B11930, Discusses Effects of Hurricane Gloria,Including Preparations for Storm & Loss of Offsite Power Events at Millstone Units 1 & 2 on 850927.Advance Notification Associated W/Severe Weather Events Permits Advance Precautionary Actions

Discusses Effects of Hurricane Gloria,Including Preparations for Storm & Loss of Offsite Power Events at Millstone Units 1 & 2 on 850927.Advance Notification Associated W/Severe Weather Events Permits Advance Precautionary Actions

ML20141F323
Person / Time
Site:	Millstone, Haddam Neck, 05000000
Issue date:	12/31/1985
From:	Opeka J CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Harold Denton Office of Nuclear Reactor Regulation
References
B11930, NUDOCS 8601090214
Download: ML20141F323 (6)

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HARTFORD. CONNECTICUT 06141-0270 k L J [, % [ ,3 [ , C (203) 665-5000 December 31, 1985 Docket No. 50-213 50-245 50-336 50-423 Bi1930 Mr. Harold R. Denton Director of Nuclear Reactor Regulation U.S. Nuclear Regulatos y Commission Washington, D.C. 20555 Gentlemen:

Haddam Neck Plant Millstone Nuclear Power Station, Unit Nos.1,2 and 3 Effects of Hurricane " Gloria" On September 27, 1985 Hurricane Gloria moved through Connecticut with sustained As reportedwinds in License of upEvent to 53Reports mph and gusts (LER) of up to 75 85-018-00(l) andmph at the Millstone site}

35-014-00,t2 Millstone Unit Nos. I and 2 experienced loss-of-off-site power (LOOP) events as a result of Hurricane Gloria, in order to maximize the extent to which the insights derived from assessing this event can be appropriately factored into the Staff's ongoing efforts to resolve Unresolved Safety Issue (USI) A-44, Station Blackout, Connecticut Yankee Atomic Power Company (CYAPCO) and Northeast Nuclear Energy Company (NNECO) are providing this informational letter to more fully explain the details associated with the effects of Hurricane Gloria.

Preparations for the Storm On September 26, 1985, the Millstone site hurricane action plan was implemented. The hurricane action plan included a checkout of the Emergency Response Facilities (ERF), the selection of two Station Emergency Organization (SEO) shif ts and successful testing of the emergency on-site AC power sources.

At 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on September 26, 1985 the National Weather Service declared a Hurricane watch for Connecticut and the on-call emergency organizations for the Millstone site, the Haddam Neck Plant and the Corporate Emergency Operations Center were notified to report to duty stations at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> on September 27,1985.

8601090214 051231 3 PDR ADOCK 050 F

(1) W. D. Romberg letter to U.S. NRC concerning LER 50-245/35-013-00, dated Octcher 25,1985.

(2) W. D. Romberg letter to U.S. NRC concerning LER 50-336/35-014-00, dated October 25,1985.

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The following points summarize the more important elements of our preparatory activities:

o By 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> on September 27, 1985, all Millstone ERFs were manned and ready.

o At 0745 hours0.00862 days <br />0.207 hours <br />0.00123 weeks <br />2.834725e-4 months <br />, based on predictions that the storm would reach the Millstone site between 1600 and 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, the decision was made to bring all units at Millstone and Haddam Neck to a shutdown condition.

o At 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br /> each corporate EOC Manager was requested to prepare contingency plans for dealing with a posslole loss of communications and/or loss of off-site power sources for each unit.

o At 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br /> the Governor declared a " State of Emergency" in Connecticut.

o At Millstone, all power was secured to nonessential plant areas at 0843 hours0.00976 days <br />0.234 hours <br />0.00139 weeks <br />3.207615e-4 months <br />. The hurricane was being tracked east of New Jersey at 0845 hours0.00978 days <br />0.235 hours <br />0.0014 weeks <br />3.215225e-4 months <br /> and was moving north at 30 mph. The winds at Millstone were determined to be 29 mph (lower level) and 40 mph (upper ,lgvel of approximately 142 feet) at 0915 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.481575e-4 months <br />.

