Fourth Quarter 2004
INEEL Quarterly Site Environmental Report
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Quality Assurance

The ESER Quality Assurance Program consists of five ongoing tasks which measure:

1. method uncertainty;
2. data completeness;
3. data accuracy, using spike and laboratory control samples;
4. data precision, using split samples, duplicate samples, and recounts; and
5. the presence of contamination in samples, using blanks.

The following discussion summarizes the results of the quality assurance program for the period from October 1 to December 31, 2004.

METHOD UNCERTAINTY

The Quality Assurance Project Plan (QAPP) establishes data quality and method quality objectives for the ESER surveillance program (Stoller 2002). Since the primary concern is with detection, the lower bound for the method uncertainty is set at zero. The upper bound is defined by the ESER program as the maximum concentration in the nonoutlier range of data from the past seven years. Each individual result is checked for acceptance on the basis of the result, whether it is below the lower limit (i.e., a negative value), greater than the upper limit, or between the lower and upper limit (the most common occurrence). The calculated method uncertainty is then compared to the 1s measured uncertainty. A sample is deemed acceptable when the measured 1s uncertainty is less than the calculated uncertainty. The upper bound values are currently being evaluated and revised. Preliminary results indicate that calculated method uncertainties for detected results were acceptable.

DATA COMPLETENESS

The QAPP specifies a 98 percent completeness goal for all regularly scheduled sample types. Data completeness for sample collection and delivery was 100 percent during the fourth quarter for all samples types with the following exceptions. A number of precipitation samples were not collected due to the lack of precipitation. Of the five game animals sampled, two thyroids and three livers were not collected. There were three air samples that had volumes below the 7,000 ft³ or 200 m³ threshold listed in the air sampling procedure as being a valid sample. If these are not considered valid samples, the completeness of the air filter data set is 98.8 percent. A low-volume filter was missing at sample collection time from the station at Craters of the Moon on November 3.

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DATA PRECISION

Data precision is a measure of the variability associated with a measurement system. Precision is measured using duplicate samples, split samples, and recounts. Data precision is measured using duplicate samples, split samples, and recounts. The Quality Assurance Project Plan specifies that sample results should agree within ±20 percent or 3σ, whichever is greater. For environmental samples at levels that are within the normal range found by the ESER, the 3 standard deviation criterion is the one that applies in nearly all cases. The standard deviation criterion is considered to be met if the values of the duplicate samples differ by less than the root mean square of three standard deviations of each sample result. Mathematically, this is expressed as:

│X-Y│< 3 (sqrt(σ_x² + σ_y²)),
where:
X is the result of the regular sample
Y is the result of the duplicate sample
σ_x is the uncertainty of the regular sample
σ_y is the uncertainty of the duplicate sample

Another measure of duplicate sample results is the relative percent difference. This value is the difference in the two results divided by the mean of the two results. The following sections of this report first check the sample results using the 3 standard deviation criterion. If this criterion is not met, the results are then listed for the relative percent difference.

Field Duplicate Samples

Duplicate milk samples were collected from Blackfoot on October 5 and analyzed for gamma-emitting radionuclides. Duplicate milk samples were also collected from Roberts on December 7 and analyzed for gamma-emitting radionuclides. All results were within the 3σ criteria.

Duplicate potato samples were collected from Howe and analyzed for gamma-emitting radionuclides and Strontium-90. The results met the 3σ acceptability criteria.

Duplicate drinking water samples were obtained from Minidoka on November 9 and analyzed for gross alpha and gross beta. Final tritium results were not available. Duplicate surface water samples were obtained from Bill Jones Fish Farm on May 11 and analyzed for gross alpha, gross beta, and tritium. All results reported to date were within the 3σ acceptability criteria.

