Sequential Probability Ratio Test for Long-Term Radiation Monitoring
Pacific Northwest National Laboratory is currently developing a prototype instrumented container system for the detection of illicit nuclear and radiological materials in maritime scenarios. Data collection during this long-term monitoring of radiation sensor signals will be inherently sequential in that wireless data transmission will occur at set intervals. Among the possible decision-making algorithms for sequentially-acquired radiation sensor data is the Sequential Probability Ratio Test (SPRT). The suitability of the SPRT for this long-term monitoring application is discussed, and the decision-making performance of the SPRT is compared to that of the commonly used single-interval test (SIT). The analysis spans a wide range of signal and background count rates so that results are applicable to sensors of all sizes operating in different ambient conditions, and a spectrum of alarm thresholds. It is demonstrated that for these simulated long-term monitoring scenarios, decisions to issue an alarm when the measured count rate equals the threshold count rate, are made 3-5 times faster using the SPRT than with the SIT. The ability of the SPRT to provide an ''all-clear'' indication when the measured count rate is consistent with the expected background count rate is contrasted to the inconclusive results of the SIT test under the same conditions. The need for SPRT truncation strategies for measured count rate regions where the SPRT decision times become excessive is discussed. Finally, it is shown that the truncated SPRT provides a greater probability of detection than the SIT in a case of ''early termination'' of both tests, a situation likely to occur in long-term monitoring applications.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 860077
- Report Number(s):
- PNNL-SA-42906; 400903120; TRN: US0504811
- Resource Relation:
- Conference: 2003 IEEE Nuclear Science Symposium, Conference Record, 1-5(1458-1462; Institute of Electrical and Electronics Engineers (IEEE),Piscataway,,United States.
- Country of Publication:
- United States
- Language:
- English
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