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State of Wisconsin - 2008

Introduction
WI DHS Prairie Island Environmental Monitoring Sampling Program
Program Modifications
Laboratory Services and Quality Assurance
Detection Limits
Reporting of Sample Analysis Results
Results & Discussion
References
List of Tables

Wisconsin Public Health Statues 254.41 mandates the Department of Health Services to conduct environmental radiation monitoring around the nuclear power facilities that impact Wisconsin. This environmental monitoring report is for the Prairie Island nuclear generating plant for the calendar year January - December 2008 and provides a description and results of this environmental monitoring program.

The WI DHS environmental monitoring program consists of the collection of various types of samples from the air, water and terrestrial exposure pathways.  The sampling program included samples of air, precipitation, ambient gamma radiation (TLD), surface water, fish, soil, milk, well water and vegetation that are collected from selected locations at planned sampling intervals.

Table 1 is a listing of sampling sites and includes a description, direction and distance from the monitored power plant. Table 2 provides a listing of types of samples collected, sites where samples are collected, the number of samples collected, number of samples that were missed and a listing of the required analyses.  Table 3 provides an explanation of missing samples or non-routine sample analyses.  Figure 1 is a map showing the location of each environmental sampling site.  

Program Modifications

There were no program modifications for 2008.

Laboratory Services and Quality Assurance

The analysis of the samples is performed under contract with the State Laboratory of Hygiene (SLH).  SLH maintains a quality assurance program.  Analytical procedures provide for routine replicate analyses to verify methods and instrument operation.  Traceable sources are used to regularly calibrate the counters and daily performance checks are made between calibrations.  In addition, quality control charts are maintained on the counters.

SLH participates in the Environmental Resource Associates’ Proficiency Testing program and has performed satisfactorily over the report period.  Proficiency testing results are available from the State Laboratory of Hygiene.

Detection Limits

Detection limits, required by WI DHS, will be expressed as a lower limit of detection (LLD).   The required WI DHS LLD as indicated in Table 4 under the heading “LLD” is an "a priori" estimate of the capability for detecting an activity concentration by a given measurement system, procedure, and type of sample.  Counting statistics of the appropriate instrument background are used to compute the LLD for each specific analysis.  Using 4.66 times the standard deviation (s_b) of the instrument background, the LLD for each specific analysis is defined at the 95% Confidence Level.

The LLD for each radioisotope listed in Table 4 has been calculated from the following equation:

                           4.66 s_b
LLD = ---------------------------------------------
             E * V * 2.22 * Y * S * exp(-dt)

Where:

Typical values for E, V, Y and dt have been used to calculate the LLD.

Reporting of Sample Analysis Results

Results for specific analyses will be reported as either a “less than” (<) value or an actual activity value. The reporting of results in Table 4 under the heading “Range” and in Tables 5-14 are “a posteriori” calculations based on the actual analysis performed using the actual sample values for E, V, Y and dt. Typically the reported “less than” (<) results are lower than the required WI DHS LLD indicating that the required WI DHS LLD has been met.

An actual activity value will be accompanied by an uncertainty term for that analysis.  The uncertainty term is a plus or minus counting uncertainty term at the 2 sigma (95%) confidence interval and is printed as (+- or ±).  Examples and explanations of data reporting are:

Nuclide 

Activity reported

¹³⁷Cs

< 10 pCi/liter

¹³⁷Cs

15 ± 3 pCi/liter

In example 1 we can be 95% confident that the sample activity, if any, is less than the LLD of 10 pCi/liter.  In example 2 we can be 95% confident that the actual sample activity is greater than the LLD for that analysis and is between 12 and 18 pCi/liter.

Results And Discussion

Air Particulate

A summary of reported activities by WI DHS for air particulate samples is included in Table 4.  Results from the individual sample analyses are listed in Tables 5-6.

From the individual activities or quarterly averages for gross beta activities it may be noted that there are no significant differences between sites at different distances from the Prairie Island facility.  With no significant difference with distance from the Prairie Island site, an increase in gross beta activity attributable to the Prairie Island plant operation is not evident. 

The gamma isotopic analysis of the quarterly air particulate filter composites detected only small amounts of the radioisotopes listed in Table 4.  Beryllium-7 (⁷Be), detected in all composites, is a naturally occurring radioisotope that is constantly produced through nuclear reactions between cosmic rays and nuclei in the atmosphere and is detected in air composites from other areas of the state. 

Influence by the Prairie Island nuclear generating facility on air quality is not evident from air particulate analysis.

Air Iodine

A summary of reported activities by WI DHS for air iodine samples is included in Table 4.  Results from the individual sample analyses are listed in Table 5.

Air iodine measurements were all below the LLD of 0.07 pCi/m³ for all sites.

