Reactor Types:	|	RBMK	|	VVER 440/213	|	VVER 440/230	|	VVER 1000

The VVER-1000

The VVER-1000 design was developed between 1975 and 1985 based on the requirements of a new Soviet nuclear standard that incorporated some international practices, particularly in the area of plant safety.

Principal Strengths:

Steel-lined, pre-stressed, large-volume concrete containment structure, similar in function to Western nuclear plants.

"Evolutionary" design incorporating safety improvements over VVER-440 Model V213 plants. The Soviet approach to standardization was based on continued use of components that had performed well in earlier plants.

Use of four coolant loops and horizontal steam generators--both considered improvements by Soviet designers.

Redesigned fuel assemblies that allow better flow of coolant, and improved control rods.

Plant worker radiation levels reportedly lower than in many Western plants, apparently due to selection of materials, high-capacity system for purifying primary coolant, and water-chemistry control.

Principal Deficiencies:

Substandard plant instrumentation and controls. Wiring of emergency electrical system and reactor-protection system does not meet Western standards for separation--control and safety functions are inter connected in ways that may allow failure of a control system to prevent operation of a safety system.

Fire-protection systems that do not appear to differ substantially from earlier VVER models, which do not meet Western standards.

Quality-control, design and construction significantly deficient by U.S. standards.

Protection measures for control-room operators essentially unchanged from earlier VVER-440 Model V213 design, which does not meet U.S. standards. Unlike all U.S. nuclear plants, and most in Western countries, VVER-1000s have no on-site "technical support center" to serve as a command post for stabilizing the plant in an emergency. Technical support centers were incorporated in U.S. and many Western nuclear plants following the accident at Three Mile Island Unit 2 in 1979.

Operating and emergency procedures that fall far short of Western standards and vary greatly among opera tors of VVER-1000 plants.

Higher power densities and smaller volume of primary and secondary systems result in a somewhat less forgiving and stable reactor.