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INTRODUCTION:

Fort St. Vrain (FSV) is the nuclear generating facility located in northern Colorado in the
United States. It had been operated as a nuclear generating power plant from 1979 until 1989.
It was one of the biggest high temperature gas cooled power reactors (HTGR) in the United
States. which was rated at 330 MWe and was successively defueled and decommissioned

with the plant site allowed for unlimited use in August, 1997.

Early Plant dismantlement decommissioning technique chosen instead of 60 years safe
storage choice. The cost and schedule objectives were achieved under the decommissioning
plan while accomplishing an outstanding personnel safety history and with radiological

exposures below the original measurement.

There are following steps in the decommissioning process of a Reactor.

 DEFUELING:
The first step in the decommissioning process was the disposition of the spent nuclear fuel.
There held an agreement between PSco and The US department of Energy to ship the fuel to
a location in Idaho. PSco place the plant’s fuel in an independent Spent Fuel Storage (ISFSI)

installation because of the restriction put by the Governor of Idaho.

NCR licensed it per
10CFR Part 72 which was totally independent from the Power reactor license. GEC Alsthom
Engineering System LTD designed the ISFSI. The structure of the reactor is hexagonal
graphite containing fuel elements 31 meters in diameter and 14 feet in thickness. There are

six fuel elements per canister and the fuel elements are stored vertically in these steel
canisters.

Each of these six vaults in the modular dry vault storage system contains 45 storage
locations. A removable shield plug closes each storage location enables easy access to load
and unload the ISFSI.

The modular dry vault storage system is cooled by natural circulation.
Fort ST. Vrain
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The fuel blocks removed by the utility and stored in an onsite air cooled storage vault and
replaced in the core with un irradiated defueling blocks. The core sits on the Core Support
Fuel, which is about 29 feet in diameter, 5 feet thick and weighs Summary of fort st vrain about 270 tons. Air passes

down through the vaults, warmed and rises through the Chimney Structure for removal into
the environment. Fuel and air are completely separated there is no contact of them inside the

container, air remains free of any contamination.
 PRIMARY SYSTEM COMPONENT REMOVAL:
The next step after defueling is the removal of radioactive components from the Pre stressed
Concrete Reactor Vessel (PCRV) containing more than 95 percent of radioactivity at FSV.
This is done by flowing the PCRV with water to secure the workers from radioactivity. Water
is filtered to assure the cleanliness and clarity by using two circulation loops of 500 gallons
per minute and stream demineralised….