SCM Product Line
SRA has spent the last 15 years developing sophisticated methods for automation of collecting and reporting survey data. One of the field proven instruments that has come from this experience is the SRA Surface Contamination Monitor (SCM). The SCM uses a patented Position Sensitive Proportional Counter (PSPC) that is capable of establishing where along the length of the detector an event occurs (the system is described in detail in NUREG/CR-6450). Survey data that is spatially correlated allows the discovery of new relationships from the data collected. Logging of spatial data allows the visualization of the distribution of contamination and anomalies in the data. This then allows things such as a crack in the floor to be easily identified. Process efficiency is greatly improved and data collection chain of custody is enhanced. Imagine having the capability of handing a decontamination crew a picture of what they need to clean.
The SCM may be operated in a qualitative (scanning) mode or a quantitative mode, either of which can utilize large-area PSPCs in either rolling (dynamic) or static modes. A dynamic mode PSPC has a trapezoidal cross-section, whereas the static mode detectors have a rectangular cross-section with very small 1/16th of an inch flanges. Static mode is used to survey areas that are generally inaccessible in dynamic mode, such as corners. Data acquired using any detector may be combined into a single survey. The SCM is mechanically equipped to survey floors and walls (up to 2 meters high) by rotating and elevating the detector carrier. An additional elevator attachment, the EV-4, can allow the SCM to do walls (up to 4 meters high) or ceilings (3 meters or less). Therefore, note that dynamic mode may be used to survey a floor, a wall, or a ceiling depending on how the SCM is configured.
PSPCs differ from traditional proportional counters in that they not only provide information about the total charge collected, but indicate where along the length of the counter the event occurred. Hence, a long detector may be split (electronically) into a continuous array of small, "virtual" detectors that have the same efficiency as a traditional small-area proportional detector, but with a lower background than "ganged" detectors. These virtual counters therefore have greater sensitivity than a traditional detector; in addition to being able to precisely identify the location of radioactivity along the length of the counter as a whole. In dynamic mode, the SCM logs information in 25 cm2 bins by logging data for each 5 cm width of the PSPC and for every 5 cm of forward travel. The distance the SCM travels is measured by a precision wheel encoder. Data are recorded in 25 cm2 pixels over the entire surface surveyed, thus the SCM records 400 measurements for every square meter it covers. When SCM data is analyzed, the software algorithm considers each 25 cm2 measurement as one fourth of four separate 100 cm2 areas. This technique ensures that the highest-activity 100-cm2 area is identified because it is not sensitive to registration of the detector, as may occur using systems that employ multiple, non-overlapping detectors. The fact that the SCM records 400 measurements for every square meter it covers allows data to be evaluated via statistical methods in the Survey Information Management System (SIMS) that considers the distribution of activity on a surface in addition to its average concentration.
The SCM is only available as a lease (not available for purchase) due to a limited scope market. Regulatory agencies may qualify for a single price long-term lease based on their intended use.
