Audeen W. Fentiman
Matthew E. Jorat
Ronald J. Veley
The purpose of an environmental monitoring program at a commercial low-level radioactive waste disposal facility is to protect both the environment and human populations. Monitoring programs are designed to ensure that a disposal facility is in compliance with Nuclear Regulatory Commission and Environmental Protection Agency regulations.
One goal of the monitoring system is to detect any infiltration of water into the low-level radioactive waste disposal facility so that remedial action can be taken to keep water away from the waste. In addition, air and water at and around the site are continually monitored so that if any radioactive materials are released from the disposal facility, they will be detected immediately. Radiation monitors are extremely sensitive and can detect low levels of radioactive materials, making early detection of releases possible. This allows remedial action to be taken before any release threatens public health and safety.
Each environmental monitoring program has four phases: (1) site characterization, (2) pre-operational monitoring, (3) operational monitoring, and (4) post-operational monitoring.
This fact sheet provides a brief description of the four phases of a monitoring program.
The purpose of site characterization is to determine whether or not a low-level radioactive waste disposal facility can be properly and safely designed, operated, closed, and controlled after closure at a given location. The facility must meet Nuclear Regulatory Commission and Environmental Protection Agency standards for environmental and human radiation exposures. During site characterization, the potential site is studied to determine whether it has characteristics that will enhance the facility's ability to confine the radioactive waste and protect people and the environment from radiation. In addition, studies are conducted to determine whether the site can be monitored to detect any release from the disposal facility quickly. At this time, site developers must also plan where monitors should be placed and how frequently measurements should be taken.
During pre-operational monitoring, data are collected and evaluated at and around the proposed low-level radioactive waste disposal facility site. Data may be collected on hydrology, meteorology, seismology, geochemistry, and demographics, along with information on existing concentrations of radioactive material. The Nuclear Regulatory Commission requires at least one year's worth of data to be collected for characteristics that are subject to seasonal variation. Some of these characteristics for which data are typically collected are described in the following paragraphs.
Hydrological monitoring involves both surface water and groundwater characterization. Surface water is water found above the ground, such as lakes, streams, or rainwater. Groundwater is water found under the ground. For groundwater, data such as the distance to any aquifers below the proposed site location and the rate and direction of groundwater flow are gathered. These data are used to determine how quickly radioactive materials introduced into the groundwater could reach the surface. Surface water data include information needed to minimize the infiltration of water into the low-level radioactive waste disposal facility.
Meteorological monitoring is used in determining the atmospheric dispersion of radioactive materials if an airborne release occurs. Some examples of the conditions monitored include wind speed and direction, precipitation, relative humidity, temperature, and barometric pressure. A weather station will be permanently installed at the site of the low-level radioactive waste disposal facility.
Air, water, and soil at the proposed low-level radioactive waste disposal facility site are monitored for the presence of radioactive materials. Some radioactive materials are present at every site. Initial concentrations (also called baseline levels) of these materials, such as naturally occurring minerals and fallout from weapons testing, are measured. During the operational phase of the disposal facility, the concentration of radioactive materials will continue to be monitored and compared with these baseline levels. This comparison will be used to assure that the disposal facility is retaining the waste. If an increase in radioactive material is found, the point of release can be located and remedial action can begin.
Collection of meteorological data continues during the operational phase. Periodic re-evaluation of geological and hydrological data will allow detection of any changes that may occur.
Air quality also will be monitored both at and around the low-level radioactive waste disposal facility. The on-site monitoring of radioactive material in the air can provide an early indication of any releases from the disposal facility. Off-site air monitoring is conducted for two reasons. First, it is used to detect any changes in the background radiation levels so that baseline values, against which operational data are compared, can be adjusted. In addition, off-site air monitoring can indicate the presence of radioactive material from other sources that might affect the environment or local population.
Water quality is monitored during the operation of a low-level radioactive waste disposal facility. Groundwater and surface water at and around the disposal facility site are monitored for the presence of radioactive materials above baseline levels. Also, the direction, rate, and velocity of water flow around the site are periodically updated.
Soils, crops, and animals (both domestic and game) are also tested for changes in the levels of radioactive materials present.
The post-operational monitoring program begins when the low-level radioactive waste disposal facility is closed, capped, and no longer accepting waste. The disposal facility's license holder, that is, the company that operated the facility, must continue all monitoring activities for at least 5 years after closure. In addition, the site owner, usually the state government, will continue some monitoring activities for as long as the state deems necessary after closure.
After closure of the low-level radioactive waste disposal facility, groundwater is the most likely transporter of radioactive materials from the disposal site. As a result, many of the post-operational monitoring activities concentrate on groundwater. Air, soil, and vegetation are monitored as well. The data collected during this phase are compared with similar information collected during the operational and pre-operational monitoring programs. The comparison of data can assist environmental scientists in analyzing trends that may benefit other existing and (or) proposed disposal facilities.
If you want to read more about monitoring programs at low-level radioactive waste disposal facilities, some of the references listed below may be helpful.
Code of Federal Regulations, Title 10, Part 61, "Licensing Requirements for Land Disposal of Radioactive Waste", 1992.
Low-Level Waste Management Handbook Series: Environmental Monitoring for Low-Level Waste Disposal Sites, DOE/LLW-131G, Vol. 1, EG&G Idaho, Inc., Idaho Falls, February 1990.
Dr. Audeen W. Fentiman is an Assistant Professor in Nuclear Engineering at The Ohio State University. Matthew E. Jorat is a Graduate Research Associate in Nuclear Engineering. Ronald J. Veley is a Graduate Research Associate, Ohio State University Extension.
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