Lead shielding efficiency from the gamma background measurements in the salt cavern of the Polkowice-Sieroszowice copper mine.

The studies of lead shielding efficiency from the gamma background measurements were performed in the salt cavern of the copper mine - a site considered for an underground laboratory. Within the energy range of 50-2700 keV, the measured gamma-ray count rates normalized to the mass of the high-purity detectors germanium crystal are 5.93 and 6.32 s-1kg-1 for the used low-background and portable spectrometers, respectively. The gamma-ray flux of 0.124 (2) cm-2s-1 connected with the natural radioisotopes was observed by the portable HPGe, including 0.026 (1) cm-2s-1 contribution of radon decay products, whereas the photon flux at the spectrum continuum was 0.18 (5) cm-2s-1.

Gamma background measurements in the Gran Sasso National Laboratory.

In situ gamma-ray measurements were taken at eight locations in the Gran Sasso National Laboratory (Italy). Count rates for gamma radiation within the energy range of 7-2,734 keV varied from 8 to 60 Î³ s-1. The arithmetic mean was 49 Î³ s-1 for measurements taken without a collimator. The average gamma flux inside the Lab was 0.25 Î³ cm-2 s-1. The sedimentary rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium, equal to 1.7 and 1.4 Bq kg-1, respectively.

Gamma background measurements in the Boulby Underground Laboratory.

To determine background radiation levels that might influence experiments, we measured in situ gamma-ray emissions at ten locations in the Boulby Underground Laboratory. For gamma radiation in the energy range of 7-2,734 keV, the counts varied from 6.5 to 28 Î³ s-1. For measurements inside the Lab, the arithmetic mean was 24 Î³ s-1. The sedimentary rocks that surrounded the Lab, halite and mudstone, were characterized by very low activity concentrations of uranium (0.8-7.1 Bq kg-1) and thorium (0.6-3.9 Bq kg-1).

Gamma background measurements in the Laboratoire Souterrain de Modane.

In situ gamma-ray measurements were taken at six locations in the Modane Underground Laboratory. Count rates for gamma radiation within the energy range of 7-2734 keV varied from 15 to 108 Î³s-1. The arithmetic mean was 79 Î³s-1 for measurements taken without a collimator. The metamorphic rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium equal to 12 and 10 Bq kg-1, respectively.