ML031130461
| ML031130461 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/16/2003 |
| From: | Hartz L Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML031130461 (17) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 April 16, 2003 U.S. Nuclear Regulatory Commission Serial No.03-150 Attention: Document Control Desk NLOS/GDM R2 Washington, D.C. 20555 Docket Nos.
50-280 50-281 License Nos.
DPR-32 DPR-37 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATIONS CHANGE BURIED FUEL OIL STORAGE TANK INSPECTION AND RELATED REPAIR REQUEST FOR ADDITIONAL INFORMATION In a letter dated September 5, 2002 (Serial No.02-561), Virginia Electric and Power Company (Dominion) requested changes to the Surry Power Station Units 1 and 2 Technical Specifications (TSs). These changes include the addition of a 7-day allowed outage time for a buried fuel oil storage tank to permit the inspection and, if necessary, related repair of the tank during plant operation.
During staff review of the proposed TS changes, the NRC determined that additional information was necessary to complete their review. A conference call was held on February 26, 2003, to discuss the staff's questions. At the conclusion of the conference call, Dominion agreed to provide a written response to the NRC's questions, and this response is provided in the attachment. We have evaluated the proposed TS change previously submitted with respect to the supplemental information provided herein and have determined that the supplemental information does not require revision of the No Significant Hazards Consideration or Environmental Assessment provided in our September 5, 2002 submittal.
If you have any further questions or require additional information, please contact Mr. Gary D. Miller at (804) 273-2771.
Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering Attachment 6D
Commitments made in this letter:
- 1. We will ensure that provisions to obtain fuel from Gravel Neck using the station tanker truck are verified prior to a buried fuel oil tank being removed from service.
- 2. In addition to the actions required by the proposed TS regarding fuel oil availability, our planning and scheduling activities to remove a buried fuel oil tank from service will specifically identify restrictions/contingency measures.
- 3. Transfer pump operability will be verified prior to removing a buried fuel oil storage tank from service.
cc:
U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center Suite 23T85 61 Forsyth Street, SW Atlanta, Georgia 30303 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station Commissioner Bureau of Radiological Health 1500 East Main Street Suite 240 Richmond, VA 23218
SN: 03-150 Docket Nos.: 50-280/281
Subject:
RAI - Proposed TS Change Buried Fuel Oil Storage Tank Inspection &
Related Repair COMMONWEALTH OF VIRGINIA
)
)
COUNTY OF HENRICO
)
The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Leslie N. Hartz, who is Vice President - Nuclear Engineering, of Virginia Electric and Power Company. She has affirmed before me that she is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of her knowledge and belief.
Acknowledged before me this 16th day of April, 2003.
My Commission Expires: March 31, 2004.
N 4
otary Public N
_ N
(,
EAL')~
Attachment Response to NRC Request for Additional Information Proposed Technical Specifications Change Request Buried Fuel Oil Storage Tank Inspection/Repair Surry Power Station Units 1 and 2 Virginia Electric and Power Company (Dominion)
- 1. Provide a complete description of the regulatory basis for the proposed Technical Specification amendment request, including references to applicable NRC safety evaluations and other documents that support this position.
The regulatory basis for Technical Specification (TS) 3.16, Emergency Power, is to ensure the availability of electrical power for safe operation of the station during an emergency. The emergency diesel generators (EDGs) provide an independent, onsite, back-up power source for the emergency power system. Should a loss of offsite power (LOOP) occur, the EDGs will power the engineered safety features and other essential loads to safely shut down and maintain the units in a safe shutdown condition.
The following design and regulatory criteria, as well as standards, are applicable to the EDGs:
10CFR50 Appendix A, General Design Criteria (GDC) 17, "Electric Power System",
requires an onsite electric power system and an offsite electric power system to permit functioning of structures, systems, and components important to safety. As discussed in UFSAR Section 8.5, "Emergency Power System", onsite and offsite power systems are provided that can independently supply the electric power required for operating safety-related systems. This capability is maintained with a single failure in either the onsite or offsite system. In the unlikely event of a LOOP, the emergency buses are energized by the EDGs.
At the time of the initial licensing of Surry, the 10CFR50 Appendix A version was dated 1968 and included (draft) Criterion 24, "Emergency Power for Protection Systems", and (draft) Criterion 39, "Emergency Power for Engineered Safeguards".
