RESUMEN
Neutron field measurements around individual DPT type spent fuel transport and storage casks were performed at the storage installation of Trillo Nuclear Power Plant. Neutron spectra were determined at five different positions using a Bonner sphere system. These measurements were used to validate the dosimetry measurements of two neutron monitors. Axial and angular measurements were used to determine the ambient dose equivalent. The results are consistent with the cask design and no field correction is needed when using these monitors.
RESUMEN
The Neutron Standards Laboratory of CIEMAT has conducted the characterization of the independent spent fuel storage installation at the Trillo Nuclear Power Plant. At this facility, the spent fuel assemblies are stored in ENSA-DPT type dual purpose casks. Neutron characterization was performed by dosimetry measurements with a neutron survey meter (LB6411) inside the facility, around an individual cask and between stored casks, and outside the facility. Spectra measurements were also performed with a Bonner sphere system in order to determine the integral quantities and validate the use of the neutron monitor at the different positions. Inside the facility, measured neutron spectra and neutron ambient dose equivalent rate are consistent with the casks spatial distribution and neutron emission rates, and measurements with both instruments are consistent with each other. Outside the facility, measured neutron ambient dose equivalent rates are well below the 0.5 µSv/h limit established by the nuclear regulatory authority.
Asunto(s)
Neutrones , Plantas de Energía Nuclear , Monitoreo de Radiación/métodos , Protección Radiológica/instrumentación , Residuos Radiactivos/análisis , Simulación por Computador , Diseño de Equipo , Humanos , Método de Montecarlo , Dosis de Radiación , Protección Radiológica/métodosRESUMEN
Neutron fields inside and outside the independent spent fuel storage installation of Trillo Nuclear Power Plant are characterized exhaustively in terms of neutron spectra and ambient dose equivalent, measured by Bonner sphere system and LB6411 monitor. Measurements are consistent with storage casks and building shield characteristics, and also with casks distribution inside the building. Outer values at least five times lower than dose limit for free access area are found. Measurements with LB6411 and spectrometer are consistent with each other.
RESUMEN
BACKGROUND AND PURPOSE: Small radiation beams (<4 cm width) are being increasingly used in the delivery of advanced techniques as Intensity Modulated Radiotherapy (IMRT) and Stereotactic Radiosurgery (SRS). Dose measurements in small beams present challenges not encountered for larger beams. A postal audit with Thermoluminiscent Dosimeters (TLD) was developed to check the doses in small photon beams. A validation test in real conditions was carried out in fourteen centres. MATERIAL AND METHODS: The TLD postal audit employs very small chips (1×1×1 mm(3)) of TLD-100 inserted at 5 and 10 cm of depth in a cylindrical PMMA phantom designed for this purpose. This experimental system is mailed to the audited centres to be irradiated with beams of 1 and 3 cm of side or diameter. The prescribeddose is 1.5 Gy at 10 cm. The properties of this system were studied experimentally and by Monte Carlo (MC) simulation, before the external test. RESULTS: Deviations between the prescribed and measured absorbed doses are below 5% for 69% (1×1 cm(2) beam) and 64% (3×3 cm(2) beam) of the audited centres. When deviations are above 5%, their causes have been investigated and led to corrections. CONCLUSION: The developed postal audit is suitable to verify the absorbed doses in small photon beams with an accuracy of 2.9% (1 s).