ENS 46693
ENS Event | |
|---|---|
04:54 Mar 24, 2011 | |
| Title | Pressure Transmitters Needed for Auxiliary Feedwater Suction Path Not Analyzed for Potential High Energy Line Break |
| Event Description | While performing an extent of condition review of high energy line break (HELB) analyses, a detailed review of the auxiliary steam system was being performed. During this review, sections of pipe that run through rooms 1206/1207 in the Auxiliary Building were identified that have design ratings indicating that they could possibly be classified as high energy lines.
The pipes were verified to have not been considered in the current HELB analyses. This condition affects pressure transmitters ALPT0037, 38, & 39 which are not qualified for operation in a harsh environment. These pressure transmitters provide the Auxiliary Feedwater Pump [AFW] Suction Transfer signal on low suction pressure from the non safety Condensate Storage Tank to the Safety Related supply (Essential Service Water). Technical Specification [TS] 3.3.2-6.h bases state: "since these detectors are in an area not affected by HELBs or high radiation, they will not experience any adverse environmental conditions and the Trip Setpoint reflects only steady state instrument uncertainties." Based upon the above bases, with the identified aux steam lines in service, the pressure transmitter's operability could not be assured. This represented an unanalyzed condition and had the potential to affect equipment used for accident mitigation. TS 3.0.3 was entered at time 2354 [CST] on 3/23/2011. At 0009 [CST] on 3/24/2011, Aux Steam valves FBV0158, FBV0I48, FAV0002, and FAV0003 were isolated, removing the HELB concern [TS 3.0.3 was exited at this time]. These are the active feed [isolation valves] to the lines passing through the Aux Building Rooms 1206/1207. The licensee notified the NRC Resident Inspector.
On March 23, 2011, event notification EN 46693 documented that a harsh environment from a postulated High Energy Line Break (HELB) could affect pressure transmitter ALPT0037, 38 and 39. These pressure transmitters provide the Auxiliary Feedwater Pump suction transfer signal on low suction pressure from the Condensate Storage Tank to the safety-related water supply (Essential Service Water). This break was postulated to occur on auxiliary steam lines in Auxiliary Building rooms 1206 And 1207. This condition was initially reported both as an unanalyzed condition that significantly degraded plant safety and as a condition that could have prevented fulfillment of a safety function. When EN 46693 was reported, it was assumed that breaks were required to be postulated at any intermediate fitting, welded attachment, or valve on the subject auxiliary steam lines. Subsequent analysis shows that these sections of auxiliary steam piping are able to withstand safe shutdown earthquake (SSE) loadings and rupture loadings. For piping of this qualification, breaks at all intermediate fittings, welded attachments, and valves do not need to be postulated. Instead, line breaks are only required to be assumed at the terminal ends of the lines and at the locations specified for ASME Class 2 and 3 piping. None of these postulated break locations are located inside rooms 1206 and 1207. Analysis has been performed on these auxiliary steam lines for the remaining break locations that are required to be postulated. This analysis demonstrates reasonable assurance that safety related equipment, including pressure transmitters ALPT0037, 38 and 39, would have performed their safety functions following a postulated break of these auxiliary steam lines. Therefore, this condition does not meet the reporting requirements for an unanalyzed condition that significantly degraded plant safety or a condition that could have prevented fulfillment of a safety function. Event notification 46693 is hereby retracted. The NRC Resident Inspectors have been notified. Notified the R4DO (Shannon). |
| Where | |
|---|---|
Callaway  Missouri (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.13 h0.0471 days <br />0.00673 weeks <br />0.00155 months <br />) | |
| Opened: | David Hurt 06:02 Mar 24, 2011 |
| NRC Officer: | John Shoemaker |
| Last Updated: | May 19, 2011 |
| 46693 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Callaway with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
WEEKMONTHYEARENS 548062020-07-30T13:15:00030 July 2020 13:15:00
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