25-29 November 2019

Bahadurgarh, India

Ivan Stoyanov

Kozloduy NPP

Bulgarian Nuclear Power Plant is located 200 km north of Sofia and 5 km east of Kozloduy, a town on the Danube River, near the Romanian border. It is the country's only nuclear power plant. The construction of the plant started on 6 April 1970.The commercial operation of Kozloduy NPP started in 1974 with the commissioning of Unit 1 WWER-440 (V-230 type).

Now at Kozloduy NPP site there are 6 power reactors - 4 WWER-440 and 2 WWER-1000 (V-320 type). Total installed capacity-3760MW.

Unit Reactor type Power,

MW

Commissioning Status

1 WWER – 440, model B-230 440 1974 Shut down

31.12.2002

2 WWER – 440, model B-230 440 1975 Shut down

31.12.2002

3 WWER – 440, model B-230 440 1980 Shut down

31.12.2006

4 WWER – 440, model B-230 440 1982 Shut down

31.12.2006

5 WWER – 1000, model B-320 1000 1987 In operation

6 WWER – 1000, model B-320 1000 1991 In operation

The fuel of the reactors is uranium dioxide (UO2), which is compacted to cylindrical pellets of about 9 mm height and 7.6 mm diameter. The uranium pellets are inserted into a tube (cladding) made of a zirconium alloy (Zr +1% Nb), which is sealed hermetically. The rods are bundled into assemblies.

The cross section of the WWER-440 fuel assemblies is a hexagon and each contains 126 fuel rods.

The fuel enrichment was 1.6 %, 2.4 % or 3.6 %.

The distance of the centre lines of the assemblies is 14.4 cm. Altogether 349 assemblies can be inserted into the reactor core.

The WWER-440 spent fuel assemblies are with reached burn up in the range 31-39 MWd/kgU.

The Fuel cycle of Units 5 and 6 of Kozloduy NPP is based on 2 types of fuel assemblies: TVSA and TVSA-12.

One WWER-1000 fuel assembly has 312 fuel elements, 6 or 12 of them contain Gd2O3

absorber. Core zone contain 163 fuel assemblies.

TVSA fuel assembly was introduced for first time in 2004. Maximum enrichment – 4,4%, Maximum reached burn-up of spent fuel (average per volume), 54,5 MWd/kg, Maximum allowed by manufacturer - 55 MWd/kg and for fuel rod burn-up – up to 64 [MWd/kgU].

TVSA-12 fuel assembly was introduced for first time in 2016 in order Unit 6 to operate in 104%. Maximum enrichment – 4,95%, maximum allowed by manufacturer - 63 MWd/kg and for fuel rod burn-up – up to 72 MWd / kgU.

The facilities for storing SNF at the Kozloduy NPP site:

reactor pools at Unit 5 and 6;

wet storage facility for spent fuel (WSFSF);

dry storage facility for spent fuel (DSFSF).

The full capacity of pool 5 is 612 fuel assemblies (at least 163 has to be free when the rector is in operation).

The full capacity of pool 6 is 611 fuel assemblies (at least 163 has to be free when the rector is operation).

The nuclear safety is ensured by the designed assembly pitch and boric acid concentration

not less then 16g/kg.

The cooling system have to maintain the water temperature <50°C.

Construction –1982 –1988

Commissioning –1990

4 pools

max. 168 Baskets

Wet Storage Facility (WSF) – for the WWER-440 and WWER-1000 spent fuel – commissioned 1990.

The full WSF capacity – 224 baskets (168 in use, 56 reserve).

The baskets with the spent fuel are stored in the chemical desalted water.

Each WWER-440 basket contains 30 assemblies with maximum allowed residual heat 15kW and activity 1.73 E+17 Bq.

Each WWER-1000 basket contains 12 assemblies with maximum allowed residual heat 20kW and activity 2.41 E+17 Bq.

The nuclear safety is ensured by the designed assembly pitch.

The cooling system have to maintain the water temperature <45°C.

Dry Storage Facility (DSF) – for the WWER-440 spent fuel with capacity for 78 CONSTOR containers –commissioned 2011.

CONSTOR 440/84 – 84 assemblies with maximum allowed residual heat 20.3kW and activity 2.3 E+17 Bq.

