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The aim of this paper is to contribute to a more rapid determination of a series of samples containing Sr-90 by making the Cherenkov measurement of the daughter nuclide Y-90 more time efficient. There are many instances when an optimization of the measurement method might be favorable, such as; situations requiring rapid results in order to make urgent decisions or, on the other hand, to maximize the throughput of samples in a limited available time span. In order to minimize the total analysis time, a mathematical model was developed which calculates the time of ingrowth as well as individual measurement times for n samples in a series. This work is focused on the measurement of Y-90 during ingrowth, after an initial chemical separation of strontium, in which it is assumed that no other radioactive strontium isotopes are present. By using a fixed minimum detectable activity (MDA) and iterating the measurement time for each consecutive sample the total analysis time will be less, compared to using the same measurement time for all samples. It was found that by optimization, the total analysis time for 10 samples can be decreased greatly, from 21 h to 6.5 h, when assuming a MDA of 1 Bq/L and at a background count rate of approximately 0.8 cpm.

An electron spectrometry set-up was built at IRMM consisting of a vacuum chamber with a moveable source holder and windowless Peltier-cooled silicon drift detector (SDD). The SDD is well suited for measuring low-energy x rays and electrons emitted from thin radioactive sources with low self-absorption. The attainable energy resolution is better than 0.5keV for electrons of 30keV. It has been used to measure the conversion electron spectra of three plutonium isotopes, i.e. (238)Pu, (239)Pu, (240)Pu, as well as (241)Am (being a decay product of (241)Pu). The obtained mixed x-ray and electron spectra are compared with spectra obtained with a close-geometry set-up using another SDD in STUK and spectra measured with a Si(Li) detector at IRMM. The potential of conversion electron spectrometry for isotopic analysis of mixed plutonium samples is investigated. With respect to the (240)Pu/(239)Pu isotopic ratio, the conversion electron peaks of both isotopes are more clearly separated than their largely overlapping peaks in alpha spectra.

231Pa is the longest-lived decay product in the 235U decay chain and precise standards of this radionuclide are required to enable accurate, traceable measurements in nuclear dating applications such as geochronometry and nuclear forensics. Three independent techniques were used at NPL to determine the activity per unit mass of a freshly separated 231Pa solution as part of an international CCRI(II) comparison: CCRI(II)-K2.Pa-231.The first method was defined solid angle α counting and is the first result reported in a BIPM comparison with this instrument. The second method was 4πα liquid scintillation (LS) counting combined with the CIEMAT/NIST method using commercially available LS counters. The third technique used was 4π(LS)α-γ coincidence counting on an NPL-built system comprising an LS counter with dual photomultiplier tubes (PMTs) coupled to a 70% relative efficiency HPGe γ-spectrometer. Excellent agreement between the three methods was obtained.

Auger electron therapy is an attractive modality for targeting microscopic tumors. Rhodium-103 m (103mRh, T½ = 56.1 min) is a promising Auger electron emitter that can be obtained as the decay product of palladium-103 (103Pd, T½ = 16.99 days). 103Pd was chelated in a lipophilic derivative of the 16aneS4 macrocycle and the complex was trapped on a C18 cartridge. Elution with dilute hydrochloric acid gave radiochemically pure 103mRh. We hypothesize this to be through a combination of the Szilard-Chalmers effect and transient ionization.

Measurements for determining the activity of Sr-89 and Sr-90 in reactor coolant water are associated with limitations due to interferences from radionuclides with similar chemical properties and beta(-)-energies. From a measurement bias point-of-view these interferences would result mainly in an overestimated activity concentration of Sr-90. In order to address the interference problem, a common and well-known method was used in order to show the need for sufficient decontamination. An improvement was achieved by taking the sample through two initial strontium separations in order to increase the decontamination factor. This method determines the activity concentration of Sr-89 and Sr-90, via its daughter nuclide Y-90, by Cherenkov counting. This work is primarily based on theoretical calculations of strontium-, yttrium- and other potential interfering radionuclide ratios after instant fission. The work done to confirm the theoretical calculations were carried through on spiked strontium standard solutions and fresh reactor coolant water. The reactor coolant water was known to contain interferences at a composition resembling that of instant fission. The detection limit for double separation was calculated to 0.17 Bq/kg for Sr-90 and 0.38 Bq/kg for Sr-89. When using methods that solely rely on strontium resins, this paper shows that the decontamination factor (DF) is significantly higher when using double separation than that of a single separation. The paper also shows that the DF of an initial double strontium separation is as effective when it comes to removing high ratio interferences as separations done with both Sr- and Ln-resin (EiChrom Technologies, Inc., 2003; Tovedal at at, 2009b). However, 'old' samples, where e.g. Ba-140 and Sr-89 has decayed, does not benefit from double separation. Furthermore, samples with low ratios of interfering radionuclides does not benefit from using this method either, seeing as this is a more time consuming method due to the double separations.

