Here is a list of common terms used in the Nuclear Power Information Tracker interactive map.
Boiling Water Reactor
A reactor in which the thermal energy produced by the nuclear fuel boils water inside a vessel to create steam. This steam spins a turbine generator to create electricity, and is then condensed back into water and returned to the vessel for reuse.
See also:
How does a boiling water reactor work? — Additional detailed information and diagrams outlining how this type of reactor works. Download the pdf
Elevated Spent Fuel Pool
The storage location for used (or “spent”) nuclear fuel is located above ground instead of in a deep pit, making it more vulnerable to terrorist attack.
See also:
What is the spent fuel pool? — Additional detailed information and diagrams of the spent fuel pool and why this type of storage makes U.S. power plants vulnerable to attack. Go to web page | Download the pdf
Groundwater Leaks Reported
The nuclear power plant has reported a past spill, leak or other inadvertent release of radioactively contaminated water to the environment. This contaminated water could potentially make its way onto public lands and into drinking water supplies.
Heightened NRC Attention
Within the NRC's reactor oversight process, safety levels at all operating reactors are evaluated every three months using performance indicators for approximately two dozen key parameters coupled with findings from NRC's inspections. A reactor is flagged as "heightened NRC attention" if its safety levels drop below specified thresholds. For these reactors, the NRC responds with additional inspection efforts to ascertain the causes of their declines and verify that steps are being taken to correct the problems.
See also:
NRC Reactor Oversight Process— The Nuclear Regulatory Commission's report summary on nuclear power plant safety and performance. Go to NRC website
High Temperature Gas-Cooled Reactor
A reactor in which the thermal energy produced by the nuclear fuel heats a gas (usually helium). This hot gas flows through a heat exchanger surrounded by water; the heat boils the water to generate steam, which spins a turbine generator to create electricity. The steam is then condensed back into water and returned to the heat exchanger for reuse.
Inherently Safe Reactors
An inherently safe reactor, in theory, would be designed, operated, and monitored in such a way that the reactor would never be damaged and, as a result, no radioactivity would ever be released to the environment. No such reactor currently exists. The risk from existing reactors is so real and so large that liability insurance from private companies is financially impossible, thereby requiring federal liability protection.
Liquid Metal Fast Breeder Reactor
A reactor in which the thermal energy produced by the nuclear fuel heats liquid sodium. This hot liquid sodium enters a heat exchanger and transfers the heat to a second loop of liquid sodium. The sodium in this second loop then enters a heat exchanger surrounded by water; the heat boils the water to generate steam, which spins a turbine generator to create electricity. The steam is then condensed back into water and returned to the heat exchanger for reuse. This type of reactor is called a “breeder” reactor because it is designed to generate more fuel than it consumes, by converting certain unusable uranium atoms into usable plutonium atoms.
Pressurized Water Reactor
A reactor in which the thermal energy produced by the nuclear fuel heats water inside a vessel to over 500ºF, but high pressure within the vessel (nearly two thousand pounds per square inch) prevents the water from boiling. This hot water flows through a heat exchanger surrounded by water; the heat boils the water to generate steam, which spins a turbine generator to create electricity. The steam is then condensed back into water and returned to the heat exchanger for reuse, and the pressurized water is cooled down and returned to the reactor.
See also:
How does a pressurized water reactor work? — Additional detailed information and diagrams outlining how this type of reactor works. Download the PDF
PWR Containment Sump
A safety incident in which a hole opens in the metal pressure vessel or attached piping in a pressurized water reactor (PWR), causing the water to empty from the reactor and spill onto the floor of the containment building. The high-pressure water, as it escapes through the hole, scours thermal insulation and protective coatings (i.e., paint) off adjacent piping, equipment, and structures. This debris is carried to the floor of the containment building as well, where it can block the inflow of water into the sump, thereby preventing water from getting pumped back to the pressure vessel to cool the nuclear fuel.
See also:
Regulatory Malpractice: The NRC's Handling of the PWR Containment Sump Problem — This report exposes regulatory malpractice by the NRC regarding the pressurized water reactor (PWR) containment sump problem. This problem afflicts 68 of the 103 nuclear reactors operating in the United States and makes it much more likely that one of these reactors will experience the ultimate disaster: meltdown with containment failure. Download the report
Year Plus Outages
An outage at a nuclear power plant that lasts more than a year. The majority of such occurrences resulted from numerous violations of federal regulations that require plant owners to find and fix safety problems in a timely, effective manner, coupled with the NRC's inability to detect those violations (allowing problems to multiply and worsen as a result).
See also:
Walking a Nuclear Tightrope: Unlearned Lessons from Year-plus Reactor Outages — This report by the Union of Concerned Scientists identifies common themes among extended outages and steps the NRC must take to end these costly and avoidable threats to public health and the U.S. economy.
Go to web page | Download the report | Download the fact sheet
