Analysis of Radionuclide Contamination Features in Solid Radioactive Waste of the “Light” Eastern Compartment of Solid Waste Repository of Chornobyl NPP

O. V. Mykhailov¹, V. M. Bezmylov¹, A. K. Terzi²

¹Institute for Safety Problems of Nuclear Power Plants, NAS of Ukraine,
36a, Kirova st., Chornobyl, 07270, Ukraine,
²SSE “Chornobyl NPP”, Slavutych, 07101, Ukraine

DOI: doi.org/10.31717/2311-8253.20.1.5

Abstract

Chornobyl NPP’s operational wastes accumulated before 1986 accident in State Specialized Enterprise “Chornobyl Nuclear Power Plant” solid waste repository (SWR) were studied. Material content of SRW at around 1 m depth in “light” eastern compartment was identified. After a visual examination, the waste materials were split into four streams. Representative samples for laboratory analysis were collected from each waste stream. Specific activities of 24 radionuclides to be certi-fied before the waste is disposed at the Plant for solid radwaste treatment, were in vestigated. Parameters of correlation between radionuclide activities in specimens were defined. A statistical correlation can be checked for data set without abnormal results and results on values of radionuclide specific activities being less than minimum detectable activity (MDA). The research results demonstrated that the total radioactivity of SRW in the outer layer of eastern compartment storage is, mainly, determined by the content of such radionuclides as ¹³⁷Cs, ⁶⁰Co, ⁹⁰Sr, ⁹⁴Nb, ²³⁵U, ²³⁸U, ²⁴¹Am, ³H and ¹⁴C. The data obtained indicate that the scaling factor method can be applied to quantify the specific activity of difficult-to-measure (DTM) radionuclides in the waste. Specific activity of DTM radionuclides such as ⁹⁰Sr, ⁹⁴Nb and ²⁴¹Am can be evaluated with high enough accuracy with using gamma spectrometry of ¹³⁷Cs and/or ⁶⁰Co key nuclides (KN). For the rest DTM radionuclides to be certified in the waste, their content according to gamma-ray spectrometry data of KN can be estimated with using Medium Activity Method technique.

Keywords: Chornobyl NPP, solid radioactive waste, specific activities, difficult-to-measure radionuclides, key nuclides, correlation factor, scaling factor.

References

1. Nosovskyi A. V., Vasylchenko V. M., Klyuchnykov O. O., Yashchenko Ya. V. (2005). [Decommission of nuclear power installations]. Kyiv: Tekhnika, 288 p. (in Russ.)

2. Mikhailov A. V., Pavljuchenko N. I., Mjasnikov A. V., Terzi A. K., Krasnov V. A. (2019). [Results of radionuclide vectors determination to be used in characterization of SSE NPP’s solid radwaste]. Problemy Chornobylskoi zony vidchuzhennia [Problems of Chornobyl exclusion zone], vol. 20, pp. 13-26. (in Russ.)

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 SESRSRW. Revision 5. Endorsed by acting Director General of State Corporation “UkrSE “Radon”. Chornobyl, 2009, 38 p. (in Ukr.)

4. Lukauskas D., Plukiene R., Plukis A., Gudelis A., Duskesas G., Juodis L., Druteikiene R., Lujaniene G., Luksiene B., Remeikis V. (2006). Method to determine the nuclide inventory of low-activity waste of the RBMK-1500 reactor. Lithuanian J. Phys., vol. 46, no. 4, pp. 497-503. doi: 10.3952/lithjphys.46413.

5. Plukis A., Remeikis V., Juodis L., Plukiene R., Lukauskas D., Gudeli A. (2008). Analysis of nuclide content in Ignalina NPP radioactive waste streams. Lithuanian J. of Phys., vol. 48, no. 4, pp. 375-379. doi: 10.3952/lithjphys.48409.

6. Improvement of Radioactive Waste Characterization Systems at Existing Nuclear Power Plants of Ukraine and Procedures and Methodology of Clearance from Regulatory Control of Materials. Contract NSI/2014/341-505. Detail Task B3 report. Appendix 1. Kyiv, 2017, 37 p.

Full Text (PDF)