE PITEŞTI

Calibration and references in neutron field measurements

Csaba ROTH

Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


Calibration and references in neutron field measurements

  • The large utilization of the neutrons, starting from simple devices working with neutron sources up to the nuclear reactors, involves a large diversity of tools used for specific measurements.

  • Any apparatus used for measurements affecting the public interest is subject of the state metrological control

  • Neutron measurements - no apparatus or tools mentioned in the Official List and no standards available in our national standards system.

  • Calibration and measurement certificates issued by foreign organizations are valid.

Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


Calibration and references in neutron field measurements

  • Standards and references in neutron measurements:

  • Neutron fields with well known characteristics

  • Reference apparatus

  • Reference sources (fast neutrons)

Status in Romania: “reference field” type facility developed at the VVR-S Reactor operated by the National Institute for Physics and Nuclear Engineering, authorized as National Standard of the Thermal Neutron Flux Density Unit – no more in available

Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


Calibration and references in neutron field measurements

The reference thermal neutron irradiation facility developed at the Institute for Nuclear Research from Pitesti is a dry cavity placed into the graphite thermal column of the TRIGA-SSR core.

Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


Calibration and references in neutron field measurements

  • Characteristics of the irradiation facility :

  • Temperature: (40 ± 4) oC

  • Cadmium ratio for 197Au(n,) reaction: 52.1 ± 3%

  • Neutron flux density (fluence rate), as function of monitors count rate:

    • Φ/MON1 = (6.48±0.32)x108 neutrons/m2•s•cps

    • Φ/MON2 = (9.14±0.46)x1010 neutrons/m2•s•cps

  • Thermal neutron weight (E<0.135 eV) = (95.2±1)%

  • Gamma dose rate reported to monitor 2 count rate: 0.27 Gy/hour/cps

  • Neutron flux densities values from 2•1010 neutrons/m2•s up to 5•1014 neutrons/m2•s.

  • Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


    Calibration and references in neutron field measurements

    • Computation & measurements:

    • MCNP computation

    • Multifoil activation method

    • Fission rates measurements

    • Spectrum unfolding

    • Similar results obtained using the Wescott classical method

    Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


    Calibration and references in neutron field measurements

    Flux density space distribution

    Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


    Calibration and references in neutron field measurements

    • National standard qualification related problems

    • The irradiation facility has well known and reproducible neutron characteristics.

    • According to the national standard certification procedures requirements, resulting from the MRA requirements, the main problems are:

      • the traceability

      • the capability of transferring the measurement units to lower rang standards or tools.

    Conferinţa “Progrese în Criogenie şi Separarea Izotopilor”, Călimăneşti-Căciulata


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