ML18153A304
| ML18153A304 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/22/1998 |
| From: | Saunders R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 98-120, GL-87-02, GL-87-2, NUDOCS 9804280313 | |
| Download: ML18153A304 (8) | |
Text
...,-
- J. ~. :. :..
e e
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555-0001 Gentlemen:
April 22, 1998 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.
SPS/CGL Docket Nos.
License Nos.98-120 R6' 50-280 50-281 DPR-32 DPR-37 REQUEST FOR ADDITIONAL INFORMATION REGARDING SEISMIC QUALIFICATION OF MECHANICAL AND ELECTRICAL EQUIPMENT (GL 87-02)
NRC letter, dated February 23, 1998, requested additional information necessary for the NRC staff to complete its review of our summary report addressing seismic qualification of mechanical and electrical equipment.
Our summary report was transmitted by a November 26, 1997 letter (Serial No.97-664). The responses to your request for additional information are provided in the Attachment to this letter.
If you hav~ any further questions, please contact us.
Very truly yours, R. F. Saunders Vice President - Nuclear Engineering and Services Attachment Commitments made in this letter:
No new commitments.
)
V) f\\/
~()
cc:
U.S. Nuclear Regulatory Commission
'Region II Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30323 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station
e e
ATTACHMENT TO LETTER SERIAL NO.98-120 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING THE VERIFICATION OF SEISMIC ADEQUACY OF MECHANICAL AND ELECTRICAL EQUIPMENT
- a. Describe what reviews were performed to determine if any local operator actions required to safely shut down the reactor (i.e., implement the safe shutdown equipment list (SSEL)) could be affected by potentially adverse environmental conditions (such as loss of lighting, excessive heat or humidity, or in-plant barriers} resulting from the seismic event. Describe how staffing was evaluated and describe the reviews which were conducted to ensure operators had adequate time and resources to respond to such events.
Response
In selecting the method(s) to be used to shut down the plant following a design basis earthquake (DBE), a conscious effort was made to utilize the processes and components relied upon in existing operating procedures. The potential for loss of instrument air, HVAC, and electrical loads (such as lighting) were anticipated, and a path/process for shutdown was selected which would work for such contingencies. The Appendix R report was reviewed as part of the process of developing the SSEL since it was recognized that many of the same operational limitations may be present following a seismic event.
Support for remote operating equipment and performing line-ups on an as-needed basis was considered. It was determined that the supplies (such as portable lights, respirators, ice vests, etc.) necessary to perform these evolutions in accordance with approved procedures under adverse operating environmental conditions would be available. In addition, the necessary hardware needed to block air operated valves or to cycle them by means of connection to portable air bottles was confirmed to be available, should such actions be required.
Following a seismic event, instrumentation on the SSEL was verified to be sufficient to allow a timely evaluation of the following:
the condition of the plant, the equipment available for operation based on the extent of the damage to the instrument air system, and the electrical buses that may be lost.
Following an assessment of plant conditions and the determination of the need for dispatching operators throughout the plant, a decision would be made whether additional operators would be called in to supplement the on-shift staffing.
Page 1 of 6
e e
- b. As part of the licensee's review, were any control room_ structures which co~ld impact the operator's ability to respond to the seismic event identified?
Such items might include but are not limited to: MCR ceiling tiles, non-bolted cabinets, and non-restrained pieces of equipment (i.e., computer keyboards, monitors, stands, printers, etc.).
Describe how each of these potential sources of interactions has been evaluated and describe the schedule for implementation of the final resolutions.
Response
The control room and associated structures and safe shutdown pieces of equipment located in the control room, as well as the ability of the operators to respond to safely shut down the reactor following a safe shutdown earthquake (SSE), were evaluated.
The main control boards, the benchboards, and other safe shutdown pieces of equipment located in the control room were evaluated as part of Surry's A-46 review.
The method used for evaluating potential sources of seismic spatial interaction is described in Generic Implementation Procedure, Revision 2 (GIP-2), Part II, Section 4.5 and Appendix D.
Our review concluded that the control room structures and components satisfied the GIP screening criteria, and they are well anchored with sufficient margins* to withstand a SSE. As identified in our A-46 summary report, an exception was the control room ceiling which represents a potential source of interaction. The control room ceiling light diffuser panels will be further reviewed and, if required, they will be tied together with clips to the tee frames to prevent their falling during a SSE.
As stated in our summary report, the schedule for completing this evaluation/modification is by the end of the second Unit 2 refueling outage from the time of the submittal of the summary report, currently scheduled to commence in September 2000.
In addition, a few minor housekeeping issues were identified. A station procedure is being prepared to address housekeeping concerns in all safety significant areas of the plant, including the control room. As noted in our summary report, implementation of this procedure is planned by the end of the outage scheduled to commence in September 2000.
