Fourth 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 briefly summarizes the results of the quality assurance program for the period from October 1 to December 31, 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 for the range of data over the past ten years, excepting those values determined to be extremes using box plots generated by a statistical data program. 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 were recently re-evaluated and revised. Preliminary results indicate that more calculated method uncertainties for detected results were acceptable. In the fourth quarter of 2005, approximately 97 percent of method uncertainties were in the acceptable categories.

DATA COMPLETENESS

The Quality Assurance Project Plan (QAPP) specifies a 98 percent completeness goal for all regularly scheduled sample types (Stoller 2002). Data completeness for sample collection and delivery was 100 percent during the fourth quarter for all sample types with these exceptions: a number of precipitation samples were not collected due to lack of precipitation. All of the 45 scheduled PM₁₀ samples were collected; however, one ran from noon to noon instead of midnight to midnight due to a motor change out.

The first analysis for ⁹⁰Sr in potatoes failed. Sufficient sample was left to resubmit potatoes from eight of the ten sampling locations.

Americium-241 yields for all fourth quarter quarterly composite samples were low. Further discussion is provided in the Other QA Problems Noted section.
 

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

• Milk spike analyzed for Iodine-131 by ISU.
• Precipitation spike analyzed for tritium by ISU.
• Milk spike analyzed for Strontium-90 by Teledyne Brown.

All parameters measured were within the criteria specified in the Quality Assurance Project Plan.

Performance Evaluation Samples

The QAP 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 Teledyne Brown Engineering participated in the MAPEP Study reported in November 2005. Results are tabulated below for those analyses performed by each laboratory. (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 fourth quarter of 2005, 20 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, single charcoal cartridge screening, 500 ml 0.8 g/cc samples, 500 ml 1.0 g/cc samples, and 1 L 1.0 g/cc samples. A total of 127analytical results were generated. There were eight results outside the ±20 percent range. Of these, four results for Te-123m and three results for Sn-113 were within the three-sigma test criterion. One result for Y-88 was outside both criteria. This radionuclide had decayed for approximately 8.5 half-lives, and probably has an activity below detectable levels.

Water samples spiked with tritium received six analyses during the quarterly reporting period. All were well within the ±20 percent criterion, ranging from -4 percent to -9 percent. Gross beta spikes analyzed in the fourth quarter were within 20 percent of the expected values; three of four gross alpha spikes were within 20 percent; the one sample outside this range was within the 3s criterion. A tritium in milk spike was within 0.5 percent of the expected value.

Teledyne Brown analyzed a laboratory control sample (LCS) with each batch of samples submitted by the ESER. During the fourth quarter this consisted of strontium-90 and actinides in air, and strontium-90 in milk and potatoes.

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 and Roberts on December 6 and analyzed for gamma-emitting radionuclides. All results were within the 3σ criteria. Results also met the acceptability criteria for gamma-emitting radionuclides in a duplicate potato sample from Aberdeen.

A duplicate drinking water sample was obtained from Fort Hall and a duplicate surface water sample was collected from Hagerman. These were analyzed for gross alpha, gross beta and tritium. The tritium result for the surface water sample was outside the 3σ criterion. All other results met the acceptability criteria.

Duplicate air samplers are operated at two locations adjacent to regular air samplers. In the fourth 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 fourth quarter for gamma spectrometry at the EAL and for ⁹⁰Sr and transuranics at Teledyne Brown. All of these result met the acceptability criteria in the fourth quarter.

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 difference in results (Main sampler - QA duplicate sampler) over time. The figures show that the bias is generally small and is usually not consistent in one direction. However, the graph for the Howe/QA-2 gross beta comparison during the fourth quarter seems to indicate a bias where the duplicate sampler trends higher than the regular sampler. Further data evaluation is needed to determine whether this trend has continued or whether it is a statistical anomaly.
 

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 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. For the fourth quarter reporting period, all 199 recounts met the criteria for acceptance.

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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. Blanks are also submitted for milk and some other sample types.

Ideally blank results 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. In the fourth quarter, all results were within the 3σ significance level except for one gross alpha blank.
 

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 milk. The blank was below the MDC for the analysis and less than two standard deviations. Two water reagent blanks were analyzed for tritium and were also within two standard deviations.

Teledyne Brown analyzes a blank with each set of results. All blanks for fourth quarter samples met Teledyne Brown’s acceptance limits.

OTHER QA PROBLEMS NOTED

Teledyne Brown Engineering issued a Nonconformance Report regarding the spike sample from the third quarter where the known/reported ratio of Americium-241 was good, but the result was below three standard deviations and therefore did not pass. The laboratory has been experiencing an increased frequency of low recoveries for Am-241. In the fourth quarter, Am-241 recoveries were as follows:

05-QT-0064 0.2 percent
05-QT-0065 10.2 percent
05-QT-0071 6.9 percent
05-QT-0072 2.8 percent
05-QT-0075 2.3 percent
05-QT-0076 2.4 percent
05-QT-0078 2.7 percent
05-QT-0079 4.9 percent
05-QT-0080 3.1 percent
05-QT-0082 No recovery

The problem is attributed in the report to a difficulty with the pre-packed resin columns. As the pre-packed columns age, they can release chemicals that impair the performance of the columns. The laboratory plans to buy bulk resin and pack the columns at the time of the analysis as a corrective action. Testing has indicated that columns packed at the laboratory produce significantly higher recoveries.

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