Direct Radiation - Thermoluminescent Dosimeters (TLD's)

A summary of reported activities by WI DHS for direct radiation is included in Table 4.  Results from the individual sample analyses are listed in Table 7.

Direct radiation (TLD) data for 2008 from the WI DHS network was comparable for all sites.  Significant differences in exposure were not noticed at different distances from the Prairie Island nuclear facility.  The average quarterly exposure from the ten sites located within Wisconsin was 15.2 ± 2.1 milliroentgens.  The average quarterly exposure for 2008 is at background levels and is comparable to other areas within Wisconsin.

Precipitation 

A summary of reported activities by WI DHS for precipitation is included in Table 4.  Results from the individual sample analyses are listed in Table 8.

The gross beta activity in precipitation was within the normal range of activity when compared to previous year’s data.

Surface Water

A summary of reported activities by WI DHS for surface water samples is included in Table 4.  Results from the individual sample analyses are listed in Table 9.

The surface water samples showed no unusual activities and are at background levels comparable to previous years.  From the gamma isotopic analysis all radioisotopes were below their respective LLD.  All reported activities for gross beta, gross alpha and tritium (³H), except for one tritium (³H) activity at site PRI-2, are at background levels.  The reported activity at PRI-2 is a site closest to the plant and could possibly be attributed to a Prairie Island waste release. The surface water samples uniformly show activities well below state or federal standards.

Fish

A summary of reported activities by WI DHS for fish samples is included in Table 4.  Results from the individual sample analyses are listed in Table 10.

The fish samples showed no unusual activities.  Naturally occurring potassium-40 (⁴⁰K) was detected in all samples.  All other radioisotopes were below their respective LLD.

Well Water

A summary of reported activities by WI DHS for well water samples is included in Table 4.  Results from the individual sample analyses are listed in Table 11.

The well water samples showed no unusual gross alpha and gross beta activities and all activities for tritium (³H) were less than its LLD.  The activity levels are all below state and federal standards.

Milk

A summary of reported activities by WI DHS for milk samples is included in Table 4.  Results from the individual sample analyses are listed in Table 12.

Analysis of the milk samples showed no unusual activities.  Naturally occurring potassium-40 (⁴⁰K) was detected in all samples.  The detected activities for strontium-90 (⁹⁰Sr) are attributable to residual fallout from previous atmospheric nuclear weapons testing and were also detected in previous years at similar activity levels.

Vegetation

A summary of reported activities by WI DHS for vegetation samples is included in Table 4.  Results from the individual sample analyses are listed in Tables 13.

Analysis of the vegetation samples showed no unusual activities.  The gamma isotopic analysis detected only small amounts of the naturally occurring radioisotopes beryllium-7 (⁷Be) and potassium-40 (⁴⁰K) listed in Table 4.  All other radioisotopes were below their respective LLD.

Soil

A summary of reported activities by WI DHS for soil samples is included in Table 4.  Results from the individual sample analyses are listed in Table 14.

Analysis of the soil samples showed no unusual activities.  The gamma isotopic analysis detected only small amounts of the radionuclides listed in Table 4.  Potassium-40 (⁴⁰K) is a naturally occurring radioisotope.  The reported activities for cesium-137 (¹³⁷Cs) were also detected in previous years and are largely attributable to fallout from previous atmospheric nuclear weapons testing.  Naturally occurring radioisotopes such as radium-226 (²²⁶Ra), bismuth-214 (²¹⁴Bi), lead-214 (²¹⁴Pb), actinium-228 (²²⁸Ac), bismuth-212 (²¹²Bi) and lead-212 (²¹²Pb) from the naturally occurring uranium-238 (²³⁸U) and thorium-232 (²³²Th) decay series are commonly detected but have not been quantified or reported.

Dose to an Average Individual

Federal regulations 10 CFR 20, 10 CFR 50 Appendix I and 40 CFR 190 restrict the annual exposure of the population from all parts of the nuclear fuel cycle, including nuclear power plants. Doses resulting from gaseous and liquid effluent releases from the Prairie Island nuclear generating facilities are less than the limits as stated in these Federal regulations.

The WI DHS limits for permissible levels of radiation exposure from external sources in unrestricted areas is defined in the Wis. Adm. Code section DHS 157.23.  Doses resulting from gaseous and liquid effluent releases from the Prairie Island nuclear generating facilities are less than the limits as stated in Wis. Adm. Code section DHS 157.23.

References

State of Wisconsin, Wisconsin Administrative Code, DHS 157.23.

U.S. Environmental Protection Agency, Environmental Radiation Requirements for Normal Operations of Activities in the Uranium Fuel Cycle, EPA 520/4-76-016, 40 CFR Part 190, November 1976.

U.S. Nuclear Regulatory Commission, Title 10, Part 20.

U.S. Nuclear Regulatory Commission, Title 10, Part 50, Appendix I.

Last Revised:  September 21, 2009