IR 05000280/1988006
| ML18152A850 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 02/29/1988 |
| From: | Adamovitz S, Kahle J, Ross W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML18152A849 | List: |
| References | |
| 50-280-88-06, 50-280-88-6, 50-281-88-06, 50-281-88-6, NUDOCS 8803160012 | |
| Download: ML18152A850 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION
REGION II
101 MARIETTA ST., ATLANTA, GEORGIA 30323
'n°\\1' n 0 1QA~
.........
- .,*
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Report-Nos.:
50-280/88-06, 50-281/88-06 Licensee:
Virginia Electric and Power Company Richmond, VA 232161 Docket Nos.:
50-280, 50-281 Facility Name:
Surry Inspectors:
Inspection Conducted JI w. *Approved by:
License Nos.:
DPR-32, DPR-37 16-19, 1988 and Safeguards SUMMARY Scope:
This routine, unannounced inspection was conducted in the area of plant chemistr Results:
No violations or deviations were identifie sg~~ao PDR ADOCK O PDR G
REPORT DETAILS Persons Contacted Licensee Employees J. Agler, Supervisor, Water Treatment
- R. Blount, Superintendent, Technical Services D. Bostwick, Chemist D. Dotson, Nuclear Site Engineer
- E. Grechek, Assistant Station Manager A. Hall, Engineer, Surveillances and Testing (S&T)
J. Lamberton, Senior Chemistry Technician R. Riley, Nuclear Project Technician 0. Sloane, Senior Chemistry Technician
- E. Swindell, Supervisor, Chemistry R. Tolbert, Nuclear Site Engineer D. Valdivieso, Engineer, Inservice Inspection D. Wong, Engineer, S&T Other Organization T. Schneider, Westinghouse NRC Resident Inspectors
- W. Holl and L. Nicholson
- Attended exit interview Exit Interview Tne inspection scope and findings were summarized on February 19, 1988, with_ those persons indicated in Paragr~ph 1 abov The inspector described the areas inspected and discussed in detail the inspection finding,$,:'~\\):No dissenting comments were received from the license The 1 i cens~¢'fd,;fd-not identify as proprietary any of the ma teri a 1 provided to
- --- or revfew.~:~tby the i nsp~ctor during this inspectio.
License~ A~tion on Previous Enforcement Matters This subject was not addressed in the inspectio.
Plant Chemistry (79701)
During this inspection the_inspectors reassessed the licens~e's capability to maintain the integrity of plant components, especially the reactor coolant pressure boundary, through prevention of corrosio In addition to reviewing the effectiveness of plant design, plant operation, and
/
chemistry control the inspectors also reviewed actions being taken by the licensee to monitor and eliminate thinning of carbon steel pipe and transport of oxidation products to the steam generator Review of Corrosion Control The last inspection in this area was performed in September 1986, the third month of the current fuel cycle for Unit 1 and immediately prior to the last refueling outage for Unit 2 (Inspection Report 86-25).
As the result of that inspection the licensee's effort to minimize degradation of plant components was considered to be benefitting from continued upgrading of the secondary water system and from adherence to chemistry control criteria recommended by the Steam Generator Owners Group (SGOG).
However, the 1 i censee I s progress suffered a setback on December 9, 1986, when a pipe break occurred as the result of erosion/corrosion of an 18-inch carbon steel feedwater line in Unit 2 soon after restart for the current fuel cycl The significant loss of metal associated with this pipe break forced the licensee to review and revise the objectives of a chemistry control program that had previously focused principally on preventing leaks in or failure of steam generator tube Increased attention has subsequently been given to surveillance, materials of construction, and operating p*arameters that can cause erosion/corrosion of pipe that transport.both single-phase and two-phase water system Although, as will be discussed later in this report, the licensee has been reevaluating the effectiveness of its chemical control program, this program continued to be based on guidelines recommended by the SGOG and the Electric Power Research Institute (EPRI), as well as on guidance provided by Westinghous The extent to which the rec9mmended control criteria had been maintained was assessed by the inspectors through a review of chemistry logs and other reports and discussions with cognizant plant*
personne (1) Audit of 1987 Operation Unit This unit had been shutdown from mid-December 1986
- .u.ntil February 1987 so that pi pe-thi nni ng concerns could be
- {}\\addresse For the remainder of 1987 this unit operated at 100%
- :--'.})j:,ower except. for lengthy shutdowns in May, September, and
- :~:,<October due to mechanical problem Briefer shutdowns and power
- transients also occurred throughout this period. This unit was scheduled to shutdown in April 1988 for its next refuelin Unit This unit was shutdown from December 9, 1986, until March 25, 1987, as the result of the feedwater pipe brea Beginning in April 1987, this unit had an excellent operational history,. including 247 days at or near ful'l powe During 1987, the licensee had maintained chemistry control at a level that significantly exceeded SGOG criteria. This favorable
~tondition was attributable in part to the effectiveness of the
