DESCRIPTION OF MAJOR SCIENTIFIC PROGRAM AREAS

Currently, the Center's scientific activities are organized into five major areas of specialization with corresponding assignment of staff roles and responsibilities. Although some of the Center's projects involve only one or two of the program areas, all of the program areas collaborate in carrying out the WIPP Environmental Monitoring project, and this type of integrative research is anticipated to characterize many of the Center's future projects.

Internal Dosimetry

The internal dosimetry program conducts analyses and consultation for the study and management of internal radiation exposure. The analyses include collection of information on work and residence history, past and current radiation exposure, bioassays to measure the presence of radionuclides within body tissues (in vivo) or body fluids and excretions (in vitro), and calculation of dose associated with observed uptakes. Consultation includes interpretation of bioassay results and can extend to collaboration with health care professionals and workplace supervisors. The internal dosimetry program includes a documented quality assurance program for in vivo and in vitro bioassays and a comprehensive technical basis for the assessment of internal exposure. The program meets the requirements and recommendations of the DOE Implementation Guide for Internal Dosimetry Programs (10 CFR 835) and the American National Standards Institute Performance Criteria for Radiobioassay (N13.30). The Center is also involved in the DOE Laboratory Accreditation Program for internal dosimetry and radiobioassay.

The internal dosimetry program is provided as an outreach service to the public to support education about the Center's environmental studies and naturally occurring radiation, and to provide assessment of potential exposure to radioactive contaminants of concern. The program also provides support to the WIPP by conducting bioassays for radiation workers on a routine basis. Full-spectrum dosimetry services are available to evaluate internal radiation exposure to radiation workers and members of the public in the case of an accident at the WIPP. In addition, internal dosimetry services can be provided to other entities that employ the use of radioactive materials.

The Center's fixed in vivo bioassay facility occupies approximately 966 square feet, and provides the primary analytical infrastructure for the internal dosimetry program. The facility includes a large shielded counting chamber, dedicated instrument control workstation, two change rooms with showers and toilets, and a reception area. The counting chamber measuring 8 feet x 8 feet x 8 feet and is constructed of 10 inch thick cast iron, with a full graded-Z liner consisting of lead, tin and stainless steel. The cast iron composing the chamber was produced for industrial use prior to 1945, and re-cast for the chamber using a specially selected foundry, resulting in very low background radiation from anthropogenic and naturally occurring constituents. The instrument control workstation includes a video display terminal and intercom that are used to monitor subjects during the examination. Signal processing electronics are located outside the counting shield next to the instrument control workstation. The in vivo bioassay facility was commissioned in July 1997.

The counting chamber is equipped with a lung and whole body counting system using technologically advanced, hyperpure germanium detectors. Lung and whole body counts are simultaneously performed with the counting subject lying horizontally on a specially designed counting bed. Two, four-detector germanium arrays designed for lung and whole body counting are positioned over the chest and under the bed, respectively. Under routine operation, photon interactions in the lung counting detectors are integrated using two independent signal processing chains: one chain for low photon energies (5 to 250 keV) and one chain for high photon energies (200 to 2000 keV). The high-energy chain is analyzed independently and then added to the output of the whole body counting detectors to increase sensitivity. This combination of technology allows for sensitive monitoring for internally deposited transuranics, naturally occurring radioactive materials, and mixed fission / activation products. A dedicated computer serves the integrated electronic system for the acquisition, storage and analysis of gamma-ray spectra collected by the instrument. Resolution of the system is 450, 750, and 2100 eV at photon energies of 5.9, 122, and 1332 keV, respectively. Routine sensitivities for ²³⁸Pu, ²³⁹Pu and ²⁴¹Am in lungs are approximately 930, 2400 and 4 Bq, respectively. Routine sensitivities for ¹³⁷Cs, ⁶⁰Co and ¹⁵²Eu in the whole body are approximately 10, 10, and 60 Bq, respectively. Ultrasound techniques are used to measure subjects' chest wall thickness and composition to account for photon attenuation for positive lung burdens. The Center's staff schedule subjects participating in in vivo bioassays, with a total of 60 minutes allocated for each appointment. Prior to undergoing the lung and whole body count, subjects view a videotape that explains the procedure, and further explanation is provided by internal dosimetry staff.

In addition to providing services in bioassay, staff of the internal dosimetry program carry out basic research in radiation detection technology and novel applications of in vivo bioassay techniques to environmental studies. The staff of the internal dosimetry program are also responsible for the Center's radiation protection program to ensure compliance with the Center's Radioactive Material License, granted under the authority of the New Mexico Environment Department.

Radiochemistry

The primary focus of the radioanalytical program is measurement of radionuclide activities at environmental background levels. Analysis capabilities for environmental media include air, soil, surface water and sediment, groundwater, and biota. In addition to environmental media, the laboratory will be developing bioassay analysis capabilities for urine, feces, and tissue. Standard reference materials for instrument calibration and analytical quality control and quality assurance programs are being implemented for the laboratories. The radiochemistry laboratory currently participates in the DOE Environmental Measurements Laboratory, Quality Assessment Program. The Center is also a pilot participant in the National Institute of Standards and Technology (NIST) Radiochemistry Intercomparison Program (RIP) for evaluation of low-level radionuclide measurements.

