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

1. data completeness;
2. data accuracy, using spike and laboratory control samples;
3. data precision, using split samples, duplicate samples, and recounts; and
4. 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, 2003.

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 established as the maximum concentration from the past seven years of applicable data. 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. Those results that did not meet this requirement are shown in Table 3.

Table 3.                    Analytical results determined to be unacceptable.

DATA COMPLETENESS

The QAPP specifies a 98 percent completeness goal for all regularly scheduled sample types. Data completeness was 100 percent during the third quarter for all sample types with the exception of low volume air which was 92 percent. The August 20 sample for the Craters and the July 16 samples from Dubois and FAA Tower were invalid due to insufficient sample volume collection as a result of equipment failures. The July 2 FAA Tower was also invalid for insufficient sample volume collection as a result of a tripped circuit breaker.

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. The QAPP specifies that sample results should agree within ±20 percent or 3s, whichever is greater. For environmental samples at levels that are within the normal range found by the ESER, the 3s criterion is the one that applies in nearly all cases. Mathematically, the 3s criterion is expressed as:

│X-Y│ < 3 × (sqrt(s_x² + s_y²)),

where:

X is the result of the regular sample
Y is the result of the duplicate sample
sx is the uncertainty of the regular sample
sy 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.

Revisions to the QAPP will establish Warning and Control limits for duplicate/recount analysis. This method will evaluate the absolute difference between the duplicate/recount when the original result is below the upper bound and the standard relative percent difference when the original result if greater than or equal to the upper bound.
 

Field duplicate samples

Duplicate milk samples were collected from Terreton on July 1 and analyzed for gamma-emitting radionuclides. Only the analysis of the naturally occurring radionuclide potassium-40 (⁴⁰K) was not within the ± 3s criterion. A second duplicate from Howe was also collected in July. All analyses were within the acceptable limits.

Duplicate analyses were also performed on wheat (Rupert) and lettuce (Arco) samples. Again only the naturally occurring potassium-40 result for the duplicate wheat sample did not meet the acceptability criteria.

Duplicate air samplers are operated at two locations adjacent to regular air samplers. In the fourth quarter of 2003 these samplers, designated as Q/A-1 and Q/A-2, were in operation at the Blackfoot CMS and Mud Lake, respectively. Particulate filters were analyzed for gross alpha and gross beta activity. All valid results from the duplicate samplers met the 3s criterion for both gross alpha and gross beta during the third quarter.

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.

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 (<2) 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.

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 third quarter 2003.

The EAL also recounts a number of samples of each media type. The lab tests each recount using both 20 percent criterion and the 3s criterion, subject to the limitations described in the previous paragraph. All third quarter 2003 results were within the criteria for acceptance.

Severn-Trent split one wheat and one lettuce sample for ⁹⁰Sr analysis and the results were within the 3s criterion.

Sample Recounts

The ISU EAL recounts a number of samples of each media type. The lab tests each recount using both the 20% 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.

• Thirty-nine low-volume air filters were recounted for alpha activity. All were within the 3s criterion.

• Thirty-nine low-volume air filters were recounted for beta activity. All were within the 3s criterion.

• Eighteen milk samples were recounted for ⁴⁰K; three were recounted twice and one was recounted three times. Five were not within the 3s criterion. The EAL has started using 40K instead of ¹³¹I data for recount and split comparisons.

• Twelve groups of charcoal cartridges were recounted for ¹³¹I. All were within the 3s criterion.

• Fifteen tissue samples were recounted for ¹³⁷Cs. All were within the 3s criterion.

• Sixteen low-volume composites were recounted for beryllium-7. All were within the 3s criterion.

• Four wheat samples were recounted for ⁴⁰K. Two were not within the 3s criterion, but were within the 20 percent criterion.

• Five lettuce samples were recounted for ⁴⁰K; three were recounted twice and two were recounted three times. Four of the comparisons were not within the 3s criterion or the 20 percent criterion.

• Six precipitation samples were recounted for tritium. The results were within the 3s criterion.

• Two water samples were recounted for tritium. The results were within the 3s criterion.

• Two milk samples were recounted for tritium. One result was not within the 3s criterion, but was within 20 percent.

• One atmospheric moisture samples was recounted for tritium. The result was within the 3s criterion.

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. During the third quarter of 2003, spikes of the following types were submitted for analyses by ESER:

• Milk sample spike analyzed for gamma-emitting radionuclides by the ISU EAL.

• Low-volume air filter composite analyzed for ²⁴¹Am, ²³⁸Pu and ^239/240Pu by Severn Trent.

• Results were reported in the third quarter for a tritium in precipitation spike submitted at the end of the second quarter.

The Quality Assurance Project Plan specifies a required accuracy of ±10% for tritium in precipitation, ±20% for gamma-emitting radionuclides in milk and ±25% for actinides in air. The tritium spike was the only sample to not meet the specified criteria. Revisions to the QAPP will require spikes to be within a certain calculated range based on the concentration of the spike added. The ⁹⁰Sr blank for the third quarter met also this new criterion.

