IR 05000280/1988027
| ML18152B109 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/12/1988 |
| From: | Bernhard R, Jape F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML18152B108 | List: |
| References | |
| 50-280-88-27, 50-281-88-27, NUDOCS 8808300322 | |
| Download: ML18152B109 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION'
REGION II
101 MARIETTA STREET, ATLANTA, GEORGIA 3032 Report Nos.:
50-280/88-27 and 50-281/88-27 Licensee:
Virginia Electric and Power Company Richmond, VA 23261 Docket Nos.:
50-280 and 50-281 Facility Name:
Surry 1 and 2 License Nos.: DPR-32 and DPR-37 Inspection Conducte9:
July 5-8, 1988 tJ
/
11
1 1 u/77
.
Inspector:
/!.--1._ jlc~(/ { h. IT/) L{-2 8/;2-/&8 Date -Signed R. A. Bernhai'
Approved by:
7;:pzc~ 9 ~
F. Jape, Ch1
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"1,2;n{J'/
Scope:
Results:
Test ProQrams Section Engineering Branch Division of Reactor Safety SUMMARY This routine, unannounced inspection was conducted in the area of design review of the Reactor Building Recirculation Spray Heat Exchangers (RSHX).
The inspection included a review of FSAR design requirements, interviews with the responsible engineering staff and walkdowns of the accessible service water piping to the RSHXs, the RSHX in containment and the intake structures for the circ/service wate In the areas inspected, violations or deviations were not identifie One Unresolved Item (URI) is identified in Section 6.0. It involves the adequacy of the engineering evaluation with respect to the impact of the new RSHXs on the design basis of service water and recirculation spra With the resolution of this URI, the heat exchangers new design and the new plant procedures for insuring the heat exchangers stay dry should resolve the past problems with the RSHX :::eoa:::0032"".)
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REPORT DETAILS Persons Contacted Licensee Employees
- J. A. Bailey, Superintendent of Operations
- D. L. Benson, Station Manager
- C. T. Duonh, ISI Engineer
- E. S. Grecheck, Assistant Station Manager
- R. V. Green, Senior Staff Engineer M. W. Henig, Project Engineer, Power Engineering Services (PES)
- H. L. Miller, Assistant Station Manager R. L. Rasnic, Supervisor, Mechanical Engineering, Nuclear, PES
- D. W. Wong, Senior Engineer Other 1 i censee emp 1 oyees contacted during this inspection included craftsmen, engineers, operators, technicians, and administrative personne NRC Resident Inspector
- L. E. Nicholson
- Attended exit interview Detai 1 s The Reactor Building Recirculation Spray System (RS) at Surry consists of four subsystems, each containing.a pump, piping, a.heat exchanger and spray nozzle The system provides containment heat removal by using the Reactor Building Sump as a suction source, pumping the water through the Recirculation Spray Heat Exchangers (RSHX) whose cooling water is supplied by service water, and spraying the cooled water through spray nozzles inside containmen The RSHX are designed to be in a dry, isolated condition during normal plant operations, on both the RS (shell) and service water (tube) sides of the heat exchange The original RSHX were found to have fouling and corrosion caused by inleakage of service wate The Unit 1 RSHX have been replaced by newly designed titanium tubed heat exchanger Replacement on Unit 2 1s to occur at the next refueling outage, currently scheduled for September 198 This inspection effort reviewed the new heat exchanger replacement effor Engineers from the Power Engineering Services group were interviewed, and quest ions on design of the new heat exchangers were discusse The service water system providing cooling water to the RSHX was walked down, as well as the RSHX, themselve The FSAR was reviewed, and calculations were made to verify design assumption Answers to questions asked by the inspector while at the site were sent to the inspector in the week
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following the onsite portion of the inspectio An in office review of the material was conducte The results of the inspection follo Design Review In order for the new heat exchangers to remove the design heat loads, adequate flow through both the shell and tube side of the exchanger must be availabl The efficiency and heat transfer coefficients of the new exchanger must also be high enough to insure the heat passes from one load to the othe These were the items concentrated on by the inspecto Discussions with two Virginia Power Engineering Services engineers were conducted onsite at the Surry Statio One engineer was the Project Engineer for the Surry faci 1 i ty and the other a supervisor in the Mechani ca 1 Engineering group who was res pons i b 1 e for the engineering evaluation for the heat exchanger replacemen It was established in the discussions that the new RSHX were essentially a newly designed heat exchanger using current Tubular Exchanger Manufacturers Association (TEMA) codes, but mai ntai ni ng the bo 1 t up arrangement, seismic cons i de rat ions and fl ow paths of the o 1 d heat exchanger The replacements have titanium tubes to preclude future corrosion problems if in 1 eakage of service water into the exchangers occur The new
- exchangers were designed for the same total heat removal in btu/hour at rated condition With the new tube material, the tube wall thickness is less than the original tube In addition, the new heat exchanger design has more tubes (1650 vs 1615 tubes).
