Study of the capabilities of a detector based on a lanthanium bromide crystal for assessing 137Cs activity concentration in deep soil layers

During expeditionary radiation-hygienic studies of territories, there is often a need to assess activity concentration of radionuclides in soil at depths greater than 20 cm. This is associated with certain methodological and technical difficulties in sampling. The aim of this study was to carry out a series of calibration measurements and evaluate the capabilities of a collimated scintillation detector for determining ¹³⁷Cs activity concentration in soil at different depths in boreholes in situ. Materials and Methods: A comprehensive calibration was carried out for the MKSP-01 RADEK gamma spectrometer with a LaBr₃(Ce) crystal, including a study of the axial sensitivity and detection efficiency for the ¹³⁷Cs radionuclide from both a point source and a volumetric soil source with known activity. This made it possible to determine the optimal measurement parameters, including the distances between collimators and calibration coefficients for accurate determination of activity concentration at different distances and with different sample volumes. Results and Discussion: This article presents the results of calibration of the detector based on a LaBr₃(Ce) crystal measuring ∅30х30 mm, designed to measure the intensity of ¹³⁷Cs gamma radiation in boreholes at depths of up to 1 m. The calibration measurements showed that the detector design allows measuring activity concentration of ¹³⁷Cs from 200 Bq/kg in boreholes with a diameter of 90 mm, with the ¹³⁷Cs peak detection efficiency of about 0.1% and a measurement time of 30 min. The detector ensures reliable detection of soil layers with ¹³⁷Cs activity above the minimum significant activity concentration. Conclusion: Collimators providing access of gamma radiation to the open part of the LaBr₃(Ce) crystal allow adjusting the thickness of the studied soil layer (horizon view width) during the measurement process. With a distance between the collimators of 1.5 cm, the detector allows studying the activity concentration horizons with a step of 5 cm, with an increase in the distance to 2 cm – 10 cm.

1. Verutin MG, Kobruseva ON. Nuclear and geophysical research methods: laboratory and field radiometric methods: a practical guide. Gomel: Gomel State University named after F. Skorina; 2021. 44 p. (In Russian).

2. Review of domestic radiometric and spectrometric systems that can be used for accounting and control of nuclear materials. Available from: https://vniia.ru/rgamo/literat/obzor/doc/obzorrus.pdf [Accessed: 30 Jun 2025]. (In Russian).

3. Ivanov MM, Ivanova NN. Express analysis of the vertical distribution of 137Cs in soil to assess the rate of erosion and accumulation processes in the zone of intense radioactive contamination. Soil science = Pochvovedenie. 2023.4: 510-520. (In Russian). DOI: 10.31857/S0032180X22601104.

4. Pak DYu, Pak YuN, Esendosova AN, Smagulova AB. On the possibility of spectrometric gamma logging in solving problems of oil and gas field geophysics. Mezhdunarodnyy zhurnal prikladnykh i fundamentalnykh issledovaniy. Tekhnicheskie nauki = International Journal of Applied and Fundamental Research. Technical Sciences. 2016.4: 1069-1072. (In Russian).

5. Ivanov MM, Komissarova OL, Koshovsky TS, Tsyplenkov AS. Application of field gamma-ray spectrometry and dosimetry to study sedimentation in the floodplain of the small plain river in the zone of radioactive contamination. Vestnik Moskovskogo universiteta. Seriya 5. Geografiya = Bulletin of the Moscow University. Series 5. Geography. 2021.1: 120-127. (In Russian).

6. Pak DY, Pak YuN, Tabaeva AYu. Prospects of geophysical research of wells based on spectrometric gamma logging. Trudy universiteta = Proceedings of the University. 2022.86(1): 81-89. (In Russian).

7. Khramtsov E. Radiation situation on the territory of the peaceful nuclear explosion «Globus-1» before performing the rehabilitation works. Radiatsionnaya Gygiena = Radiation Hygiene. 2019.12(2): 81-88. DOI:10.21514/1998-426x-2019-12-2-81-88. (In Russian).

8. Tsvetnova OB, Alexandrov MN, Shcheglov AI. Modern radioecological situation on the territory of the Globus -1 facility. Vestnik Moskovskogo universiteta. Seriya 17. Pochvovedenie = Bulletin of the Moscow University. Series 17. Soil science. 2013;2: 11-16. (In Russian).

9. Varfolomeeva K.V., Sednev K.A., Biblin A.M., Ivanov S.A., Zelentsova S.A., Repin V.S., Georgieva A.G. Radiation-hygienic characteristics and sanitary condition of the territories of the Globus-3 and the Quartz-2 peaceful nuclear explosions in the Komi Republic. Radiatsionnaya Gygiena = Radiation Hygiene. 2025;18(1):100-111. DOI:10.21514/1998-426X-2025-18-1-100-111. (In Russian).

10. Kazachyonok NN, “Patterns of Formation of Technogenic Biogeochemical Provinces of Radioactive Isotopes.” Doctoral Dissertation in Geoecology (Earth Sciences). St. Petersburg; 2018. 313 p. (In Russian).

11. Educational and Methodological Manual on Radioactive, Acoustic, and Thermal Methods for Well Investigation / Federal Agency for Education, State Educational Institution of Higher Professional Education, Ufa State Petroleum Technological University. Ufa; 2009. 101 p. (In Russian).

12. Yazikov VG, Legavko AV. Features of Conducting Geophysical Surveys in Wells during the Study and Development of Infiltration (Hydrogenic) Uranium Deposits. Tomsk: TPU Publishing House; 2012. 12 p. (In Russian).

13. Barreto PM. Recent Advances in Uranium Deposit Exploration. IAEA Bulletin. 23(2): 18–24.

14. Geikhman MG, Kolesnichenko VP, Klimov VV et al. New Technical Means, Technologies, and Methodologies for Geological and Geophysical Monitoring of the Technical Condition of Gas and Gas-Condensate Well Casings, Including Wells with Abnormally High Formation Pressures and Temperatures. Krasnodar: Prosveshchenie-Yug; 2011. 265 p. (In Russian).

15. Semenov VN. Monitoring of Oil and Gas Reservoir Development Using Field Geophysical Methods: Monograph / VN. Semenov; Ministry of Science and Higher Education of the Russian Federation, Tyumen State University. Tyumen: Tyumen State University Publishing House; 2020. 224 p. (In Russian).

16. Akinshin AV, Kantemirov YuD. Practical Guide to Interpreting Well Geophysical Surveys: Monograph. LLC “Tyumen Oil Scientific Center”; 2021. 122 p. (In Russian).

17. Utkin VI. Selective Gamma-Gamma Logging in Coal Deposits. Nauka, Moscow; 1975. 127 p. (In Russian).

18. Urmanov EG. Neutron Logging of Oil and Gas Wells: Its Modifications, Processing, and Interpretation of Results: Educational and Methodological Manual. Moscow, Vologda: Infra-Engineering; 2023. 80 p. (In Russian).