Environmental Impact Statement - radioactive monticello

Description of Site and Environment
Natural surface drainage of the Monticello site is generally to the southwest at a 2- to 3-percent
grade away from the Mississippi River. The land cover of the site is predominated by formerly
cultivated fields in various stages of ecological succession (NMC 2005a).
2.1.2 Reactor Systems
Monticello is a single-unit electric generating plant. The unit is a single-cycle, forced circulation,
low-power density boiling water reactor. General Electric Company designed and supplied the
nuclear steam supply system, the initial reactor fuel, and the turbine-generator unit and its
related systems. Monticello was designed for operation at power levels up to 1670 megawatts
thermal (MW[t]) and an electrical output of up to 545 megawatts electric (MW[e]) (AEC 1972).
However, an uprate license amendment was submitted and subsequently approved by the
Nuclear Regulatory Commission (NRC) on January 21, 1998 (NRC 1998). The current rated
thermal power level for the unit is 1775 MW(t) and 600 MW(e).
The Monticello facility is depicted in Figure 2-3. The reactor containment structure consists of a
drywell, which encloses the reactor vessel and recirculation pumps; a pressure suppression.
chamber, which stores a large volume of water; a connecting vent system between the drywell
and the suppression chamber; and isolation valves. The concrete reactor building serves as a
radiation shield and fulfills a secondary containment function. The reactor building is
maintained under a slight negative pressure, with the building exhaust monitored prior to
release to the atmosphere through the reactor building ventilation exhaust stack. The
containment for the unit is designed to withstand an internal pressure of 56 pounds per square
inch above atmospheric pressure (NMC 2005b). Monticello uses low-enriched uranium dioxide
fuel with enrichments below 5.0 percent by weight uranium-235, with peak fuel-rod burn-up
levels less than 62,000 megawatt-days per metric ton uranium (MWd/MTU) (NMC 2005c).
2.1.3 Cooling and Auxiliary Water Systems
The Mississippi River is the source of water at Monticello for plant condenser cooling and some
auxiliary water systems, such as service water cooling, screen wash, and fire protection. Five
groundwater wells provide water for other auxiliary systems, such as water for the reverse
osmosis/make-up demineralizer system used to produce purified water for the plant primary
systems and seal water to pumps located at the intake structure. Groundwater is also used for
domestic potable use, including drinking water, lavatories, and showers at the plant. Figure 2-4
shows the locations of the two induced-draft cooling towers and the discharge canal.
NUREG-1437, Supplement 26 2-4 AUgust 2006 1