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Maryland Power Plants and the Environment (CEIR-18)

4.5.3 Monitoring Programs and Results

Because of the potential direct impact of nuclear power generation (specifically routine releases of radioactivity) on Maryland’s natural resources, PPRP conducts monitoring in the vicinity of Calvert Cliffs and Peach Bottom to assess the radiological effects on the environment attributable to each of the power plants (Table 4-7).  PPRP has monitored radionuclide levels in the environment surrounding Calvert Cliffs since 1975 and surrounding Peach Bottom since 1979 and publishes its environmental assessments biennially.

Table 4-7 Nuclear Power Plant Environmental Monitoring Elements

Matrix No. Stations Locations Analytes Collection Frequency
1. Air Filter 8 Calvert County, Baltimore, Cecil County, Harford County, Eastern Shore α, β, 7Be, 137Cs continuous (exchanged weekly)
2. Charcoal Filter 8 Calvert County, Baltimore, Cecil County, Harford County, Eastern Shore 131I continuous (exchanged weekly)
3. Potable Water 7 Calvert County α, β, 3H quarterly
1 Baltimore City monthly
1 Patuxent River quarterly
1 Potomac River quarterly
4. Raw Water 1
Patuxent River
α, β, 3H monthly
1 Potomac River monthly
5. Precipitation 1 Baltimore City α, β, 3H, 7Be weekly
6. Raw Milk 1 Cecil County 89Sr, 90Sr, 131I, 140Ba, 137Cs, 40K quarterly
7. Processed Milk 1 Baltimore City 89Sr, 90Sr, 131I, 140Ba, 137Cs, 40K quarterly
8. Sediment 28 Chesapeake Bay
(near CCNPP)
γ quarterly
9. Tray Oysters 2 Chesapeake Bay γ quarterly
10. Sediment 19 Chesapeake Bay &
Susquehanna River
(near PBAPS)
γ semi-annually
11. Finfish 1 Susquehanna River γ semi-annually
12. Submerged Aquatic Vegetation (SAV) 3 Chesapeake Bay &
Susquehanna River
γ semi-annually

Monitoring by PPRP is conducted to satisfy NRC requirements to verify that any releases from normal plant operations result in potential doses to humans that are below regulatory limits. The monitoring also meets Maryland requirements to research the environmental effects of electric power generation and to maintain State oversight of environmental monitoring.

The most recently compiled results (for the years 2012 to 2014) from weekly air and annual vegetation monitoring conducted by Constellation Energy Nuclear Group (previous owner of Calvert Cliffs), Exelon Generation Company, and independently by PPRP indicate that releases of radioactivity to the atmosphere from the Calvert Cliffs plant were not detectable in air, precipitation, or vegetation.

Estuarine (e.g., Chesapeake Bay) and riverine (e.g., Susquehanna River) sediments are also useful indicators of environmental radionuclide concentrations because they serve as natural sinks for both stable and radioactive metals. PPRP collects sediment samples periodically from a network of transects in both study areas in the vicinity of Calvert Cliffs and Peach Bottom. No plant-related radionuclides, specifically 60Co, were detected in Bay sediments near Calvert Cliffs during the 2012-2014 reporting period (see Figure 4-34).

At Peach Bottom, plant-related 60Co was detected on twelve occasions (detection frequency of 10.5%) in sediments collected from Conowingo Reservoir and Susquehanna River, but not within the upper Chesapeake Bay. As shown in Figure 4-34, the quantity of 60Co in sediment samples, when detected, was proportionally far below the levels contributed by residual radioactive fallout and natural sources.  Further, the detection frequency of 60Co in sediment samples from Peach Bottom during the 2012-2014 reporting period was lower than the average for historical samples (16.4% since 1996).

