ML23184A129

Nuclear Power Plant Effluents

ML23184A129
Person / Time
Issue date:	06/29/2023
From:	NRC/NMSS/DMSST
To:
References
Download: ML23184A129 (1)

Text

1 Nuclear Power Plant Effluents Current Events

Overview

• Nuclear power plants need to discharge radioactive effluents in small amounts in order to operate and have been doing so safely since initial start-up

• Rules limit the amount that can be released to ensure they are a fraction of what is received from background sources 2

• A measurement of the energy imparted by radiation

• Conventional units used are mrem (millirem)

• Can be thought of as the overall risk from radiation to a person

• Average dose an individual receives per year from natural sources of radiation (sun, soil, etc.) is about 300 mrem.

3 Dose

• Focus on limiting the dose to people living around the site

• All NRC licensees must limit does to the public to 100 mrem/year

• Nuclear power plants must limit dose to the public to 25 mrem/year

• Plants are designed to operate well below 25 mrem/year

• Liquid discharge design criteria is 3 mrem/year 4

Regulations

5 Public Health &

Safety Land Use Census Effluent Controls REMP GPI

6 Public Health &

Safety Land Use Census Effluent Controls REMP GPI

Land Use Census

• How the public is exposed to radiation depends on how the land around the plant is used

• Plants annually perform a census to identify changes in how the land is used

• Looks for things such as large gardens, dairy cows, where residents are located, etc.

7

8 Public Health &

Safety Land Use Census Effluent Controls REMP GPI

Effluent Controls

• We are using effluent as a generic term to describe radioactive material released from the site in gaseous or liquid form

• Effluent controls ensure that what is being released is monitored and controlled to ensure dose limits are met 9

Effluent Controls

• Doses to the public are too small to measure directly

• Sites sample and analyze effluents from the plant piping or tanks they are being released from

• Information from the land use census used to model how an individual would be exposed to the effluent release

• Doses are calculated based on the model 10

11 Effluent Controls

12 Public Health &

Safety Land Use Census Effluent Controls REMP GPI

• Measures radiation in the environment during the lifetime of the plant

• Determines if any measurable levels of radiation are from plant operation

• Determines if results are commensurate with the radioactive effluents 13 REMP Radiological Environmental Monitoring Program

14 REMP

15 Public Health &

Safety Land Use Census Effluent Controls REMP GPI

Industry standard is NEI 07-07 16 GPI Groundwater Protection Initiative Revision 0 (ML072610036)

Revision 1 (ML19142A071)

• Objectives include

• Provide timely detection and effective response to inadvertent on-site releases to groundwater in order to prevent migration off-site and to quantify impacts on decommissioning

• Improve communication with external stakeholders

• Perform program oversight to ensure effective implementation 17 GPI

• Site hydrology

- How does the groundwater move?

• Risk ranking

- Where is there potential for leaks?

• Groundwater monitoring

- Monitoring wells established in strategic locations based on hydrology and risk ranking

• Remediation

- Pumping contaminated water out of the ground for appropriate handling

• Communications

- Protocols established between site and State/Local governments 18 GPI

19 GPI

• November 2022

- Site identified elevated tritium levels in one of the GPI monitoring wells during routine monthly sampling

- Site notified the State and NRC of the elevated levels

- Sampling frequencies of nearby monitoring wells increased

- Site started investigation to determine source of the leak 20 Monticello Tritium Leak

• December 2022

- Site identified source of leak in pipe that runs between the reactor and turbine buildings, which have a small gap between them.

- Leak was captured and rerouted back into the plant

- Site started recovering contaminated groundwater

• Stored in tanks on-site and reused as plant make-up water

- Site started installing additional monitoring wells 21 Monticello Tritium Leak

• March 2023

- Routine sampling of monitoring well indicated some of the leak was again making it to groundwater

- Site shut down the plant to replace the section of pipe 22 Monticello Tritium Leak

• Ongoing

- Site continues to monitor location of tritium

- Monitoring well sample frequency adjusted for each well based on current conditions

- Evaluation for additional monitoring wells continues

- Recovery of contaminated groundwater routinely adjusted for current conditions

- Sites actions are aimed at preventing uncontrolled migration of the tritium off-site 23 Monticello Tritium Leak

• Risk from off-site release

- The amount of tritium leaked to the groundwater would not pose a health concern even if all of it reached the Mississippi River

- Dose to a member of the public would be well below 1 mrem

• Remember, 300 mrem/year from natural sources 24 Monticello Tritium Leak

• Even though there is no health concern, it does not mean it is okay to do nothing

- NRC expects effluents to be released in a monitored and controlled fashion

- Recovery of contaminated groundwater to mitigate off-site release through groundwater is expected

- Extensive monitoring of the groundwater will ensure that any off-site release through the groundwater will be appropriately accounted for

- NRC will verify appropriate control 25 Monticello Tritium Leak

• Monticello has not performed liquid discharges in a few decades and does not currently plan on discharging the recovered groundwater

• Storage of recovered groundwater is a major evolution

- Pumping of groundwater must proceed to control plume

- That water must go somewhere

- Short term storage solutions being used while long term solutions are being developed 26 Monticello Tritium Leak

• The NRC has specialized inspectors perform periodic on-site inspections of the programs discussed today

• The NRC maintains at least two resident inspectors at each site to oversee the day-to-day operation of the site

• NRC will continue to follow the sites actions through the routine inspection program 27 Inspections

Nuclear power plants are required to submit annual reports detailing effluent releases, on-site groundwater monitoring results, and REMP results.

28 Annual Reports https://www.nrc.gov/react ors/operating/ops-experience/tritium/plant-info.html These reports can be found at

29 Questions