The activity of 210Pb in a solution with 210Pb-210Po in the radioactive equilibrium was determined through its decay product 210Po by liquid scintillation counting (LSC), which has, after separation, as a pure α emitting nuclide, detection efficiency practically equal to 1. For the separation of 210Po from 210Pb solution, two methods based on precipitation of Pb, and Pb with Bi, leaving Po in the solution, were introduced. The first one was precipitation of Pb in the form of Pb(NO3)2 from a mixture of acetic acid, toluene, water and HNO3. The second one was based on co-precipitation of Bi and Pb with KCl from a mixture of organic solvents, where 210Bi with 210Pb was fixed to the precipitate. The relative standard uncertainty of 210Pb activity concentration was estimated to be lower than 0.45%.

A method for retrospectively assessing the average radon concentration in a dwelling, for a period as long as 40 years or more, is described. It is based on the free penetration of radon gas into bulky spongy materials called volume traps, and subsequent trapping of radon decay products inside them. This leads to a build-up of 210Pb, a radon decay product with a half life of 22.3 years, which reaches an equilibrium with the alpha emitter 210Po, indicative of the average radon concentration over the exposure period. The stuffing of mattresses, chairs, cushions, etc. can be considered a good volume trap. A chemical separation procedure is described, transforming the volume trap into a 210Po alpha source, whose activity is determined through alpha spectroscopy. The technique has been applied in over 300 samples, retrieved from dwellings in Serbia, Germany, Norway and Sweden. The technique has proven to be very robust and reproducible. In cases where radon data were available during the exposure period of the volume trap, a remarkable agreement was found. The best volume traps appeared to be polyester sponges found in many stuffings. The major drawback is the destructive nature of the method, its major advantage is the direct relationship between the radon gas and the 210Po signal. The technique can be useful in epidemiological studies of the lung cancer risk from indoor radon, for assessing the long term radon exposure.

The standardization of 237Np presents some difficulties: several groups of alpha, beta and gamma radiation, chemical problems with the daughter nuclide 233Pa, an incomplete radioactive equilibrium after sample preparation, high conversion of some gamma transitions. To solve the chemical problems, a sample composition involving the Ultima Gold™ AB scintillator and a high concentration of HCl is used. Standardization by the CIEMAT/NIST method and by pulse shape discrimination is described. The results agree within 0.1% with those obtained by two other methods.

A re-evaluation is made of the k0-factor and related nuclear data for the 555.8 keV gamma-ray of the 104mRh-104Rh mother–daughter pair that are important in neutron activation analysis (NAA). This study considers that the relevant level is also fed by the 4.34 min 104mRh mother (with an absolute gamma-ray emission probability γ2=0.13%) and not only, as assumed in former work, by the 42.3 s 104Rh daughter isotope (with γ3=2.0%). In view of this, generalised equations were developed for both the experimental determination and the analytical use of the k0-factor and of the associated parameters k0(m)/k0(g), Q0(m) and Q0(g) [(m):104mRh; (g): 104Rh], requiring the introduction of the γ2 and γ3 data and also of the 104mRh→104Rh fractional decay factor F2(=0.9987). The experimental determinations were based on irradiations performed in the BR1 reactor in Mol and the WWR-M reactor in Budapest. Furthermore, considering the special formation of the 555.8 keV gamma-ray, the procedure for true-coincidence correction was revised as well. All this led to the compilation and recommendation of a new set of ‘k0-NAA’ data.

Carrier-free 199Au produced in neutron activated platinum as a β-decay product of 199Pt has been separated from bulk matrices through liquid–liquid extraction (LLX) using the liquid cation exchanger, di-(2-ethylhexyl) phosphoric acid (HDEHP), as an extractant for the target element from an aqueous ammonia medium. The effect of octanol on the extraction was also studied. Production, extent of separation and purity of the radiotracers at different stages of their LLX separation have been verified by taking recourse to γ-ray spectroscopy.

A new single phototube liquid scintillation counting system for automatic determination of 222Rn in ground water for earthquake prediction is described. About 40% of radon is transferred from 1.0 L of water with a stream of air into 25 ml of toluene in a sample vial. Delayed coincidence counting of 214Bi and its decay product, 214Po reduces the background to 0.02 cpm. The 214Po detection efficiency is above 90%. Water containing 20 mBq/L of radon can be measured with 10% accuracy in 3 h.

A generator has been developed for the production of the α-emitting radionuclide 212Bi and its parent nuclide 212Pb. The genrator is based on the emanation of 220Rn from [228Th]barium stearate. The decay product of 220Rn, 212Pb deposits on the walls of a polyethylene botlle, and can be washed off with distilled water. The generator shows no leakage of any long-lived parent nuclides, is easy to operate and has a high degree of radiation safety.