Severn-Trent prepares an internal laboratory control sample (LCS) for analysis with each batch of samples submitted by the ESER. During the third quarter these consisted of ⁹⁰Sr, ²⁴¹Am, ²³⁸Pu and ^239/240Pu in air, and ⁹⁰Sr in wheat and lettuce. The QAPP specifies accuracies of ± 10 percent for ⁹⁰Sr and actinides in air and ± 25 percent for ⁹⁰Sr in wheat. Only the LCS for ⁹⁰Sr in air failed to meet the applicable criteria. All other air LCS results were within acceptable parameters. Since the ⁹⁰Sr LCS was higher than the acceptance criteria this would indicate a positive, or high, bias to the associated samples. Strontioum-90 was failed the revised LCS criteria for composite blanks and wheat. This issue is being resolved with the laboratory.

The ISU EAL also prepares internal laboratory spikes. During the third quarter of 2003, 16 analyses were conducted on NIST-traceable standards for gamma-emitting radionuclides. Geometries tested included low-volume air filter composites, 500 mL water spiked at 0.8 and 1.0 g/mL, and 1000 mL water sample spiked at 1.0 g/mL. A total of 66 analytical results were generated. All of the results within the ± 20 percent range.

Eighteen analyses of spiked tritium in water were also run during the quarter. All results met the ± 20 percent criterion. A gross alpha and gross beta water spike was analyzed and was within 20 percent of the known value.

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 low-volume air sampling program includes the use of two field blanks, designated as Blank A and Blank B, that each accompanies one of the air filter collection routes. These blank filters are also submitted as quarterly composites. After gamma spectrometry analysis, one of the blanks is analyzed for ⁹⁰Sr and the other for transuranics (²⁴¹Am, ²³⁸Pu and ^239/240Pu).

The QAPP also specifies that one milk sample blank will be submitted per year (although this is now being done monthly) and one precipitation blank for each month. The precipitation blanks are also used for atmospheric moisture samples collected during the month. Blanks for milk and gamma-emitting radionuclides were in control.

The QAPP does not specify requirements for blank performance, but ideally the result should be within ± 3s of zero on most analyses. Two gross alpha results were greater than the ± 3s criterion. For those weeks where the blank samples exceeded the ± 3s criterion calls into question the validity of the results from the associated field samples. An out-of-control blank could suggest significant filter contamination or laboratory contamination. Revisions to the QAPP will detail blank acceptance criteria, again based on the upper limit and method uncertainty. Using the revised criteria only the blanks for ¹³¹I in charcoal cartridges and ²⁴¹Am and ⁹⁰Sr in wheat failed.

Using this method three gross alpha blank measurements were deemed to be at the warning level and two were considered out-of-control. These samples correlated with those that missed the ± 3s criterion. In addition to the gross alpha results six ¹³¹I results received a warning and three were deemed out-of-control.

Blank analysis results for tritium in atmospheric moisture (water) blanks during the quarter both exceed the ± 3s criterion.

The EAL also analyzes reagent blanks to help determine if the analysis will yield a zero result when no activity is present. One such blank was analyzed for tritium in water during the third quarter. The results were less than the calculated MDCs or less than the 3s criterion. Severn-Trent also analyzes a laboratory blank with each sample set. Third quarter blanks were less than three standard deviations of zero for plutonium-238 and strontium-90 in air. Blanks for plutonium-239/240 and americium-241 were greater than three standard deviations. The laboratory blank for strontium-90 in wheat was high enough on the first run to have to re-analyze the samples. The blank on the re-run was less than one standard deviation of zero.

ASSESSMENTS

A schedule for routine surveillances of ESER program activities was initiated at the beginning of 2002 and most procedures were assessed during that year. One surveillance was conducted in the third quarter of 2003 on wheat sampling and preparation. The conclusion of the surveillance was that the procedure needed revision to reflect recent changes in the process. These included sample collection occurring directly from farm fields instead of grain elevators and sample processing being performed at the town office instead of the INEEL laboratory.

SUMMARY OF QUALITY ASSURANCE ACTIVITIES

There were no significant QA problems noted for the third quarter. A few recount and duplicate results did not meet the reproducibility criteria of the EAL. The laboratory has begun using potassium-40 for comparison purposes because this radionuclide is normally seen in samples. However, fluctuations in ambient background sometimes cause variations in reported concentrations.

In summary the quality assurance and data quality objectives for analyses were met in the third quarter of 2003 with the following exceptions:

• ¹³¹I charcoal cartridges, failed both general and blanks;
• All analytes in quarterly composites; ¹³⁷Cs also failed for recounts, and ²⁴¹Am and ⁹⁰Sr failed in composite blanks;
• ¹³⁷Cs in lettuce; and
• ⁹⁰Sr in wheat.

All QA issues, particularly those associated with the quarterly composites are being resolved with the laboratory. As of the writing of this report the composite issue appears to be related to laboratory contamination related to spiked samples.



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