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Monday, June 04, 2012

Browns Ferry


Idly browsing through the US Nuclear Regulatory Commission's Current Event Notifications today (as one does) I came across Event 47986 dated June 1st, 2012, for the Browns Ferry nuclear plant in Alabama.

"Cable Routing Error Could Fail DC Control Power to Shutdown Board in a Fire":
"During NFPA 805 transition reviews, a cable routing error has been identified that would fail the DC control power to credited 4kV Shutdown Board 3EA for an Appendix R fire in Fire Area 23. "Cable 3B181 provides alternate DC Control Power to 4kV Shutdown Board 3EA from Battery Board 2. Cable 3B181 is routed in Fire Area 23. However, cable 3B181 is not identified as being in Fire Area 23 in Browns Ferry Nuclear Plant (BFN) calculation EDQ099920030037, Appendix R Computerized Separation Analysis. This error allowed the analysis to credit alternate DC Control Power to 4kV Shutdown Board 3EA. The normal DC Control Power to 4kV Shutdown Board 3EA is not available in the event of an Appendix R fire in Fire Area 23. The routing error results in the credited 4kV Shutdown Board 3EA being unable to perform its function for Fire Area 23 Appendix R fires due to both the associated normal and alternate DC Control Power cables being routed In Fire Area 23. The failure of 4kV Shutdown Board 3EA could result in a loss of power to credited safe shutdown equipment that would challenge the ability to provide adequate core cooling during performance of BFN Safe Shutdown Instructions. "Compensatory actions in the form of fire watches to mitigate this condition are in place in accordance with the BFNP Fire Protection Report. "This event is reportable as an 8 hour notification to the NRC in accordance with 10CFR 50,72(b)(3)(ii)(B). This is also reportable as a 60 day written report in accordance with 10CFR 50.73(a)(2)(ii)(B)." The licensee has notified the NRC Resident Inspector.

Oh dear, primary and failover control cables being routed in the same area. If a fire broke out, both cables could be damaged. Don't worry, that's not very likely, is it?

Well, unfortunately, such a scenario has happened before at an American nuclear power facility, back on March 22nd, 1975, in which a candle set fire to insulating foam in an electrical conduit, taking out both primary and secondary control circuits.

Not just any plant, though, but Browns Ferry.

David Dinsmore Comey wrote a damning article in Not Man Apart about the accident. He cites a report to the NRC made by the Factory Mutual Engineering Association of Norwood, Massachusetts, the fire underwriters the NRC engaged as consultants:

"The original plant design did not adequately evaluate the fire hazards of grouped electrical cables in trays, grouped cable trays and materials of construction (wall sealants) in accordance with recognized industrial 'highly protected risk' criteria.... It is obvious that vital electrical circuitry controlling critical safe shutdown functions and control of more than one production unit were located in an area where normal and redundant controls were susceptible to a single localized accident .... A re-evaluation should be made of the arrangement of important electrical circuitry and control systems, to establish that safe shutdown controls in the normal and redundant systems are routed in separated and adequately protected areas."

I wonder how many reactors are still susceptible 37 years on from the Browns Ferry fire.

We learn from history that we do not learn from history, it appears.

Related material:

NUREG-0050, Recommendations related to Browns Ferry fire, U.S. Nuclear Regulatory Commission, February 1976.

Cable Fire at Browns Ferry Nuclear Plant, Robert G. Sawyer and James A. Elsner, P.E., Fire Journal, July 1976.

Browns Ferry Fire, M. Ragheb and Jim Kolodziej, January 2011.

Safety Deficiencies at the Brown's Ferry Nuclear Power Complex, Nuclear Information and Resource Center, December 2010. Read this carefully, then read about the March 2011 Fukushima meltdowns, and weep.

Browns Ferry Unit 2, Union of Concerned Scientists.

Footnote:

Apologies for the missing apostrophe in Browns. Much as I'd love to write it as Brown's, that does not appear to be the common usage. And as I'm playing 'boy reporter' and not 'grammar teacher', I've left it apostropheless, except where I'm directly quoting others.

Postscript:

See also, "Fission Stories #98: Fires at Browns Ferry: Get Your Fiddles Ready"

Postscript, Nov 1st, 2012:

Notification 48467, October 31st, 2012:

POTENTIALLY UNABLE TO PROVIDE POWER TO SAFE SHUTDOWN EQUIPMENT DURING APPENDIX R FIRE
"During BFNP [Browns Ferry Nuclear Plant] NFPA [National Fire Protection Association] 805 transition review, it was determined in the event of an Appendix R fire, the ability to provide power to equipment needed to achieve and maintain safe shutdown may be adversely impacted. In certain fire zones/areas, feeder breakers for the 480V Shutdown Boards are credited for backup control operation using the 43 emergency switches, which isolate the breaker controls from circuits going to the control bay, and allow for local operation of the breaker. Fire damage to Main Control Room 480V Shutdown Board transfer switch cables could cause the control circuit fuses for the credited breaker to clear prior to the use of the 43 emergency switch. In addition, cable fire damage in the same fire areas could also cause the normal and/or alternate feeder breakers to spuriously trip. These breakers do not have separate emergency fuses like other BFNP breakers equipped with backup controls. Therefore, Safe Shutdown Instruction (SSI) procedure steps to use 43 switches to perform local breaker operation to supply power to safe shutdown equipment may not work as written where this cable fire damage can occur.
"Compensatory actions in the form of fire watches to mitigate this condition are in place in accordance with the BFNP Fire Protection Report. "
This condition is being reported pursuant to 10CFR50.72(b)(3)(ii)(B) and 10CFR50.72(b)(3)(v)(A),(B),(C).&(D).
"The NRC Resident Inspector has been notified."

Posted by Phil at 6:20 PM
Edited on: Thursday, November 01, 2012 8:41 PM
Categories: Environment