ML20236F595
| ML20236F595 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/22/1998 |
| From: | Desmond N BOSTON EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR BECO-2.98.066, GL-87-02, GL-87-2, NUDOCS 9807020239 | |
| Download: ML20236F595 (5) | |
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Sootor Edisors l
Pilgrim Nuclear Power Station l
Rocky Hill Road l
Plymouth, Massachusetts 02360-5599 1
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l Nancy L. Desmond Regulatory Relations Group Manager June 22,1998 BECo Ltr. 2.98.066 L
U.S. Nuclear Regulatory Commission Attentiorv Document Control Desk Washington, DC 20555 Docket No. 50.293 l
License No. DPR-35 Response to the NRC March 24.1998. Reauest for Additional Information on Pilarim Station's USI A-46 Implementation (TAC NO. M69471) i This letter responds to the March 24,1998, NRC Human Factors Assessment Branch request for l
additional information (RAl) on the Pilgrim Station, Generic Letter 87-02 (USI A-46) Summary l
Report submittal of September 30,1996.
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This letter does not contain any commitments.
Should you have any questions, please contact Mr. J.D. Keyes, Regulatory Affairs Department, at (508) 830 7942.
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N. L. Desmond
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Regional Administrator, Region 1 Mr. Alan B. Wang U.S. Nuclear Regulatory Commission Project Manager Project Directorate 1-3 475 Allendale Road Office of Nuclear Reactor Regulation King of Prussia, PA 19406 Mail Stop: OWFN 14B2 U.S. Nuclear Regulatory Commission 1 White Flint North Senior Resident inspector 11555 Rockville Pike Pilgrim Nuclear Power Station Rockville, MD 20852 9907020239 900622 PDR ADOCK 05000293 P
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RESPONSE TO THE NRC HUMAN FACTORS ASSESSMENT BRANCH REQUEST FOR ADDITIONAL INFORMATION ON PILGRIM STATION'S USI A-46 IMPLEMENTATION Question (aj..
l Describe what reviews were performed to determine if any local operator actions, required to safely shutdown the reactor (i.e., implement the safe shutdown equipment list (SSEL)),
could be affected by potentially adverse environmental conditions (such as loss oflighting, excessive heat orhumidity, orin-plant barriers) resulting from the seismic event. Describe how staffing was evaluated. Describe the reviews which were conducted to ensure operators have adequate time and resources to respond to such events.
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' Response (a)
. Environmental conditions affecting local operator action As described in GIP-2, Part II, Section 3.2.5, the only potential events that must be considered in the USl A-46 program are a safe shutdown earthquake (SSE) and loss of offsite power (LOOP). The plant operating procedures used to shut down the reactor following a LOOP have previously been validated for local operator actions. This includes potentially adverse environmental conditions such as loss of lighting and excessive heat and humidity. Note that the USl A-46 accident scenario (SSE + LOOP) explicitly excludes loss of coolant accidents (LOCA) and high energy line breaks (HELB). Therefore, the heat and humidity conditions in the plant are postulated to be equivalent to those in a LOOP scenario which are neither excessive nor adverse.
The potential for in-plant barriers caused by failure of plant structures and equipment is not considered a credible obstacle to local operator actions for safely shutting down the plant.
Industry earthquake experience has shown that typical industrial structures are able to withstand earthquakes larger than the SSEs for eastern U.S. nuclear plants without collapse or failure. The potential for local failure of architectural features (such as suspended ceilings in the control room) and the potential for adverse seismic spatia l interactions in the vicinity of safe shutdown eq Apment, where local operator actions may be required, was explicitly evaluated as required in GIP-2, Part II, Section 4.5 and Appendix D. For example, this review included a check that the masonry walls near safe shutdown equipment are seismically adequate based on the results of the IE Bulletin 80-11 program.
The systems and equipment selected for seismic review in the USl A-46 program are those for which Normal, Abnormal, and Emergency Operating Procedures are available to bring the plant from a normal operating mode to a cold shutdown condition. As required by GIP-2, Part II, Sections 3.2.8 and 3.7, the safe shutdown equipment list (SSEL) was reviewed by the plant Operations Department to confirm that it is compatible with existing plant procedures.
Additional operator actions, beyond those associated with the LOOP accident scenario to bring the plant from a normal operating mode to a cold shutdown condition are those actions associated with the effects of the vibratory motion of the SSE. The results of the review of these operator actions with respect to whether there is adequate time and resources to respond to the postulated events are summarized below.
- Adequacy of operator staffing, time, and resources.
Operator actions to reset or restore systems to operation were validated in simulator scenarios and were determined acceptable based on the following results:
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t RESPONSE TO THE NRC HUMAN FACTORS ASSESSMENT BRANCH REQUEST FOR ADDITIONAL INFORMATION ON PILGRIM STATION'S USI A-46 IMPLEMENTATION The operator was provided with speci'ac indications of system status such as relay targets and control room instruments indicating the status of key parameters such as voltage, amperage, or fluid flow.
There was sufficient time for the operator or an assistant to perform the necessary diagnostic evaluations and take the necessary resetting or restoring actions.
The indications and controls necessary to perform the evaluation and resetting or restoring action located in the control room were immediately accessible. Other controls and indications were located in rooms that could be reached within a few minutes.
The number of svstems required to be restored or reset was small enough such that the operating staff a.id their assistants were able to manage the resetting or restoring activities along with their other duties.
