Environmental Monitoring at Nuclear Power Plants

Nuclear power plants release small amounts of radiation and radioactive materials while they are 

operating. The NRC’s strict rules for these releases keep environmental radiation levels very low and 

protect public health and safety. NRC reviews of reactor license applications include analysis of the 

possible impacts to people, animals, plants and sea life. This analysis, part of the NRC’s Environmental 

Impact Statement for the application, also addresses ways to minimize the impacts. After nuclear plants 

begin operating, the NRC inspects and verifies the plant is complying with regulations. 

The NRC requires nuclear power plants to 

keep radioactive material releases as low as is 

reasonably achievable – otherwise known as ALARA. 

Plant operators must also:

• Comply with radiation dose limits for the 

public

• Monitor what they release and the 

environment around the plant

• Report their results annually to the NRC. 

These reports are posted on the NRC website.

Regulations

Radiation is all around us, much of it from natural sources such as cosmic rays, radon gas, and 

uranium and other elements in the ground. These sources generate an average annual dose of about 310 

millirem to U.S. residents. Radiation from a reactor generally cannot be detected further than one mile 

away. Within one mile, it could be a small fraction of the background dose.

Nuclear power plants must comply with specific public dose limits set by the NRC and the 

Environmental Protection Agency. EPA’s rules can be found in 40 CFR Part 190. The NRC rules are in 

10 CFR Part 20. The NRC’s rules define ALARA, and each reactor license also specifies ALARA 

levels; plant operators must report to the NRC any time those levels are exceeded. Meeting these rules 

ensures reactors keep doses to the public so small that they are difficult to distinguish from background 

radiation.

h

Device for monitoring airborne radiation
Page | 2

Monitoring Releases and the Environment

Reactor operators must monitor the release of 

radioactive materials in liquid or the air, as well as direct 

radiation from the plant. Operating plants have controlled 

their releases so well that, to this point, all releases have 

been below the ALARA levels.

Reactor operators also measure radiation levels in 

the environment. Environmental samples come from the 

air, surface water (such as ponds, streams and lakes), 

groundwater, drinking water, milk, fish and shoreline 

sediment. Independent labs regularly verify the accuracy of licensees’ measuring systems. Licensees 

must report their release data, sampling and system verification results every year to the NRC. 

The NRC posts these annual reports online. 

Radioactive releases (called effluents) appear in a plant’s 

Effluent Report. Any plant radiation measured in the 

environment appears in the Environment Report.

The NRC has on-site inspectors that live near the 

plants and work there full-time. They check regularly to 

make sure plants are monitoring their releases and 

keeping them below ALARA levels. Other NRC 

inspectors who are radiation experts go to the sites for 

routine radiation inspections. The NRC documents the 

results of its inspections in reports available to the public. 

Tritium in Groundwater at Nuclear Plants

Tritium is a mildly radioactive form of hydrogen that occurs naturally and also forms during 

reactor operation. Several nuclear power plants have leaked or spilled water with tritium, sometimes 

found on-site in wells used to monitor groundwater. In these cases, the NRC expects each licensee to 

find the source of contamination (often leaks from buried pipes). The licensee must also have a program 

to prevent leaks, which the NRC reviews. Measurements of drinking water supplies near tritium leaks

have consistently shown the supplies’ tritium levels remain below the EPA’s safe drinking water 

standards. In most cases, the tritium cannot be detected in groundwater samples off-site.

January 2021

NRC inspector watches sample-testing at Seabrook

Technicians process soil samples