It is amazing, they basically do leak rate pressure testing to assure operation of the accumulators every outage or maybe every other outage. If the accumulators hold pressure in the test it is assumed to be operable for thee next 5 years. Browns Ferry mixed up the hose connections to the accumulator in 2007. This basically caused the accumulator not to be connected to this ADS Safety Relief Valve. They discovered it in Oct 20014. This ADS valve has been in inop sense 2007.
The ADS system is the backup to the HPIC system. If the ADS doesn't work, then you can't use your low pressure systems for a prolonged period of time.
Basically the accumulators have been un-testable and in a unknowable condition since 2007... they have no indication in the control room these important safety components can work. This was an extremely deep and unknowable flaw...almost the inop is untestable and undetectable until the scary unstoppable accident is at the door of the plant.
The accumulators are basically a cheap add on component. It goes to show you how dangerous the add-on systems and component are in the nuclear industry safety systems. These important safety components need to be holistically included in the initial designs of the nuclear plant, least a cheap and quick fix add on system becomes nothing but a ghostly "facilitative assumption" justifying the continuous operation of a dangerous plant.
SRVs are air operated valves. Mostly the SRVs accumulators would be used in a station blackout and lost of containment air. Basically you would get to cycle the valve maybe two times which is a joke to a licence operator. This is a very infrequent accident at a plant. It is really a dirty deed where these utilities take shortcuts and refuse to spend money on on adequate safety systems used only in the catastrophic accidents seen only infrequently.
It is really easy to keep a plant up at power...a professional nuclear licence operator always keeps the plant aligned to meet the worst conceivable accident. That is a really hard job.
Conservatism says you should call all the ADS valves inop because there never was any way to detect if the accumulator were operational. I remember when in the early 1980s these accumulators were installed at Vermont Yankee. It came from the lessens learned in TMI.
The senior resident says they are looking at what kind of violation this will become?
Licensee Event Report50-25912014-005-00 Automatic Depressurization System Valve Inoperable for Longer Than Allowed by Technical Specifications On October 29, 2014, during performance of the Browns Ferry Nuclear Plant (BFN) Unit 1 Main Steam Relief Valve (MSRV) Manual Cycle Test, MSRV 1-19 failed to open. Investigation of the failure revealed a misconfiguration of the control air lines to both the MSRV 1-19 and MSRV 1-18 which occurred during installation of the flex hoses in 2006. MSRV 1-19 has an Automatic Depressurization System (ADS) function which was defeated by the air line misconfiguration. The ADS function for MSRV 1-19 has been inoperable since May 2007. This condition would have prevented MSRV 1-19 from performing its specified ADS safety function for longer than allowed by Technical Specifications.
The cause of this event was a latent organizational and programmatic gap associated with the BFN Unit 1 Restart Organization. Specifically, the management and organizational infrastructure in place during the BFN Unit 1 restart was inadequate to preclude numerous human performance errors during the 2005-2007 time period, including the multiple human performance errors associated with this event.
Licensee Event Report 50-259/2011-008-02 High Vibrations on High Pressure Coolant Injection Booster Pump Thrust Bearings.
Licensee Event Report 50-259/2011-008-02 High Vibrations on High Pressure Coolant Injection Booster Pump Thrust Bearings On July 20, 2011, Browns Ferry Nuclear Plant (BFN) personnel performed quarterly surveillance procedure 1-SR-3.5.1.7, "HPCI Main and Booster Pump Set Developed Head and Flow Rate Test at Rated Reactor Pressure." During this surveillance, BFN personnel recorded an unexpected increase in the vibration level on the High Pressure Coolant Injection (HPCI) booster pump thrust bearings. Upon performing a disassembly for inspection on July 23, 2011, the bearings were discovered to be in a tandem arrangement, which transmits thrust in only one direction (away from the gearbox). The correct bearing configuration is back-to-back. New bearings were installed in theproper configuration. The Tennessee Valley Authority (TVA) has determined that this condition affected the HPCI system mission time and thus the operability of the HPCI system for an unknown period. Therefore, it was conservatively concluded that the BFN Unit 1 HPCI system was inoperable longer than allowed by Technical Specification 3.5.1 Actions. The TVA is reporting this event in accordance with 10 CFR 50.73(a)(2)(i)(B), as an operation or condition which was prohibited by the plant's Technical Specifications, and 10 CFR 50.73(a)(2)(v)(B) and (D), as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat and to mitigate the consequences of an accident, respectively.
No comments:
Post a Comment