Measurements of 60Co in spoons activated by neutrons during the JCO criticality accident at Tokai-mura in 1999

Low-level germanium gamma-ray spectrometry at the μBq/kg level and future developments towards higher sensitivity

“…Only after the conversion to a diode (2.2 kg active volume, Ø 77.5 mm x 88.5 mm, relative efficiency 102 %) and successful testing in a test cryostat at Olen, the direct cladding parts, insulation can and holder, were machined at Heidelberg to match the size. During the production phase of the low-level cryostat the crystal was placed underground in HADES 5 , close to Olen. Immediately after the transfer of that crystal into its final cryostat system and the positive performance test, the detector was transported to the low-level laboratory at Heidelberg.…”

“…Here first background tests were performed in a provisional shield made of 15 cm lead and one large cosmic veto detector (multiwire proportional chamber) placed on top. The measured background spectrum is shown below (section.3.1) in comparison with the starting 2 analysed by M. Wojcik, Institute of Physics, Jagellonian University, Cracow, Poland 3 small piece taken from a large roll screened to be radio-pure 4 GCE-Druva, Eppelheim, Germany 5 Underground Research Facility (URF) operated by SCK/CEN Nuclear Research centre at Mol, Belgium background obtained at the much deeper Gran Sasso laboratory. Calibration measurements of the spectrometer have been carried out with various sources under different geometry and the detector was scanned horizontally and axially with collimated sources to create a data base for Monte Carlo simulations [9,10] based on the code GEANT 3.21 (CERN Program Library).…”

“…Its high sensitivity makes the spectrometer also very well suited for environmental studies, as e.g. in measurements of activation products from accidental neutron exposures [5]. Special attention in the construction of the spectrometer was devoted to achieve low background rates at the lines of the primordial decay chains 238 U and 232 Th and of 40 K, the most prominent contaminants.…”

Advanced Measuring (Instrumentation) Methods for Nuclear Installations: A Review

“…The measurements were performed by Rehovot Pelletron Accelerator (RPA) and Accelerator Mass Spectrometry (AMS). Gasparro et al described γ-ray spectrometry measurements undertaken in a range of underground laboratories for the purpose of measuring 60 Co more than 2 years after the Chernobyl nuclear reactor criticality event [74]. The measurements consequence showed that neutron fluence determined from 60 Co activity is in agreement with previous measurements using the short-lived radionuclides 59 Fe and 51 Cr.…”