Criterion 24 required sufficient alternate sources of power to permit the required functioning of the protection systems. Criterion 39 required alternate power systems adequate to permit the required functioning of the engineered safety features.
These criteria are addressed in UFSAR Sections 1.4.24 and 1.4.39, respectively.
The EDGs provide the alternate onsite electric power source to supply power to the Emergency Power System in the event of a LOOP.
- Also at the time of the initial licensing of Surry, AEC Safety Guides 6 and 9 were considered. These Safety Guides were titled "Independence Between Redundant Standby (Onsite) Power Sources and Between Their Distribution System" and "Selection of Diesel Generator Set Capacity for Standby Power Supplies". IEEE-308 (1970), titled "IEEE Criteria for Class 1E Electric Systems for Nuclear Power Generating Stations", was also considered. The Safety Evaluation issued by the NRC for the Surry Operating License concluded in Section 3.2.4.2 "...that the emergency power system meets the requirements of IEEE-308 and conforms with the regulatory position stated in AEC Safety Guides Nos. 6 and 9 and is acceptable."
In addition to the above design and regulatory criteria, as stated in letter Serial No.02-561, similar provisions to allow buried fuel oil storage tank inspection during power operation are included in the North Anna TSs. Letter Serial No.90-099, dated March 26, 1990, submitted the North Anna TS change to permit cleaning and Page 1 of 13
inspection of buried fuel oil storage tanks. The NRC approved the North Anna TS change request and issued TS Amendments 128/112 on July 3, 1990. The NRC's Safety Evaluation for North Anna TS Amendments 128/112, as well as the March 26,1990 North Anna TS change request, states that the operable buried fuel oil tank would provide fuel for EDG operation for 3-1/2 days at full load and that backup capabilities to refill the tank in this time frame are established; the backup capabilities provide the means to continue to satisfy the 7-day full load operation requirement. The NRC's July 3, 1990 Safety Evaluation also concluded that the proposed North Anna change was acceptable. Likewise, the same allowed outage time, along with the same provisions, was included in the North Anna conversion to the Improved Technical Specifications, which was approved by TS Amendments 231/212 on April 5, 2002. The basis and approach to the North Anna TS requirements are directly applicable to the Surry proposed change for both the allowed outage time and the backup capabilities. In both the North Anna and Surry cases, it is recognized that the backup capabilities (i.e., from the above ground tank or from the offsite replacement source) are necessary to satisfy the 7-day full load operation TS requirement.
- 2. What is the expected frequency of the fuel oil storage tank(s) maintenance activities that will require implementation of the following proposed modification?
Inspection of each of the buried fuel oil storage tanks is planned on a ten-year frequency. This frequency is consistent with the guidance in Regulatory Guide 1.137 for cleaning of fuel oil storage tanks to permit inspection.
- 3. Describe the worst-case event scenario that could occur with only one buried fuel oil storage tank available containing 17,500 gallons of fuel oil. Explain in detail how this event will be mitigated and how both Surry units will be placed and maintained in a safe shutdown condition given the constraints of the proposed TS change.
Scenarios that involve seismic events, hurricanes, or tornadoes should assume that offsite power is not available and that the above ground fuel oil tank has failed. Note that it is not necessary to assume a single active failure while in the TS LCO. (Other criteria as reviewed and approved by the staff for use at Surry may be used, as applicable.)
As stated on page 3 of Attachment 1 to letter Serial No.02-561, Surry TS 3.16.A.1 currently requires a minimum onsite supply of 35,000 gallons of fuel oil. The TS 3.16 Basis states a minimum of 35,000 gallons of fuel oil is contained in the buried fuel oil storage tanks and is required for a seven day supply of fuel oil for full load operation of one EDG. The proposed TS change does not assume that only 17,500 gallons of fuel oil is available since it is recognized that 17,500 gallons of fuel oil is only one-half of the amount of fuel oil currently required by TS.
The proposed TS change requires a) > 17,500 gallons in the remaining buried fuel oil tank, b) 50,000 gallons of replacement fuel available offsite and deliverable within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, and c) > 50,000 gallons in the above ground fuel oil storage tank. Verification of the offsite replacement fuel supply is required should the above ground tank become inoperable.
Page 2 of 13
These requirements will ensure at least 67,500 gallons of fuel oil, which results in greater availability of fuel oil than with both buried fuel oil tanks in service.