Figure 4-34 Proportion of Natural vs. Man-Made Radionuclides in Sediment Samples near CCNPP and PBAPS

Figure 4-34 - pie charts of portion of natural vs. man-made radionuclides in sediment samples of PBSPA and CCNPP

Bay oysters are ideal indicators of environmental radionuclide concentrations because they do not move and readily ingest and concentrate metals. Oysters have been historically commercially harvested near Calvert Cliffs, and have the greatest potential for contributing to a human radiation dose through seafood consumption. The oysters are collected at scheduled time intervals and analyzed for radionuclide content in their tissues. Radiosilver (110mAg) has historically been the principal plant-related radionuclide accumulated by test oysters and oysters on natural beds. Since the fourth quarter of 2001, concentrations of 110mAg in oysters have fallen below analytical detection limits. The lack of detectible 110mAg reflects a downward trend in 110mAg releases, as well as other principal environmentally active radionuclide releases, from Calvert Cliffs.

Finfish are the primary pathway for Peach Bottom-related radionuclide releases to contribute to a human radiation dose because the reservoir contains a recreational fishery. Finfish are collected semi-annually by PPRP from the Conowingo Reservoir area near Peach Bottom. During 2012-2014, finfish samples contained no radionuclides attributable to PBAPS.

As part of its assessment program, PPRP estimates doses of radiation to individuals consuming seafood. The doses are calculated based on maximum or worst-case estimates of the amount of plant-related radioactive material potentially available in the seafood. Results indicate that radiation doses attributable to operations at Calvert Cliffs are well below federally mandated limits (see Table 4-8). As shown in Figure 4-32, the annual total body dose that originates from industrial releases of radionuclides, and subsequent consumption of seafood and drinking water, is small relative to other modes of dose accumulation.

Table 4-8 Comparison of Radiation Doses to Humans and Applicable Regulatory Limits

Exposure Route Maximum Dose Estimate
Maximum Dose Estimate
Maximum Dose Estimate
EPA Regulatory Limit
(40CFR190 Subpart B)
NRC Regulatory Limit
(10CFR50 Appendix I)
Ingestion (mrem)
Oyster ingestion, whole body dose (from CCNPP) < 0.0024 (child)a 25 3
Oyster ingestion, other organ dose (from CCNPP) < 0.0133 (adult gastro-intestinal tract)a 25 10
Finfish ingestion, whole body dose (from PBAPS)  0.0066 (adult)a 25 3
Finfish ingestion, other organ dose (from PBAPS) 0.0105 (teen liver)a 25 10
Inhalation (mrem)
Whole body dose (gaseous, from CCNPP) 0.00029 (child)b 0.00035 (child)b 0.00032 (child)b 25 3
Other organ dose (gaseous, from CCNPP) 0.00093 (child skin)b 0.00053
(child skin)b
(child skin)b
25 10
Whole body dose (gaseous, from PBAPS) 0.224 (any age class)b 0.225
(any age class)b
(any age class)b
25 3
Other organ dose (gaseous, from PBAPS) 0.292 (any age class skin)b 0.293
(any age
class skin)b
(any age
class skin)b
25 10

a Source: PPRP biennial reports

b Source: Annual Radiological Environmental Operating Reports for 2012, 2013, and 2014, Exelon Generation

Results of analyses of environmental samples collected in the vicinity of Calvert Cliffs and Peach Bottom can be found in the periodic environmental reports described above. A comparison of radionuclide concentrations in environmental samples collected in 2012 to 2014 with historical levels shows the following:

In summary, environmental, biological, and human health effects from releases of radioactivity from Calvert Cliffs and Peach Bottom were not significant.

Figure 4-35 Environmentally Significant* Annual Aqueous Releases, 1994-2014

Figure 4-25 - dotted chart of environmentally significant annual aqueous releases from 1994-2014

* Environmentally significant refers to radionuclides that are known to be assimilated by biological organisms and are discharged in detectable amounts. Aqueous releases of noble gases, tritium, and very short-lived radionuclides are not included because they do not bioaccumulate or they decay rapidly to stable forms.