IR 05000244/1991201
| ML17265A527 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 01/29/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17265A526 | List: |
| References | |
| 50-244-91-201, NUDOCS 9902030187 | |
| Download: ML17265A527 (13) | |
Text
(I1.AR REGS
~o Cy A,0
~ g
+)t*++
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&0001 SAFETY EVALUATIONFOR ACTION ITEMS IDENTIFIED IN INSPECTION REPORT 50-244/91-201 RELATINGTO SERVICE WATER SYSTEM BYTHE OFFICE OF NUCLEAR REACTOR REGULATION ROCHESTER GAS AND ELECTRIC CORPORATION R.E. GINNA NUCLEAR POWER PLANT DOCKET NO. 50-244
'I.O INTRODUCTION The service water (SW) system operational performance inspection (SWSOPI) was conducted from December 2 through 20, 1991, at the Ginna Nuclear Power Plant (GNPP). The findings were reported in Inspection Report 50-244/91-201, dated January 30, 1992. Several outstanding actions were Identified in the inspection report for which additional licensee review and corrective actions were judged to be necessary to assure the continued functionality of the service water system.
These action items are as follows:
1.
2.
3.
4.
5.
6.
Application of hydraulic model to the service water system (SWS)
SW pump discharge check valve single failure vulnerability Basis for the SWS low pressure setpoint Single failure vulnerabilities with open cross-connect valves Resolution of preoperational test discrepancies Technical Specification requirements for operable pumps The licensee submitted its response in a letter dated April6, 1992. The staff found that each of the outstanding issues was addressed and there were no immediate safety concern.
However, the action items required further review; in particular, the item regarding the number of pumps required for post-loss-of-coolant-accident (LOCA) recirculation phase.
An additional item was identified during the review. This item is as follows:
7.
Licensing basis for cross-connection valves and isolation valves.
The licensee submitted additional information between April9, 1992, and November 4, 1998, in response to the action items.
2.0 BACKGROUND The SWS at GNPP is an open loop system that takes suction from Lake Ontario via a screen house and supplies cooling water to various turbine plant loads and auxiliary reactor plant loads.
The SWS discharges back to Lake Ontario via the plant discharge canal. The SWS
- 9902030i87 890i29.',':
', ',~,;
PDR ADOCK 05000244.,
P
'DR'
Enclosure
a 4I (4/~'it j 'I imp f I
W'
-2-contains four pumps, each with a rated fiowof 5300 gpm. Allportions of the SWS serving safety-related equipment are seismic Category I. Allnon-seismic portions of the systems serve non-safety-related loads and can be isolated from the safety-related portion of the system.
The current licensing basis states that the plant loads require two or three SW pumps for normal full operation, one SW pump during the post-LOCA injection phase and two SW pumps during the post-LOCA recirculation phase.
The SWS provides cooling water to two diesel generator lubricating oil and jacket water cooler sets, three safety injection pump thrust bearings, four containment area coolers, the safety-related pump motor room coolers (residual heat removal, charging, and safety injection), two reactor compartment coolers, two spent fuel pool heat exchangers, two component cooling water (CCW) heat exchangers, and other loads that are non-safety-related.
Many modifications to the SW system have been performed at Ginna since the initial NRC finding in 1991. These modifications include the replacement of the original containment recirculation fan coolers (CRFCs), retubing of the emergency diesel generator (EDG) coolers, replacement of the SW pump motors, replacement of the CRFC fan motor coolers, replacement/refurbishment of the SW system motor-operated valves and replacement of various piping. The licensee is also in the process of replacing the SW pump bronze impellers with stainless steel impellers.
In support of this activity, the licensee conducted tests to confirm the performance of the SW pumps under runout conditions in August and October 1998. The results of this testing were provided to the staff to support the analysis for one pump operation.
Because of these modifications, the licensee has re-performed the SW system flowanalyses for the two limiting cases for one pump operation.
The results were provided in the licensee's RAI responses in the submittal dated November 4, 1998.
3.0 EVALUATION The licensee submitted assessments and corrective actions regarding the action items on January 31, April6, July 2, and,September 1, 1992. The staff continued its review and asked for additional information, which was supplied by the licensee on July 27, 1993; March 30,1994; September 21, 1995; and November 4, 1998. The staff also met with the licensee in June 1995 to discuss the open issues.
The open items and the staff's findings are as follows:
1.
Application of hydraulic model to the SWS This was categorized as Unresolved Item No. 91-201-02.