The requirements in the proposed TS change request continue to support the existing requirement for full load operation of one diesel generator for seven days (i.e., a minimum of 35,000 gallons).
In addition and not addressed in our TS change request, an additional fuel oil supply is available at Dominion's Gravel Neck Combustion Turbine Facility, located adjacent to Surry Power Station.
Gravel Neck has three above ground storage tanks with a capacity of 6,340,000 gallons, normally containing approximately 3,000,000 gallons of fuel oil. Related to the Surry Hurricane Response Plan, measures are in place to obtain back-up fuel from Gravel Neck for Surry using the on-site 1200-gallon station tanker truck. In the very unlikely event that the above ground tank and the offsite replacement fuel supply would not be available with one buried fuel oil tank out of service, these measures would be initiated to obtain fuel from Gravel Neck.
We will ensure that provisions to obtain fuel from Gravel Neck using the station tanker truck are verified prior to a buried fuel oil tank being removed from service.
The events of particular interest for this discussion are a Loss of Offsite Power (LOOP),
an earthquake, a severe weather event, a Loss of Coolant Accident (LOCA), and each of the latter three in conjunction with a LOOP.
As discussed in the following paragraphs, the likelihood of these events is negligibly small based either 1) on the low frequency of the event or 2) in view of restrictions that will be in place prior to removing a buried fuel oil tank from service.
- LOOP - A LOOP event is a low frequency event since Surry is a middle-of-the-grid plant and has a 30-year history of no sustained LOOP events.
Refer to the responses to Questions 8b and 9 for a detailed discussion of this event.
- Earthquake - The probability of a severe seismic event at Surry is extremely low.
The Surry Individual Plant Examination of External Events (IPEEE) -
Seismic Summary Report was submitted by letter Serial No.97-665, dated November 26,1997, and estimated the seismic event frequency at 1.5E-5/year. The expected frequency of the unavailability of a single buried fuel oil tank is also low.
As discussed in the response to Question 9, the frequency is estimated at less than 0.004. Therefore, the frequency of a seismic event concurrent with a single tank outage is 6E-8/year; which is negligibly small.
Severe Weather Event -
Severe weather events of concern are hurricanes, tornadoes, and severe winter weather (snow and/or ice storms), each of which are briefly discussed as follows:
Due to the nature of a hurricane's development, there is advance warning of a hurricane's approach toward the mid-Atlantic states. Under these circumstances, a buried fuel oil tank would not be taken out of service or could be returned to service as discussed in the response to Question 4.
In this area, tornadoes are typically associated with major weather fronts with severe thunderstorms that can spawn tornadoes. In this case also, there would be advance notice of the approach of impending weather, and again a buried fuel oil tank would not be taken out of service or could be returned to service.
Page 3 of 13
Similarly, there would be advance warning of severe winter weather (snow and/or ice storms), and a buried fuel oil tank would not be taken out of service or could be returned to service.
LOCA - As currently modeled, the estimated event frequency for a LOCA is 4.5E-6/year.
The frequency of a LOCA concurrent with a single tank outage is 1.8E-8/year, which is negligibly small.
In light of these considerations and the likelihood of the occurrence of these events, the provisions in our proposed TS change request will ensure the availability of at least 67,500 gallons of fuel oil and support the removal of a buried fuel oil tank from service for inspection/repair.
- 4. Considering the various hazards that could result in a loss of offsite power situation (grid loading/stability, maintenance, external events, etc,), discuss measures that will be implemented to minimize the likelihood that offsite power will be lost while one of the buried fuel oil storage tanks is removed from service for inspection and repairs.
Surry's 10 CFR 50.65(a)(4) compliance program requires analysis and management of planned maintenance configuration risk prior to entering the maintenance configuration.
The Surry (a)(4) program fully satisfies the recommendations of Regulatory Guide (RG) 1.177 Tier 3. RG 1.177 Section 2.3 states that "The licensee should develop a program that ensures that the risk impact of out-of-service equipment is appropriately evaluated prior to performing any maintenance activity. A viable program would be one that is able to uncover risk-significant plant equipment outage configurations in a timely manner during normal plant operation." RG 1.177 also refers to the Tier 3 program as a Configuration Risk Management Program.
The Surry (a)(4) program performs full probabilistic risk assessment (PRA) analyses of planned maintenance configurations in advance.