- c. Describe what reviews were performed to determine if any local operator actions were required to reposition "bad actor relays." For any such activities describe how adverse environmental conditions (such as loss of lighting, excessive heat or humidity, or in-plant barriers) resulting from the seismic
- event were analyzed and dispositioned. Describe how staffing was evaluated and describe the reviews which were conducted to ensure operators had adequate time and resources to respond to such events. -
Response
Based on the evaluation conducted to assess the seismic functionality of relays, one "bad actor relay" (Westinghouse SV relay model) was discovered in each of the three Page 2 of 6
e e
emergency diesel generator (EOG) circuits. Engineering has determined that the EDGs would be capable of functioning following a seismic event.
Therefore, no operator action
- will be needed to reset it in the event of postulated relay chatter.
This "low ruggedness" relay is in the process of being replaced by a seismically qualified relay.
In addition to this "bad actor relay" identified based on the seismic functionality evaluation, a few groups of relays were screened based upon using operator action.
This screening was based on the methodology stated in Section 6.2 of the GIP-2. This screening process allows that relays, the malfunction of which is acceptable, need not be seismically rugged, and no evaluation of their seismic functionality is needed.
Therefore, no seismic evaluation was performed for these relays. The relay review section of the November 1997 USI A-46 summary report for Surry (Appendix B, Section 5 - G.4 Forms) identified the following cases screened in this manner:
Diesel Fire Pump, Main Steam Moisture Separator Reheater (MSR) Inlet Stop Valves, Main Steam Non-return Valves, Chiller Units, and Diesel Engines for the Emergency Service Water Pumps.
Upon further review, for three of these cases, initially screened as not being required to meet the ruggedness requirements based on operator action, it has since been determined that local operator action would not be required, as discussed in the following paragraphs:
For the diesel fire pump (1-FP-P-2), no operator action would be needed since only one backup source of auxiliary feedwater is required, and it is available from the Emergency Condensate Make-up Tanks (1/2-CN-TK-3).
For the Main Steam Moisture Separator Reheater (MSR) Inlet Stop Valves (1-MS-MOV-100A,B,C,D and 2-MS-MOV-200A,B,C,D), the report states that "Valves are to be manually operated... if power is lost.... " Following a seismic event, the desired status for the flow path associated with these normally-open valves is closed. If postulated relay chatter causes these valves to close, closed is the desired position. In the event of a loss of power coincident with a seismic event, these valves (MOVs) will fail "as-is." However, the MSR Reheat Control Valves (1-MS-FCV-104A,B,C,D and 1-MS-FCV-204A,B,C,D), which are downstream and in series with the MOVs, will close isolating the flow path.
In accordance with Emergency Procedure 1 / 2-E-O, operations will verify that this flow path is isolated.
For the Main Steam Non-return Valves (1-MS-NRV-101A,B,C and 2-MS-NRV-201A,B,C), the report also states that "Valves are to be manually operated... if power is lost.... " Following a seismic event, the desired status for the flow path associated with these normally-open valves is open. Upon a loss of power, these valves will fail "as-is" and the flow path will remain open.
If relay chatter causes the Non-return Valves to start to close and loss of offsite power Page 3 of 6
e e
occurs during the seismic event, these valves, which have a long stroke time and dis~ance, will travel a small portion of the total stroke before failing in the partially closed position. In this case, the flow path would still be open. If offsite power is not lost, operator action could be taken from the main control room at the direction of the Senior Reactor Operator to re-open the Non-return Valves if postulated relay chatter causes them to close.
In the two remaining cases, operator action may be required, but not for at least a few hours, if at all.
These cases, including the associated components, are further discussed in the following paragraphs:
Relay chatter might briefly start or stop the chiller units (1-VS-E-4A,4B,4C).
However, there is no seal-in of the operating relay so the unit would return to its demanded state.
Only the high and low pressure sensors and trips, which are integral to the chiller units, would need to be manually reset, if required. Although the chiller units are unlikely to be affected by a design basis earthquake, an annunciator indication (O-VSP-D5) would be received to alert operators of abnormal chiller condition if one exists.
Annunciator Response Procedure O-VSP-D5 and Operating Procedure O-OP-VS-006 provide instruction to reset a tripped chiller or to place a non-running chiller in service.
The diesel engines (1-SW-PENG-1A, 1 B, 1C) for the Emergency Service Water Pumps (ESWP) (1-SW-P-1A,1B,1C) would not be needed for at least a half-hour and most likely not for several hours.
Independent of a seismic event and postulated relay chatter, the diesels are started and operated locally from control panels at the diesels.
Operating Procedure O-OP-SW-002 provides operating instructions. Based on a reasonable assumption of unimpeded access to the Low Level Intake Structure and based on a review of the task requirements for starting these pumps, it is expected that an ESWP could be started in approximately a half-hour.
The required actions related to postulated relay chatter were reviewed against the conditions contained in EPRI NP-7148, Section 3.5.2. These criteria require that there be sufficient time, indication, access, and procedures available to reset or restore the systems controlled by these relays and that these actions can be carried out by the operators and their assistants along with their other duties. Based on a review of the above cases and the types of situations in which operator action might be used, no significant increase in operator burden is considered likely. No operations procedures were required to be changed.