- ,mail\\ condenser as a barrier against ingress of contaminants; e.g., air inleakage less than 5 SCFM, dissolved oxygen in the hotwell less than 2 ppb, cation conductivity of the hotwel l water less than or equal to 0.10 umho/cm, and concentration of sod.i um in the hotwe 11 water 1 ess than or equa 1 to 2 pp In an effort to prevent condenser tube leaks that would permit inflow of the saline cooling water, the licensee planned to double (from 4% to 8%) the number of tubes that are eddy current tested each refueling outag Most eddy current indications observed during the last outages were attributed to mechanical damage rather than to chemical or environmental cause However, plans are underway to hydrolaze the condenser tubes to remove biofouling that could result in tube damag The licensee had not observed hydriding of the titanium condenser tubes as has been found at two other plants in NRC Region I A second potential pathway for contamination of the hotwell water is through the water treatment plant and condensate makeup syste During 1987, the flash evaporator that had been used to provide pure water for Unit 2 had to be discarded because of serious corrosion by the sa 1 i ne river wate The remaining flash evaporator for Unit 1 alsd had begun deteriorating but was still being used to purify well water for makeup for both unit Whenever additional makeup capacity was required, a mobile demi nera 1 i zer pl ant had been contracte The 1 i censee was evaluating the use of reverse osmosis as the primary me~hod for purifying water from either local wells or the James Rive During the 1 ast inspection the deep-bed condensate cleanup system was being operated very effectively to produce high purity steam generator feedwate However, during the latter part of 1987 the sodium concentration in the feedwater frequently increased from 1 ess than or equa 1 to 1 ppb to 10-15 pp These variations were attributed to 11 throw 11 of sodium from cation demi nera 1 i zer beds after they had been
,regenerated with sodium hydroxid There was no similar "thrown
- (* of sulfate from anion beds that had been regenerated with
.',sulfuric aci The resulting cation/anion imbalance in the feedwater and steam generator produced sufficient hydroxide ions to cause concern about the possibility of caustic-induced corrosion in the steam generators. A task group had been formed to investigate possible solutions for this proble As one method of reducing sodium "thrown the 1 icensee had started regenerating each cation bed only once per four weeks rather on the biweekly schedule previously used for both cation and anion bed This action lowered the sodium concentration in the feedwate During the refueling outages in 1986 the fifth and sixth feetlwater heater tube bundles in both units had been replaced so as to substitute stainless steel tubes for the original copper-nickel alloy tube The entire third and fourth feedwater heaters will be replaced during the next refueling outages for each unit, and the remaining heaters (first and second) are scheduled for replacement during the following refueling outages (eighteen months later).
These actions were to be taken to reduce transport of copper corrosion products to the steam generators and, thus, reduce the probabi 1 i ty of degradation of steam generator tubes from dentin However, experience at other plants in Region -II has shown that
. significant amounts of copper, previously transported to the steam generators, will continue to be found in metal oxide sludge and in hideout return for several years after all copper-alloy tubes have been replace The 1 i censee had a 1 so increased efforts to monitor and to minimize transport of iron corrosion products to the steam generator This issue will be discussed further in Paragraph (2) of this report as part of the topics of general corrosion and pipe thinnin The results of the licensee 1s efforts to eliminate potential corrodants in steam generator water was evident from analyses obtained in 198 Cation conductivity, the chemical parameter that reflects the total concentrations of soluble organic and inorganic anions, had been characteristically 0.10 umho/cm or les This value was considerably below the upper limit (0.8 umho/cm) recommended by SGOG to prevent corrosion. Hideout studies indicated that insoluble species of potentially corrosive ions had been r-educed to relatively low (less than 100 ppb) levels; however; relatively large (greater than 500 ppb)
levels of silica were still being observed as hideou As will be discussed later, the inspectors considered this analytical data to be increasingly more sensitive and accurate as new
,analytical instrumentation was being used routinel finally, the licensee had continued to make good use of the s_team generat9r blowdown cleanup and recovery system to further
-':<"purify water that was being cycled back to the condenser
- hotwells for re-use as condensat (2)
General Corrosion, Pipe Thinning and Corrosion Product Transport During the 1986 refueling outages the following quantities of metal oxide sludge had been removed from each of the three steam generators of each unit:
Unit 1 - 57, 52, and 25 pound Unit 2 - 435, 104, an 125 pound The sludge was analyzed to be about 50-60% iron, 5-10% copper, 5-10% zinc (from copper alloy tubes), and 1-2% nickel (from inconel steam generator tubes).