The item identified the limitation with the SWS hydraulic model that only a limited amount of actual plant data was used to verify the flow resistance.
The licensee enhanced the capability of the hydraulic model and rebalanced the SW flow. The licensee performed a thorough review and validation of the SWS flowmodel to ensure it accurately models system flow. The staff has reviewed the licensee's actions and finds the upgrades to the computer model acceptabl JL W
I
V
~
-3-2.
SW pump discharge check valve, single failure vulnerability This was categorized as Unresolved Item No. 91-201-07.
The item identified that a failure of the discharge check valve for one of the SW pumps may prevent the performance of the SWS safety function during a safety injection (Sl). The licensee agreed that the check valve failure scenario was identified but not fullyanalyzed in the single failure report (Altran Report 90121.6, Rev. 1). The licensee considers the failure of a check valve to be outside their design basis and provided the rationale that the
scenario in question was a passive failure and was not required to be treated as an active failure. Further, the licensee demonstrated that the scenario in question was bounded by the single active failure of a diesel generator, where the design flowof only one SW pump would be available. The staff has reviewed the licensee's evaluation and finds the evaluation acceptable.
3.
Basis for the SWS low pressure setpoint t
This was categorized as Unresolved Item No. 91-201-12.
The item identified that sufficient engineering basis did not exist for the 40 psig setpoint for the header pressure in the abnormal procedure for SW. The concern was that the SWS low pressure setpoint was not sufficiently high to indicate the potential inability ofthe SWS to perform its design function. The licensee agreed with the inspection team that the basis was not formally documented.
The licensee provided its rationale for the setpoint and committed to document the basis as a corrective action. The staff has reviewed the licensee response and actions and finds they are acceptable.
Single failure vulnerabilities with open cross-connect valves This was categorized as part of Unresolved Item No. 91-201-07.
The concern was that a pipe break with cross-connected valves may result in the failure to satisfy the SWS design function due to flow diversion. The licensee determined that a SWS pipe break coincident with a design-basis accident is outside Ginna's design basis.
The licensee has evaluated system leakage cracks for flooding and found operation of the SWS to be acceptable.
The staff has reviewed the licensee's evaluation.
The staff finds that it is consistent with the applicable guidance of the AuxiliarySystems (Plant Systems)
Branch Technical Position 3-1 and is acceptable.
Resolution of preoperational test discrepancies This was categorized as Deficiency No. 91-201-14. The concern was that preoperational testing and flowbalancing was not performed using limiting system configurations.
The licensee's position is that flowbalancing for non-safety-related loads was performed using three SW pumps.
Flow balancing for critical loads cooled following a design basis event was performed with a single SW pump operating.
The licensee has procedural guidance to control CCW heat exchanger flowfor shutdown conditions and the post-LOCA recirculation phase.
The staff has reviewed the information and finds the licensee's flow balancing procedures acceptabl.
Technical Specification (TS) requirements for operable pumps This was categorized as Deficiency No. 91-201-08.
The concern was that a discrepancy existed between the SWS TS and the licensing basis.
The existing TS required that two of the four SW pumps be operable.
However, the design basis, as stated in the updated final safety analysis report (UFSAR), was that two SW pumps are needed for sufficient flowduring the post-LOCA recirculation phase.
Thus, given a single failure, the TS was insufficient to ensure adequate SW flowwould be provided when required.
As an interim measure while the NRC continued to evaluate the licensee's analyses supporting the use of only one SW pump during the recirculation phase, the licensee, by letter dated April6, 1992, implemented compensatory measures in the Ginna administrative controls. These measures require operability of three SW pumps (while
.the reactor is at power) and provisions to utilize the bus tie breaker between 480-v safeguards ac buses 17 and 18 during the recirculation phase post-LOCA in order to provide power to two SW pumps from a single diesel generator.
The administrative controls requires that ifat least three SW pumps are not restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, then place the plant in hot shutdown within a completion time of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shutdown within a completion time of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
The licensee proposed to amend its licensing basis by demonstrating that only one SW pump is required under any scenario.
The licensee determined that the limiting scenarios for one SW pump were: (1) post-LOCA recirculation phase, and (2) a loss of offsite power (LOOP) without an Sl initiation.
Post-LOCA Recirculation Phase Currently, the UFSAR requires two SW pumps to be operable during the post-LOCA recirculation phase.
