ULWR: Uranium Light Water Reactor
A light water reactor or LWR is a thermal nuclear reactor that uses ordinary
water, also called light water, as its neutron moderator. This differentiates it
from a heavy water reactor, which uses heavy water as a neutron moderator. In
practice all LWRs are also water cooled. While ordinary water has some heavy
water molecules in it, it is not enough to be important in most applications.
The most common LWRs are pressurized water reactors and boiling water reactors.
The Russian abbreviation for LWR is VVR (or sometimes WWR), meaning water water
reactor. Similarly, the Russian term for a PWR is VVER, meaning water water
energy reactor.
Many other reactors are also (light) water cooled, notably the RBMK and some
military plutonium production reactors. These are not regarded as LWRs, as they
are moderated by graphite, and as a result their nuclear characteristics are
very different.
The light-water reactor uses uranium 235 as a fuel, enriched to approximately 3
percent. Although this is its major fuel, the uranium 238 atoms also contribute
to the fission process by converting to plutonium 239 — about one-half of which
is consumed in the reactor. Light-water reactors are generally refueled every 12
to 18 months, at which time, about 25 percent of the fuel is replaced.
Light water reactors tend to be simpler and cheaper to build than heavy water
reactors. Power-generating capabilities are comparable.
Light water reactors are the type used by the U.S. military in its Naval nuclear
powered vessels. This is so due to the inherent safety of these type reactors.
Since light water is used as both a coolant and a moderator in these reactors,
if one of these reactors suffers damage due to attack, and thereby compromise of
the reactor core's integrity, the ensuing release of this light water acts to
shut down the reactor. This is due to its moderator function. Moderators help to
encourage the nuclear mass to achieve fission by lowering the average speed of
the neutrons to a level which augments the probability of occurrence of
neutron-Uranium collisions susceptible to lead to an Uranium nucleus fission.
When the moderator is removed, the average energy of the neutrons becomes too
high for the chain reaction to sustain itself. Currently-offered LWRs include
the ABWR, AP1000, ESBWR, European Pressurized Reactor, VVER and SWR-1000.
Contact Information
Call our office today to set up an appointment. Learn more about how we can
help you, and learn more about the other services that we can offer you. All
messages we receive will be answered as soon as possible. We look forward to
hearing from you.
- Electronic mail
- General Information:
