CHERNOBYL NUCLEAR POWER PLANT BASIC DESCRIPTION


Chernobyl is a town of 30,000 people, 70 miles north of Kiev, in the Ukraine. The V. I. Lenin nuclear power plant is located 10 miles from the town of Chernobyl. Adjacent to the plant is the town of Pripyat, which houses and services plant workers. The plant is on the Pripyat River, near its mouth into the Kiev reservoir.

The plant had 4 nuclear reactors, each with associated steam turbines and electric generators. Two additional units were under construction at the time of the accident, April 26, 1986. Each of these units was of the same Soviet design, designated RBMK-1000.

Chernobyl was the location of the world's worst nuclear power plant disaster. Massive amounts of radioactivity were released, a thousand square mile area will be uninhabitable for many decades.


REACTOR DESIGN : RBMK-1000
Boiling Water Reactor
Electric generating capacity 1000 Megawatt.
Thermal output of core about 2000 Megawatt.
1661 zirconium fuel rods, holding mix of U-238 and U-235; Plutonium-239 is a byproduct, which can be extracted by reprocessing the fuel rod material. Each fuel rod is enclosed in a heat transfer water channel.
211 Boron control rods with 8 fuel rods/control rod
Graphite core 1700 tons, made up of graphite bricks

CONTROL OF THE REACTOR
1. Graphite Core, moderates neutron flux from fuel rods
2. Boron control rods to reduce neutron flux for shutdown
3. Thermal transfer control — closed circuit water/steam loop, multiple water pumps Nitrogen/
Helium gas within containment — low thermal conductivity and oxygen exclusion — pressure and gas mixture are controlled. emergency core cooling water system (ECCS)

CHERNOBYL REACTOR OPERATIONS
Computer for fine control, operator controls set points of feedback controllers Central power authority dictated operating levels in managing power grid Unnecessary shutdown meant 600,000 ruble revenue loss, firing of person responsible.

Plant engineers found the plant unstable at low power levels, Local practice was to manually pull control rods if downward fluctuation threatened spontaneous shutdown. Response time to scram: 18 seconds (theoretically it was claimed to be 3 seconds). Regulations against manual control routinely excepted.

ACCIDENT\SAFETY PLANS
Published odds million to 1 against an accident. Authoritarian control staff & engineers do not question safety. Accident planning was around a scenario of 1 or 2 fuel rod/water channels bursting. No plan included a graphite fire. Administration building had emergency bunker under it. Reactor building was a water tight containment building.

EVACUATION
Plant director had authority in principle to order evacuation of Pripyat. However a standing order made any nuclear accident a state secret.

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