Calibration of Transfer Standards and Other Specialized Measurements
PNNL provides radiological calibration and measurement resources for various types of photon, neutron and beta-sensitive radiation measurement equipment. Such calibrations/measurements may satisfy a variety of purposes for clients. Most often they enable the:
- Establishment of measurement traceability
- Provide a system for evaluating measurement traceability
- Evaluate a provider's service or vendor's product
- Enable the evaluation of unique radiological conditions
Typical examples include the following:
- Reference Class Air-Ionization Chambers
- Condenser Chambers
- Beta/Gamma Survey Instruments
- Neutron Survey Instruments
- Dosimeters
Establishment of measurement traceability:
PNNL provides NVLAP-accredited calibration (lab code 105020-0) of client's suitable transfer standards to establish traceability of in-house photon, beta and neutron "reference fields". Suitability of transfer standards depends upon the particular application, but can range from a precision (reference class) cavity air ionization chamber to passive, solid state dosimeter (e.g., TLD). The transfer standard and appropriate reference field are determined via interaction with the client. It is possible that for some efforts in this category, work outside of PNNL's NVLAP-accredited (lab code 105020-0) scope may be necessary. It is therefore, highly important for the client to clearly state, and have knowledge of their need for "accredited" service. Once the calibration and/or measurement effort is clearly determined, the client submits the standard to PNNL for calibration. The calibration is performed and a "report of calibration (or test)" is prepared for submittal to the client.
Provide a system for evaluating in-house measurement traceability:
PNNL can provide an intercomparison capability for radiological calibration facilities. Such intercomparisons provide a mechanism to improve calibration and characterization capabilities and to confirm consistency on a periodic basis. This capability can be tailored to the client's specific need. PNNL offers the provision of several reference instruments and beta source sets to laboratories wishing to confirm their internal measurement capabilities. As an alternative, a "verification" format may also be implemented in which the client submits a "calibrated" artifact (electronic dosimeter, survey instrument, etc.) that would then be verified (as-found calibration) in PNNL's reference field of the client's choosing.
For this interaction, PNNL provides a "report of calibration" for the measurement. The client may wish to treat this interaction as a proficiency evaluation; however, it is left to the client to verify the "constancy" of the artifact prior to departure for, and upon it's return from PNNL to assure its stability throughout the process of transportation and measurement at PNNL.
Evaluate a provider's service or vendor's product:
Analogous to our provision of client's in-house confirmation capability, PNNL provides a means for independent testing of vendor-provided instrument calibration and/or personnel dosimetry services. The most common implementation of this activity is via the provision of irradiated "blind spike" passive dosimeters; however, this also may be applied to the attainment of offsite instrument calibrations in which a periodic independent check is desired.
NOTE: Vendors may implement comprehensive independent verification protocols. To avoid duplication of effort and cost, the potential client should consult with their provider(s) of services to identify such efforts.
Enable the evaluation of unique radiological conditions:
Occasionally, the energy or geometry characteristics of radiological fields are outside of the normal design parameters or previously evaluated range of an instrument or dosimeter device. With the various radiological sources, X-ray reference fields, characterization/calibration standards and modeling capability available at PNNL, investigation of detector performance in a variety of situations is possible.