Configurations that approach or exceed the NUMARC 93-01 risk limits (1.OE-6 for core damage probability, CDP) are avoided or addressed by compensatory measures.
(Historically, Surry rarely approaches this limit.)
Emergent configurations are identified and analyzed by the on-shift staff for prompt determination of whether risk management actions are needed.
The configuration analysis and risk management processes are fully proceduralized in compliance with the requirements of (a)(4).
The Surry (a)(4) program requires analysis and management of configuration risks. The buried fuel oil storage tanks are included in the (a)(4) scope, and their removal from service will be monitored, analyzed, and managed. In addition, possible LOOP hazards (grid loading/stability, switchyard or other electrical maintenance, external events such as severe weather) are modeled and explicitly accounted for in the (a)(4) program.
When a configuration approaches the (a)(4) risk limits, plant procedures direct the implementation of risk management actions in compliance with the regulation. If the configuration is planned, these steps must be taken in advance.
Page 4 of 13
Individually, a single out-of-;service buried fuel oil tank does not approach the required risk management thresholds of the (a)(4) regulation. While combinations of unavailable equipment and/or evolutions, including an out-of-service buried fuel oil tank, may approach the limits and even require risk management actions, the risks arising from these configurations will be dominated by factors other than the buried fuel oil tank. As a result, the risk significance of unavailability of a buried fuel oil tank does not warrant limitations upon other equipment.
Despite this conclusion regarding the risk significance of unavailability of a buried fuel oil tank, planning and scheduling documentation associated with removal of a buried fuel oil tank from service will specifically identify the following restrictions/contingency measures:
- A buried fuel oil tank will not be taken out of service with a severe weather forecast for this area.
- Station switchyard activities and other electrical maintenance that could cause any unstable offsite or on-site power conditions will not be scheduled while a buried fuel oil tank is out of service.
- The Alternate AC Diesel Generator will be operable prior to removing a buried fuel oil tank from service.
- Provisions to obtain fuel from the Gravel Neck facility using the station tanker truck will be verified prior to removing a buried fuel oil tank from service.
These contingency measures are in addition to the actions required by the proposed TS regarding fuel oil availability.
As previously discussed in our TS change request submittal, in the event that EDG operation is required while a buried fuel oil tank is out of service, work on the out-of-service tank will be stopped or completed as appropriate to return the tank to service in an expeditious manner. In order to return the tank to service, completion of the following activities would be required: 1) suspension of cleaning/inspection/repair activities, 2) flushing of cleaning residue and of the tank, 3) removal of pipe plugs/ladders/equipment, evacuation of personnel, 4) completion of a foreign material exclusion inspection, and 5) gravity fill of the buried fuel oil tank. It is anticipated that the out-of-service buried fuel oil tank could be refilled and available within twelve hours.
- 5. Describe how the fuel oil supply system typically fails, how often, and how often it should be inspected, as well as what is involved in the inspections and typical repairs.
The fuel oil supply system for the EDGs has been very reliable.
A review of the maintenance history for the fuel oil supply system was conducted for the last ten years.
Our review identified the following:
Page 5 of 13
No buried fuel oil tank failures have occurred.
- In the 1994 time frame, the fuel line associated with fuel transfer pump 1 E developed a leak. The long-term corrective action was to abandon the schedule 80 carbon steel lines in place and replace them with six new schedule 160 carbon steel lines. This fuel line replacement activity was implemented using the design change process.
There have been no transfer pump operational demand failures. Our review identified ten corrective maintenance activities resulting from test demands on the fuel transfer pumps; these corrective maintenance activities addressed the following conditions:
Four occurrences of low flow in the alert range, Four occurrences of high vibration, One occurrence of low discharge pressure, and One occurrence of the motor/pump not starting due to a blown control fuse.
The following tests and inspections are conducted:
- System tests are performed monthly for flow and quarterly for performance and operability.
Preventive maintenance to inspect the suction strainers and transfer pumps is conducted on a 96-week frequency.
Preventive maintenance to replace the flow element is performed on an annual frequency.
- System walkdowns, including fuel oil level checks in tanks supplying the EDGs, are conducted once per shift by Operations.
- 6. Discuss, and if appropriate estimate, the risk of fire associated with the proposed change. During the February 26, 2003 conference call, the NRC asked about the safety/risk associated with the planned maintenance.