With the new heat exchanger design, the pressure drops across the heat exchanger at rated conditions a 1 so chang The inspector requested the eva 1 uat ion that considered these changes to determine their effect on system performanc Another factor effecting heat removal is service water flow through the heat exchanger The service water is gravity fed through the heat exchanger It originates in the high 1 eve 1 intake can a 1 maintained by the circulating water and emergency service water pump The water.
gravity flows through the circulating water inlet tunnel, branches off this tunnel, goes through two isolation valves, then into containment, through the RSHX, exits containment, through a single outlet isolation valve, and then joins the circulating water discharge tunne The circulating water discharge tunnel 1s level is not a continuous slope down to the level of the discharge canal, but slopes upward then dow A vacuum priming system is designed to keep the high point from being air boun Without air blocking the discharge tunnel, the water is siphoned to the level of the discharge cana The service water total available head (in feet of water) varies from a maximum of the upper canal level less the lower canal level to a minimum of the upper canal level less eight feet (the height of the floor of the circulation water discharge
4.
canal if vacuum priming is not available).
The nominal level of the discharge canal is roughly sea leve The service water flow rates through the system can be up to 30% greater if vacuum priming is maintaining the circulating water discharge canal free of ai The inspector asked the engineers for an imp act of the priming system operation on system operabilit Fouling of the system piping could cause the system resistance to flow to increas In addition, accumulation of shell debris in stagnant supply lines can cause blockage of heat exchanger tubes when the system is placed in service decreasing heat transfe The licensee was asked to provide
_ information on programs in place to preclude inoperability of the system due to fouling in the stagnant supply line Fouling of water caused by accumulation has been found in the o 1 d heat exchanger The inspector questioned the licensee as to the steps taken to insure the new heat exchangers stay in a dry layup conditio The licensee's answers to the preceding questions and requests for infor-mation were addressed in a memorandum dated July 12, 1988, report and are discussed in Section 6 of this repor System Walkdown The inspector performed a system walkdown of the accessible piping of the service water flowpat The intake structure and moving screens at the high level intake canal were looked at to obtain perspectives on the plant physical layout and areas of potential biofoulin The canal side and the traveling screen wash areas were full of crabs and fish of various sizes indicating presence of marine life in the cana Plant construction drawings were examined to show the placement of the underground piping forming the circulation water intake tunne Inside the plant, accessible piping and valves were examine Layout drawings were used to estimate position of buried piping in the turbine building and yard and the amount of piping that would be subject to flooding in the event of inleakage past the 103 valve The location of the 104 and 105 valves in the safeguards bui 1 ding was examine A containment entry was made to wa 1 kdown the service water piping to and from the RSH The new RHSXs were examine The walkdown showed the inspector that most of the service water piping to the RSHX was inaccessible during normal operation With the exception of the 103 valve pits in the turbine building and the limited piping in the safeguards building around the 104 and 105 valves, the piping outside containment, if inspection was necessary, would be limited to inspecting the inside of the piping by draining and crawling through the pip A walkdown of control room instrumentation and controls for the RSHX service water piping was conducted.* Flow indicators for heat exchanger outlet flows were available in the control room, as well as control and indication for the major valve,..