The UFSAR analysis assumes a LOCA, LOOP, and a failure of an EDG supporting two of the three operating SWS pumps.
This scenario is not the bounding case for maximum pump flowfor one SW pump operation.
However, it is a concern due to the below normal flowrates to the required equipment, such as CRFCs, CCW heat exchangers, and EDGs. To evaluate this scenario, the licensee performed flow balancing and component cooling evaluation.
Conservative conditions for minimum cooling such as piping resistance from 40 years of water exposure, maximum degraded in service inspection (ISI) pump performance, minimum lake level, and a maximum lake temperature of 85 'F were used in the analyses.
I The licensee determined the most limiting containment conditions would occur with the loss of an EDG. Due to the reduced cooling flow, heat removal from containment via the CRFCs and the CCW heat exchangers (which cools the residual heat removal system) is decreased.
The licensee evaluated these 'components to determine ifthey would be able to maintain containment temperature and pressure within the Ginna
. equipment qualification (EQ) profile. In the November 4, 1998, submittal, the licensee
-5-re-analyzed the design-basis LOCA with reduced SW cooling and compared the long term containment pressure and temperature to the Ginna EQ profile. With the reduced cooling flow, the licensee determined that the containment temperature and pressure would take longer to decrease but remained below the EQ profile.
For the reduced cooling flowto other equipment, the licensee evaluated the required heat loads during the post-LOCA recirculation phase.
The actual loads on the EDGs were used, which would be less than fullyloaded, and therefore heat rejected to the coolers would be reduced.
However, the licensee conservatively assumed cooling flow to both EDGs. The licensee's analysis used flowrates of 242 gpm and 162 gpm to the EDGs, and 1425 kW loading for the operating EDG. Since only one SW pump would be in operation, the licensee would re-establish flowto only one CCW heat exchanger.
The licensee concluded that SW flowis sufficient to maintain EDG cooling. Inadequate SW cooling flowwould be detected by alarms for low SW system pressure and high EDG temperature.
The licensee stated that all necessary valves that require local manipulation or verification are in accessible areas during the post-LOCA recirculation phase.
The operator actions necessary to transfer from injection phase to the recirculation phase of a LOCA are controlled in Emergency Procedure ES-1.3.
LOOP without an Sl initiation A LOOP without an Sl initiation results in the maximum demand for SW flow because the non-safety-related SW loads would not be automatically isolated.
This case is a concern due to a possible pump operability problem and runout damage, and the below normal SW flow rate for diesel generator cooling. To evaluate this scenario, the licensee performed a flow balancing and component cooling evaluation.
Conservative conditions such as the maximum degraded ISI pump performance, minimum lake level, and a maximum lake temperature of 85 'F were used in the analysis.
Since the ECCS components would not automatically start, the actual EDG loading for this scenario are-less than the design-basis'LOCA loading.
The licensee expects that the near runout conditions may last 10-20 minutes before operator actions could isolate non-essential SW loads. As discussed previously, the licensee is replacing the SW pump bronze impellers with stainless steel impellers. The new and old impeller assemblies were tested by the vendor in August and October 1998. The tests determined the pump can operate at runout conditions of 7600-7700 gpm for at least 30 minutes without pump operation degradation.
The licensee analyzed the SW flowdistribution for this scenario with a SW flowrate of 7055 gpm. The essential component in this case is the EDG coolers.
The licensee assumed both EDGs received cooling flow. In the analysis, the SW flow rates. were approximately 94 and 157 gpm to the EDGs, which is well below the 320 gpm design flow rate. This flow rate is lower than the post-LOCA recirculation phase flow rate because the non-safety-related loads are not automatically isolated.
The licensee maximized the SW flowto the non-safety-related components by assuming the flow
-6-from three SW pumps existed prior to the LOOP. In this configuration with a large supply of cooling water, no valves would need to be throttled for flowconservation.
The low flowrate would not be sufficient to cool the EDG cooler ifthe generator was fullyloaded.
However, in a LOOP, the generators support fewer loads. To demonstrate the low flow rate was sufficient for a LOOP condition, the licensee used the actual loads on the EDG that are needed to maintain the plant in hot shutdown.
The licensee, with vendor information, determined that the lower SW demand would maintain the EDG coolers below the maximum operating temperature.
Based on the two bounding scenarios, the licensee concluded that adequate cooling would be supplied to the necessary equipment with one SW pump operating and that one pump was capable of supplying the necessary flowwithout damage to the pump.
