Third Quarter 2004
INEEL Quarterly Site Environmental Report
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The ESER Quality Assurance Program consists of five ongoing tasks which measure:
- method uncertainty;
- data completeness;
- data accuracy, using spike and laboratory control samples;
- data precision, using split samples, duplicate samples, and recounts; and
- the presence of contamination in samples, using blanks.
The following discussion summarizes the results of the quality assurance program for the period from July 1 to September 30, 2004.
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.
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 third 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, one thyroid and one liver were not collected. One (2 percent) of the 48 PM10 samples was not valid, only running for 10.4 of the scheduled 24 hours. 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.
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. 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.
Duplicate milk samples were collected from Carey on September 7 and analyzed for gamma-emitting radionuclides. All analyses were within the acceptable limits.
Duplicate lettuce samples were collected from Mud Lake on July 15 and analyzed for gamma-emitting radionuclides. Duplicate wheat samples were also collected from Howe on August 31 and analyzed for gamma-emitting radionuclides and Strontium-90. Only the naturally occurring potassium-40 result for the duplicate lettuce sample did not meet the acceptability criteria.
Duplicate air samplers are operated at two locations adjacent to regular air
samplers. In the third 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 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 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 238Pu,
239,240Pu, and 241Am at Severn-Trent. All analyses were
within the 3s criterion with the exception of 241Am 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 12 and Figure 13 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, indicating that there is no obvious bias in the duplicate sampling systems. The average bias ratios during the fourth quarter are 1.2 and 1.0 for Blackfoot gross alpha and gross beta, respectively, and 1.1 and 1.0 for Mud Lake gross alpha and gross beta, respectively.
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 third quarter 2004.
One soil sample was split by Severn-Trent and both fractions were analyzed for Plutonium-238, Plutonium 239-240, and Strontium-90. The result for Pu-238 was just outside the 3σ range. One wheat sample was also split and analyzed by Severn-Trent for Strontium-90 and the result was within the 3σ criterion.
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 third quarter is presented below.
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. During the third quarter of 2004, spikes of the following types were obtained and submitted:
The Quality Assurance Project Plan specifies a required accuracy of ±20 percent for gamma-emitters in milk and ±25 percent for all radionuclides in soil. A comparison is also provided using the 3 sigma standard described in the Data Precision section. All samples met the criteria for the radionuclides of concern.
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 third quarter of 2004, 41 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, 10-charcoal cartridge screening, single charcoal cartridge screening, 500 ml 0.8 g/cc samples, 500 ml 1.0 g/cc samples, 500 ml 1.5 g/cc samples, and one-liter 1.0 g/cc samples. A total of 272 analytical results were generated. All of the results were within the ±20 percent range except for two results for Sn-113, two results for Sr-85, and one result for Co-57. Each of these three was within the three-sigma range.
Water samples spiked with tritium received 7 analyses during the quarterly reporting period. All were well within the ±20 percent criterion, and in fact all were within 5 percent of the known value. A gross alpha and gross beta in water spike was also within 20 percent of the known value.
Severn-Trent analyzes a laboratory control sample (LCS) with each batch of samples submitted by the ESER. During the third quarter available results consisted of strontium-90 and actinides in air, strontium-90 in wheat, and strontium-90 and actinides in soil.
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 third quarter of 2004, 41 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, 10-charcoal cartridge screening, single charcoal cartridge screening, 500 ml 0.8 g/cc samples, 500 ml 1.0 g/cc samples, 500 ml 1.5 g/cc samples, and one-liter 1.0 g/cc samples. A total of 272 analytical results were generated. All of the results were within the ±20 percent range except for two results for Sn-113, two results for Sr-85, and one result for Co-57. Each of these three was within the three-sigma range.
Water samples spiked with tritium received 7 analyses during the quarterly reporting period. All were well within the ±20 percent criterion, and in fact all were within 5 percent of the known value. A gross alpha and gross beta in water spike was also within 20 percent of the known value.
Severn-Trent analyzes a laboratory control sample (LCS) with each batch of samples submitted by the ESER. During the third quarter available results consisted of strontium-90 and actinides in air, strontium-90 in wheat, and strontium-90 and actinides in soil. All results were within criteria.
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 also specifies that one milk sample blank will be submitted per year (although this is now being done monthly), and one precipitation sample blank will be submitted per month. The precipitation blanks are also used as blanks for the atmospheric moisture samples. The program now is also submitting blanks with some other sample types.
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.
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. No blank results were reported in the third quarter reporting period.
Severn-Trent analyzes a blank with each set of results. Third quarter blanks
were less than three standard deviations of zero for strontium-90,
plutonium-238, plutonium-239/240 and americium-241 in air, strontium-90,
plutonium-238 and plutonium-239/240 in soil, and strontium-90 in wheat.