Duplicate air samplers are operated at two locations adjacent to regular air samplers. In the fourth quarter of 2004 these samplers, designated as QA-1 and QA-2, were in operation at the Mountain View CMS and Mud Lake, respectively. Particulate filters receive the standard analysis for gross alpha and gross beta; charcoal cartridges are analyzed specifically for iodine-131. All gross alpha results for the co-located samplers met the acceptability criteria. Five of the gross beta results collected from duplicate stations at Mountain View did not meet the criteria. The relative percent differences ranged from 14 to 46 percent. The differences may be due to a faulty pump, which failed during the fourth week of December. Charcoal cartridge results are difficult to present because cartridges are counted in batches of nine.

Composite air samples from the two QA samplers were submitted for analysis at the end of the fourth quarter for gamma spectrometry at the EAL and for ⁹⁰Sr at Severn-Trent. All analyses were within the 3s criterion with the exception of ⁹⁰Sr at the Mountain View CMS and QA-1 stations.

A comparison of duplicate results can also show bias in the sampling system. For example, if one set of results is consistently lower or higher than the other one might suspect that this bias was due to a leak in the system or variations in the calibration of the flow meter. Figure 14 and Figure 15 show the ratio of results (QA duplicate sampler/main sampler) over time. A ratio of one means that the results of both samplers are exactly the same. The figures show that the bias is small (<4) and not consistent in Mud Lake results and Monteview gross alpha results, indicating that there is no obvious bias in the duplicate sampling systems in these cases. However, the gross beta results from Monteview indicate the QA-2 sample was consistently lower than the other sampler. This sampler stopped functioning in the fourth week of December indicating that the bias may be due to instrument malfunction.

Lab Split Samples

The EAL splits and analyzes a number of milk, precipitation, and atmospheric moisture samples each quarter. The laboratory tests each result using both the ±20 percent criterion and the 3s criterion, although it considers the former test meaningless for analyses producing fewer than 15 total counts and questionable even where counts are on the order of 100. The latter criterion is applied in nearly all cases at the levels seen in environmental samples analyzed for the ESER program. Results of the EAL split sample analyses met the criteria for acceptance during the fourth quarter 2004.

Severn-Trent split milk and potato samples for Strontium-90 analysis. The milk result was within the 3σ criterion but the potato result was just outside. Waterfowl samples were also split and analyzed for gamma-emitting radionuclides, Strontium-90, and actinides. All results were within the 3σ criterion except for the Cesium-137 result.

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Sample Recounts

The ISU EAL recounts a number of samples of each media type. The lab tests each recount using both the 20 percent criterion and the 3σ criterion, subject to the limitations described in the previous section.

A summary of the recount results for the fourth quarter is presented below.

• 41 low-volume air filters were recounted for alpha activity. All were within the 3σ criterion.
• 41 low-volume air filters were recounted for beta activity. One was outside the 3σ criterion but within the 20 percent criterion.
• 19 milk samples were recounted for potassium-40. All were within the 3σ criterion.
• 4 groups of charcoal cartridges were recounted for iodine-131. All were within the 3σ criterion.
• 2 tissue samples were recounted for cesium-137. Both were within the 3σ criterion.
• 9 low volume composites were recounted for beryllium-7. All were within the 3σ criterion.
• 7 soil samples were recounted for cesium-137; four were recounted twice. All results were within the 3σ criterion.
• 5 potato samples were recounted for potassium-40. Two results were outside the 3σ criterion but within the 20 percent criterion.
• 2 atmospheric moisture samples were recounted for tritium. Both results were within the 3σ criterion.
   

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DATA ACCURACY

Accuracy is a measure of the degree to which a measured value agrees with the "true" value for a given parameter; accuracy includes elements of both bias and precision.

Spike Samples Submitted with Field Samples

During the fourth quarter of 2004, spikes (samples prepared with known amounts of radionuclides) of the following types were obtained and submitted:

• Milk spike analyzed for Strontium-90 by Severn-Trent.
• Low-volume air filter analyzed for gross alpha and gross beta by the EAL.
• Low-volume air filter composite analyzed for actinides by Severn-Trent

The Quality Assurance Project Plan specifies a required accuracy of ±20 percent for gross alpha and gross beta in air and ±25 percent for Strontium-90 in milk and for actinides in air. A comparison is also provided using the 3 sigma standard. All spike samples met the criteria during the fourth quarter.

