Intai proj

COAL There are two coal fired thermal power plants included in the Croatian power system. Both of the plants are situated close to town of Plomin, in Istria County.

Air-view of Istria Peninsula	Map of Istria Peninsula
THE POWER PLANTS CFPP Plomin is a 125 MW coal powered plant. Built on the Adriatic coast, at the end of the Plomin bay in Istria region of Croatia, it started to operate in 1970 using coal from local mines from the nearby Rasa area. Up to the beginning of the nineties, the majority of coal used was anthracite from Istrian local mines. The deposited waste material was characterized by relatively high 226Ra and 238U activities, while potassium and thorium content was very low. The coal that had been mined in Istria for decades is characterized by some typical features of coals lying in karsts regions. In particular, it has: a) a high sulfur content: 10-14% of sulfur. b) increased radioactivity which varies not only from mine to mine, but also between the coal layers. The Istrian coal is characterized by: •²³⁸U specific activity varying between 25-4,900 Bq/kg (average of 310 Bq/kg) •²²⁶Ra specific activity of 28-2,000 Bq/kg (average of 260 Bq/kg) •Specific activities for ⁴⁰K and ²³²Th not significantly higher than world mean values for coals Construction of the second block, Plomin 2, started in 1985. The Ministry for Construction and Environmental Protection called on the investor to add a desulphurization system. At the same time it became clear that no domestic hard coal reserves were available for operation, even for the first block, Plomin 1. Domestic coal would be abandoned in any case because of poor ecological, technical and economic parameters. In April 1992 the construction stopped. After the end of the war, the construction was resumed. After usual operation tests, from 1999 Plomin 2 has been in commercial operation. This second block with maximum power output of 210 MW (net out 192 MW) will produce around 1.2 billions kWh/year of electric energy. Coal consumption (hard coal = 24 MJ/kg) will be around 80 t/h. The height of the chimney is 340 m. The plant will be in operation for 30 years, and upon revitalization it is expected to run additional 10 years.
	Fuel for these plants now is imported low-sulphur (1%) hard coal. Plomin 2 is the only CFPP with desulphurization in the Mediterranean. At the beginning, the majority of coal used was anthracite from Istrian local mines, lignite and brown coal from Dinaride. Over the past ten years domestic coal was substituted with a mixture of coals (Istrian coal and imported coals). Recently, due to the closure of local coal mines, only imported coals are used in the plant. A significant difference in natural radionuclides of uranium and thorium decay series and 40K exists between domestic and imported coals. Transportation of coal to Plomin Port is by tow-boats, and from Plomin Port to the power plant is through a closed system.
Radioactivity in coal samples of different origin
Dust from the exhaust gas is removed using electrostatic filters. Emissions are limited to 50 mg/m³. Waste water is refined up to the level at which water can be used as a technological water, or up to level at which water is acceptable for the drain to river Boljuncica. As expected, the radioactivity of slag/ash is increased, so it can be considered as TENORM (technically enhanced naturally occurring radioactive material). MAIN CHARACTERISTICS OF THE THERMAL POWER PLANTS:
PLOMIN 1 • Output power: 125 MW • In operation since 1970 • Origin of the coal: - Anthracite from Istrian, lignite and brown coal from Dinaride mines • Characteristic of the coal: - High sulfur content (10-14% of sulfur) - Increased radioactivity • Waste characteristic (ash/slag): - Approximately 900 t - Area of 120,000 m²	PLOMIN 2 • Output power: 210 MW • In operation since 1999 • Origin of the coal: - Hard coals from South Africa, Columbia, Indonesia - Coal consumption (hard coal = 24 MJ/kg) will be around 80 t/h • Characteristic of the coal: - Low sulphur content (1% of sulphur) - Low radioactivity • Waste characteristic: - Location: same land field as for Plant 1 - Area of 120,000 m² - Present volume about 900 000 m³ - The thickness of the accumulated slag/ash not over 8 m - The thickness of the soil layer is about 60 cm, seeded with grass - Drainage system and a retention pond
THE WASTES Collected flying ash has radioactivity of: •²³⁸U specific activity varying over years from 500-8,600 Bq/kg •²²⁶Ra specific activity of 2,600 Bq/kg (average) Bottom ash has radioactivity of: •²³⁸U specific activity from 400-1,800 Bq/kg •²²⁶Ra specific activity of 800 Bq/kg (average)
	Radioactivity in ash/slag samples from coals of different origin
With the start of CFPP Plomin operation slag/ash landfill was set up in a small valley close to the power plant site as a heap of waste generated by routine operation. No engineering structures were built to contain the material. The landfill is situated at the eastern coast of the Istria peninsula, approximately 5 km from the seaside, and some 10 km north-west from the urban area but with some of the houses less 1,000 m from it. Approximately 20,000 inhabitants live in 10 km radius. The landfill is placed over the downstream section of the Bizac torrent, along the contact zone of proluvial fan of the Boljuncica river (at the non-inundated section of the Plomin bay), and the slope of karst hilly area surrounding the bay. The bottom of the repository is composed of limestone. Thus, a typical karst hydrology is present in the area where locally occurring groundwater flows directly towards the sea. Plant and pile are located in carbonate terrain of Cretaceous and Palaeogene age. Soils, terra rossa mainly, are poorly developed, even completely missing and carbonate bedrock is exposed sporadically. Few flysch and terra rossa soil profiles were analysed in the nineties. Table 1.
Activities of uranium and thorium series radionuclides in terra rossa soils are relatively high. Lower activities of naturally occurring radionuclides characterise soils developed on flysch sediments of Eocene age. Slag/ash is transported by conveyers. Disposed material is leveled by machinery. The maximum thickness of the accumulated slag/ash does not exceed 8 m, whilst the present volume of disposed material is some 900.000 m³, covering an irregular area of 24 ha. Approximately 70% of landfill area is covered by a 60 cm thick soil layer and partially topped with grass. In order to decreases erosion and proluvial processes, the landfill is provided with a drainage system and a retention pond which diminishes transport and deposition of eroded terrestrial material (primarily disposed ash/slag) into the Plomin Bay.
Due to variability in radioactive content of domestic coal, use of the coals of low radioactivity and random placement of dumped waste material at the landfill, the distribution of radioactivity throughout the pile is pronouncedly uneven, varying considerably both horizontally and vertically. During the last ten years the local coal was mixed with imported coals having low sulfur content and low radioactivity. Finally the local mines were closed and since then only imported coals have been used. When domestic Istrian coal has been completely substituted with imported coal, uranium series radionuclide concentrations in deposited waste materials decreased significantly. For practical reasons the same landfill was used for slag/ash generated by the operation of the recently new 210 MW coal fired power plant block. CFPP Plomin 2 uses imported low-sulphur (1%) hard coal. After the wet desulphurisation, the by-product is gypsum. The SO₂ concentrations in the area are at a level approved by the WHO. Considerable quantities of by-products from the CFPP operation, which are considered industrial waste, were in 2000 put to commercial use as secondary raw material for the TC Koromacno cement plant. This waste included about 18,000 t of fly ash, 2,500 t of slag and 8,300 t of gypsum. Such an approach results in considerable reduction in quantity of waste that would otherwise be land filled in the power plant neighbourhood. Mediterranean climate prevails, locally characterized by an average annual rainfall of 1,294 mm and occasional strong winds up to 11 ms^-1. Hence, aeolian transportation of disposed and uncovered slag/ash is quite possible. Surface streams are rare in the Palaeogene flysch terrains. Springs of underground waters in carbonate terrains, with relatively high uranium concentrations, undergo the influence of numerous closed and flooded coal mines. ( Table 2).