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3.9 On-Going Special Studies

  • Issued: September 2014
  • Content last reviewed: September 2014

The monitoring of media such as precipitation, surface waters, milk and vegetation provides information regarding the movement of certain radionuclides in the environment. Unlike the surveillance programs, the results of measurements made in the "On-going Special Studies" cannot be used to provide dose estimates. Therefore the objective of the "On-going Special Studies" program is to monitor these media at regular intervals in order to provide information and enable year-to-year comparisons.

3.9.1  Precipitation Monitoring

Surface waters, grass and produce may receive radioactive deposits as the result of airborne particulates being washed out by precipitation. While precipitation is not a primary pathway for radiation exposure, the analyses of rain and snowfall samples does serve an important role as part of the emergency preparedness program.

Eleven precipitation collectors are in use in the following locations: one collector has been placed at the Arthur Control Site and two are in the Bruce Surveillance Area. Seven precipitation collectors are located at air sampling sites in the Darlington and Pickering Surveillance Areas. The eleventh collector is in place at the RPS Laboratory.

Precipitation collectors are fabricated out of a large funnel placed on top of a four litre plastic bottle. A metal cylinder encloses the funnel and bottle. The bottles are collected every four weeks and are returned to the laboratory for analysis to determine the tritium concentrations of their contents. The results of the precipitation monitoring are reported in Table 5a.

3.9.2  Recreational Surface Water Monitoring

During the recreational season, between May and October, monthly grab samples are taken from the surface waters in public areas adjacent to each nuclear power generating facility. The samples are analysed for tritium using liquid scintillation counting and for γ-emitters using gamma spectroscopy. The results for the isotopes Cesium-134, Cesium-137, Cobalt-60 and Iodine-131 are reported in Table 5b.

Two sampling locations are used on opposite sides of each nuclear installation. In the Pickering Surveillance Area, samples are taken at Rotary Park Beach and Liverpool Beach Playground. The two locations used for the Darlington Surveillance Area are Port Darlington West Beach and Darlington Provincial Park. In the Bruce Surveillance Area, samples are taken at Scott Point Beach and Inverhuron Park Beach. Port Elgin Beach was added as a third location in the Bruce Surveillance Area in 2011. While further north than Scott Point Beach, this location was chosen as it is used more frequently by the public.

3.9.3  Milk Monitoring – Farm Sampling

Radioactive materials in precipitation or in air can be deposited on grass or in water that is consumed by dairy cattle. These radionuclides, once ingested, would become concentrated in milk and meat.

The Dairy Farmers of Ontario (DFO) collect samples of raw milk from the dairy producers at regular intervals and sends them to the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) laboratory in Guelph for chemical and biological analyses. Through an arrangement with OMAFRA and the DFO, a second raw milk sample is collected from the selected farms are provided to the RPMS for radiological analyses.

Six dairy farms in the Bruce Surveillance Area and nine in the Darlington and Pickering Surveillance Areas have been selected for radiological monitoring. It should be noted that the individual farms that provide milk samples in the On-going Special Studies are not shown on the maps.

The milk samples are picked up monthly from OMAFRA by RPMS staff. Portions of the samples are analyzed for tritium using liquid scintillation counting.

Each month, all of the milk samples received from each surveillance area are combined to form a collective composite of the farms. The ß emitters Strontium-89 and Strontium-90 are chemically separated and analyzed using proportional counting. Gamma spectroscopy is also conducted on these monthly composites and the isotopes Cesium-134, Cesium-137, Cobalt-60, Iodine-131 and Potassium-40 are reported. Potassium-40 is a naturally occurring radioisotope associated with the formation of the earth. Trace levels of Potassium-40 are found in most food. Determining its presence, like Beryllium-7 in Air Particulate monitoring, is used as a laboratory indicator.

3.9.4  Foodbasket Monitoring Program – Milk and Vegetation

The Foodbasket program has been established to sample milk that is sold and food that is grown in the Bruce, Darlington and Pickering surveillance areas. This analysis is carried out as a means of providing an estimate of the activities of reactor products and other radionuclides found in the foodchain of each region. This information enables year-to-year comparisons of these radionuclides.

The RPMS has continued in 2012 with the method introduced in 2010 where a blended milk sample is used to provide a representative sample of what is being consumed by the citizens of Ontario. Almost all of the milk sold to consumers in Ontario is processed at three large dairies which are all located in the Toronto area: Neilson's, Beatrice (Parmalat) and Natrel/Sealtest (Agropur). Because of this, the RPMS has chosen to purchase a sample from each of these principle manufacturers for analysis each month. These samples are analyzed for tritium and γ-emitters. The gamma spectroscopy results are reported for the isotopes Cesium-134, Cesium-137, Cobalt-60, Iodine-131 and Potassium-40.

Vegetation samples from the Bruce, Darlington and Pickering surveillance areas were purchased from road-side stands that are within the Secondary Sone, several kilometres from the nuclear stations (i.e. < 50 km) during July and August 2012. A variety of fruits and vegetables were selected based on seasonal availability and water content.

Juice was extracted from the fruit and vegetable samples using a Hamilton-Beach Type CJ08 juice extractor. The condensate from the juice extract was analysed for tritium using liquid scintillation counting. The tritium concentration is reported in Bq/kg of sample.

3.9.5 On-Going Special Studies Results

The results of the five sampling programs included in this section are summarized in the following tables.

The results of tritium analysis conducted on the precipitation samples collected throughout 2012 extend from less than the MDC to a maximum of 420 Bq/L. The median concentrations in the respective surveillance areas are presented in Table 5a. These values range from < 5 to 53 Bq/L, which is comparable to those observed in previous years.

