05000348/FIN-2009006-02
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Finding | |
|---|---|
| Title | Degraded Emergency Air System Conditions (Section 1R21.2.11) |
| Description | The team identified an unresolved item (URI) related to performance monitoring of the emergency air system. There was no maintenance or operational documentation that would provide reasonable assurance that the emergency air system could provide an emergency air supply to the end use components. The end use components were the SG ARVs and the TDAFW pump steam admission valves. The downstream flow path components had not been operated or maintained since 1977 and 1981 during startup testing, for Units 1 and 2, respectively. This flow path included piping, check valves, manual valves, pressure control valves, and three-way solenoid valves. The emergency air system was scoped into the station maintenance rule program (FNP-0-M-87, Maintenance Rule Scoping Manual) in 1994. The scoping document stated that the emergency air system provided a mitigating function to prevent core damage and radioactive release by providing back-up air to the ARVs and the TDAFW steam admission valves to allow the cooldown of the reactor coolant system. The use of the emergency air for these purposes was directed by the emergency operating procedures. The FSD for Instrument Air (A-181012) stated that the ARVs and TDAFW steam admission valves shall be provided with an emergency air supply. The UFSAR, Section 10.3.8, Main Steam Atmospheric Power Relief Valves, stated that in the event a high-energy line break prohibits operator access for local operations of the power relief valves with the simultaneous loss of offsite power and valve air supply, an alternate air supply consisting of two seismic category I air compressors (emergency air compressors) was provided for remote operation of the ARVs. The team noted that although the emergency air compressors were periodically started and run for approximately one hour to an isolated header, the flow path between the emergency air compressor and the end use components was not verified. Following identification of this issue by the team, the licensee initiated CR 2009101539, No Assurance that Air from the Emergency Air Compressors Will Supply the ARVs During the inspection, the licensee performed a test to verify the flow path between the emergency compressors and the end use components for both trains of each unit. The test identified a blocked flow path due to a seized closed check valve (NV075A) in the train 1A emergency air header downstream of the compressor. The licensees investigation of the check valve determined that the valve failure was caused by rust build-up inside this piston type check valve. Each unit has five of these check valves in the emergency air start system The team identified a common cause vulnerability of the emergency air systems for both units related to the system air quality and degradation of the piping. The system contained carbon steel piping, did not include dryers or filters, and was subject to moisture in stagnant piping; conditions that would contribute to the formation and transport of rust. In the equipment history, the inspectors noted two previous indications of degraded piping conditions. Two Unit 2 work orders (WOs 2062451701 and 2082451701) documented the repair of seized (stuck open) check valves (NV075A and NV075B) in July 2006 and August 2008. The WOs documented the cleaning of rust from the valve internals. A stuck open check valve could result in inadequate air flow being provided to downstream components or could allow air from the opposite train to be diverted away from the SG ARVs and TDAFW steam admission valves. Additionally, the rust in the degraded piping could be transported to the end use components and adversely impact their operation. In the week following the onsite CDBI, the licensee performed piping internal inspections which provided additional indications of common cause vulnerability due to degraded piping in both units as well as an additional seized check valve (NV075B). The team noted that the Unit 1, Emergency Air Train B compressor had operational deficiencies which reduced its reliability during the time that the Unit 1 train A was inoperable due to flow path blockage. These included the following: Elevated motor amps which significantly reduced the margin to thermal overload setpoint. A running current of 14.5 amps was identified. The motor nameplate current was specified as 11.5 amps. The calculated minimum overload trip setpoint was 16 amps. Licensee analysis determined that degraded grid operation of the 1B motor could result in a motor current or 15.9 amps. Deficiencies with the unloader device (pressure control) were identified during semi-annual surveillances in June 2008, and December 2008. Repair was was not implemented until March 13, 2009. On February 20, 2009, the malfunctioning unloader resulted in the lifting of relief valve (PSV 2B) during performance of the licensees troubleshooting plan. On February 20, 2009, to prevent the continuous cycling of the relief valve, the operators manually started/stopped the compressor to maintain adequate system pressure. It was stated in the licensees evaluation of this condition that excessive starting of the compressor would eventually trip thermal overloads. On February 20, 2009, the operators did not have procedural guidance for operating the 1B compressor with a faulty unloader device. On March 13, 2009, the station established compensatory actions to manually control header pressure (100 psig) to prevent excessive staring of the compressor. Based on the above, the inspectors concluded that the 1B compressor operational deficiencies adversely impacted the reliability and availability of the Unit 1 Emergency Air System between June 2008 and March 2009, during the period when the 1A train was inoperable. The inspectors identified no immediate safety concern because the end use components were normally supplied by the instrument air system via a different flow path with one of the non-safety instrument air compressors supplied by the emergency diesel generator. Additionally the station had the capability for local-manual operation of the end use components. This finding was identified as URI 05000348,364/2009006-02, Degraded Emergency Air System Conditions, pending further inspection and interface with the licensee to determine the extent of condition and impact from the degraded emergency air system conditions. |
| Site: | Farley  |
|---|---|
| Report | IR 05000348/2009006 Section 1R21 |
| Date counted | Mar 31, 2009 (2009Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | A Nielsen D Jones E Crowe G Kuzo H Gepford L Miller R Moore S Sandal S Shaefferb Desaib Sherbin C Even C Peabody D Jones J Eargle P Braxton R Moore R Patterson S Kobylarzj Earglep Braxton R Moore D Jones B Sherbin S Kobylarz C Peabody C Even R Patterson B Desai |
| INPO aspect | |
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Finding - Farley - IR 05000348/2009006 | ||||||||||||||||||||||||||||||||||
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Finding List (Farley) @ 2009Q1
Self-Identified List (Farley)
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