Detailed procedures were available to assist the operator in diagnosing the situation and carrying out the proper restoring sequence.
As an examplo of the above, the Reactor Core isolation Cooling (RCIC) system is credited for high pressure reactor water level control, and this system is susceptible to a spurious high turbine exhaust pressure trip from mercury type pressure switches located in that trip circuit. This trip unlatches the turbine trip / throttle valve. The mercury switches will automatically reset when the SSE induced vibration ceases. This trip would be annunciated in the control room and will require reset of the turbine trip / throttle valve in the southwest quadrant of the reactor building. Operators are routinely trained to perform this particular reset, and sufficient time is available for the necessary actions. (This is described in further detail in Enclosure A, Section 4.1.3.1.2 of our September 30,1996 submittal.)
Question (b)
As part of BECo's review, were any control room structures identified which could impact the operator's ability to respond to the seismic event? 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 ofinteractions was evaluated and provide the schedule forimplementation of the finalresolutions.
Response (b)
A Control Room review for generalinteraction hazards of structures and components that could impact the operator's ability to respond to a safe shutdown earthquake was conducted. The inspcction included the area above the suspended ceiling. The method used for evaluating these potential sources of seismic spatial irneraction is described in GIP-2, Part II, Section 4.5 and Appendix D. In general, the inspection confirmed that the Control Room is free from interaction hazards; however, a limited number of anomalies were observed.
' 'ypical anomalies that were observed and resolved included, open S-hooks on light panels, unattached tie wires on ceiling tee bars, and light panel covers not fastened with screws.
Recognizing that the Control Room is an area that uses many ancillary items (many of which 2
- . RESPONSE TO THE NRC HUMAN FACTORS ASSESSMENT BRAN ADDITIONAL INFORMATION ON PILGRIM STATION'S USI A-46 IMPLEMENTATION
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are already excluded), such as furniture, cleaning equipment, and small hand tools, Pilgrim J
Procedure 1.17.1, " Potential Seismic Interaction Hazards"is utilized by the operations staff as the continued means to avoid the introduction of potential new seismic interaction hazards into the Control Room.
l Question (c)
Describe what reviews were perfc,med to determine if anylocal operator actions were required to reposition
- bad actor relays". Forany such activities describe how adverse environmental conditions (such as loss oflighting, excessive heat or humidity, orin-plant barriers) resulting from the seismic event were analyzed and dispos,tioned. Describe how staffing was evaluated. Describe the reviews which were conducted to ensure operators have adequate time and resources to respond to such events.
Response (c)
Initial reviews were conducted of essential relay lists to identify " bad actor relays". If a " bad actor relay"is fulfilling an essential function, it will be replaced. Other " bad actor" relays that have been identified and are not planned for replacement have been screened as chatter acceptable and do not require operator reset of the relay itself but rather reset of the affected end device. For example, as discussed in Response (a), the Reactor Core Isolation Cooling (RCIC) system is credited for high pressure reactor water level control, and this system is susceptible to a spurious high turbine exhaust pressure trip from mercury type pressure switches located in that trip circuit. This trip unfatches the turbine trip / throttle valve.
The mercury switches will automatically reset when the SSE induced vibration ceases.
Question (d)
Describe which of the operatoractions 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 that operators willperfonn the actions required to reset affected equipment?
Response (d)
Resetting of SSEL equipment affected by postulated relay chatter is consistent with the skill and training required of our operators. Resetting both relays and SSEL equipment is an
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activity included within the scope of expected operator actions contained in our Normal, Abnormal, and Emergency Operating Procedures.
Question (e)
Assume the alarms associated with " bad actor relays"are expected to annunciate during the seismic event. Do the operators have to respond to those annunciators and review the annunciator response procedures associated with them forpotential action? How would those additional actions impact the operators ability to implement the Normal, Abnormal, and Emergency Operating Procedures required to place the reactorin a safe shutdown condition?
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' RESPONSE TO THE NRC HUMAN FACTORS ASSESSMENT BRANCH REQUEST FOR
" ADDITIONAL INFORMATION ON PILGRIM STATION'S USl A-46 IMPLEMENTATION Response (eY As described in Section 3.5.3 of EPRI Report NP-7148, " Procedure for Evaluating Nuclear Power Plant Relay Seismic Functionality", 50 to 100 or more alarms are expected to annunciate following an earthquake which causes the turbine to trip and the reactor to
- scram. 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 multitude 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 scram and trip and l
checking important levels, temperatures, pressures, flows, and electrical switching resulting from associated power transfers. These confirmatory checks will take more than a minute to complete during which time the operators will not be responding to specific alarms. 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.
. The NRC staff and SQUG representatives discussed this topic extensively, including discussions held at one or more meetings. The results of that evaluation and review are summarized in EPRI NP-7148, Section 3.5.3 where the following conclusion is reached.
"Accordingly, there appear 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 do not consider it necessary to perform any additional reviews of the effect spurious alarms caused by " bad actor relays" or other causes as a result of a seismic event.
Question (O 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 otherplant staff required to respond to such events.
Response (O As part of Pilgrim Station's A-46 project implementation, additional guidance on mitigating the A-46 Seismic Event is being added to Pilgrim Station Procedure 5.2.1, " Earthquake".
This additional guidance will identify the success paths to safe shutdown that are seismically qualified and will clarify rugged, redundant, equipment paths and identified equipment vulnerabilities. Operator training regarding the procedure additions will be addressed through Pilgrim's operator requalification training program.
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