| Coal Burning Power
Plants (CBPP)
In some regions of Hungary (mainly in the region
of Mecsek mountains and on the territory
from the Balaton highland to Tatabanya city)
the natural radioactivity of the coals is 20-100 times higher
than that of the worldwide average. Those mines mostly have
been closed, but the ash and slag remained after combustion
was deposited in huge tailings ponds. |
| Coal mining site |
238U
series |
232Th
series |
40K |
| Oroszlány |
99 |
24 |
163 |
| Ajka |
120-480 |
12-35 |
56-190 |
| Borsod* |
38-52 |
32-62 |
190-264 |
| Pécs |
175 |
127 |
560 |
| Várpalota* |
220 |
20 |
30 |
| Visonta |
20 |
15 |
80 |
| Komló* |
150 |
97 |
384 |
| Dorog* |
40 |
36 |
194 |
| Tata* |
100-140 |
30 |
162-270 |
|
With most of the coal mines closed, the existing
CBPP work on imported coals or switched to gas combustion. As
a result of coal combustion, around 100 million tons
of slag and ash was produced, more of this material
is still in the environment.
The highest Th-232 concentration was measured in the ash and
slag mixture in the tailings ponds of the Pannonpower Co. near
Pecs city (186 Bq.kg-1), and the lowest was in the
Ajka power plant ash (19 Bq.kg-1). The U-238 concentration
was highest in the Ajka power plant ash, (1459 Bq.kg-1), the
lowest was measured in Inota.
The list of present and past operating Hungarian coal
fired power plants is presented in Table 2.
Some of the coal fired power plant tailings ponds have been
recultivated by covering with a thin (approximately 30 cm) layer
of local uncontaminated soil. At some places phytoremediation
was done.
|
| Power plant |
Power
(MW) |
| Bakony Power Co. |
|
| - Ajka Power Plant+ |
102 |
| - Inota Power Plant+ |
52 |
| Mátra Power Co. |
836 |
| Pécs Power Co. (Pannonpower Co) + |
190 |
| Borsod Energy Ltd. |
|
| - Borsod Power Plant* |
137 |
| - Tiszapalkonya Power Plant* |
200 |
| Vértes Power Co. |
|
| - Oroszlány Power Plant |
235 |
| - Tatabánya Power Plant |
34 |
|
Pecs coal fired power plant
During several years of operation of the CBPP near city Pecs
in Southern Hungary, 28 million tons of ash and slag, containing
elevated levels of naturally occurring radioactive materials
(NORM) have been produced. This ash and slag mixture in a
water suspension form has been released to the environment
into a controlled and monitored area near the plant, surrounded
by dams. The wastes formed huge ponds, gradually drying as
the water from the ponds has been recovered and recycled.
|
| The area of the tailings ponds comprises approximately
270 hectares. The ash and slag mixture was deposited directly
on the soil surface without any pretreatment. The thickness
of the deposited material varies between 18 and 21 m. Outskirts
of the city Pecs are near the Northern edge of the tailings
ponds, and in the South the area borders agricultural lands.
The area consists of old dumping areas that have been restored
by 30 cm soil layer and vegetated by mixed gramineous plants
and trees, and unrestored dried tailings ponds and fresh tailings
ponds which are currently in use. |
|
According to the market strategy of the company,
coal buring will be terminated in 2004 and the electric power
production in the future will be based on gas burning. In view
of this long-term strategy and taking into account the demands
of the growing urban and industrial areas of the nearby city
Pecs the power plant company decided to launch an environmental
restoration program, which is in progress now.
The main goals of the planned remediation are: reduction of
the contamination of the surrounding territories by resuspension,
decreasing the external gamma dose rate and of the radon exhalation
from the surface. An important task is to work out recommendations
for future industrial, agricultural, and urban utilization.
Intensive radiological pre-remediation survey in this area is
in progress, the tailings ponds systems could be used as reference
test site for remediation. |
| Ajka coal fired power plant |
| The
coal combustion near city Ajka started in the 30-ies of the
last century, and approximately 14 million tons of ash was
damped out covering now around 170 hectares. According to
the decision of the appropriate authorities coal combustion
seems to come to an end in 2004. The tailings ponds will be
subject for remediation. At present parts of the ash and slag
produced in the Ajka coal fired power plant are used as dam
and cover material for the nearby red mud tailings pond. Part
of the tailings is located closed to the city. On the tailings
ponds water-recycling pools were created, some of them has
been already temporarily covered by soil layers.
|
|
| Aluminium: Neszmely red
mud tailings pond
Intensive bauxite mining was going on in Hungary in the 70-80-ies.
The average bauxite production was about 2 million tons per
year. In the 90-ies most of the bauxite mines have been closed,
but as in the case of the coal fired power plants, the wastes
are still in the environment. Nowadays the bauxite production
is stabilized on the 1 million tons per year level.
In the alumina production industry the Bayer ore processing
is used exclusively, producing by a series of processing procedures
alumina earth (Al2O3). During the processing of poor quality
Hungarian ores a lot of red mud is produced. Production of
1 ton of alumina earth resulted in production of 1.2-1.4 tons
of red mud.
The natural radioactivity of Hungarian bauxite ore is in the
range of the world average. At some places, however, the radioactivity
is 2-3 time higher.
Alumina earth production was terminated everywhere except
in Ajka city and Mosonmagyarovar city, the production is 300-400
thousand tons and 100 thousand tons respectively. The tailings
ponds contain approximately 20 million tons of red mud on
a 200 hectare territory. The ponds are partly recultivated
by using soil and ash and slag material from the Ajka CBPP.
For the case study the tailings pond of Almasfuzito Alumina
Earth Co. near Neszmely village is proposed, as it is completely
intact and located very close to the Danube river bed. Around
4 million tons of red mud is deposited in a valley closed
by dam, the underlaying soil consists of clay minerals in
a large proportion. The external gamma dose-rate varies in
a range 200-400 nSv/h at 1 m above the surface of the tailings
material. The area is in an intensively cultivated agricultural
region, the territory is privatized and remediation is planned
in the future. |
In bauxite treatment the Bayer process is used
in Hungary. By this technology producing 1 ton of aluminium
ore appr. 1,2-1,45 tons of red mud is produced. Only the part
of the produced aluminium ore was melted in Hungary in plants
in Ajka and Inota, the first plant has been shut down. The
radioactivity of the Hungarian bauxite is in the range of
the worldwide average, only in Csordakút mine was found
higher radioactivity ore. |
| Most of the radioactivity of the aluminium ore
is accumulated in the red mud. Typical radioactivity of the
red mud in Hungary is shown in Table 5. |
