7. ENVIRONMENTAL AND RADIOACTIVE WASTE MANAGEMENT ASPECTS OF THE
7.2. Management of radioactive waste from the accident
7.2.1. Current status of radioactive waste from the accident
7.2.1.1. Radioactive waste associated with the shelter The shelter is considered to be “the destroyed unit 4 after a radiological accident” and “a near surface storage facility for unconditioned radioactive waste at a stage of stabilization and reconstruction” [7.22, 7.23]. The amount and type of waste, debris and other radioactive material inside the shelter is presented in Table 7.3.
In addition, soil that was heavily contaminated by the deposition of fuel fragments and with radio-nuclides and debris from the accident (metal pieces, concrete rubble, etc.) was also collected and stored in the vicinity of unit 4:
(a) Three pioneer walls (west, north and south of the shelter), where contaminated soil, concrete and containers are stored and which contain an estimated 1700–4900 m3 of high level waste5 and up to 72 000 m3 of low and intermediate level waste [7.25, 7.26].
(b) The cascade wall north of the shelter, where core fragments, metal, concrete, core pit
equipment and accident cover material are stored (16 600 m3 of high level waste, 117 t of reactor core elements and 53 400 m3 of low and intermediate level waste) [7.25].
(c) The industrial site around the shelter, where concrete, gravel, sand, clay and contaminated soil are stored that contain 7000 m3 of high level waste and 286 000 m3 of low and inter-mediate level waste [7.27]. Other studies show that fuel, graphite, etc., are located in the contaminated soil [7.26].
The radioactive waste inside the pioneer and cascade walls was later covered with concrete. This material is considered to be high level waste that is not acceptable to be disposed of in near surface disposal facilities. Since it cannot be retrieved easily for conditioning, the radioactive waste recovered from these walls is to be part of a global strategy for the decommissioning of unit 4.
TABLE 7.3. ESTIMATED INVENTORY IN THE SHELTER [7.25]
Type of radioactive waste and criteria of assessment
Category of
radioactive waste Amount
FCM Fresh fuel assemblies, spent fuel
assemblies, lava type material, fuel fragments, radioactive dust
High level About 190–200 t, 700 t of graphite
Solid radioactive waste with less than 1% nuclear fuel (mass)
Fragment of the core with a dose rate at 10 cm of more than 10 mSv/h
Liquid radioactive waste Changing inventory based on precipitation (e.g. pulp, oils, suspensions with soluble uranium salts)
Low level (up to 3.7¥105 Bq/L)
2500–5000 m3
Intermediate level (more than 3.7¥105 Bq/L)
500–1000 m3
Solid radioactive waste Metal equipment and building material, for example concrete, dust, non-metal material (organic, plastic)
High level 38 000 m3 (building material), 22 240 t (metal constructions) Low and
intermediate level
300 000 m3 (building material and dust), 5000 m3 (non-metal)
5 High level waste falls into two subcategories: low temperature waste with a heating rate of less than 2 kW/m3 and heat generating waste with a heating rate higher than 2 kW/m3 [7.24].
It is estimated that the current and expected radioactive waste from unit 4 can be categorized as short lived low and intermediate level waste (soil from the construction of the NSC, construction material, concrete, metal constructions, etc.) and high level waste (e.g. FCM) according to Ukrainian legislation [7.28, 7.36].
7.2.1.2. Mixing of accident related waste with operational radioactive waste
During 1986–1993, some low and intermediate level radioactive waste and high level waste with transuranic elements were stored together with some operational radioactive waste from units 1, 2 and 3 in an above ground storage facility (see Fig. 7.9) at the Chernobyl nuclear power plant site.
This waste amounts to about 2500 m3, with a total radioactivity of about 131 TBq [7.19], and is stored unconditioned. Once filled, the storage facility was backfilled with concrete grout and covered with a concrete roof to reduce radiation levels and water infiltration. Thus the retrieval of the radioactive waste stored in this facility cannot be easily achieved and will require particular care.
Plans for such retrieval are currently under study.
At present, this facility is being extended and is intended to be used for the disposal of radioactive waste produced during the decommissioning of units 1, 2 and 3.
7.2.1.3. Temporary radioactive waste storage facilities
The largest volumes of radioactive waste generated by unit 4 remediation activities are
located in the CEZ (see Fig. 7.8). Sites for temporary storage of radioactive waste, of the trench and landfill type, were constructed shortly after the accident at distances of 0.5–15 km from the nuclear power plant site. They were created from 1986 to 1987 and intended for radioactive waste generated after the accident as a result of the cleanup of contaminated areas to avoid dust spread, reduce radiation levels and provide better working conditions at unit 4. These facilities were established without design documentation, engineered barriers or hydrogeological investigations.
The total area of temporary radioactive waste facilities is about 8 km2, with the total volume of disposed radioactive waste estimated to be over 106m3. The main inventories of activity are concen-trated in the Stroibaza and Ryzhy Les temporary radioactive waste facilities along the western trace of the Chernobyl fallout (see Fig. 7.8). The specific activity of the radioactive waste in the temporary radioactive waste facility at Ryzhy Les is 105-106Bq/kg of 90Sr and 137Cs and 103–104 Bq/kg of plutonium isotopes (total).
Most of the facilities are structured in the form of trenches 1.5–2.5 m deep in the local sandy soil.
The radioactive material (soil, litter, wood and building debris) is overlain by a layer of alluvial sand 0.2–0.5 m thick. The majority of the temporary radioactive waste facilities consist of trenches in various types of geological setting, in which waste was stacked and covered with a layer of soil from the nearby environment. These facilities are therefore very variable with regard to their potential for release, which depends on the total radioactivity stored, the waste form (in particular timber), the retention capacity of the substratum along migration pathways and the location of the sites in hydrogeological settings. At least half of these temporary radioactive waste facilities have been studied (see Table 7.4) [7.19, 7.29].