The buried fuel oil tanks are constructed of uncoated carbon steel. Each tank measures approximately 10 feet in diameter and approximately 35 feet in length. The 10-year inspection of the buried fuel oil tanks will include the following activities:
- The buried fuel oil tank will be drained.
- The interior of the tank will be cleaned and dried.
- The interior of the tank will be repaired if necessary. Based on buried fuel oil tank inspections that have been performed at Surry and North Anna, it is anticipated that minor sludge accumulation on the tank bottom and minor surface corrosion on the tank walls may be seen, neither of which would necessitate a major repair effort.
- Equipment, ladders, and pipe plugs will be removed.
- Personnel will be evacuated.
- The foreign material exclusion closeout will be performed.
Page 6 of 13
These activities will be conducted in accordance with station procedures addressing personnel safety including confined entry, material control, foreign material exclusion control, control of combustibles, etc. Consequently, these considerations will minimize the risk of fire and other safety concerns during tank inspection activities.
Regarding the risk of fire from a probabilistic risk assessment perspective, in the original IPE analysis (submitted by letter Serial No. 91-134A, dated August 30, 1991), fire risk was quantified at 6.3E-6, which is only 8.5% of the IPE internal events plant risk (7.4E-5/year). Fire risk was quantified for the Emergency Switchgear Room, the Normal Switchgear Room, the Cable Vault and Tunnel, and the Main Control Room. None of these areas has a significant dependence upon the buried fuel oil storage tank. The fire risk did not credit the MC diesel generator, which had not been installed at that time.
An updated risk analysis would yield a significantly lower risk for the current plant configuration. At least an order of magnitude reduction is likely for fire risk due to EDG failures, including fuel supply failure.
The fire risk was not specifically revisited in support of this TS change request, but the impact of the proposed change is expected to be proportionally low.
- 7. Discuss the industry peer review findings concerning the Surry Probabilistic Risk Assessment (PRA) and how the sensitivity calculations summarized in Tables 3, 4, and 5 address them.
The industry peer review findings and observations (F&Os) were individually reviewed for applicability to the proposed TS change request. Of the 23 F&Os, 12 have already been addressed by model or programmatic changes, eight do not pertain to the electrical power system, two were evaluated as inconsequential, and one human error issue was addressed by a sensitivity case in the change request package. The review is summarized in the attached Appendix A.
The human error event probability (HEP) sensitivity in Table 3 of our TS change request submittal was performed to address F&O HR-5 (see Appendix A).
The other sensitivities in the submittal package were performed to demonstrate that the conclusions remain valid even while accounting for uncertainty in the fuel oil transfer pump failure rate, uncertainty in the LOOP frequency, and the possibility of common cause degradation of both buried fuel oil tanks.
Page 7 of 13
- 8. To verify that Regulatory Guide 1.174 guidance criteria are met, please provide the following:
- a. The current average best estimate core damage frequency (CDF) and large early release frequency (LERF) for Unit 1 or 2, which ever is greater (based on the current unavailability for the buried tanks); and Table 2 in Attachment 1 of our TS change request submittal lists the baseline CDF and LERF as 2.97E-5/year and 8.36E-7/year, respectively, for the average maintenance model with no tank unavailability included. These values would not be impacted if the current unavailability was accounted for, as discussed in the response to Question 8.b.
- b. The projected average best estimate CDF and LERF for Unit 1 or 2 (based on the projected unavailability for the buried tanks on implementation of the proposed TS change and anticipated plant operations).
The calculated average maintenance CDF and LERF, accounting for a 7-day outage of each buried fuel oil storage tank once every ten years, is unchanged from the baseline values.
This sensitivity falls below roundoff error for the following reasons. First, the LOOP frequency is low at Surry, based upon the historical reliability of offsite power for a middle-of-the-grid plant. Second, the duration of LOOP events is low. A review of the historical database shows that approximately 97% of LOOP events are recovered within the time required to drain a day tank and the first buried fuel oil tank, so the likelihood of use for the second buried fuel oil tank is very low. Third, when one buried fuel oil tank is removed from service, the failure rate for the remaining, in-service tank is very low.
Fourth, the tanks will be scheduled for inspection only once every ten years, so that the average annual unavailability is very small.
