Intai proj

Assessment of environmental risk of radioactively contaminated industrial tailings

INTAILRISK

Problem statement

The INTAILRISK project:

Project results

Project partner information

Test sites

TEST SITES:

Bosnia &
Herzegovina

Serbia & Montenegro

COAL	In the project, the following sites are considered: (1) "Nikola Tesla A", (2)"Nikola Tesla B" and (3) Kolubara in Serbia, (4) Obilic in Montenegro. The power plant “Nikola Tesla B” (TENT B) has been considered as field test site for the first year. Ada park was chosen as control area. It is located on an island in the Sava river, in the eastern part of Belgrade (53 km far from TENT B and 4 km from Belgrade). The distance from the TENT B area, the similar geological conditions, and its characteristics make ADA park a suitable control field site. Coal characteristics The main coal supplier for the thermal power stations in Serbia and Montenegro is the Kolubara basin which is located 30 km SW of Belgrade and is composed of lignite, included in Miocene sediments. The Kolubara basin comprises an eastern and western part that are productive and a northern non productive part. The productive part of the Kolubara coal basin covers about 600 km². The eastern part, which represents 20% of the total productive surface, covers some 120 km², and consists of four open mines A, B, C, D. Field A is exhausted since many years, and other fields are coming to the end. At present, the exploitation operates in open pit mines. The western part of the basin, at the opposite side of river Kolubara is promising for future exploitation, and covers 80% of the basin or 480 km².

*Geochemical characteristics of the coal* The geochemical characteristics of the coal are as follows :

	Radioactivity of coal on input at TENT B in period 1990-2003
Technical characteristics of the power plant TENT B The next table summarizes the technical characteristics of the thermo power plant TENT B.

Waste characteristics *Ash transport and disposal* The ash disposal site of the Nikola Tesla B power plant is located approximately 4.5 km from the power plant.The total quantity of ash deposited per year is about 2,1 Mt. of which approximately 7% is bottom ash.
The bottom ash is removed mechanically by a de-asher and is transported by a belt conveyor. The fly ash is conveyed via pneumatic flow channels. Fly ash from the air preheater-hoppers and boiler hoppers is collected in the same way. The ashes are mixed together and flushed with additional water to the ash slurry sump. From there the water/ash mixture is pumped via a pipeline to the ash disposal site for final disposal. The planned mixture of 10 parts of water per 1 part of ash (‘thin slurry’) is mostly exceeded.
This system, which provides sufficient operational reliability, however, results in significant adverse environmental impacts: • Susceptibility to dust blow in moderate to high winds: nuisance and health effects • Discharge of excess water to surface waters (overflow & drainage): chemical stress on receiving waters • Infiltration of excess water into ground waters: chemical stress on ground waters • Occurrence of swamping of surrounding agricultural land. The slurry is pumped into an active cassette surrounded by dams with a height of 3 m. Within the cassette the ash settles and consolidates. Once an intermediate height for the settled ash is reached, no further ash slurry is discharged to it and the cassette is kept passive for a period of several years before being used again. It is vegetated to reduce dust blow susceptibility. The operation is then shifted to another adjacent cassette. Before the other cassettes reach their target intermediate height, new dams are constructed on top of the old ones and ash slurry can be pumped again. This sequential use of cassettes continues until the final height of the disposal site is reached. At that time the cassette is permanently capped and vegetated. After settlement has occurred, some of the excess water overflows and is directly discharged into the drainage canals and rivers without any waste water treatment. Some of the excess water infiltrates into the ground and may penetrate into aquifers if not captured and discharged by well gallery systems. The dried surface of the cassettes is subject to wind erosion. The 10:1 transport technology results in ash deposits particularly susceptible to dust blow because, during the settlement process, the smaller particles deposit at the surface. Moreover, those components of the ash which could provide surface consolidation (e.g. CaO) are washed away. *Ash characteristics* The ash consists of some 90 to 95% of fly ash and 5 to 10% of bottom ash. Its chemical composition is characterised by: ƒ High SiO2 contents of 50–60% • high Al₂O₃ content of around 20% • low CaO content of around 7% • relatively high amounts of heavy metals The grain size distribution of the ash shows that about 80% of the ash particles are smaller than 0.1 mm. That is why the ash is prone to be wind blown from exposed ash deposit surfaces. The high dust-blow incidents which occur typically 6-15 days each year around Nikola Tesla B may be a health hazard due to shear overload of the body’s dust filtration and clearance mechanisms, regardless of particle size. There is also the associated potential hazard of heavy metals ingestion, either directly from the dust or via the food-chain, from dust dispersion during the wind-blow incidents. *Environmental impacts on surface and groundwaters*
For the transportation of the ash from Nikola Tesla B power plant to the ash deposit site large quantities of water are needed. The approximate amount of water per year pumped to the individual ash deposit site is 30 Mm³. In the current systems, dissolved chemicals are leached and transported with the large quantities of slurry water. A proportion is emitted to surface waters and partly ground waters after undergoing physical and chemical change within the ash disposal site. The main pollutants are sulphate, pH (OH) and arsenic. Concentrations of such pollutants in ash slurry are variable, reflecting variations in lignite and mixing as well as the composition of the source water for transport, and can be many times EQS values. Plant process water can also be mixed with the ash slurry. At Nikola Tesla B it is now the practice to direct waste water from regeneration of the water treatment plant resins to the ash slurry mixing station without prior neutralization.
	Specific activity of the radionuclides from the fly ash and slag from the TENT B in period 1990-1999

Specific activity of the radionuclides from the fly ash and slag from the TENT B in period 1990-1999
*Industrial application of waste material* Industrial application is very small. Minor quantities of ash are used for production of building materials.