O. V. Mykhailov
Institute for Safety Problems of Nuclear Power Plants,
NAS of Ukraine, 36a, Kirova st., Chornobyl, 07270, Ukraine
The first radionuclide vector (RV) for characterization of operational solid radioactive wastes (SRW) of Chornobyl Nuclear Power Plant (ChNPP) according to the IAEA methodology was established in 2018 and consisted of a set of scaling factors (SF), which have never been refined and updated, as it is recommended to be done from time to time. In this work, verification algorithm of previously established SF values, provided for by RV setting technique, was tested, and their values were updated with taking into account the implementation of a new approach for sorting ChNPP SRW into the streams. It was established that for such nuclides as 90Sr, 94Nb and 241Am, geometric mean values of SF or correlation function (CF) established on the basis of regression analysis of logarithms of nuclide content, can be used. For the other radionuclides (14С, 3Н and 235, 238U), whose activity levels were higher than the minimum detectable activity (MDA), arithmetic mean values of SF only can be used. For uranium isotopes 235, 238U, a high degree of correlation between their content is observed in all SRW materials, regardless of whether they belong to combustible or non-combustible operational waste of the ChNPP. According to the test results (testing for significance of difference under the null hypothesis) using the Student’s t-statistics, it was established that the same SF values can be applied to the waste temporarily stored in the eastern and western compartments of the ChNPP SRW repository. The waste should be separated into non-combustible and combustible materials only. This follows from the fact that combustible solid waste, if they are to be burned as it is planned, must be re-characterized using the SF value already determined for ash and by a different technique. However, until these wastes are burned, the obtained data allow estimating the expected levels of nuclide content in their ash residue.
Keywords: solid radioactive waste, Chornobyl NPP, difficultto-measure nuclides, key nuclides, specific activity, correlation factor, radionuclide vector.
1. Mikhailov A. V., Pavliuchenko N. I., Miasnikov A. V., Terzi A. K. (2019). [Results of radionuclide vectors determination to be used in characterization of SSE NPP’s solid radwaste]. Problems of Chornobyl Exclusion Zone, vol. 20, pp. 13–26. (in Rus.)
2. Production process control system. Methodology for the determination of radionuclide vectors for the characterization of batches of solid radioactive waste. STP 2.035–2018. SSE ChNPP, Slavutych, 2018, 24 p. (revised 2020) (in Rus.)
3. Criteria for acceptance of waste for burial in specially equipped near-surface repository for solid radwaste (SESRSRW). First stage of SESRSRW operation. Acceptance of RAW from SSE “ChNPP” PTLRW and PTSRW for burial in two symmetrical compartments of ESRSRW. Revision 5. Endorsed by acting Director General of State Corporation “UkrSE ‘Radon’”. Chornobyl, 2009. 38 p. (in Ukr.)
4. IAEA (2009). Determination and use of scaling factors for waste characterization in NPP. IAEA Nuclear Energy Series NW-T-1.18. Vienna: IAEA, 142 р.
5. Taddei M. H. T., Macacini J. F., Vicente R., Marumo J. T., Terremoto L. A. A. (2015). Determination of scaling factors to estimate the radionuclide inventory of wastes from the IEA-R1 research reactor. J. Radioanal. Nucl. Chem., vol. 303, no. 3, рp. 2467–2481. doi.org/10.1007/s10967-014-3789-3.
6. Mikhailov A. V., Krasnov V. A., Bezmylov V. N. (2018). [Methodology for using radionuclide vectors to characterize NPP RAW]. Nuclear Power and the Environment, vol. 12, no. 2, pp. 52–58. (in Rus.)
7. Kim T. H., Park J., Lee J., Kim J., Kim J. Y., Lim S. H. (2020). Statistical methodologies for scaling factor implementation: Part 1. Overview of current scaling factor method for radioactive waste characterization. Journal of Nuclear Fuel Cycle and Waste Technology, vol. 18, no. 4, pp. 517–536. doi.org/10.7733/jnfcwt.2020.18.4.517.
8. Kim A. M., Lietzmann F. (2019). Nuclide vector for decommissioning and release measurements in Germany. Proceedings of the Transactions of the Korean Nuclear Society Autumn Meeting (Goyang, Korea, October 24–25, 2019). Available at: https://www.kns.org/files/pre_paper/42/19A-032-AndreaMaria.pdf.
9. Mykhailov O. V., Bezmylov V. M., Terzi A. K. (2020). Analysis of radionuclide contamination features in solid radwaste of “light” eastern compartment of solid waste repository of Chornobyl NPP. Nuclear Power and the Environment, vol. 16, no. 1, pp. 40–48.
10. Maksymenko А. М., Bondarkov M. D., Oskolkov B. Ya., Seida V. A., Dubas V. N. (2019). [Results for studies of hard-to-measure radionuclides in the metal of Chornobyl Nuclear Power Plant equipment being dismanlted, and estimation of scaling factor]. Nuclear Power and the Environment, vol. 13, no. 1, pp. 67–75. (in Rus.)
11. Mykhailov O. V., Terzi A. K. (2021). Investigation of radionuclide contamination of materials stored in solid radwaste repository of Chornobyl NPP. Nuclear Power and the Environment, vol. 22, no. 3, pp. 28–36.
12. Kim T., Kang K., Ha J. (2008). Determination and verification of the scaling factor for the radionuclide inventory of the radioactive waste from nuclear power plants. Journal of Nuclear Science and Technology, vol. 45, sup. 5, pp. 756–757. doi.org/10.1080/00223131.2008.10875965.
13. Ross S. M. (2004). Introduction to probability and statistics for engineers and scientists. Third Edition. USA: Elsevier Academic Press, 641 p.
If the article is accepted for publication in the journal «Industrial Heat Engineering» the author must sign an agreement on transfer of copyright. The agreement is sent to the postal (original) or e-mail address (scanned copy) of the journal editions.
Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License International CC-BY that allows others to share the work with an acknowledgement of the work’s authorship and initial publication in this journal.