Determination of 45Ca and γ-emitting radionuclides in concrete from a nuclear power plant

Abstract

For estimation of the activity of the long-lived 41 Ca isotope in seven concrete samples exposed to a varying neutron flux, 45 Ca activities in the samples were determined. Instead of total dissolution the concrete samples were treated with 8 M HCl and HNO 3 for partial dissolution of calcium. From the leachate, stable calcium was determined by AAS and 45 Ca activity with LSC after radiochemical separation while the total stable calcium in the concrete samples was determined by XRF. Calcium was separated from the leachates using cycles of precipitation and ion exchange. In addition to 45 Ca, seventeen γ -emitting radionuclides were detected directly in the concrete samples by γ -spectrometry. Ratios of 45 Ca activity concentrations to those of γ -emitting nuclides in the concrete samples with varying dose were more or less identical. Determination of 63 Ni activity in the concrete samples failed because activity levels were below the detection limit.

Development of 3H, 14C, 41Ca, 55Fe, 63Ni radiochemical analysis methods in activated concrete samples

“…CoreF correction is a mathematical corrective function for deviations of TDCR at higher quench levels. [2,[22][23][24]28]. Three parallel subsamples of 0.5 g inactive concrete were used for experimenting the initial Method 2.…”

“…For later tests and analyses of the activated concrete, efficient purification cycles were planned in order to remove interfering radionuclides from the final purified fractions. In a previous study [24], Ca fractions were treated with (at least) three carbonate precipitations and 2-3 anion exchange column pairs in order to efficiently purify 41 Ca fraction. Additionally, based on previous experiences with activated steel containing higher concentration of 60 Co compared to concrete [13], Ni fractions of activated concrete would require at least two Ni resin column separations for decreasing the concentration of 60 Co to a tolerable level, concerning LSC measurement.…”

Intercomparison exercise on difficult to measure radionuclides in activated concrete—statistical analysis and comparison with activation calculations

“…The radiochemical methods utilised in the DTM analysis of the activated concrete have been summarised by Leskinen et al [4]. The utilised procedures were mainly based on published references [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], but also internal procedures and modifications based on discussions between the participating laboratories. The main focus was given for 3 H, 14 C, 55 Fe and 63 Ni whereas 36 Cl and 41 Ca were optional.…”

“…Precipitations were carried out with and without heating and the precipitates and supernatants were separated using centrifugations. Contrary to referenced procedures in which the final hydroxide precipitate was dissolved in 4 M HCl and pH of the solution raised to pH 6-7 [19] or dissolved in 0.1 M HCl [17], the precipitate was recommended to be dissolved into conc. HCl and evaporated to dryness in order to produce water soluble CaCl 2 .…”

“…Although in this work the concrete matrix did not contain 60 Co at disturbing concentration level, in other cases of activated concrete 60 Co can be present in higher amounts. In that case, 60 Co should be removed carefully from the 41 Ca fraction by several repeating precipitations and monitoring the decontamination progress by gamma measurements of the purified fractions [17]. Last critical step is dissolution of the evaporation residue containing 41 Ca, either to HCl or to H 2 O prior to adding scintillation cocktail.…”