The coal deposit
of Kansk-Achinsk basin
The Kansko-Atchinskiy coal basin is unique due to its immense
dimensions and giant reserves of brown coal suitable for open-cut
mining. Its reserves are estimated as 1 220 billion
tons. The Lower-Middle Jurassic coal-bearing formations
in the western part of the basin forma great syncline with
gently sloping northern and southern limbs. The thickness
of coal layers reaches 60-80 m, the ash content mostly ranges
9-16%. From West to East nine great coal deposits were distinguished:
Tisul’ (1), Uryup (11), Barandat (3), Beryezovo
(7), Kibiten’ (8), Altat (9), Nasarovo
(10) (southern limb of syncline), Itat (2), Bogotol
(4) (northern limb of syncline) (Fig. 1).
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| Among these two large deposits are intensively
exploited by open-cut mining: Nazarovo since
1953 and Beryezovo since 1975. Others were
mined mainly for local needs. |
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The coal of the largest open-cut mines (Nasarovo, Beryezovo)
is used in the nearby coal-fired thermal power plants. Besides
this the coal is transported to the large thermal power plants
in Krasnoyarsk and Novosibirsk. Power plants that consume coal
of the Kansk-Atchinsk basin (In the 80ies their total power
was planned up to 6400 Mwt) leave annually about 1,5 million
tons of ash and slag. From this quantity only 50-70 thousands
tons are annually utilized. Fly ash retained by electrofilters
contains 25-50% of total CaO, including 2-13% free CaO .
This is why after hydraulic removal to the tail storage, the
waste waters create a high alkaline environment (pH of waste
water reaches 11-12,5) which is suitable for uranium extraction
and migration. High calcium ash can be used for cement production
and remediation of acid soils. The coal from several small mines
is burned in local boiler-houses. |
The unaltered brown coals of Kansk-Atchinsk basin stand
out by its extremely low radioactivity. That’s why the
waste and fly ash of CBPP’s using these coals are mostly
far from the activity limit for use in building industry (370
Bq/kg) (Table 1).
The upper parts of some coal layers, mainly 0,5-1,5 m thick,
are locally are converted to soot by oxidizing weathering.
Just these sooty varieties of coal are somewhere highly enriched
in uranium. In the past sooty and friable coal was burned
in domestic stoves. Besides that clear evidences of underground
fires can be seen in several open-cut mines (Fig. 2). |
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| The mean uranium content in sooty coal in Beryezovo
open-cut mine was estimated at 0,023 %. Similar altered coals
were discovered in the Nazarovo open-cut mine. These coals have
to be regarded as dangerous for working personnel, but the distribution
and migration path’s of uranium and its progeny from mines
and thermal power plants to the soil, air and water up to date
are almost not investigated. Indications of anomalous radioactivity
up to 5-10 kBq/kg were discovered in Itatsky open-cut mine in
relation to the natural underground fires and in ash from Itatsky
power plant. Moreover, the uraniferous coals are characterized
by very high emanating rate. |
