Natural Radioactivity of Coal and Fly Ash at the Nikola Tesla B Tpp

Abstract

Serbian thermal power plants (TPPs) produce Siliceous fly ash from lignite in the quantity of approximately 6 million tons per year. The Potential. Market for the use of fly ash is operational, but for the time being, only Used by cement producers. Fly ash radioactivity could be one of the major points of concern When larger use of fly ash is planned, particularly in the Serbian construction industry. Radioactivity measurements have been conducted regularly from 1980. This paper presents the results of a ten-year fly ash radioactivity measurements at the Nikola Tesla B TPP located in Obrenovac. In addition, the paper compares the natural radionuclides coal content data combusted by the Nikola Tesla B TPP boilers coming from the Kolubara Basin and ash created during coal combustion. Fly ash created in the Nikola Tesla TPPs boilers is characterised by the increased concentration of the natural radionuclides content compared to coal. This is the so-called technologically enhanced natural radioactivity (Technologically Enhanced Occurring Radioactive Material - TENORM) of industrial waste, whereas the average specific activities: Th-232 in coal amount to 25.2 Bq/kg, and in fly ash and coal 84.2 Bq/kg and U-238 38.3 Bq/kg, respectively. Following the obtained natural radionuclides content results it may be concluded that the Nikola Tesla B TPP ash may be disposed into the environment. Ash may be used also in the construction industry (civil engineering). In building construction applications, ash share as the additive to other building materials depends from its physical and chemical characteristics, as well as from the radionuclides activity: Ra-226, Th-232 and K-40. Unlike the thermal power plants regularly (once a year) testing the specific natural radionuclides activity in the combusted coal and boiler fly ash, the Electric Power Industry of Serbia has not performed large-scale investigations of the natural radionuclides content in coal within the Kolubara Mining Basin. Natural radionuclides content in fly ash is compared to the combusted coal some 3-4 times higher and may present a limitation for applying ash in the construction industry. In view of the above, and considering the construction industry interests in using the Nikola Tesla B TPP ash, regular investigations of the natural radionuclides content in ash created in the thermal power plants should be carried out, together with the Kolubara Mining Basin coal combusted by the Nikola Tesla B TPP and other PE EPS thermal power plants. The current Kolubara Mining Basin coal characteristics investigation programme should be supplemented by the natural radionuclides content of the uranium (U-238 and Ra-226) and thorium series (Th-232) and potassium 40(K-40).

U termoelektranama (TE) Javnog preduzeća 'Elektroprivreda Srbije' (JP EPS) koje u kotlovima sagorevaju lignit, kao nus produkat nastaje godišnje oko 6 miliona tona letećeg pepela. Potencijalno tržište za upotrebu letećeg pepela postoji, ali ga za sada koriste isključivo cementare. Radioaktivnost letećeg pepela može da predstavlja jedan od važnih razloga protiv njegove šire upotrebe u građevinskoj industriji Srbije. Merenje radioaktivnosti u termoelektranama redovno se sprovodi od 1990. godine. U radu su prikazani rezultati dvadesetogodišnjih merenja radioaktivnosti letećeg pepela u termoelektrani Nikola Tesla B (TENT B) u Obrenovcu. Uporedno su prikazani podaci o sadržaju prirodnih radionuklida u uglju koji se sagoreva u kotlovima TENT B poreklom iz kolubarskog basena i pepelu koji nastaje prilikom sagorevanja uglja. Na osnovu dobijenih rezultata o sadržaju prirodnih radionuklida zaključuje se da se pepeo iz termoelektrane Nikola Tesla B može odlagati u životnu sredinu. Pepeo se može koristiti i u građevinarstvu, u niskogradnji. Kod primene u visokoj gradnji udeo pepela kao dodataka drugim građevinskim materijalima zavisi kako od njegovih fizičkih i hemijskih karakteristika, tako i od specifične aktivnosti 226Ra, 232Th i 40K.