Naslov
Problems with storage of samples for OBT analysis

Autori
Sironić, Andreja ; Krajcar Bronić, Ines

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
9th Organically Bound Tritium Workshop

Mjesto i datum
Antwerpen, Belgija, 10.05.2023. - 12.05.2023

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Organically bound tritium, LSC, inter-comparison, sample storage

Sažetak
In the Laboratory for Low-level Radioactivities, of the Ruđer Bošković Institute, Zagreb, Croatia, first tests of organically bound tritium (OBT) analysis were made in 1980’s using gas proportional counter (GPC) and measuring matrix methane. Since the amount of required material was large and sample preparation procedure was long, it was abandoned at the time. The Laboratory acquired liquid scintillation counter (LSC) in 2001 for radiocarbon and tritium analysis. The LSC requires about seven times lower amount of material than GPC for OBT analysis and due to scientific and market demand the laboratory has been routinely performing the OBT analysis since 2020. The laboratory procedure for OBT analysis is as follows: the sample is cut, dried at 80 °C, combusted in custom-made vacuum rig (also used for CO2 production for 14C analysis), produced water is collected, Na2O2 and KMnO4 are added to oxidize remaining organic compounds, sample is distilled and mixed with Ultima Gold LLT. The tritium activity of the cocktails is measured by liquid scintillation counter Quantulus 1200. The Laboratory participated in three international intercomparison exercises: 2017 (“grass”), 2018 (“fish”) and 2019 (“quinces”). Samples of “grass” and “quinces” were analyzed after four and two years, respectively, as a part of laboratory quality control. The samples had been kept in their original storage package, plastic bag sealed with tape, at room temperature. The activity of the “grass” (T-4832) has not changed (434 ± 20 Bq/L in July 2017 and 427 ± 24 Bq/L in March 2022, k=2). However, for the “quinces” (T-5160) a decrease of about 25 % is obtained (50.3 ± 1.8 Bq/L in June 2019 and 38.4 ± 4.4 Bq/L in December 2021, k=2). A sample of apples (T-5551) was also measured twice three months apart with no markable change: 3.1 ± 2.2 Bq/L in December 2021 and 5.7 ± 2.2 Bq/L (k=2) in March 2022. In case of the quinces sample, probably due to high saccharose content the exchange between environment water vapor and exchangeable organic hydrogen in sample was far more pronounced that in high cellulose one (the grass sample). The proper storage procedure of the samples for OBT analysis will be discussed in presentation.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija, Interdisciplinarne prirodne znanosti

POVEZANOST RADA