The staff has reviewed the licensee's evaluations and responses and finds they are acceptable.
7.
Licensing Basis for Cross-connect Valves and Isolation Valves During its review, the staff identified a discrepancy between the description of the SWS in the UFSAR and the SWS configuration in the plant. The UFSAR described the SWS as normally split into two separate headers and isolated from non-safety-related loads following a Sl signal. This description was not correct for the operating condition on the Ginna SWS at the time. The licensee concurred that the UFSAR description did not reflect the operating configuration of the SWS.
However, the licensee has tested with the cross-connection open and determined that this operating condition improved SWS flow balancing.
The licensee also determined that operation in this configuration did not create an additional system failure within the design basis.
The staff has reviewed the licensee's evaluation and finds it acceptable.
4.0 CONCLUSION Based on the review above, the staff finds that the licensee has adequately addressed the six action items from IR 50-244/91-201 and the additional review item. Further, the staff finds that the operation of one SW system is acceptable for post-LOCA recirculation phase.
Thus, the licensee can now remove the administrative controls that required operability of three SW pumps and the provisions to utilize the bus tie breaker between 480-v safeguards ac buses 17 and 18 during the recirculation phase post-LOCA in order to provide power to two SW pumps from a single diesel generator.
Principal Contributor. D. Jackson Date:
0mmpy p)
)ggg
CHRONOLOGY Letter dated November 4, 1998, from Robert Mecredy of Rochester Gas and Electric to NRC,
"Response to Request for Additional Information (RAI) Related to the Effects of One Service Water Pump Available - Post-Loss-of Coolant Accident."
Letter dated June 26, 1998, from NRC to Robert Mecredy of Rochester Gas and Electric,
"Request for Additional Information (RAI) Related to the Analysis to Evaluate the Effects of One Service Water Pump Available - Post-Loss-of-Coolant Accident."
Letter dated September 21, 1995, from Robert Mecredy of Rochester Gas and Electric to NRC, "Response to Request forAdditional Information on Service Water System."
Letter dated March 30, 1994, from Robert Mecredy of Rochester Gas and Electric Corporation to NRC, "Additional Information - Service Water System."
Letter dated November 16, 1993, from NRC to Robert Mecredy of Rochester Gas and Electric, regarding a Request for Additional Information.
Letter dated July 27, 1993, from Robert Mecredy of Rochester Gas and Electric Corporation to NRC, "Additional Information - Service Water System."
Letter dated May 24, 1993, from NRC to Robert Mecredy of Rochester Gas and Electric Corporation, "Request for Additional Information Re: R. E. Ginna Nuclear Power Plant-Service Water System - Rochester Gas & Electric Corporation's Response to Deficiencies Identified in NRC Report 50-244/91-201), January 30, 1992."
Letter dated September 21, 1992, from Robert Mecredy of Rochester Gas and Electric Corporation to NRC, "Response to Additional Questions on Service Water System, R. E.
Ginna Nuclear Power Plant."
Letter dated September 1, 1992, from Robert Mecredy of Rochester Gas and Electric Corporation to NRC, "Service Water System Operational Performance Inspection (SWSOPI),
Response to Deficiency 91-201-08, Inconsistency between Licensing Basis and Technical Specification Operability Requirements."
Letter dated July 2, 1992, from Robert Mecredy, Rochester Gas and Electric Corporation to NRC, "Service Water System Operational Performance Inspection (SWSOPI) - Re-balancing of Flow to Safety-Related Coolers."
C Letter dated May 4, 1992, from Robert E. Smith, Rochester Gas and Electric Corporation, to NRC, "Response to Notice of Violations, NRC Inspection Report 50-244/92-02 (1/19/92-3/9/92), dated, March 26, 1992, R.E. Ginna Nuclear Power Plant."
Letter dated April6, 1992, from Robert Mecredy, Rochester Gas and Electric Corporation to NRC regarding the licensee's 60-day response to the NRC Service Water System Operational Performance Inspection of Ginna.
Letter dated January 30, 1992, from NRC to Robert Mecredy, Rochester Gas and Electric Corporation, "Service Water System Operational Performance Inspection."
-2-Letter dated January 21, 1992, from Robert Mecredy, Rochester Gas and Electric Corporation to NRC, "R.E. Ginna Service Water System Operational Performance Inspection (SWSOPI)
-'e-balancing of Flow to Safety-Related Coolers."
~
'f