10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown

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Tech Spec Required Shutdown

If not reported under 10 CFR 50.72(a) or (b)(1), an ENS notification is required. The initiation of any nuclear plant shutdown required by the plant’s Technical Specifications (TS) should be apparent at the time of occurrence. Therefore, if all events are reported properly, it is expected that all reports under 10 CFR 50.72 are as a result of an on-going condition. If the shutdown is completed, an LER is required.

Discussion

The 10 CFR 50.72 reporting requirement is intended to capture those events for which TS require the initiation of reactor shutdown to provide the NRC with early warning of safety-significant conditions serious enough to warrant that the plant be shut down. For 10 CFR 50.72 reporting purposes, the phrase “initiation of any nuclear plant shutdown” includes action to start reducing reactor power; i.e., adding negative reactivity to achieve a nuclear plant shutdown required by TS. This includes initiation of any shutdown due to expected inability to restore equipment prior to exceeding the LCO action time. As a practical matter, in order to meet the time limits for reporting under 10 CFR 50.72, the reporting decision should sometimes be based on such expectations. (See Example 4.) The “initiation of any nuclear plant shutdown” does not include mode changes required by TS if they are initiated after the plant is already in a shutdown condition.

A reduction in power for some other purpose, not constituting initiation of a shutdown required by TS, is not reportable under this criterion.

For 10 CFR 50.73 reporting purposes, the phrase “completion of any nuclear plant shutdown” is defined as the point in time during a TS-required shutdown when the plant enters the first shutdown condition required by an LCO (e.g., hot standby (Mode 3) for PWRs with the Standard Technical Specifications (STS)). For example, if at 0200 hours a plant enters an LCO action statement that states, “restore the inoperable channel to operable status within 12 hours or be in at least Hot Standby within the next 6 hours,” the plant must be shut down (i.e., at least in hot standby) by 2000 hours. An LER is required if the inoperable channel is not returned to operable status by 2000 hours and the plant enters hot standby.

An LER is not required if a failure was or could have been corrected before a plant has completed shutdown (as discussed above) and no other criteria in 10 CFR 50.73 apply.

Examples

(1) Initiation of a TS-Required Plant Shutdown

While operating at 100-percent power, one of the battery chargers, which feeds a 125-volt direct current vital bus, failed during a surveillance test. The battery charger was declared inoperable, placing the plant in a 2-hour LCO to return the battery charger to an operable status or commence a TS-required plant shutdown. Licensee personnel started reducing reactor power to achieve a nuclear plant shutdown required by a TS when they were unable to complete repairs to the inoperable battery charger in the 2 hours allowed. The cause of the battery charger failure was subsequently identified and repaired. Upon completion of surveillance testing, the battery charger was returned to service and the TS-required plant shutdown was stopped at 96-percent power.

The licensee made an ENS notification because of the initiation of a TS-required plant shutdown. An LER was not required under this criterion because the failed battery charger was corrected before the plant completed shutdown.

(2) Initiation and Completion of a TS-Required Plant Shutdown

During startup of a PWR plant with reactor power in the intermediate range, two of the four reactor coolant pumps tripped when the station power transformer supplying power de-energized. With less than four reactor coolant pumps operating, the plant entered a 1-hour LCO to be in hot standby. Control rods were manually inserted to place the plant in a shutdown condition.

The licensee made an ENS notification because of the initiation of a TS-required plant shutdown. An LER was required because of the completion of the TS-required plant shutdown.

(3) Failure that Was or Could Have Been Corrected Before Shutdown Was Required

  • Question: What about the situation where you have 7 days to fix a component or be shut down, but the plant must be shut down to fix the component? Assume the plant shuts down, the component is fixed, and the plant returns to power before the end of the 7-day period. Is that situation reportable?

Answer: No. If the shutdown was not required by the TS, it need not be reported. However, other criteria in 50.73 may apply and may require that the event be reported.

  • Question: Suppose that there are 7 days to fix a problem, and it is likely that the problem can be fixed during this time period. However, the plant management elects to shut down and fix this problem and other problems. Is an LER required?

Answer: No. Some judgment is required. The shutdown is reportable, however, if the situation could not have been corrected before the plant was required to be shut down.

(4) Initiation of Plant Shutdown in Anticipation of an LCO-Required Shutdown

The plant lost one of two sources of offsite power due to overheating in the main transformer. The TS allow 72 hours to restore the source or initiate a shutdown and be in hot standby within the next 6 hours and cold shutdown within the following 30 hours.

The licensee estimated that the transformer problem could not be corrected within the LCO action time. Therefore, the decision was made to start a shutdown soon after the transformer problem was discovered.

The shutdown was uneventful and was completed, with the plant in hot standby, before the expiration of the LCO action time. After the plant reached hot standby, further evaluation indicated that the transformer problem could not be corrected before the requirement to place the plant in cold shutdown. Based on this time estimate, it was decided to place the unit in cold shutdown.

The event is reportable under 10 CFR 50.72(b)(2)(i) as the initiation of a plant shutdown required by TS because, at the time the shutdown was initiated and the time the report was due, it was not expected that the equipment would be restored to operable status within the required time. This is based on the fact that the reporting requirement is intended to capture those events for which TS require the initiation of a reactor shutdown.

The event is reportable under 10 CFR 50.73(a)(2)(i)(A) because the plant shutdown was completed when the plant reached hot standby (Mode 3). Had the transformer been repaired and the shutdown process terminated before the plant reached Mode 3, the event would not be reportable under 10 CFR 50.73(a)(2)(i)(A).