o Twelve hour shift rotations were established for all Corporate EOC functions.

o The National Weather Service issued a tornado watch for a? of Connecticut for the hours between 1000 and 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />.

o In order to assure the availability of service water following the storm, preventative measures were taken to protect the integrity of the service water system during the storm.

o Th6, power level at 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> was 25% for Unit I and 43% for Unit 2.

o At IO40 hours the Millstone meteorological conditions included 40 mph winds at the lower level and 50 mph at the upper level. The speed of the eye of the storm was estimated at 40 mph. .

o The Millstone Unit No. I gas turbine was successfully tested at 1045 hours0.0121 days <br />0.29 hours <br />0.00173 weeks <br />3.976225e-4 months <br />.

o Millstone Unit No. 2 was taken off-line at 1112 hours0.0129 days <br />0.309 hours <br />0.00184 weeks <br />4.23116e-4 months <br />.

o Millstone Unit No. I was taken off-line at 1140 hours0.0132 days <br />0.317 hours <br />0.00188 weeks <br />4.3377e-4 months <br />.

o The Millstone EOF shif ted to emergency power at 1216 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.62688e-4 months <br />.

o At 1220 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.6421e-4 months <br /> the winds at Millstone were determined to be 49 mph at the lower level and 57 mph at the upper level.

o Millstone Unit No. 2 shutdown at 1227 hours0.0142 days <br />0.341 hours <br />0.00203 weeks <br />4.668735e-4 months <br />. Both units were shutdown by 1255 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.775275e-4 months <br />.

Details of LOOP Everits At Millstone Unit Nos. I and 2, the first or " preferred" source of off-site power is supplied via each of the unit's reserve station service transformers (RSST). At Millstone Unit No.1, an alternate source of off-site power is via the Flanders line, a distribution line originating in the Flanders Substation, approximately 5 i miles from the Millstone site, and terminating at Millstone Unit No.1. On '

September 27, 1985, at 1023 hours0.0118 days <br />0.284 hours <br />0.00169 weeks <br />3.892515e-4 months <br />, the Flanders line to Unit No. I was intermittently lost.

o At 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br /> t).ere was voltage fluctuation on the 345 kV line supplying the switchyard.

o At 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> the Millstone Unit No. 3 RSST was sparking. .

o At 1307 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.973135e-4 months <br /> Millstone Unit No. 2 was proceeding to natural circulation.

o At 1317 hours0.0152 days <br />0.366 hours <br />0.00218 weeks <br />5.011185e-4 months <br /> Millstone Unit No. 2 manually disconnected from the RSST. Both of the Unit No. 2 emergency diesel generators automatically started and loaded, o At 1334 hours0.0154 days <br />0.371 hours <br />0.00221 weeks <br />5.07587e-4 months <br /> Millstone Unit No. I lost normal power and both the emergency diesel generator and the gas turbine automatically started and loaded (additionally, both of the Unit No. 3 emergency diesel generators automatically started).

o At 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> the Millstone lower level winds were 49 mph and the upper level winds were 59 mph.

Recovery From LOOP Events The Station Emergency Organization had been activated and in place since 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> on the morning of the storm to ensure that all actions taken were performed under 'a coordinated and planned effort. Extra personnel were kept at the station to provide assistance and all non-essential personnel were sent home well before the peak of the storm hit the area. A relief schedule was prepared and put into effect which provided for adequate relief for those who remained at the station during the storm.

Millstone Unit No.1 The Millstone Switchyard was reenergized at 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on September 27, 1985.

The 23 kV Flanders line into Unit No. I was reenergized at 1705 hours0.0197 days <br />0.474 hours <br />0.00282 weeks <br />6.487525e-4 months <br /> on September 27, 1935; however, operators elected to stay on emergency AC power.

