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The radioactive chlorine isotope, 36Cl, decays with a half-life of 3×105 years by emitting a beta particle (98 %) and by electron capture. The aim of this paper is to propose a radiochemical separation method of 36Cl from the other beta-gamma emitters present in low and medium radioactive wastes such as spent ion exchange resins and evaporator concentrates, that arise from Nuclear Power Plants and particularly in the wastes that come from decommissioning activities of graphite reactors, in order to provide data for 36Cl inventory calculations. The separation method proposed is based on an oxidation technique where chlorine is trapped by NaOH. 36Cl beta emissions are measured by liquid scintillation counting by the dual label technique in order to avoid the contamination produced by 14C which is also trapped by NaOH and which is the main contaminant present in graphite samples. The sensitivity of this method is sufficient to achieve the needed thresholds for the radiological characterization of the radioactive materials to which this method can be applied.

The zirconium isotope 93 Zr is a long-lived pure β -particle-emitting radionuclide, which is produced by nuclear fission and neutron activation of the stable isotope 92 Zr. This element is a constituent of the structural components of nuclear reactor vessels. A selective liquid–liquid extraction method for radiochemical separation of Zr, based on liquid–liquid extraction with 1-(2′-thenoyl)-3,3,3-trifluoroacetone in xylene and a subsequent stripping of 93 Zr by an aqueous acid solution, has been developed. The method was utilised to separate Zr from other pure β -particle and β – γ emitters in different kinds of samples. Decontamination factors higher than 99% for the pure β -particle and β – γ emitters and an overall chemical yield of 80% were obtained. The sensitivity of the method allows the determination of the isolated 93 Zr by liquid scintillation counting and the minimum detectable activity value obtained was 0.067 Bq over a counting period of 60 min.

The radioactive isotopes of calcium, 41Ca ( t 1/2 =1.03×10 5 yr ) and 45Ca ( t 1/2 =163 d ), are produced by neutron capture in the stable isotopes 40Ca and 44Ca, respectively. These radionuclides are present in the environment due to the reactions between the galactic cosmic rays and the earth's surface, and in nuclear power plants by the activation of the structural components of nuclear reactor vessels. The aim of this paper is to propose a radiochemical separation method of 41Ca and 45Ca from the other beta–gamma emitters present in radioactive materials, based on selective precipitation reactions. The activities were measured by liquid scintillation counting (LSC). The obtained decontamination factors are satisfactory for each radioactive component of the initial sample in that their activities in the final product were lower than the minimum detectable activity (MDA) due to the effectiveness of the radiochemical procedure. The sensitivity of the method allows the radiological characterization of 41Ca and 45Ca content in radioactive materials.

Qualification tests of coatings for inner walls in a Boiling Water Reactor (BWR) were performed under request for decontamination purposes. Several types of coatings were contaminated with fission products obtained from a UO 2 solution irradiated in a nuclear research reactor, afterwards a successive decontamination process according with standards based on γ activity was applied. In each decontamination stage, α and γ activity measurements were made on the probes. Results obtained for α activity using nuclear track detectors are presented as an alternative assessment method during the decontamination process.

A whole body counter determined the presence of radioactivities up to 21.8 kBq for 214Bi and up to 18.7 kBq for 214Pb attached to clothes of workers in a Nuclear Research Laboratory. A radon survey reveals that 80% of the monitoring areas have radon concentration values lower than 500 Bq m−3, while 10% of the sampling points with values bigger than 1 kBq m−3 correspond to the workers mentioned above. By exposing samples of 0.04 m2 clothes in a radon chamber, it was observed that radon decay products 214Bi and 214Pb were attached to them with an activity of 315–618 Bq per each kBq m−3 of Rn concentration additionally, fibres characterised with a lower electrostatics build up showed the lower attachment.

Low-level technological radioactive wastes, in Spain, are commonly produced in research and medical centers. These wastes must be characterized before conditioning in order to determine their radioactive content for inventory purposes. A prototype has been designed for beta–gamma radiological characterization of standardized 25 l bags containing heterogeneous low-density technological radioactive wastes within the density range 0.05–0.6 g/cm 3 . The system consists of an iron shielding box with three NaI(Tl) and a silicon implanted detectors for gamma and gross beta activity determinations, respectively. The study of the measurement method, carried out with rotating scanning, included the optimization of the detection solid angle to minimize the uncertainties and the influence of the relative position of the radioactive material. Several materials and densities, in the range aforementioned, were considered to obtain the experimental attenuation factors, used for fitting a correction algorithm in function of density and γ-emission energy. The sensitivity of this method, calculated for the most frequent average density of this kind of waste (0.1 g/cm 3 ), is lower than 50 Bq/kg for the main β – γ emitters ( 137 Cs and 60 Co) and lower than 480 Bq/kg for gross beta activity.

A controlled radon chamber was used to test the detection performance of a portable active radon detector. The elapsed time to reach detection equilibrium with the radon atmosphere was three hours; the radon detector was sensitive to daily temperature changes. After using the radon detector three hours waiting time is required to place it in a new radon environment.

Fluences data profile inside four beam tubes at a nuclear research reactor has been using activation foils together with CR39 plastic detectors covered with lithium borate converter, to obtain discrete and continuous neutron fluence measurements.