In order to validate the operators' ability to access equipment to perform local actions, paths were walked down by engineering and operations personnel. The walkdowns considered the building structure ruggedness, anchorage of the equipment inside the building structures, potential seismic interactions, and other possible adverse effects due to a seismic event.
As a result of the walkdowns, no adverse environmental conditions are expected to impede operator access for the above cases following._a safe shutdown earthquake.
Page 4 of 6
e e
- d. Describe which of the operator actions associated with resetting SSEL equipment affected by postulated relay chatter are considered to be routine and consistent with the skill of the craft. If not considered skill of the craft, what training and operational aids were developed to ensure the operators will perform the actions required to reset affected equipment?
Response
Abnormal Procedure O-AP-37.00 provides guidance for required actions in the event of a valid seismic event. As discussed in the response to Question c., required actions related to postulated relay chatter are within the scope of expected operator activities, consistent with the skill and training required of operators, and addressed in existing procedures. Therefore, development of specific training and operational aids was not necessary.
- e. Assume the alarms associated with "bad actor relays" annunciate during the seismic event. Do the operators have to respond to those annunciators and review the annunciator response procedures associated with them for potential action? How would those additional actions impact the operators' ability to implement the Normal, Abnormal, and Emergency Operating Procedures required to place the reactor in a safe shutdown condition?
Response
As described in EPRI Report NP-7148, Section 3.5.3, following an earthquake that causes the turbine to trip and the reactor to scram, 50 to 100 or more alarms are expected to annunciate.
In addition to this large number of alarms, there may be several earthquake-induced, spurious alarms resulting from such events as water sloshing in tanks, oil sloshing in transformers, actuation of vibration protective instrumentation on rotating equipment, and contact chatter of relays.
When the avalanche of alarms occurs, the operator will clearly be aware that the plant has tripped. Plant procedures and operator training require that operators respond to the turbine trip and reactor scram by confirming the trip and scram and checking important levels, temperatures, pressures, flows, and electrical switching resulting from associated power transfers. These confirmatory checks will take more than a minute, during which time the operators will not be able to respond to specific alarms because they will be busy performing these checks. The earthquake motion is assumed to last
- less than a minute and the causes of the spurious alarms will have gone away during this period while the operators are responding to the plant trip.
As noted in the response to Question d., Abnormal Procedure O-AP-37.00 provides guidance for required actions in the event of a valid seismic event. Following the seismic event, the operators will immediately evaluate the plants' critical parameters and the remaining alarms will be acknowledged and prioritized. Expectations concerning the maintenance of critical parameters during Emergency and Abnormal situations have been conveyed by Operations Standard OP-STD-016.
Page 5 of 6
e We understand that the NRC staff and SQUG representatives discussed this topic extensively, including discussions held at one or more meetings. The following related
'conclusion is summarized in EPRI NP-7148, Section 3.5.3 (page 3-12) where the following conclusion is reached:
"Accordingly, there appears to be no reasonable bases or evidence which would suggest that spurious alarms resulting from an earthquake may lead to abnormal operator responses. Therefore, special operating procedures or relay evaluation actions to address potential spurious alarms are not considered warranted and relays affecting alarms need not be seismically adequate."
The NRC staff accepted the relay functionality review procedure summarized in GIP-2 and described in detail in EPRI NP-7148 (including the above conclusion) in Supplemental Safety Evaluation Report No. 2 on GIP-2. Therefore, we did, and still do not consider it necessary to perform any additional reviews of the effect of spurious alarms caused by "bad actor" relays or other causes as a result of a seismic event.
- f. To the extent that Normal, Abnormal, and Emergency Operating Procedures were modified to provide plant staff with additional guidance on mitigating the A-46 Seismic Event, describe what training was required and provided to the licensed operators, non-licensed operators, and other plant staff required to respond to such events.
Response
Since it is assumed that there are no accidents (LOCA, HELB, etc.) or abnormal conditions (floods, high winds, fires, sabotage, etc.) to contend with at the same. time that the plant is being shut down as a result of a seismic event, the selection of equipment for the SSEL was straightforward.
For the worst case scenario, it was assumed that instrument air may not be available.
Reliance on only on-site power sources (the diesels and batteries) was also assumed. Also, the decision was made to take the units to cold conditions, rather than maintaining them at hot conditions. This approach resulted in the inclusion of components of the Residual Heat Removal (RHR)
System on the SSEL.
Procedures (normal and abnormal) existed for shutting down the units under these conditions. In compiling the SSEL, the approach used was to credit the equipment specified in these existing procedures and not to develop new approaches for bringing the units to safe shutdown conditions.
Operations was involved during the development and finalization of the SSEL to assure that the equipment credited was consistent with operating procedures and that the necessary instrumentation to monitor the process was included on the SSEL.
Since it was not necessary to modify operating procedures to address the mitigation of an A-46 seismic event, there was no need to provide specialized training on procedural changes.
Page 6 of 6