Maximum dose rate at the surface of container is Pγ+n ~ 40-200 μSv/h (middle of the upper lid).

In the terms of reference the maximum allowed value was 2000 μSv/h.

Maximum surface temperature 90°C.

Storage term – 50 years.

Bulgaria has no capability to conduct a full NFC.

„Strategy for Managing the Spent Nuclear Fuel and Radioactive Waste Until 2030“ was issued in 2011 and updated in 2015.

spent fuel management is to store the spent fuel fromreactors in spent fuel pools and spent fuel wet and drystorage facilities

further transportation for reprocessing if it is economicallyviable

The SF generated in the territory of the country is a material containing usefulcomponents. This material has to be processed in the country of origin of the fuelor at international level in a mutually advantageous economical, technical andtechnological manner;

The SF for which the processing is proven to be economically inexpedient may beclassified as radioactive waste following the ASUNE requirements and managedbased on the concept for „deferred decision for further utilization”;

In long-term prospective, accepting the global and all European consensus on thedeep geological disposal, it is presumed that this is the most convenient way forpermanently guaranteed safety in isolating SNF and high level radioactive waste.

Taking into account the geological and climate conditions of the country,legislation, public opinion, financial possibilities and the volume of SNF, theparticipation of the country in regional and international initiatives is accepted asexpedient.

Minimize the quantities of SNF stored on site, so as not to allow any harmful consequences on the staff, the population, the environment, and the future generations

Implementing new, better types of NF, which lead to reduction of the generated quantity of SNF

Safe management and storage of HLW generated during the reprocessing of SNF

Ensuring the required minimum of free volume for emergency core unloading of the Units 5,6 of Kozloduy NPP

Spent fuel temporary storage at the reactor spent fuel pools. Period of storage is in accordance to the technical documentation.

Spent fuel transportation:

- from reactor spent fuel pools to Wet Spent Fuel Storage Facility (interim storage WWER-1000 SNF);

- from Wet Spent Fuel Storage Facility to Dry Spent Fuel Storage Facility (WWER-440 SNF);

-from reactor spent fuel pools to Russia for storage and reprocessing (WWER-1000 SNF);

-from Wet Spent Fuel Storage Facility to Russia for storage and reprocessing (WWER-440 and WWER-1000 SNF).

Packaging capacity, FA, pcs. 30; Mass of a packaging, not more than

81.0 t Mass of a loaded package, not more

than 92.0 t

Packaging capacity, FA, pcs. 12

Mass of a packaging, not more than 104.0 t

Mass of a loaded package, t, not

more than 113.0 t

During transportation a special convoy is arranged, including fire engine, ambulance, security and police vehicles. Special trailers are used for transport of spent fuel casks

For SNF shipment along the Danube River a special dumb-barge is used with a capacity of 8 containers TUK-6 or TUK-13.

The barge is equipped with passive and powered cooling systems; 2 diesel generators, decontamination system; radiation monitoring system; containers parameters control system and other equipment.

The containers with SNF are transported in special railroad train consisting of up to eight freight wagon-containers with ventilation system, two escort wagons for accompanying persons, means for control of containers’ parameters and two protection wagons.

Both containers TUK-6 and TUK-13 are designed accordingrequirements of SSR-6, IAEA and meet all the following criteria:

General requrements for all type packages (SSR-6 (Rev. 1) paragraphs 607–618)

Requrements for type B(U) packages (SSR-6 (Rev. 1) paragraphs 636–649)

Requrements for type B(M) packages (SSR-6 (Rev. 1) paragraphs 667–668)

Heat dissipation (SSR-6 (Rev. 1) paragraph 653–666)

Shielding (SSR-6 (Rev. 1) paragraph 617)

Storage option assures safely storing until spent fuel reprocessing.

The presence of operating Wet Spent Fuel Storage Facility where the fuel assemblies from both types of reactors are stored and Dry Spent Fuel Storage Facility for only WWER-440 fuel assemblies provide the possibility for safe and effective management of Nuclear Fuel Cycle back-end for at least 50 years.

Reprocessing SNF provides long term strategic flexibility and confidence and reduce the volume of high-level waste to be disposed.

The entire transportation and technological equipment is certificated and tested, the process is well documented and has a long-term operational experience.