The radiochemistry laboratory employs procedures for low-level measurement of actinides, fission products, activated corrosion products, and naturally-occurring radionuclides. These analyses employ advanced instrumentation including alpha spectrometry, low background alpha-beta counting, gamma spectrometry, gas proportional counting, and liquid scintillation. Detection levels achievable with the laboratory's current alpha spectrometry instrumentation and techniques are on the order of 370 µBq for actinides.

Approximately 1700 square feet of space is allocated to the radiochemistry program, including a primary radiochemistry laboratory, and separate tracer and counting laboratories. The primary laboratory room is equipped with one 6-foot chemical hood, five 8-foot chemical hoods, a separate deionized water system, refrigerator, centrifuge and approximately 400 square feet of bench surface.

Environmental Chemistry

The environmental chemistry program has capabilities similar to that of radioanalytical in determining low levels of a variety of inorganic substances in environmental media. Approximately 1400 square feet of laboratory space is allocated to environmental chemistry, including a primary laboratory for sample preparation, and an instrumental analysis laboratory. The primary laboratory room is equipped with three 8-foot chemical hoods, a separate ultra-pure water system, dishwasher, refrigerator, electronic balance, and approximately 170 square feet of bench surface.

The instrumentation laboratory is equipped for the analyses of trace elements, including heavy metals. An atomic absorption spectrometer with flame and graphite furnace was installed in July 1997, and a low-resolution inductively-coupled plasma mass spectrometer was installed in February 1999. An ion chromatograph is used for routine analyses of anions (chloride, fluoride, nitrate and sulfate) in water and air samples. The ion chromatograph can also be configured as a high performance liquid chromatograph, for use in the determination of polycyclic aromatic hydrocarbons.

Field Sampling

The Center's field sampling program is focused on design and implementation of protocols for collection and initial processing of samples of environmental media. The field sampling program uses and maintains a wide variety of sampling equipment, including two fully instrumented meteorological stations; low-volume, high-volume, dichotomous, and multiple orifice inlet aerosol samplers; soil and sediment collection devices; ground water and surface water collection equipment; in situ water quality instrumentation; an in situ NaI gamma radiation detection system; a global positioning system; four-wheel drive vehicles; and a small boat with outboard motor.

Approximately 1300 square feet of working area is dedicated to staging field sampling activities, and for processing and storing collected samples. This area includes approximately 500 square feet of shelving and storage space and 200 square feet of bench top workspace. Sample preparation and storage equipment includes a muffle furnace, drying ovens, refrigerator, freezers, dishwasher, ultrasonic cleaners, soil sieves, high-volume jar mill soil grinder, mixer soil mills, cross-flow high-volume water filtrator, and electronic balances.

In conjunction with the Center's other programs, staff in the field sampling area carry out experimentation and development related to sampling design, techniques, and instrumentation. As part of the field sampling program development in 1997, a special soil handling program was developed, and a license was obtained from the U.S. Department of Agriculture to allow receipt of soil samples from other states and from foreign countries. In addition to activities related to the WIPP EM, the field sampling program currently conducts weekly analyses of water quality at Brantley Dam Reservoir under a cooperative agreement with the U.S. Department of Interior, Bureau of Reclamation.

Informatics and Modeling

One of the Center's primary objectives is to establish a health and environmental database accessible to all sectors. It is the role of the informatics program to carry out this function for the Center by developing and implementing information management systems. The informatics program includes formal systems for data archival and documentation that facilitate analyses and accurate interpretations. Commercial relational data base management systems (RDBMS) are one component of the program. For example, the lung and whole body counting system uses an integrated RDBMS for data collection and storage. An Access data base is used to store aerosol and meteorological data collected by the field sampling program. A commercial Laboratory Information Management System (LIMS) is being implemented during 1999. The LIMS will provide systematic identification and tracking of samples and reporting of analytical results.

The Center operates Sun servers running Unix to provide network services, such as file sharing, electronic mail, and automatic daily backup to all of the Windows and UNIX computers in the Center. A Sun server also supports an Oracle RDBMS. Sun workstations currently provide support for general computing, but will eventually function as platforms for numerically intensive applications, such as simulation modeling and statistical analyses. The Center also operates a DEC Alpha workstation running OpenVMS, which mirrors the computational support for the lung and whole body counting system. This allows testing of maintenance and upgrades on the secondary system, prior to introduction to the functioning counter, thereby protecting the integrity of the primary counting support system.

The research activities of the informatics program include developing methods for linking data to simulation models, and investigations on representing uncertainty when incorporating analytical data in models. For example, estimates of contaminant doses and risks can be made, using models to project potential exposure via environmental pathways. The model projections are based on estimates of contaminant movement through the atmosphere, deposition in water and soil, direct uptake by humans or other organisms, and secondary transfer between components of the environment and living organisms.

Related Links

• History and Current Status
• WIPP Environmental Monitoring Project