This decision was based on the excellent performance of all 3 units' emergency AC power sources and the stable configuration of the plant. This allowed the unit to stay with the emergency power source until the RSST was energized via the switchyard. Unit No. I energized its RSST at 0910 hours0.0105 days <br />0.253 hours <br />0.0015 weeks <br />3.46255e-4 months <br /> on September 23, 1985, following a complete washdown of switchyard and station insulators.

While the unit relied on on-site power for approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, off-site power,if needed, could have been restored via the Flanders line within 3h hours.

Millstone Unit No. 2 The Millstone Switchyard was reenergized at 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on September 27, 1985.

The 23 kV Flanders line into Unit No. I was reenergized at 1705 hours0.0197 days <br />0.474 hours <br />0.00282 weeks <br />6.487525e-4 months <br /> on September 27,1985. At 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on September 27 natural circulation had been verified in the Millstone Unit No. 2 Reactor Coolant System, with heat removal via both steam generators. The steam generators were being supplied with feedwater by the electrically driven auxiliary feedwater pumps. The auxiliary feedwater system functioned normally with an adequate supply of water being maintained in the condensate storage tank.

Normal off-site power via the RSST was restored to Millstone Unit No. 2 at 1527 hours0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.810235e-4 months <br /> (on September 28, 1985) following a complete washdown of the outside transformers, transmission lines, switchyard circuit breakers, and the replacement of several damaged lightning arresters.

At the Millstone units, there are no automatic features which will energize any of the buses via the " alternate" off-site AC power sources since the decision to utilize an alternate off-site AC sources is based on an operator assessment of the situation. In the case of Hurricane Gloria, emergency on-site AC power source performance was excellent, thus operations personnel did not elect to utilize their alternate sources of off-site power, which in all cases were available earlier than the " preferred" sources. It is possible to provide Flanders line power to Unit No. 2 via the Unit No. I outdoor bus at its' connection to Unit No.2. This requires the defeat of several interlocks. However, it is an option that the EOC support team mentally exercises during each training drill, and in the event resulting from Gloria, also considered. Conservatively,2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> would be required to complete this connection. Thus, Millstone Unit No. 2 could have had off-site power restored, if needed, within Sh hours.

While the unit relied on on-site power for approximately 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br />, off-site power, if needed, was available within SS hours. As noted by the Staff during the November 14, 1985 Commission briefing on the resolution of USI A-44, this decision allowed for power to be restored in a prudent fashion:

...they did in anticipation of some of the salt spray shut down the plant and they took some very prudent procedures in restoring power. Indicated here, actual loss of time to restore was about 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. They might have been able to restore power sooner but they were cleaning the salt off the switchyard, off the insulators checking the breakers before they actually went in and restored power. The diesels were operating successfully during that event."

Additionally, as indicated in Inspection Report No. 50-245/84-24, Inspection Findings,

"...the licensee's actions taken in preparation for the storm were timely and appropriate."

As indicated by the Staff, the LERs report the amount of time the plant was without off-site power without respect to when power was available if needed.

In this case for Unit No. 2, off-site power could have been restored af ter 3Ya hours.

. . ~

Millstone Unit No. 3 On September 27, 1985 Millstone Unit No. 3 had not yet loaded fuel and accordingly did not have core cooling requirements. However, upon loss of normal power, the emergency diesel generators automatically started and loaded. The circumstances of this event had no impact on Unit No. 3 which was undergoing final preparations for initial fuel load.

Haddam Neck Plant While the Haddam Neck Plant did not experience a loss of off-site power event, it is worth noting that the Haddam Neck Facility took essentially the same precautions as the Millstone Units. The EOF was staffed at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> on September 27, 1985, and the unit was at 0% power at 1106 hours0.0128 days <br />0.307 hours <br />0.00183 weeks <br />4.20833e-4 months <br /> on September 27, 1985. The emergency diesel generators were successfully tested, started and operated during the storm. The unit was back on-line later that same day.