The Quality Assessment Program, administered through the Environmental Monitoring Laboratory was terminated following the June 2004 test session. A new performance testing program though the Radiological and Environmental Sciences Laboratory’s Mixed Analyte Performance Evaluation Program (MAPEP) was initiated. Idaho State University’s Environmental Assessment Laboratory analyzed the first set of samples in October 2004. Results are tabulated below.

Internal Laboratory Spikes

The Idaho State University Environmental Assessment Laboratory uses NIST standards to prepare spiked water samples and uses commercially prepared calibration standards as NIST-traceable spiked samples. ISU considers a performance to be acceptable if results pass either the ±20 percent test specified by the ESER program or the three-sigma test described in the data precision section. A variety of checks are made each quarter on different geometries.

During the fourth quarter of 2004, 17 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, 10-charcoal cartridge screening, 500 ml 1.0 g/cc samples, and one-liter 1.0 g/cc samples. A total of 114 analytical results were generated. All of the results were within the ±20 percent range except for one result for Sr-85. This result was within the three-sigma range, and the sample had decayed for 8.5 half-lives, which may have contributed to the result outside the 20 percent range.

Water samples spiked with tritium received 14 analyses during the quarterly reporting period. All were well within the ±20 percent criterion, and in fact all were within 6 percent of the known value with one exception. A tritium in milk spike was also about 7 of the known value. Gross alpha and beta spikes analyzed in the fourth quarter were within 10 percent of the expected values.

Severn-Trent analyzes a laboratory control sample (LCS) with each batch of samples submitted by the ESER. During the fourth quarter available results consisted of strontium-90 and actinides in air, strontium-90 in milk and potatoes, and gamma-emitters, strontium-90, and actinides in waterfowl tissue. All results met acceptability criteria.
 

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BLANKS

Field blanks

The ESER program submits field blanks along with the regular samples to test for the introduction of contamination during the process of field collection, laboratory preparation, and laboratory analysis. The current program includes the use of two field blanks, designated as Blank A and Blank B, that each accompanies one of the air filter routes. Quarterly composites of the blanks are also submitted. After gamma spectrometry analysis, one of the blanks is analyzed for Sr-90 and the other for transuranics.

The Quality Assurance Project Plan does not specify requirements for blank performance, but ideally the result should be within ±2σ of zero and preferably within ±1σ of zero on most analyses. It would be expected, based on counting statistics for a sample that was truly a blank (i.e., the true value of the analyte was zero), that 68.3 percent of analyses would fall within one standard deviation, 95.5 percent would fall within two standard deviations, and 99.7 percent would fall within three standard deviations. With a few exceptions in gross alpha and gross beta analyses, all results were within the 2σ significance level.

Reagent Blanks

The Environmental Assessment Laboratory prepares and analyzes reagent blanks to help determine if the analysis will yield a zero result when no activity is present. ISU considers the result within specification if the concentration is less than the minimum detectable concentration (MDC) for the analysis. One such blank was analyzed for tritium in the fourth quarter for water. The blank was below the MDC for the analysis and less than one standard deviation. A water blank analyzed for gross alpha and gross beta was also below the MDA for the analysis and within one standard deviation for both parameters.

Severn-Trent analyzes a blank with each set of results. Fourth quarter blanks were less than three standard deviations of zero for strontium-90, plutonium-238, plutonium-239/240 and americium-241 in air (for one of two blanks run). The other americium-241 blank was over three standard deviations of zero. Milk and potato blanks were within three standard deviations for strontium-90. For waterfowl blanks, all parameters were within three standard deviations of zero.
 

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