Each of these factors independently contributes to the limited CDF impact of the proposed TS change. The model takes no credit for the above ground or offsite fuel sources.
- 9. As a bounding case for evaluation of risk significant plant configurations, provide an estimate of the conditional CDF and LERF given a loss of offsite power event during a buried fuel oil storage tank maintenance allowed outage time.
The Conditional Core Damage Probability (CCDP) for a LOOP is 5.OE-5 with one buried fuel oil tank out of service. The corresponding Conditional Large Early Release Probability (CLERP) is 6.4E-8.
Page 8 of 13
The PRA model does not address the issue of a LOOP and the corresponding dual-unit drain upon available fuel oil. This factor was screened out for the following reasons.
First, the LOOP frequency is low. A value of 0.0268/year is used in the model. This number is a conservatively high estimate for a middle-of-the-grid plant like Surry with an actual 30-year history of no sustained LOOP events.
Second, most LOOP events
(-57%) are recovered within one hour (i.e., the minimum time to drain an EDG day tank). By the time a single buried fuel oil tank is drained by the dual-unit loads, the industry database shows that approximately 97% of LOOP events are recovered. The LOOP subset of concern is thus only -3% of the 0.0268 frequency.
Much of the remaining 3% must be addressed by alternate fuel sources (the above ground storage tank, the offsite replacement fuel supply, or the Gravel Neck tanks) whether only one buried fuel oil tank is available, or two are available. Next, the estimated exposure time of the proposed allowed outage time is also small; seven days per tank, once every ten years, yields an exposure fraction of 0.004. The combined effect is a negligibly small probability of a LOOP requiring the use of the second buried fuel oil tank, while it is unavailable. The CDF impact is several orders of magnitude smaller.
While the above ground and offsite fuel oil sources are potentially vulnerable to a common cause failure during a seismic or weather-related event, the probability of such a common cause failure is negligibly low, as discussed in the response to Question 3.
The likelihood of such a common cause failure, concurrent with the rare outage of a single buried fuel oil tank, is negligibly small.
- 10. Regarding the operability of the fuel oil system:
- a. Why do the new TS requirements call for verification of greater than or equal to only 67,500 gallons of fuel oil in the combined volumes of the above ground fuel tank and the available buried fuel tank (which have a net capacity of 230,000 gallons) prior to removing a tank from service, when 70,000 gallons minimum is required to operate two diesels for 7 days?
As discussed during the February 26, 2003 conference call with the NRC, the response to Question 3 also addresses Question 1 O.a.
- b. Does Surry plan to verify the operability of the fuel pumps of the available buried fuel tank before removing the other tank for maintenance?
Transfer pump operability will be verified prior to removing a buried fuel oil storage tank from service.
Page 9 of 13
Appendix A "A" and "B" Level Findings & Observations Surry PRA Model PEER Assessment Applicability to Buried Fuel Oil Tank Inspection TS Change Request Element F&O Level of Description Impact on Application Significance AS - Accident AS-2 B
No process is in place to identify and incorporate plant None. Although a formal process was not seen Sequence Dev changes into the PRA model.
by the Certification Team, the SOA update did review plant changes since the previous update.
AS-8 B
The RCP Seal LOCA model does not include a None: This was included in a recent update.
contribution from early seal failure DA - Data Analysis DA-6 B
The models for the EDGs do not consider common None. Adding the probability of common cause cause miscalibration of instrument channels miscalibration to the EDG system would raise the baseline CDF/LERF and the CDF/LERF from this calculation by the same amount, so the change (delta) of each would be the same.
DA-8 B
The approach used for defining common cause failure None. This was included in a recent update. As (CCF) terms, by adding fail to start and fail to run data for FOTP common cause added in this variables can lead to conservative or non-conservative application, the FOTP CCFs created for this results.
analysis separate the start and run values.
DA-9 B
The beta factor used for CCF of valve plugging may None.
This was fixed in a recent update.
In be too conservative.
addition, similar to DA-6, any changes to the CCF terms that do not appear in cutsets with the tank testing and maintenance term would not change the delta CDF/LERF reported in this analysis.
DE - Dependency DE-3 B
The methods used to determine CCF groups is None. Addressed by a recent update.
simplistic, and other CCF terms should be considered.
