05000382/LER-2005-004

LER-2005-004,

Year
Event date:	08-29-2005
Report date:	10-27-2005
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3822005004R00 - NRC Website

REPORTABLE OCCURRENCE

On August 29, 2005 at 07:59, a Loss of Offsite Power (LOOP) occurred with the plant in Mode 4. At the time of the LOOP, the plant was experiencing the effects of tropical storm force winds. The NRC Operations Center was notified of this condition on August 29, 2005 at 08:08 due to the LOOP in accordance with 10 CFR 50.72(a)(1)(ii). This condition is being reported in accordance with the following 60-day written reporting requirements:

1. 10 CFR 50.73(a)(2)(iv)(A) due to the automatic actuation of the emergency AC electrical power systems.

2. 10 CFR 50.73(a)(2)(v)(A, B, and D) due to the loss of offsite power that could have prevented the fulfillment of the safety function of structures or systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition, remove residual heat, and mitigate the consequences of an accident. Technical Specification (TS) 3.8.1.1.a Limiting Condition for Operation (LCO), which requires two physically independent circuits between the offsite transmission network and the onsite Class lE distribution system, was not met.

INITIAL CONDITIONS

On August 27, 2005 at 22:04 Waterford 3 declared an unusual event based on issuance of a Hurricane Warning for St. Charles Parish by the National Weather Service. On August 28, 2005 at 10:59 Waterford 3 commenced an orderly shutdown in accordance with Off Normal Operating procedure OP-901-521, Severe Weather and Flooding, in anticipation of a Loss of Off-Site Power due to the approach of Hurricane Katrina, a Category 4 hurricane on the Saffir-Simpson scale. The reactor was manually tripped at 13:16 and a cooldown was commenced at 17:05 with the plant entering Mode 4 at 20:58 on August 28, 2005.

The plant experienced a voltage excursion to 236kV at 02:54 on August 29, 2005. At 06:24 offsite power was declared inoperable due to system voltage exceeding 241kV and TS 3.8.1.1 ACTION STATEMENT 'e' was entered. At 07:45, the plant experienced a loss of instrument air pressure ILL)] due to lowering grid voltage and Off Normal Operating procedure OP-901-511, Instrument Air Malfunction, was entered. At 07:59 with the plant in Mode 4, the plant experienced a Loss of Offsite Power (LOOP) and Emergency Operating procedure OP-902-003, Loss of Offsite Power/Loss of Forced Circulation Recovery procedure, was entered.

In anticipation of the loss of offsite power and the need to rely on the emergency diesel generator onsite power supply, temporary portable diesel generators were brought onsite on August 28, 2005 and installed with the capability of being manually connecting to one of the safety busses if its associated plant EDG was lost.

BACKGROUND

The arrangement of the Waterford 3 switchyard [FK] is presented in Figure 1. The physical configuration of the Waterford 3 Switchyard (SWYD) and Switching Station (SWSTA) is designed to minimize degraded switchyard conditions. The Waterford 3 SWYD uses a breaker and half scheme with East and West busses. Waterford 3 is connected to the utility grid by two transmission lines [FK] to the Waterford 3 - 230 kV Switchyard via the Switching Station [FK]. Each line is designed to carry the full load required for safe shutdown of the plant. Each line can carry 100% output of the main generator. Transmission lines to the Waterford 3 SWSTA from the SWYD are each tied to the busses by one dedicated breaker (double bus double breaker scheme). These two 230 kV transmission lines, along with the 6.9 kV busses and bays connecting the Waterford 3 - 230 kV SWYD with the Waterford 3 SWSTA, are addressed in Waterford 3 TS 3.8.1.1 Limiting Condition for Operation (LCO) as the two physically independent circuits between the offsite transmission network and the onsite Class lE distribution system that are required operable in Modes 1, 2, 3, and 4.

The Waterford 3 - 230 kV Switchyard also has several other 230 kV transmission lines connected to it.

Three of these transmission lines connect Waterford Units 1 and 2 to the Switchyard. Three of the transmission lines cross the river on two separate river crossing towers to tie into the Little Gypsy 230 kV Switchyard. There is a 230kV tie to the adjacent 500kV Switchyard. There are other transmission lines which tie to other areas of the Entergy grid. The system is designed such that no transmission lines cross the 230kV lines connecting the Waterford 3 switching station to the Waterford 3 230kV Switchyard. A single failure such as spurious protective relay operation, breaker failure or transmission line failure associated with the offsite power source will be limited to one train of offsite power only.

EVENT

On August 29, 2005, the plant was in Mode 4 with the reactor coolant loops filled; two Reactor Coolant Pumps (RCP) [AB:P] 1B and 2B were operating as well as Shutdown Cooling (SDC)[BO] Train A. Due to the approach of Hurricane Katrina, several electric plants that connect to the SWYD via 230kV transmission lines were shutdown e.g. Little Gypsy Units, Waterford Units 1 & 2, Ninemile Units, and the Dow (formerly Union Carbide) facility. At 07:59, the LOOP occurred. At the time of the LOOP, the plant site was experiencing tropical storm winds of approximately 48 miles per hour. All loads supplied by the non-safety 6.9 kV busses were lost including the RCPs 1B and 2B. However, RCP 2B breaker failed to trip. Details of the RCP failure to trip are discussed in the "Related Equipment Issues" section of this report. The two emergency diesel generators (EDG) started in response to the LOOP conditions and safe shutdown loads were sequenced onto the two safety busses. Following successful load sequencing onto the EDGs, SDC Train A was placed back in service at 08:15. The plant safety loads remained energized from the two EDGs with temporary diesel generators installed and capable of being manually connected to one of the safety busses if its associated plant EDG was lost.

