Second Quarter 2005
INL 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 April 1 to June 30, 2005.

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 non-outlier 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 more calculated method uncertainties for detected results were acceptable.

DATA COMPLETENESS

The Quality Assurance Project Plan (QAPP) specifies a 98 percent completeness goal for all regularly scheduled sample types (Stoller 2004). Data completeness for sample collection and delivery was 100 percent during the second quarter for all sample types with these exceptions: a number of precipitation samples were not collected due to lack of precipitation and one (2 percent) of the scheduled PM₁₀ samples did not run when the timer did not trip.

Five air samples were determined to invalid due to insufficient volume collected because of equipment failure or electrical work (one from Arco and two each from Dubois and Howe). The completeness of air filter data is thus considered to be 98.1percent.

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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 second quarter of 2005, spikes (samples prepared with known amounts of radionuclides) of the following types were obtained and submitted:

• Quarterly composite spike analyzed for gamma-emitting radionuclides by the Environmental Assessment Laboratory (EAL).
• Low-volume charcoal cartridge analyzed for Barium-133 by the EAL.
• Drinking water spike analyzed for tritium by the EAL.
• Milk spike analyzed for gamma-emitting radionuclides by the EAL.
• Strontium-90 quarterly composite spike analyzed by Severn-Trent.

A total of 16 values for comparison were generated by the analysis of the spike samples. All results were within the criteria during the second quarter except for Cobalt-60 in milk and Barium-133 in the charcoal cartridge.

The Quality Assessment Program was discontinued following the March 2004 distribution. Performance evaluation samples are now prepared through the Mixed Analyte Performance Evaluation Program (MAPEP), administered by the Department of Energy’s Radiological and Environmental Sciences Laboratory. DOE has mandated that all laboratories performing analyses in support of the Office of Environmental Management shall participate in MAPEP. The program distributes samples of air, water, vegetation and soil for analysis in approximately January and June. Both radiological and nonradiological constituents are included in the program.

Both the Idaho State University EAL and Severn-Trent participated in the program in May 2005. Results are tabulated below for those analyses performed by each laboratory for the ESER program. (A = Acceptable, W = Acceptable with warning, N = Not acceptable)

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 second quarter of 2005, 19 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, single charcoal cartridge screening, 10-charcoal cartridge screening, 500 ml 1.0 g/cc samples, and one-liter 1.0 g/cc samples. A total of 115 analytical results were generated. All of the results were within 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 7 percent of the known value. Gross beta spikes analyzed in the first quarter were within 20 percent of the expected values; two of four gross alpha spikes were within 20 percent and all were within three standard deviations. An internal tritium milk spike was within approximately 2 percent of the known value.

Severn-Trent analyzes a laboratory control sample (LCS) with each batch of samples submitted by the ESER. During the second quarter this consisted of strontium-90 and actinides in air and strontium-90 in milk.

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 Moreland on April 5, Dietrich on June 7, and Howe on June 7 and analyzed for gamma-emitting radionuclides. All results were within the 3σ criteria.

Duplicate water samples were collected from Arco (drinking water) and Bliss (surface water) and analyzed for gross alpha, gross beta, and tritium. All results were within the 3σ criteria.

Duplicate air samplers are operated at two locations adjacent to regular air samplers. In the first quarter of 2005 these samplers, designated as QA-1 and QA-2, were in operation at the INL Main Gate and Howe, respectively. Particulate filters receive the standard analysis for gross alpha and gross beta; charcoal cartridges are analyzed specifically for iodine-131. All gross alpha and gross beta results for the co-located samplers met the acceptability criteria. Charcoal cartridge results are difficult to present because cartridges are counted in batches of ten.

Composite air samples from the two QA samplers were submitted for analysis at the end of the second quarter for gamma spectrometry at the EAL and for ⁹⁰Sr at Severn-Trent. All analyses were within the 3s criterion.

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 15 and Figure 16. show the difference in results (Main sampler - QA duplicate sampler) over time. The figures show that the bias is small and not consistent in one direction, indicating that there is no obvious bias in the duplicate sampling systems in these cases.
 

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 second quarter 2005.

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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 second quarter is presented below.

• 56 low-volume air filters were recounted for alpha activity. All were within the 3σ criterion.
• 6 water samples were recounted for alpha activity; one was recounted twice. All results were within the 3σ criterion.
• 56 low-volume air filters were recounted for beta activity. One was outside the 3σ criterion but within the 20 percent criterion.
• 6 water samples were recounted for beta activity; one was recounted twice. All results were within the 3σ criterion.
• 19 milk samples were recounted for potassium-40; one was recounted twice. All were within the 3σ criterion.
• Two individual charcoal cartridges and 7 groups of charcoal cartridges were recounted for iodine-131. All results were within the 3σ criterion.
• 15 lovol composites were recounted for beryllium-7. All were within the 3σ criterion.
• 1 water sample was recounted for tritium activity. The result was within the 3σ criterion.
• 3 precipitation samples were recounted for tritium. All results were within the 3σ criterion.

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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 single exception in a gross beta analysis, all results were within the 3σ 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 second quarter for milk. The blank was below the MDC for the analysis and less than two standard deviations. A water blank analyzed for gross alpha and gross beta was also below the MDA for the analysis and within two standard deviations for both parameters.

Severn-Trent analyzes a blank with each set of results. Second quarter blanks were less than three standard deviations of zero for strontium-90, plutonium-238, plutonium-239/240 and americium-241 in air and for strontium-90 in milk.

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