First Quarter 2006
INL Quarterly Site Environmental Report
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The ESER Quality Assurance Program consists of five ongoing tasks which measure:
The following discussion briefly summarizes the results of the quality assurance program for the period from January 1 to March 31, 2006.
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 first quarter of 2006, approximately 96.5 percent of method uncertainties were in the acceptable categories.
The 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 first quarter for all sample types with these exceptions:
No samples were lost in analysis during the first quarter.
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.
The ESER obtains spike samples from the Department of Energy’s Radiological and Environmental Sciences Laboratory, which prepares the spikes and issues data reports with the results. During the first quarter of 2006, no spikes were scheduled. A schedule was prepared for spike samples for the remainder of the year.
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.
The Idaho State University EAL uses National Institute of Standards and Technology (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 first quarter of 2006, only two analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. The geometries tested were single and ten charcoal cartridge screening. All of the results were within the ±20 percent range. Due to an oversight by the EAL the additional analyses normally performed were not conducted during the quarter. According to the EAL Quality Control Procedure, spike samples are only required for water samples; however, the usual practice is to perform at least one spike analysis for each geometry used during the quarter. Additional efforts will be made by the laboratory to ensure that this practice is maintained in future quarters.
Water samples spiked with tritium received 11 analyses during the quarterly
reporting period. All were well within the ±20 percent criterion, generally -4
percent to -9 percent.
Teledyne Brown analyzed a laboratory control sample (LCS) with each batch of
samples submitted by the ESER. During the first quarter this consisted of
strontium-90 and actinides in air.
|
Media |
Analyte |
QAPP Accuracy |
LCS Result |
Within Criterion? |
|
Air |
Strontium-90 |
±10 percent |
TBD |
TBD |
|
Air |
Americium-241 |
±10 percent |
TBD |
TBD |
|
Air |
Plutonium-239/240 |
±10 percent |
TBD |
TBD |
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(σx2 + σy2)), where:
X is the result of the regular sample
Y is the result of the duplicate sample
σx is the uncertainty of the regular sample
σy 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.
Duplicate milk samples were collected from Blackfoot and Terreton on March 7 and analyzed for gamma-emitting radionuclides. 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 2006 these samplers, designated as QA-1 and QA-2, were in operation at the EFS 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 and 25 of 26 gross beta results for the co-located samplers met the acceptability criteria. One result was outside of 3σ but had a relative percent difference of 13 percent, within the 20 percent range. 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. The result for 241Am failed to meet the acceptability criteria in the first quarter; other parameters were within specifications.
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 12 and Figure 13 show the difference in results (Main sampler - QA duplicate sampler) over time. The figures show that the bias is generally small and is not consistent in one direction.
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 first quarter of 2006.
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 first quarter reporting period, all 108 recounts met the criteria for acceptance.
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 two gross alpha 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 gross alpha and gross beta in the first quarter for water. The blank was well below the MDC for the analysis and also less than one standard deviation.
Teledyne Brown analyzes a blank with each set of results. All blanks for fourth quarter samples met Teledyne Brown’s acceptance limits.
There were no additional QA problems noted in the first quarter.