EVENT (continued) On 8/30/2005 at approximately 18:00, plant experienced a major loss of emergency preparedness offsite communications [Fl] capability because of the loss of Reactor Auxiliary Building (RAB), Emergency Operations Facility (EOF) telecommunication switches, and the Operational Hotline and NRC ENS lines. The Offsite communications remaining available were the industrial hotline, civil defense radio, satellite telephones and cellular telephones. This loss of offsite communications capability was reported to the NRC under 10 CFR 50.72(a)(1)(i) at 20:20, as part of the existing Unusual Event declaration.

Grid restoration activities continued due to the transmission network in the vicinity of Waterford 3 having damaged towers and limited connections. The 230 kV transmission lines from Waterford 3 Switchyard to Waterford 3 Switching Station remained intact during the hurricane and did not require any work for restoration of offsite power. Waterford 3 continued to run its safe shutdown loads on the EDGs as grid restoration progressed. Following analysis of the surrounding infrastructure and grid capabilities, the decision was made to cool the plant down to Mode 5. The plant transitioned to Mode 5 at 14:18 on September 1, 2005. Grid evaluations were performed to consider transfer of safety busses from onsite emergency power sources (EDGs) to the preferred offsite power sources. The evaluations concluded that safety busses could be reconnected to offsite power; however, to maintain diversity and conservatism, only one train of shutdown equipment was connected to offsite power source until the grid was further strengthened with additional spinning reserves. Train A offsite power source was available at approximately 19:00 and declared operable at 23:21 on September 1, 2005. Following additional grid evaluations, Train B offsite power source was available at 21:54 and declared operable at 22:20 on September 2, 2005. The plant remained shutdown pending continued grid and infrastructure restoration activities and the results of the NRC and Federal Emergency Management Agency's (FEMA) restart readiness inspection.

Emergency Preparedness offsite communications capability that was previously lost had been reestablished through the use of a functional Operational Hotline, a dedicated open line to the NRC to replace the Emergency Notification System (ENS) and the routing of key plant telephone numbers through Little Rock, AK. Because of the restoration of communication circuits, the Unusual Event was terminated at 17:40 on September 7, 2005.

Following satisfactory completion of the NRC and FEMA's restart readiness inspection and authorization to resume operation on September 9, 2005; plant startup commenced. The plant was synchronized to the grid at 12:16 on September 13, 2005.

RELATED EQUIPMENT ISSUES

1. During the LOOP, RCP 2B 6.9kV breaker [EA] failed to trip. The breaker was manually opened and racked out. Investigation into the failure determined the shunt trip coil failed open electrically. A review of past failure trends and operating experience for this model breaker determined there is no adverse trend of GE Magne-Blast circuit breaker failures nor misaligned trip coils that could prevent breakers from tripping at Waterford 3. There are no generic implications and the failure of the shunt trip coil is judged to be a random failure and not age related due to the low number of cycles experienced by the breaker.

CAUSAL FACTORS

The Loss of Offsite Power occurred due to the Entergy transmission system damage caused by Hurricane Katrina.

CORRECTIVE ACTIONS

The grid in the vicinity of Waterford 3 had limited connections and could have been subjected to voltage and frequency variations due to grid restoration efforts. The 230 kV transmission lines from Waterford 3 Switchyard to Waterford 3 Switching Station remained intact during the hurricane and did not require any work for restoration of off site power. Close coordination was established between the Entergy Transmission System operator and Waterford 3 personnel to evaluate the capability of the offsite power sources to support plant safe shutdown loads. Grid evaluations were performed prior to major plant evolutions to ensure grid frequency was within acceptable range and grid voltage was above the minimum acceptable voltage (223kV) at the Waterford 3 SWSTA. These evolutions consisted of the following examples: (1) Transfer of safe shutdown plant loads on the onsite emergency power sources to the offsite power sources; (2) Starting and operating large auxiliary motors on the grid; (3) Plant startup; (4) Power ascension; and (5) Power operation.

SAFETY SIGNIFICANCE

The Loss of Offsite Power event is safety significant, however, the switchyard system did operate as designed and disconnected transmission circuits from the switchyard busses when the integrity of the grid was challenged by the environmental conditions present during Hurricane Katrina. The plant was shutdown to Mode 4 in anticipation of a LOOP. The control room operators were prepared for losing the RCPs and taking appropriate action while on natural circulation to restart SDC. The EDGs started and aligned to the safety busses as designed and thus provided electrical power for other accident mitigating systems.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (1-2001) SAFETY SIGNIFICANCE (continued) There was no significant equipment problems noted while maintaining shudown conditions during and after the hurricane. If the EDGs were lost during operation, the temporary diesel generators, which were brought onsite prior to the hurricane landfall, could have been connected to one of the safety busses to maintain safe plant shutdown conditions. Based on the above, this event did not have a significant effect on the health and safety of the public.

SIMILAR EVENTS

A review of events occurring within the past three years did not identify any previous similar occurrences.

ADDITIONAL INFORMATION

Energy Industry Identification System (ENS) codes are identified in the text within brackets [ ].

FIGURE 1 Waterford 3 Switchyard Arrangement Frisco 230kV U3 Segni Nkternile 230kV Vs hone 230W as Hooker 230kV LOyny dR e2 A A 7120 11. 71307 54 8972 8962 7142 7151 I I 7102 7182 78127172 7625I 6975 6985 7161 1 7106 7186 76 5 I I 76287176MEI I 6978 6 7166 J� 17112 I 7198 Waterford 230kV Main 230kV Leypsy cktValentine 230W Waterford 600W Raceland 230kV