Type: VVER-440 Model V270 (a variant of the V230)
Units: Two
Total megawatts (net): 752
Location: Medzamor, Armenia
Dates of initial operation:
For an overview of the principal strengths and deficiencies of Soviet-designed plants, see Soviet Nuclear Power Plant Designs.
On Oct. 15, 1982, a short circuit in a power cable of a large boron make-up pump in Unit 1 caused electrical protection failure and overheating of cable and motor. Fire started in several places along the cable way simultaneously, and smoke spread through open shafts to the main control room. Fire spread rapidly to four parallel cable tunnels serving both units. The destruction of many power and control cables caused several malfunctions.
The automatic fire alarm in the cable tunnels worked, but the fixed foam extinguishing system failed to discharge. The fire led to a total station blackout. The power supply from diesel generators was lost because of fires in the cable tunnels, and the external grid connections were also lost. Control of the plant was endangered because of smoke in the main control room and the total lack of emergency control provisions.
After the fire, a separate shutdown train was installed in the boron pump room. In addition, cables were given a fire-resistant coating, cable penetrations were tightened and fire fighting arrangements were improved.
In 1988, Unit 1 was annealed.
Unit 1 was shut down in February 1989 and Unit 2, in March 1989--following the devastating earthquake of December 1988--because of public concern about the plant's safety. The plant itself was undamaged by the earthquake. Unit 2 was restarted in October 1995 and connected to the grid in November; Unit 1 remains closed.
Training. Prior to the restart of Unit 2, plant operating staff were trained on simulators at Russia's Novovoronezh plant, Finland's Loviisa plant (a VVER-440 V213), and Germany's Greifswald plant (now closed). In addition, selected plant staff were sent for training, under the auspices of the IAEA, to various countries, including Finland, Bulgaria, the Czech Republic and the Slovak Republic. The training covered licensing, accident management and fire protection. Operating personnel were examined by a panel of five inspectors from the country's regulatory body to qualify for a reactor operator's license. At the regulators' request, the IAEA sent observers from Hungary and the Slovak Republic with experience in training VVER personnel.
The operating staff of Unit 2 includes one trained Russian operator on each shift.
According to Armenian radio, the country's unstable power network prevented Unit 2 from reaching its desired capacity in December 1995. The unit was operating at 310 megawatts, not the target 376 megawatts.
Both units are variants of the VVER-440 Model V230--sometimes referred to as the Model V270. They have been seismically upgraded for Armenian conditions, with reinforcements made to the reactor building and structures, electrical cabinets and cooling towers. In addition, the Model V270s have primary coolant pumps with longer coast-down time, an additional emergency feedwater system and an additional residual heat removal system.
After the fire in 1982, several modifications were made, including installation of an additional control panel, fitting of an additional independent emergency power cable network, improved separation of safety-related cabling and the implementation of numerous fire protection measures.
The main backfits approved by Armenian regulators include hardware modifications of: primary circuit, protection and control systems; emergency cooling systems; thermal insulation; and fire and explosion protection.
Specific upgrades carried out or under way include new seismic-resistant storage batteries from Germany, an additional DC panel to provide backup power, a new diesel generator hookup that provides twice the redundancy of the original configuration, and rerouting of power lines to separate trains. In addition, all monitoring equipment has been replaced, and additional reactor protection system shutdown logic installed for water levels in the steam generators and for water and steam levels in the pressurizer. Sealing gaskets and other components providing isolation in the system's confinement were upgraded using materials and technology from a U.S. company, and the reactor hall sprinkler system was modernized. Following an inspection of the unit's steam generators, 1-2 percent of the tubes were plugged.
According to the plant manager, over 500 tons of equipment needed to refurbish and upgrade the unit--most of it from Russia--was airlifted to the site because of the land-route blockade by neighboring Azerbaijan.
A system of five large basins is under construction at the plant site to upgrade the essential service water supply. It is expected to begin operating in 1997.
Croatian Contract. Croatia's Inetec has a contract, running from 1994 to 1999, to carry out steam generator tube eddy current testing and tube plugging of Unit 2. The scope of the project depends on the tube inspection results.
December 1995