The walkdown did not reveal any problems that could effect operability of the new RSHX * Documentation Review The FSAR, Technical Specifications and plant drawings for the effected portions of the service water system and RS system were reviewe Technical Specification sections reviewed were 3.4, 4.5, and 3.1 The inspector Is ons i te review of these sections indicated the new heat exchangers would not impact technical specification A review was performed of the following documents:
RSHX Fouling Analysis, Project NP-1020, memorandun dated March 24, 1984, to Kansler from Rasnic
RSHX Fouling Reanalysis, Project NP-511, memorandum dated July 30, 1984, to Kansler from Rasnic Surry 2 Recirculation Spray Heat Exchanger Integrity Evaluation, Final Report, December 1987 Heat Transfer Capability of Surry Unit 2 Reci rcul at ion Spray Heat Exchangers, June 10, 1988 (Technical Report No. ME-0166)
These documents were used to provide a history of the RSHX problems experienced in the past at Surr The following drawings were reviewed:
11448-FM-071A, Rev. 24, Flow Diagram Circulating and Service Water System 11448-FM-0718, Rev. 25, Flow Diagram Circulating and Service Water System 11448-FM-071C, Rev. 26, Flow Diagram Circulating and Service Water System 11448-FM-21C, Rev. 7, Flow Diagram Circulating and Service Water System 11448-ESK-613R, Rev. 11, Elementary Diagram, Motor Operated Valves 11448-ESK-613N2, Rev. 9, Elementary Diagram, Motor Operated Valves 11448-FC-2A, Rev. 4, Foundation Key Plans, Turbine and Service Buildings 11448-FC-2C, Rev. 6, Foundation Details, Turbine Building 11448-FC-5E, Rev. 2, Service Water Lines Encasement 11448-FC-5F, Rev. 1, Service Water Lines Encasement 11448-FP-4A, Rev. 12, Service Water Lines 11448-FP-48, Rev. 9, Service Water Lines 11448-FP-4C, Rev. 7, Service Water Lines 11448-FP-4D, Rev. 11, Service Water Lines In Office Review of Licensee Responses During the inspect ion period, the inspector raised the fo 11 owing question Responses were not available until after the inspection and were, therefore, reviewed in offic **
QUESTION:
RESPONSE:
QUESTION:
RESPONSE:
The fl ow rate of service water through the RSHX Is would be adversely affected by a loss of vacuum priming in the Circulating Water discharge tunne Has this adverse effect on the service water fl ow rate been considered in the accident analyses?
The service water flow rate with the vacuum priming system in operation on the discharge tunnel is about 8000 gpm per RSH If the vacuum priming system is not in operation and the discharge tunnel is not primed, the service water flow rate is about 6000 gpm per RSH The 6000 gpm va 1 ue is used for a 11 design basis accident analyse The new RSHXs which were just installed on Unit 1 and are scheduled for installation in Unit 2 during the September 1988 refueling outage have slightly different pressure losses at design flow rates when compared with the original RSHX' What is the effect of this change on system operation and on system heat transfe The new Unit 1 and Unit 2 RSHX's have a lower pressure drop than the old heat exchangers.. The shell side pressure drop reduced from 6.34 psi to 5.38 psi while the tube side drop went from 1.82 psi to 1.1 ps these reductions in head loss are small when compared with the system head 1 oss and result in sma 11 increases in flow rate (shell side less than 1/2%; tube side less than 3%).
These small increases in flow would improve the heat transfer characteristics slightly, but as a conservative measure, they will not be factored into any accident analysi By the same logic, no redefinition of the system head and flow characteristics is required given the minor but conservative nature of the new value The UoA for the original RSHX's is 3.797 x 106 BTU/hr.~ The UoA utilized for accident analyses for the new RSHX's is also 3.797 x 106 BTU/hr.~ The actual TEMA data sheet UoA for the new RSHX's is 3.989 x 106 BTU/hr.~ All UoA values provided here are calculated using an inside fouling factor of 0.0005 hr. ft.~F/BT QUESTION: Discuss the effect of marine growth in stagnant areas of the service water system on the design flow rate..
- RESPONSE: A review of service water piping diagrams has been performed to identify areas of stagnant flow conditions upstream of the 103/203 inlet isolation valves and downstream of the 105/205 outlet isolation valve The 103/203 A, 8, C & D valves have stagnant piping sections upstream with the following respective lengths:
22 ft. 6 in., 17 ft, 6 ft and 6 f The two return headers downstream of the 105/205 valves each have a wetted stagnant length of about 20 f QUESTION:
The stagnant regions upstream of the inlet isolation valves are regularly dewatered to perform valve maintenance during refueling outage Inspection of these areas has revealed no evidence of any type of marine growth other than that commonly found in the full flowing portions of the service water system, circulating water system and bearing cooling water system (service water side).