Page 10 of 13
Appendix A "A" and "B" Level Findings & Observations Surry PRA Model PEER Assessment Applicability to Buried Fuel Oil Tank Inspection TS Change Request Element F&O Level of Description Impact on Application Significance HR - Human HR-2 B
The Surry IPE did not include and human errors None.
Potentially risk significant calibration Reliability related to instrument miscalibration, or CCF due to errors will only occur in the RPS and ESFAS miscalibration systems. There are no applicable miscalibration faults for the buried fuel oil tanks.
HR-4 B
HEPs in post-IPE updates were not well documented, None: Addressed by a recent update.
and need to be evaluated in detail.
HR-5 B
The evaluation of dependencies between operator None: The HEP sensitivity case adequately actions focused too much on time between actions addresses this observation.
and not enough on different clues being present and additional crews evaluating the situation.
IE - Initiating IE-3 B
Initiating Event frequencies have not been updated None: Addressed by a recent update.
Events since the IPE.
IE-4 B
The Surry charging line connection to the RCS needs None - not related to EDG fuel oil storage tank to be evaluated for a potential failure mechanism that portion of the PRA model.
a small break LOCA event at Oconee.
IE-5 B
The Surry ISLOCA analysis needs to be reviewed for None - not related to EDG fuel oil storage tank the potential pathway from a leak in the RCP thermal portion of the PRA model.
barrier heat exchanger and a failure to isolate the CCW lines to the heat exchanger IE-8 B
The potential for an initiating event due to None - not related to EDG fuel oil storage tank failure/clogging of the screen wash system portion of the PRA model.
IE-9 B
Need to ensure that the effects of increased core None - not related to EDG fuel oil storage tank power (upgrade to 2586 MWt since the IPE) have portion of the PRA model (EDG oil requirement been properly accounted for in the PRA analysis unaffected by power uprate).
Page 11 of 13
Appendix A "A" and "B" Level Findings & Observations Surry PRA Model PEER Assessment Applicability to Buried Fuel Oil Tank Inspection TS Change Request Element F&O Level of Description Impact on Application Significance L2 - Cont Perf L2-2 B
The Level 2 analysis needs to be updated to consider None: Current LERF model is conservative.
Analysis the effects of the SAMGs.
MU - Maint &
MU-2 B
The PRA model needs to be evaluated for effects of None - not related to EDG fuel oil storage tank Update the power ugrade.
portion of the PRA model (EDG oil requirement unaffected by power uprate).
MU-3 B
The requirements for review of operating experience, None. Although a formal process was not seen plant procedures and plant-controlled documents in by the Certification team, the SOA update did support of a PSA update are not detailed in the PSA review plant changes since the previous update.
guidance documents.
MU-4 B
Activities to evaluate the effects on the PSA of None: Addressed by a recent update.
changes to equipment failure
- rates, initiator frequencies, and human error probabilities are minimal, and should be reevaluated each major PSA update.
SY - Systems SY-2 B
The program does not appear to have a formal None: The plant design changes were reviewed Analysis requirement for incorporating plant design changes.
in a recent update.
The programmatic issue does not affect this analysis file.
SY-4 B
The RPS model does not properly identify the required None: Addressed by a recent update.
support systems.
SY-5 B
The RPS logic model is incorrect.
The fault tree None: Addressed by a recent update.
indicates that success of either logic train allows challenge to both reactor trip breakers. Actual design is logic train A sends a signal to RTA and logic train B sends a signal to RTB.
Page 12 of 13
Appendix A "A" and "B" Level Findings & Observations Surry PRA Model PEER Assessment Applicability to Buried Fuel Oil Tank Inspection TS Change Request Element F&O Level of Description Impact on Application Significance SY-1 1 B
The system notebook for HHSI does not discuss Unit None:
Any differences in the HHSI system 1/Unit 2 differences, and the dependency table was between units would not impact the delta not up to date.
CDF/LERF calculations in this analysis file. Any such differences would not be within cutsets containing tank unavailability.
TH - Thermal TH-2 B
The presentation of assumptions related to room None:
From the F&O itself, the assumptions Hydraulic Analysis cooling of systems other than ESGR and the Aux Bldg appear
- valid, but simply were not well Ventilation System is not well documented, although it documented in the documents reviewed by the appears that they were adequately addressed in the Certification Team.
In any
- case, such modeling process.
differences would not affect the delta CDF/LERF within this analysis file.
Page 13 of 13