IR 05000338/1988015

Insp Repts 50-338/88-15 & 50-338/88-15 on 880524-27.No Violations or Deviations Noted.Major Areas Inspected: Licensee Actions Taken Due to Svc Water Sys Fouling in Recirculation Spray HXs

ML20150B787
Person / Time
Site:	North Anna
Issue date:	06/23/1988
From:	Belisle G, Matt Thomas NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20150B784	List: IR 05000338/1988015 ML20150B780
References
50-338-88-15, 50-339-88-15, NUDOCS 8807120180
Download: ML20150B787 (6)

Text

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s Report Nos.: 50-338/88-15 and 50-339/88-15

  .Lict ane: Virginia ~ Electric and. Power Company Richmond, VA 23261 Docket Nos.:  50-338 and 50-339    . License Nos.:   NPF-4 and NPF-7 Facility-Name: . North Anna 1 and 2 Inspection Conducted: May 24 - 27, 1988~

Inspector: 71

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      #        Z 8b M. Th'omas  /       Uate Signed Approved by:   f //bT        [[2 h Date' Signed
,    .G. A.'Belisie,' Chief Quality Assurance Programs Section Operations Branch Division of Reactor Safety SUMMARY Scope:  This routine, announced inspection was conducted in the areas of reviewing licensee accions taken due to service water system fouling in the recirculation spray heat exchanger Results:  In the areas inspected, violations or deviations were not identified.

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REPORT DETAILS Persons Contacted Licensee Employees J. Bailey, Nuclear Engineering

 *M.' Bowling, Assistant Station Manager, North Anna Power Station (NAPS)

R. Calder, Manager, Nuclear Engineering

 *R. Clark, Engineer, Plant Engineering, NAPS
 *R. Driscoll, Manager, Quality Assurance, NAPS
 *R. Enfinger, Assistant Station Manager, NAPS J. Erb, Nuclear Analysis and Fuel S. Harvey, Supervisor of Advisory 0 *ations, NAPS
 *D. Heacock, Superintendent of Techn1 cal Services, NAPS
 *G. Kane, Station Manager, NAPS P. Kemp, Licensing Coordinator, NAPS L. Lee, Assistant Supervisor, Chemistry, NAPS M. Matras, Nuclear Analyis and Fuel
 *T. Porter, Supervisor, Nuclear Safety Engineering, NAPS D. Quarz, Licensing Engineer, NAPS R. Rasnic, Supervisor, Mechanical Engineering
 *J. Smith, Supervisor, Nuclear Safety Engineering, NAPS T. Snow, Supervisor, Chemistry, NAPS
 *J. Stall, Superintendent of Operations, NAPS Other licensee employees contacted during this inspection included engineers, operators, security force members, technicians, and admini-strative personne Other Organizations Calgon_ Corporation A. Smith, Corporate Biologist C. Szymke, Account Supervisor NRC Resident Inspectors
 *J. Caldwell, Senior Resident Inspector
 * Attended exit interview Heat Exchanger Fouling Problems At North Anna This inspection reviewed actions taken by Virginia Power in response to recirculation spray heat exchanger (RSHXs) fouling. This inspection also included reviewing system design reqLirements for the recirculation spray (RS) system and the service water syste The review results are discussed in the following paragraphs.

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a. System Design Review (1) Recirculation ' Spray System The RS system and the Quench Spray (QS) system are the' subsystems which comprise the containment depressurization system. .Two major functions of the RS system are: a) combines with the QS system to depressurize containment to 'subatmospheric pressure - " within 60 minutes during a loss of coolant accident (LOCA) or a main steamline break accident inside containment and to maintain subatmospheric pressure following the accident; and b) to provide the emergency core cooling system lECCS) with water for effective core cooling on a long term basis after a LOCA. There are four RSHXs per unit. The RSHXs were designed with a zero fouling factor (hour-foot 2 oF/ BTU) for both inside and outside heat exchanger tube surfaces. The RSHXs have to be clean an maintained in dry lay-up to meet this design requiremen (2) Service Water System-The service water system is a common system. . Service water sources at North Anna Units 1 and 2 are the service water reservoir and the North Anna reservoir and these two independent water sources form the ultimate heat sink. The service water reservoir is the primary water source for the' service water system and the North Anna reservoir is the alternate sourc The accident design basis for service water system pumping requirements is a simultar.eous LOCA for one unit and loss of offsite power for both unit Under these conditions, the service water system has to supply the four RSHXs on the unit with a LOCA: three charging pump lube oil, gear box, and seal coolers per unit; one air compressor per unit; one main control room air conditioning condenser per unit; and one component cooling heat exchanger for the unit without the LOC b. Recirculation Spray Heat Exchanger Fouling

. The licensee determined that leaving the RSHXs in wet lay-up resulted in unacceptable heat exchanger tube walls (inside surface) foulin The heat exchangers were placed in wet lay-up using service water, which flows through the RSHXs tube side. As a result of the fouling

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   (1) The licensee reviewed the RSHXs ability to perform their design basis function. An engineering evaluation was perforced for steady state conditions assuming a 0.002 fouling factor for the

[ service water side of the RSHXs.