Further conclusive evidence exists that there is no marine growth which could obstruct flow in these stagnant areas of the service water syste During the regular periodic testing of the 103/203 valves, these valves are cycled admitting the stagnant water to the piping section between the 103/203 and 104/204 valve This water is then drained from this piping section using 2 inch drain valve No evidence of any flow blockage has been encountered during this draining operatio Some marine growth exists on areas of the pipe wall on portions of the service water system upstream of the 103/203 valves and downstream of the valve This is an expected condition of operation for those sections of pipe and is considered in the design of the syste According to the LeQuie Center for Corrosion Technology, the marine growth attached to the wa 11 s could detach but would dissolve quickly into a fine sediment which would not represent a flow blocking concer The history at Surry for the specific types of marine growth and corrosion products which exist throughout the wetted portions of the circulating water and service water systems shows that these are not flow blocking product This conclusion is base on regular inspections of the bearing cooling, component cooling and condenser tube sheet The piping upstream of the (1)(2) 03 MOVs will be inspected during the 1989-1990 refueling outag Procedures are now in effect to periodically check the inlet piping between the 103 and 104 valves for leakage and to drain leakage that is presen Will the station institute a procedure (i.e., a formal written station procedure) to drain the RSHXs during refueling outages?
this would identify any back-leakage from the 105 valve RESPONSE:
QUESTION:
RESPONSE:
A procedure for draining the service water side of the RSHXs has been develope A copy of the approved Unit 2 procedure is attache This procedure is to be performed at anytime water potentially may have entered the RSHXs through the 104 valves; i.e., following the quarterly stroking of the 103s or if excessive leakage of the 103s is detecte We agree to drain the RSHXs at least once per cycl There have been severa 1 eva 1 uat i ans performed which considered reduced flow, increased fouling, etc. and the resulting effect on containment depressuri zat ion ti m While the containment was still depressurized within a one hour period, did the actua 1 radioactive re 1 ease to the public increase above values stated in the FSAR?
Consistent with TID-14844, the offsite dose calculations assume a constant containment leak rate for the full hou During the one hour time interval, the leak rate from the containment is assumed constant at a rate of 0.1% of the containment volume per da Therefore the caJculated dose to the pub 1 i c wi 11 not be increased as a res u 1 t of the longer depressurization tim In summary, the FSAR calculation yields a significantly greater release to the public than would result from using the depressurization characteristics of either the original RSHX analyses or the revised RSHX analyses with greater fouling and lower flow rate QUESTION: Since no nitrogen purge system or 11dry air 11 system is employed on the shell or tube side of the RSHXs, discuss the fouling factors appropriate for the new RSHX RESPONSE: The RSHXs currently installed in Surry Unit 1 and scheduled to be installed in Unit 2 in September 1988 have Titanium tube During the manufacturing process and prior to actual installation at Surry, an oxide layer was formed on these tube No mechanism has been present s i nee-manufacture and installation which would disturb this original oxide laye The tube and shell side lay-up conditions will not alter the condition of the oxide layer on the tube side or shell side, even though there are no specific measures being taken to reduce the humidity of the air in contact with the tube The design speci fi cat ion has inc 1 uded adequate conservatisms in the' calculation of the overall heat transfer coefficient (including the 0.0005 hr. ft 2°F/BTU assumed inside fouling factor) to correctly account for the oxide layer on both the inside and outside surfaces of the Titanium tube The Titanium tubes are not subject to
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QUESTION:
RESPONSE:
biological fouling, corrosion or scaling in the dry lay-up mode with no humidity contro The station leakage monitoring program on the service water system will ensure that the conservative heat transfer assumptions remain valid for Units 1 and Recently the original RSHXs were removed from Surry Unit Have plans been made to evaluate the "as-found" condition of the old heat exchanger tubes? The shell side and tube side conditions should be note A copy of any report on the "as-found" tube conditions is requeste Plans are underway to pull several tubes and submit them to an independent laboratory for evaluatio the RSHXs are now being decontaminated and negotiations are proceeding to contract an organization for this "as-found" tube evaluatio When this evaluation has been completed, a copy of the results can be provided for your informatio Calculations performed by the inspector, based upon the supplied material, did not agree with the assumptions made in all the response In addition the 10 CFR 50.59 evaluation attached did not consider all the implications of the RSHX changeou The licensee was contacted on July 14 to provide additional informatio Questions 1 and 2 of the attachment dealt with service water flows through the heat exchanger The increased flows through the RSHXs were examined only from the point of heat exchanger capabilitie FSAR Section 9.9.1.2, Emergency Service Water Pumps (ESW) deals with the design basis of the pump The FSAR assumes at minimum level in the high level canal, the maximum water flow required to the RSHXs is 12,000 gp The pumps are sized at 15,000 gpm to maintain water leve With a LOCA and concurrent loss of offsite power the requirement is stated to be 21,000 gpm (12,000 for RSHXs plus 9,000 to cool the other units component cooling water (CCW)
heat exchanger).
