I. OVERVIEW §10.1
II. QUALITY CONTROL RESULTS FOR MONITORING
TRITIUM IN AMBIENT AIR
A. Water Vapor Sampling Results §10.2
Figure 10-1: Comparison of Water Vapor
Collected on Silica
Gel vs. Available Water Vapor in Air
B. Ambient Air Sample and Split Results §10.3
Figure 10-2: Comparison of Sample and
Split Results for
Tritiated Water in Ambient Air
§10.1 I. Overview
Berkeley Lab’s quality assurance policy is documented in the Operating and Assurance Plan (OAP).1 The OAP consists of a set of operating principles used to support internal organizations in achieving consistent, safe, and high-quality performance in their work activities. OAP principles are applied to individual programs using a graded approach, with consideration given to factors such as the program’s environmental, health, and safety consequences; its programmatic significance; and its mission.
In addition to the OAP, the monitoring and sampling activities and results presented in this report were conducted in accordance with Berkeley Lab’s Environmental Monitoring Plan2 and applicable DOE3 and US/EPA4 guidance. When special quality assurance (QA) and quality control (QC) requirements are necessary for environmental monitoring (such as the National Emission Standards for Hazardous Air Pollutants (NESHAPs) stack monitoring program), a Quality Assurance Project Plan (QAPP) is developed and implemented.
On-site and off-site (contract) laboratories are utilized to analyze samples for the environmental monitoring program. Both types of laboratories must meet demanding QA/QC specifications and certifications5 that were established to define, monitor, and document laboratory performance. The QA/QC data provided by these laboratories are incorporated into Berkeley Lab’s data quality-assessment processes.
Each set of data (batch) received from the analytical laboratory is systematically evaluated and compared to established data quality objectives before the results can be authenticated and accepted into the environmental monitoring database. Categories of data quality objectives include accuracy, precision, representativeness, comparability, and completeness. When possible, quantitative criteria are used to define and assess data quality.
To verify that environmental monitoring activities are adequate and effective, internal and external oversight is performed as required on specific environmental monitoring programs. Internal oversight activities consist of technical QA assessments performed by the Environmental Protection Group and internal independent assessments conducted by the Berkeley Lab Office of Assessment and Assurance.
DOE’s external oversight of Berkeley Lab programs is performed through the Operational Awareness Program.6 Operational awareness activities include field orientation, meetings, audits, workshops, document and information system reviews, and day-to-day communications. DOE criteria for performance evaluation include (a) federal, state, and local regulations with general applicability to DOE facilities and (b) applicable DOE requirements.
In addition, US/EPA conducts external audits of the NESHAPs monitoring program under 40 CFR 61, Subpart H. EPA has also performed tritium analyses on Berkeley Lab ambient air split samples; results from those analyses are discussed in §10.3. As discussed in §3.9, EPA has requested additional sampling of the air, water, and soil in and around the Laboratory to help determine whether to include Berkeley Lab on the Superfund List. A draft Sampling and Analysis Plan for this EPA-requested sampling was developed in 1999. In 2000, this plan will be reviewed by EPA and the Environmental Sampling Project Task Force in order to produce a final approved plan and begin implementing the sampling and analysis.
II. QUALITY CONTROL RESULTS FOR MONITORING TRITIUM IN AMBIENT AIR§10.2 A. Water Vapor Sampling Results
Berkeley Lab collects atmospheric water vapor on silica gel columns in order to measure the concentration of tritiated water in air. To verify the sampling efficiency for the collection of water vapor from ambient air, in 1999 Berkeley Lab compared the mass of water vapor extracted from field air samples (at all sampling locations) with the mass of water vapor available in the sampled atmosphere. The amount of water collected on each silica gel sample was determined during laboratory analysis. The amount of water vapor in the air available for collection (absolute humidity) was calculated, based on temperature and dew-point data obtained at the on-site meteorological tower. The calculated absolute humidity (grams/cubic meter) was averaged over the monthly tritium sampling period.
To calculate the total mass of water vapor available for collection onto the silica gel column, the average absolute humidity was multiplied by the total volumetric flow through the sampler. Figure 10-1 compares the mass of water vapor collected to the mass of water vapor available.
The figure shows that the mass of water vapor collected from the air is nearly equal to the mass of water vapor available to be collected. The observed small differences between those two values can be accounted for by the uncertainties associated with sampling instrumentation, micrometeorological spatial variations, and sample analysis. Furthermore, the data clearly indicate that the water vapor collection efficiency is consistently high across periods of varying weather conditions (rainfall, temperature, and humidity).
§10.3 B. Ambient Air Sample and Split Results
Berkeley Lab routinely analyzes split samples from its ambient air tritium monitoring program as a way to determine the precision and reproducibility of its monitoring results. A split analysis is performed at a different sampling site each month. In addition, in late 1997, US/EPA began analyzing split samples from two (ENV-LHS and ENV-B13D) of the network’s six sites. The samples shared with EPA are analyzed at its National Air and Radiation Environmental Laboratory (NAREL) facility and provide an inter-laboratory comparison of results.
Berkeley Labs split samples are sent to its contract analytical laboratory and provide an intra-laboratory comparison with the sample result. Figure 10-2 shows a plot of the sample- and split-result pairs for both inter- and intra-laboratory comparisons.
For 1999, there were 24 inter-laboratory and 12 intra-laboratory result pairs. For the 1999 data collected, the average difference between all the sample- and split-result pairs was 0.7%. The average difference for the inter-laboratory result pairs was slightly higher at 1.1%, with the results from Berkeley Lab’s contract analytical laboratory the higher of the two.
Figure 10-2 shows that the sample- and split-result pairs lie close to a line that represents perfect agreement between sample and split. The nearly equal distribution of the data points above and below the ideal line indicates that the sample and split differences are random and not due to systematic errors within a laboratory or between laboratories.
*1 Bq = 27 pCi
Additional quantitative evaluations were performed on the sample and split data in order to determine whether the two sets of results were statistically different. To do that, two statistical tests were applied: T-Test for Dependent Samples and the Wilcoxon Matched Pairs Test. Both tests indicate that sample results and split results are not significantly different at the 95% confidence level. These findings strongly confirm that the ambient air tritium monitoring program at Berkeley Lab contains the required precision and reproducibility for measuring environmental levels of tritiated water in air.