' , The evaluation's purpose was to determine the required service water temperature at which the fouled RSHXs could perform their design functio =

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The inspector. asked licensee persorrel how long had the RSHXs been in wet lay-up and whether the 0.002 fouling factor provided enough conservatism. Licensee personnel stated that they had not completed their review to determine how long the RSHXs had either been maintained in wet lay-up or had service water in them during dry lay-up conditions due to leakage from service water system valves which isolate service water from the RSHX Licensee personnel -further stated that the 0.002 fouling factor was considered to be conservative. The fouling factor stated in standard industry tables for water conditions like North Anna's service water reservoir with the RSHXs in wet lay-up ( artificial spray pond with treated makeup and . water velocity less than 3 feet /sec) is 0.001. The fouling factor was doubled from 0.001 to 0.002 in order to provide additional conservatis Licensee personnel also stated that photographs taken of the RSHXs lower tubesheet area during a previous outage were reviewed and the pictures showed no indications of heat exchanger foulin In addition to determining the required service water temperature for the 0.002 fouling factor, the licensee also deterr.ined the required service water temperatures for the RSHXs for various inside tube fouling factors ranging from approximately 0.0004 to 0.00 The licensee also requested the architect engineer (Stone and Webster) for NAPS to perform a transient analysis of the effect of the increased fouling factor on the design basis accident analysi The licensee compared their steady state calculations to the architect engineer's transient calculations and found that the two were in close agreement. Assuming a 0.002 fouling factor for the RSHXs inside tube wall, the maximum service water temperature permitted to meet the containment response requirements in the accident analysis was approximately 84 The licensee placed an administrative limit on the maximum service water temperature of 83 F in lieu of the Technical Specifications (TS) limit of 95 (2) RSHXs Chemical Cleaning The licensee developed a chemical cleaning program to remove biological fouling front the RSHXs. The process included using chemicals for clean 1ng the heat exchangers, a biocide for killing the biological growth, and a molybdate corrosion inhibitor for corrosion control. Water samples were b91ng taken at various cleaning process stages for analysis. Licensee personnel stated that sample analysis would assist in determining the cleaning process effectivenes The inspector reviewed procedure 1-TOP-49.42, Chemically Cleaning 1-RS-E-1C There was a separate procedure for each of the eight RSHXs. The instructions in this procedure were typical for the other RSHX Since this procedure was developed to clean and remove biological fouling, the inspector asked licensee personnel if there was a

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9 concern with inorganic fouling on the heat. exchanger . tube Licensee personnel stated that they had determined that biological fouling was the only type of fouling likely to be

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present. This determination was made based on the RSHXs design ard lay-up conditions and discussions with various industry experts experienced in heat exchanger fouling and biological

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fouling. Included in these discussions were representatives from Calgon' Corporation. They developed the chemical treatment-program currently being used for the service water system at NAPS and are familiar with types of biological l fouling that

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might occur. Calgon also helped develop the chemical cleaning program for the RSHXs and is providing the chemicals for the cleanin The inspector observed portions of the chemical cleaning process for RSHXs 1-RS-E-1C and 2-RS-E-1 Activities were being performed in accordance with applicable procedures. The licensee had cleaned RSHXs 1A, IB, and 1C for each unit. The ID RSHX for each unit remained to be cleane The inspector asked licensee personnel if additional measures-(such RSHX inspection or heat balance testing) were planned in order to return the service water temperature to the TS limit of 95 *F. Licensee personnel stated that they believed the chemical cleaning process was adequate to restore the RSHXs to their-design condition. The licensee further stated that conservative fouling factors would be used to determine the administrative limits for the service water temperature until the cleaning process effectiveness could be verified. The licensee stated that measures for returning to the TS limit for service water ' temperature _ were described in a justification for continued operation (JCO) for the RSHXs for Units 1 and 2 dated May 25, ( 1988. Measures described in the JC0 included the following:

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After cleaning, the RSHXs will be maintained in wet lay-up l using primary grade water. A service water temperature administrative limit of 90*F would be applicable assuming a fouling factor of 0.001 for the heat exchangers in wet lay-u Once the RSHXs are placed in d y lay up and a surveillance program established to ensure that they remain in dry , l L lay-up, a service water temperature administrative limit of o 92 F would be applicable assuming a 0.00075 dry fouling facto The service water temperature limit would not be re-establ-ished at the TS ' limit of 95 F until confirming that the fouling factor was less than 0.0004. Confirmation would be by means such as a cleaning process sampling program, RSHX z inspection, or a laboratory test.

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Licensee personnel stated that they were unable to perform heat balance testing on the RSHXs because of the design of the RS system. The licensee further stated that they would review what actions were necessary to develop the capability to perform RSHX heat balance testin Another question discussed with licensee personnel was whether there was adequate service water flow through the RSHXs. This question arose during the cleaning process when RSHX flow instrumentation indicated that the service water flow was less than the design requirement of 4500 gpm. Licensee personnel stated that the low flows were due to instrumentation problems because during attempts to resolve the problem, flow instrumenta-tion in the main service water return header indicated a flow change of approximately 4500 gpm when the RSHX was isolate The low flows were attributed to debris partially blocking the RSHX flow instrument lines. It was stated that after the instrument lines were back flushed, service water flow through the RSHXs returned t' norma After reviewing actions already taken and those planned by the licensee, the inspector concluded that implementation of all the actions would provide reasonable assurance that the RSHXs were operable and capable of performing their design functions during accident condition During the exit meeting, the inspector stated that followup items would not be identified in this report concerning this issue. An unresolved item was identified by the resident inspectors and is documented in NRC Inspection Report No , 50-339/88-1 This issue is also discussed by the resident inspectors in NRC Inspection Report Nos. 50-338, 50-339/88-1 .. 3. Exit Interview The inspection scope and results were summarized on May 27, 1988, with those persons indicated in paragraph 1. The inspector described the areas inspected and discussed in detail the inspection results. Proprietary information is not contained in this report. Dissenting comments were not received from the license >

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