In addition, the station Technical Specification 3.14 basis states only 15,000 gpm is required for long term cooling for or LOCA with a loss of offsite powe The inspector's calculations show that prior to breaking vacuum on the circulating water discharge tunnel, the new heat exchangers, due to their lower resistance to flow, would pass over 8700 gpm eac Without operator action, the outflow from the four RSHXs would be about 35,000 gp Without any additional loads (CCW for instance), if two ESW pumps were operating (the FSAR assumes one out for maintenance, one fails, and one available), their capacity to supply water would. be exceeded by the losses through the component When vacuum is lost in the circulating water discharge canal, flow will drop to about 6,500 gpm per heat exchange This is about a nine percent increase over the flow through the original heat exchanger The 10 CFR 50.59 review supplied to the inspector did not consider the effect of the
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new heat exchangers increased flows on the plants ability to maintain cooling water available via the emergency service water pump An Unresolved Item, URI 88-27-01, Potential Inadequate 10 CFR 50.59 Review for RSHX Replacement, is opened for both unit Resolution of the URI will involve review of the completed engineering package for replacement of the RSHX to determine adequacy of the engineering evaluation, a review of the proposed FSAR changes, and a review of the evaluation of the impact of the RSHX on service water and recirculation spray design basi Interim review of the question by the licensee, provided via telephone to the inspector the week of July 18, indicated the 6000 gpm required flow through the heat exchangers could be maintained at canal level of 1 fee It was a 1 so indicated that this 1 eve 1 would not be reached for at least four hours after a loss of offsite power, if tunnel vacuum had also not been maintaine The plant is not currently maintaining tunnel vacuu This would allow operator action to avoid a further decline in inventory through isolation of two of the RSHX The licensee indicated operations was taking administrative action to ensure instruction is provided to the operators on actions to be taken to maintain the canal water leve On July 21, 1988, a memorandum was issued to ES Grecheck from R. W. Calder correcting the question 2 response of the July 12 mem It discuss the effect of the higher flow rates on heat transfer but does not address the canal level questio The July 12, 1988 letter contained a copy of temporary operating procedure 2-TOP-202 This procedure is to be used as the basis for permanent procedures to drain the RSHXs periodically to preclude future foulin A daily surveillance is currently being performed for the Unit 2 RSHXs, until the exchangers are replace The licensee indicated to the inspector after the heat exchanger replacement, whenever the 103 valve is cycled for periodic surveillance and once per refueling cycle, the RSHXs would be drained to check for presence of wate The procedure currently has a weakness in that no attempt is made to measure or document the amount of drainage, if an The amount of water present in the heat exchangers could impact fouling analysis, if require The current limit of 0.0005 fouling factor was set assuming dry layup condition.
Exit Interview The inspection scope and results were summarized on July 8, 1988, with those persons indicated in paragraph The inspector described the areas inspected and discussed in detail the inspection result In addition the information concerning the unresolved item was discussed with licensee representatives on July 22, 198 The unresolved item is:
URI 88-27-01, 11Potential Inadequate 10 CFR 50.59 Review for RSHX Replacement
- (Reference:
Paragraph 6.0)
Dissenting comments were not received from the licensee.