Monitoring for radioactivity in Minnesota began in 1953 in response to nuclear weapons testing. The Minnesota Department of Health (MNDH) has a database with over 50 years of information regarding the monitoring of radioactivity levels. The most recent Environmental Monitoring Report was completed in 2010.
Factors considered in monitoring radioactivity:
- Long term trends (data analysis)
- Sample Collection
- Interpretation (comparing the information to historic data, standard levels, laws, etc.).
Quantifying Potential Exposure:
- Proximity of residence to reactor
- Length of residence at this address
- Proximity of individual’s job site to reactor
- Length of employment at this site
- Frequency residence or job site downwind from reactor, based on prior site specific meteorological analysis
- Residence and job site location
- Surface Water
- Well Water
- Ambient Gamma Radiation
- Data from two Pressurized Ion Chambers (PIC)
- Data Radiation Monitors located around the plant
Air results are compared to data from the St. Paul sampler, historical data, EPA standards, and MNDH Radioactive Material Rules, Chapter 4731.2750.
Water results are compared to the EPA Safe Drinking Water Standards (limiting gross alpha particles to 15 pCi/L, tritium to 20,000 pCi/L, and beta/photon emitters to doses equivalent to 4 mrem per year) and MNDH Chapter 4731.2750 for compliance. They are also measured against the historical data for changes that may have occurred due to releases from the power plant.
Since there are no standards for Milk, except for emergency situations, sample analysis is compared to the EPA Safe Drinking Water Standards and MNDH Chapter 4731.2750. Samples are also compared to historical data and reviewed for trends. The EPA Safe Drinking Water Act (SDWA) limits the total body or critical organ dose from a single beta/photon emitter to 4 mrems.
Ambient Gamma Radiation results are compared to control readings, historical data, and MNDH regulatory limits.