There are also many other temporary radioactive waste facilities, estimated to comprise about 800 trench facilities each with waste disposal volumes in the range of 8 × 102 to 2 × 106m3 [7.29, 7.30]. The inventories of these facilities are known for about half of them. The facilities are not under regulatory control.
Estimates made for a few sites show that their radioactive contents can be high (10–1000 TBq), sometimes of an order of magnitude comparable with the total radioactivity present in soil in the CEZ (about 7000 TBq) [7.30].
FIG. 7.9. Existing above ground storage facility for solid radioactive waste at the Chernobyl nuclear power plant site.
7.2.1.4. Radioactive waste disposal facilities
The main radioactive waste disposal facilities for accident waste are the Buriakovka, Podlesny and Kompleksny sites, which are under regulatory control. These three near surface disposal sites were established after the accident to dispose of radioactive waste from remediation actions carried out during the first year following the accident.
These sites were chosen and designed for the disposal of higher level accident waste than the radioactive waste located in the temporary radioactive waste facilities [7.19].
Buriakovka, built in 1987, is the only disposal facility currently in operation in the CEZ. It comprises 30 trenches covered with a 1 m clay layer and is located on 23.8 ha. Up to 652 800 m3 of radioactive waste has been disposed of. After in situ
compaction, this was reduced to 530 000 m3, with a total radioactivity of 2.5 × 1015 Bq of solid short lived low and intermediate level waste. It consists of metal, soil, sand, concrete and wood contaminated with 90Sr, 137Cs, 134Cs, 238,239,240Pu, 154,155Eu and
241Am. Radioactive waste with dose rates at 10 cm from the surface in the range of 0.003–10 mGy/h was accepted in this facility.
The Podlesny vault type disposal facility was commissioned in December 1986 and closed in 1988. The facility was designed for the disposal of high level waste with a dose rate 10 cm from the surface in the range of 0.05–2.5 Gy/h. Material with dose rates above this was also disposed of in the facility. The total radioactive waste volume of 11 000 m3 of building material, metal debris, sand, soil, concrete and wood was placed in two vaults.
The disposal facility was covered with concrete at its
TABLE 7.4. STATUS OF TEMPORARY RADIOACTIVE WASTE FACILITIES [7.19, 7.29]
Size (ha)
Number of trenches
Number of
landfills Radioactive waste type
Radioactive waste volume
(103 m3)
Total activity (Bq)
Sites with well known inventories
Neftebaza 53 221 4 Soil, plants, metal, concrete
and bricks
104 4 ¥ 1013 Peschannoe
Plato
78 2 82 Short liveda low and
intermediate level waste of soil, rubble and concrete
57 7 ¥ 1012
Partially investigated sites Stantzia
Yanov
128 Known: more than 36
— Soil, plants, metal, concrete and bricks
30 >4 ¥ 1013 Ryzhy Les 227 Estimated at
more than 61
Estimated at more than 8
Mainly soil, some construction and domestic material
500 Up to 4 ¥ 1014
Staraya Stroibaza
130 More than 100
— Soil, metal, concrete and wood
171 1 ¥ 1015 Novaya
Stroibaza
122 — — Soil, plants, metal,
concrete and bricks
150 2 ¥ 1014
Pripyat 70 — — Contaminated vehicles,
machinery, wood and construction waste
16 3 ¥ 1013Bq (1990)
Chistogalovka 6 — — Material from demolition
of buildings, soil, wood and work clothes
160 4 ¥ 1012
Kopachi 125 — — Construction waste from
demolition
110 3 ¥ 1013
a According to Ukrainian legislation, short lived waste is radioactive waste whose release from regulatory control is achieved earlier than 300 years after disposal; long lived waste is radioactive waste whose release from regulatory control is achieved later than 300 years after disposal [7.21].
closure. In 1990 the estimated total radioactivity of the disposed waste was 2600 TBq. In 2002 a re-evaluation of the facility status showed reasons to believe that the total activity of waste disposed at this site may be higher than initially estimated, and a need for a re-estimation of the current inventory was identified. Due to the uncertainties in the inventory, it is assumed that various types of waste were disposed of, including FCM.
The Kompleksny vault type facility was based on reconstructed facilities of the unfinished units 5 and 6 at the Chernobyl nuclear power plant site.
Kompleksny was in operation from October 1986 until 1988 and was designed for low and interme-diate level waste corresponding to dose rates up to 0.01 Gy/h at 10 cm from the surface of the waste container. More than 26 200 m3 of solid waste with a total activity of 4 × 1014 Bq was disposed of in 18 000 containers and later covered with sand and clay.
This waste is mainly sand, concrete, metal, construction material and bricks. Due to the high level of groundwater at different periods of the year, the facility is flooded 0.5–0.7 m above its bottom. Significant uncertainties exist associated with the radionuclide inventory because of the lack of data about the radioactive waste disposed of at the site.
At present, a new near surface facility, the Vektor complex, for low and intermediate level radioactive waste processing, storage and disposal, is under development. This complex will include [7.19]:
(a) An engineering facility for the processing of all types of solid radioactive waste (capacity of 3500 m3/a);
(b) A disposal facility for short lived solid radioactive waste (55 000 m3 total capacity);
(c) A storage facility for long lived solid radioactive material;
(d) A storage facility for FCM;
(e) Intermediate storage for high level conditioned radioactive waste to be prepared for final disposal at the deep geological disposal facility.
7.2.2. Radioactive waste management strategy