Table 5a: Precipitation Monitoring Results
Surveillance Area Number of Samples Tritium
(Bq/L)
Arthur 12 < 5[ 1 ]
Bruce 22 11
Darlington 48 10
Pickering 36 53
Toronto-west 11 < 5[ 1 ]

Table 5b lists the results of surface water measurements made at sites adjacent to the Bruce, Darlington and Pickering reactor installations. While the difference is not that great, the median tritium concentrations were found to be lower in Lake Ontario than in Lake Huron. The activities of γ emitting nuclides in these samples were extremely low as all of the results were below the MDC. Very little change is noted in these measurements when compared with those obtained in 2011.

Table 5b: Surface Water Monitoring Results
Surveillance
Area
Number of
Samples
Tritium
(Bq/L)
Co–60
(Bq/L)
I–131
(Bq/L)
Cs–134
(Bq/L)
Cs–137
(Bq/L)
Bruce 15 16 < 0.2[ 2 ] < 0.6[ 2 ] < 0.7[ 2 ] < 1.0[ 2 ]
Darlington 10 < 5 < 0.2[ 2 ] < 0.6[ 2 ] < 0.7[ 2 ] < 1.0[ 2 ]
Pickering 10 6.2 < 0.2[ 2 ] < 0.6[ 2 ] < 0.7[ 2 ] < 1.0[ 2 ]

Dairy farms in the Bruce and Darlington/Pickering surveillance areas provided a total of 173 individual monthly samples. As in 2011 there has been some irregularity in the number of farms being sampled in the darlington/Pickering Surveillance Area. This problem has been stabilized following a request to OMAFRA to have adjustments made in the sampling carried out by DFO. The median concentrations of tritium in milk are given in Table 5c. These range from < 6 Bq/L in the Darlington/Pickering Surveillance Area to 7.5 Bq/L in the Bruce Surveillance Area. These values are only slightly more than 0.1% of the DSC of 7000 Bq/L for tritium in drinking water. The results of the analysis for Strontium-90 and γ-emitting fission products, shown in Table 5d, were consistently found to be at, or below, the limits of detection. These results remain consistent with measurements made in 2011 and other years before.

Table 5c: Farm Milk Monitoring – Tritium Analysis
Surveillance Area Number of Samples Tritium
(Bq/L)
Bruce 70 < 6
Darlington/Pickering 103 < 6

Table 5d: Farm Milk Monitoring – Beta and Gamma Analysis

Bruce

Table 5d: Bruce Farm Milk Monitoring – Beta and Gamma Analysis
Samples Composite from 6 Farms
Number of Samples 12
Sr-90
(Bq/L)
< 0.5[ 3 ]
Cs-134
(Bq/L)
< 0.7[ 3 ]
Cs-137
(Bq/L)
< 1.0[ 3 ]
Co-60
(Bq/L)
< 0.2[ 3 ]
I-131
(Bq/L)
< 0.6[ 3 ]
K-40
(g/L)
1.7

Darlington/Pickering

Table 5d: Darlington/Pickering Farm Milk Monitoring – Beta and Gamma Analysis
Samples Composite from 6 Farms Composite from 8 Farms Composite from 9 Farms
Number of Samples 1 1 12
Sr-90
(Bq/L)
< 0.5[ 3 ] < 0.5[ 3 ] < 0.5[ 3 ]
Cs-134
(Bq/L)
< 0.7[ 3 ] < 0.7[ 3 ] < 0.7[ 3 ]
Cs-137
(Bq/L)
< 1.0[ 3 ] < 1.0[ 3 ] < 1.0[ 3 ]
Co-60
(Bq/L)
< 0.2[ 3 ] < 0.2[ 3 ] < 0.2[ 3 ]
I-131
(Bq/L)
< 0.6[ 3 ] < 0.6[ 3 ] < 0.6[ 3 ]
K-40
(g/L)
1.7 1.8 1.7

The results of the analysis of milk samples collected as part of the Foodbasket program for tritium and fission products were consistently at, or below the limits of detection. These results are virtually identical with those of 2011 and even though the sampling has changed from earlier years, the overall result remains very consistent.

Table 5e: Foodbasket – Milk Monitoring Results
Milk Processor Beatrice Foods Canada Natrel/Agropur Canada Neilson Dairy Limited
Number of Samples 11 11 11
Sr-90
(Bq/L)
< 0.5[ 4 ] < 0.5[ 4 ] < 0.5[ 4 ]
Cs-134
(Bq/L)
< 0.2[ 4 ] < 0.2[ 4 ] < 0.2[ 4 ]
Cs-137
(Bq/L)
< 0.7[ 4 ] < 0.7[ 4 ] < 0.7[ 4 ]
Co-60
(Bq/L)
< 1.0[ 4 ] < 1.0[ 4 ] < 1.0[ 4 ]
I-131
(Bq/L
< 0.6[ 4 ] < 0.6[ 4 ] < 0.6[ 4 ]
K-40
(g/L)
1.7  1.7 1.7

The results of the vegetation sampling are provided in Table 5f. Where measurable results were obtained, the findings are very low. The variety of fruit and vegetables that were sampled included strawberries, blueberries, apples, cucumber, squash and tomatoes.

Table 5f: Foodbasket - Vegetation Monitoring Results
Surveillance Area Number of Samples Tritium
(Bg/kg)
Bruce 5 11
Darlington/Pickering 5 8.4

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[ 1 ]Laboratory-MDC Tritium-in-Drinking Water = 5 Bq/L

[ 2 ]MDC = 10% DSC for each nuclide except tritium

[ 3 ]MDC = 10% DSC for each nuclide

[ 4 ]MDC = 10% DSC for each nuclide except tritium

ISSN 1929-2899