Listening in real time - the case of Diablo Canyon

1 June 2010

Neutron noise analysis has been used as a diagnostic tool at California's Diablo Canyon

With the aid of neutron noise analysis, a number of problems have been resolved in nuclear power plants over the years. For example, the Diablo Canyon PWR plant in California began to experience an increasing number of neutron signal alarms at the end of one of its operating cycles. As a result, the regulators ordered the plant to identify the source of the alarms and to shut the plant down if the alarms revealed a significant safety issue. The regulators, however, gave the plant permission to continue to operate while conducting an investigation into the cause of the alarms.

It was postulated that the alarms could be due to excessive vibration of the core barrel or other reactor internal components. Therefore, using the output of the ex-core neutron detectors, the vibration of reactor internals was measured. The results showed normal vibration levels for the reactor internals. Next, neutron signals were cross correlated with core-exit thermocouples (CETs) and other sensors. This helped narrow the problem down to core flow anomalies caused by new fuel assemblies installed in the plant in a previous refuelling outage. Further analysis of the noise data demonstrated that the flow anomalies were not significant and the plant was thus allowed to continue to operate. In the meantime, the neutron alarm setpoints were raised to limit the frequency of the alarms.

Related Articles
Listening in real time
The Sizewell B experience
Diablo Canyon relicensing is delayed

Diablo Diablo

Privacy Policy
We have updated our privacy policy. In the latest update it explains what cookies are and how we use them on our site. To learn more about cookies and their benefits, please view our privacy policy. Please be aware that parts of this site will not function correctly if you disable cookies. By continuing to use this site, you consent to our use of cookies in accordance with our privacy policy unless you have disabled them.