Determination of the minimum measurement time for estimating long-term mean radon concentration.

Radon measurements, as do any measurements, include errors in their readings. The relative values of such errors depend principally on the measurement methods used, the radon concentration to be measured and the duration of the measurements. Typical exposure times for radon surveys using passive detectors [nuclear track detectors, activated charcoal, electrostatic (E-perm), etc.)] may extend from a few days to months, whereas, in the case of screening methods utilising active radon monitors (AlphaGUARD, RAD7, EQF, etc.), the measurements may be completed quickly within a few hours to a few days. Thus, the latter may have relatively large error values, which affect the measurement accuracy significantly compared with the former measurements made over long time periods. The method presented in this paper examines the uncertainty of a short-term radon measurement as an estimate of the long-term mean and suggests a minimum measurement time to achieve a given margin of uncertainty of that estimate.

Radon concentration in soil gas around local disjunctive tectonic zones in the Krakow area.

The purpose of this study was to investigate radon in the vicinity of geologic fault zones within the Krakow region of Poland, and to determine the influence of such formations on enhanced radon concentrations in soil. Radon ((222)Rn and (220)Rn) concentration measurements in soil gas (using ionization chamber AlphaGUARD PQ2000 PRO and diffusion chambers with CR-39 detectors), as well as radioactive natural isotopes of radium, thorium and potassium in soil samples (using gamma ray spectrometry with NaI(Tl) and HPGe detectors), were performed. Site selection was based on a geological map of Krakow. Geophysical methods (ground penetrating radar and shallow acoustic seismic) were applied to recognize the geological structure of the area and to locate the predicted courses of faults. Elevated levels of radon and thoron in soil gas were found in the study area when compared with those observed in an earlier survey covering Krakow agglomeration. For (222)Rn, the arithmetic mean of registered concentration values was 39 kBq/m(3) (median: 35.5 kBq/m(3)). For (220)Rn, the arithmetic mean was 10.8 kBq/m(3) and median 11.8 kBq/m(3).

The optimisation of the fast neutron and gamma-ray transmission set-up for moisture measurement of coke.

In the present paper, modelling calculations with the Monte Carlo (MCNP4C) code were performed for the optimisation of the fast neutron and gamma-ray transmission, set-up, used for the humidity measurement of coke. The optimisation focused on maximising the sensitivity of the neutron flux to humidity changes and on lowering neutron-counting error, both leading to higher accuracy of coke moisture determination. Different materials used for the source shielding and neutron collimation, together with different dimensions of the neutron collimators were studied. The results obtained from the Monte Carlo modelling correlate with the real instrument performance.

Asymptotic solutions of neutron transport equation and the limits of correct use of diffusion approximation for rocks.

The diffusion approximation solution for neutron transport has been used in well-logging geophysics for calculating tool responses in boreholes, sometimes with success. The problem of the dimension of different materials to which it can be applied with success is important for the borehole environment. The results obtained show that the diffusion approximation can be used for distances greater than a few millimetre in some rock types. For iron, barium, and other highly absorbing media the use of the diffusion approximation is inappropriate even for large distances.

A comparison of theoretical solutions of the three-layer coaxial diffusion approximation of the borehole with measurements at the Zielona Góra calibration facility.

Czubek has obtained a practically successful solution of a two-layer borehole geometry using the neutron diffusion approximation. Czubek and Woznicka solved the more realistic three-layer borehole model, which includes a middle layer consisting of mud-cake or steel tubing, in this approximation. The comparison with experimental data for 15-mm thick steel tubes shows some discrepancies. By using an exact Monte Carlo solution of the Boltzmann equation for calculating the migration length, measurements agree more closely with the "general calibration curve". This opens opportunities for cased borehole logging.

Estimation of thermal neutron absorption cross-section from K, U and Th concentrations for Miocene rocks from the Carpathian Piedmont in Poland using artificial neural networks.

The radiometric K, U and Th concentrations and neutron absorption cross-section sigma a of rock samples obtained from coring are analysed. The cores are from wellbores located in the Sucha-Jordanów region (Carpathian Mountains) and from gas producing Miocene formations in the Carpathian foothills. Correlation coefficients between the neutron absorption cross-section (sigma a) and K, U and Th concentrations are presented. Neural network representation of the function sigma a = f(K, U, Th) obtained for a region can later be used for sigma a estimation from spectrometric probe results in uncored wells.