November 14, 1985 Commission Briefing on Station Blackout, USI A-44 At the November 14, 1985 Commission briefing on USl A-44, Station Blackout, the Staff portrayed the Millstone Unit No. 2 LOOP as having a duration of approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. Additionally, the Staff indicated that Hurricane Gloria illustrated a Staff concern with the rapid movement of some severe weather events and the potential for inadequate time to take precautionary measures.

As discussed above, Hurricane Gloria, while being a rapidly moving storm, was tracked and there was ample time to take precautions such as orderly plant shutdowns, and preheating and starting the emergency on-site AC power sources.

Due to the precautionary actions taken before Gloria arrived, the Millstone Units were in very stable conditions during the LOOP events and were able to proceed to restore off-site power in a deliberate and orderly fashion.

While the units relied on on-site power for approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, off-site power, if needed, would have been restored within 3% hours for Millstone Unit No. I and within SV2 hours for Millstone Unit No. 2.

The Staff also indicated that NNECO had implemented corrective actions following a similar storm, Hurricane Belle, in 1976. Following Hurricane Belle, NNECO assessed the results of a lack of effective rainfall during a storm which would cause a buildup of salt spray in the switchyard. As a result of the assessment, NNECO:

o Installed salt monitors in the switchyard and o Installed new equipment in the switchyard to increase creep path, i.e.,

increase resistance to ground. Specifically, NNECO a) installed the largest commercially available glass insulators in the switchyard; b) replaced switchyard circuit breakers to provide better insulation capability and c) replaced transformer bushings between the unit and the switchyard.

These modifications and precautionary actions taken prior to the event enabled NNECO to respond to the recent LOOP event at the Millstone Units in a prudent,

deliberate and coordinated manner without jeopardizing the safety and health of either the public or company employees.

Summary On September 27, 1985 with the impending arrival of Hurricane Gloria, CYAPCO and NNECO commenced an orderly shutdown of the Haddam Neck Plant and Millstone operating units. Prior to and during the reactor shutdown, precautionary steps were taken which included laying out supply hoses to bring alternate cooling water to a diesel generator or the instrument air compressors installing sand bags around doorways, closing floodgate doors, installing life lines between outdoor buildings to ensure personnel could move safely between buildings when necessary, and other actions as described above.

As the storm reached its peak, it became evident that, because of a lack of any effective rainfall, a heavy buildup of salt spray was taking place as evidenced by an increased frequency of arcing on outside transformers, switchyard transmission lines and circuit breakers. Steps were taken to bring the units off-line. All the Millstone emergency on-site AC power sources successfully started and loaded and ran until prudent plant actions were completed to allow for restoration of normal off-site power. If necessary, Millstone Unit No. I could have had off-site power restored within 3% hours and Millstone Unit No. 2 could have had off-site power restored within SV2 hours. Since more rapid restoration of off-site power was not vital, NNECO elected to pursue a more deliberate and thorough cleaning and checking restoration process. This approach was in the best interest of personnel safety of company employees.

The advance notification associated with severe weather events of this kind permits advance precautionary actions not usually credited by the Staff or in plant probabilistic safety studies. As noted by members of the Advisory Committee on Reactor Safeguards (ACRS) during the November 19, 1985 Subcommittee meeting in Waterford, Connecticut (reference pages 207 through 209 of the meeting transcript), the advance warning and actions taken prior to a severe storm arrival lead to conservatisms in a probabilistic risk assessment, and perhaps, these events should be categorized in a fashion different from other than LOOP events.

We are hopeful that the information provided above will put the September 27, 1985 events at Millstone in their proper perspective. As always, we are available to answer any questions you may have on this matter.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY NORTHEAST NUCLEAR ENERGY COMPANY

% - F&L J. F. Opeka J V Senior Vice President L