The amounts of sludge found in Unit 2 steam generators were considerable more than the amounts removed during the previous (1985) refueling outage; i.e., 87, 80, and 17 pound During previous inspections the amounts of sludge removed from each steam generator had been evaluated by the inspector in terms of a buildup of potentially corrosive local environments that.could result either in steam generator tube denting or various mechanisms of stress corrosion cracking of tubes and/or tube support plates. The results of eddy current tests of steam generator tubes in Unit 1 in 1986 were reported in Inspection Report 86-2 Two tubes had been plugged as the result of these tests, although the eddy current measurements were considered to be biased conservatively by the presence of metal oxide sludge on the secondary side of the tube wa 11 Subsequent to Inspection 86-25 the licensee eddy current tested 21.5% of all tubes in Steam Generators A, B, and C in Unit Although 11dent 11 signals were observed at several tube support plate elevations on the hot legs the indications were not significan Consequently no tubes had been plugge The results of these eddy current tests indicated that the tubes had not degraded even though metal oxide sludge had deposited on the tube sheets as well as on the tubes themselve During the next refueling outage for Unit 1 the licensee pl ans to use a II pressure-pul se
tube cleaning process to remove solids from tube surfaces so that eddy current tests can be more accurately interprete This process was developed by Westinghouse and has recently been used at one other plant in Region I Subsequent to the Unit 2 feedwater line break, corrosion product transport has been viewed both in terms of steam generator fouling and in thinning of carbon steel pip The two chemical variables that are most relevant to metal wastage and formation of iron oxidation products are. pH and dissolved oxyge Consequently, the licensee had given increased attention to the optimum control of these variable ;:,~,:;_R~ther than changing. the chemistry control criteria presently
\\'kt;t~ecommended for prevention of corrosion within the steam
'}//(.generators, t_he licensee had enlarged its surveillance program
- .,:.:"~fto include both single phase and two phase pipin Also,
- changes in all-volatile-chemistry (AVT) control of pH were under study in an effort to maintain optimum pH levels throughout all water and water-steam regions of the secondary coolant cycl The first change wi 11 be to increase the pH range for steam generator water from 8.5-9.0 to 8.8-9.2.to reduce the potential for acidic attack of carbon steel. This change will be made by i ncreasi-ng the concentration of ammonia and will have two detrimental result The cation resins in the condensate polishers will be depleted faster with ammonia and will have to be regenerated more frequently; thereby, worsening the sodium
"throw" proble Also, as long as there are copper-alloy tubes in -the feedwater heaters, the rate of copper removal and transport to the steam generators will be increase Another possible variation in AVT control that is under study by the licensee is to substitute morpholine for ammoni Recent studies reported by EPRI and the industry are being reviewed to determine if morpho 1 i ne would provide better pH contro 1 throughout two-phase systems and drain lines as well as reduce the rate of loading of condensate polisher The inspectors were informed that an outside company had been contracted to perform a study of corrosion product transport throughout the secondary coolant system of the Surry unit This study will be designed to quantify the types and amounts of metal oxide that are formed in the low-and high-pressure coolant, steam, and drain lines so that piping that is vulnerable to erosion/corrosion can be better identifie All of the above activities are considered to be acceptable and to indicate prompt action by the licensee to adapt the existing chemistry control program to the protection of all of the piping in the secondary coolant system as well as the steam generator In addition, the augmented pipe survei 11 ance program is considered to meet the intent of NRG communications (IE Notice 86-106 and Supplements) relating to the Surry Unit 2 feedwater line brea A description of this program was
included in the licensee's response to IE Bulletin 87-01
"Thinning of Pipe Walls in Nuclear Power Plant" that was tfansmitted to the NRG by letter dated September 11~ 1987. This response was reviewed by the inspector Review of the Licensee's Chemistry Program Through discussions with cognizant Chemistry Department personnel, review of pertinent records, and wa l kdowns of laboratories and sampling areas, the inspectors reviewed and reassessed the following kE!Yl~l~ments of the Surry Chemistry progra *
-dii'.L'.s\\:af The Chemistry staff had been stabilized at a level of
,.,;;c'twenty two personnel and was functioning on a six-shift rotation under the Chemistry Supervisor and two assistant Chemistry Supervisors. The inspectors were informed that there had been a low rate of personnel turnover since Inspection 86-2 Consequently, the various training programs provided for both training and retraining had continued to be effectiv All technicians were trained in responsibilities in both the Primary and Secondary Laboratories and were being qualified in such state-of-the-art analytical technologies as atomic absorption and ion chromatograph l i
I
The Chemistry Department was being supported by members of the cor-porate Chemistry staff and by a Westinghouse Chemist, as part of a steam generator maintenance agreemen (2)
Facilities. Since the inspector's last site visit a new Primary Chemistry Laboratory had been constructed and equipped with state-of-the-art equipmen The first of two inline sampling panels for secondary chemistry was essentially completed and will be ready for use during the next fuel cycle for.Unit These panels were discussed in Inspection Report No. 86-2 A proposed addition to the Secondary Laboratory/Instrument Room had not been complete Therefore, chemistry personnel were continuing to test out the first of two inline -ion chromatographic systems in a temporary area that was not environmentally controlle Likewise, facilities for a new -
computer to be used to manage data obtained by the new inline system were not yet operabl Consequently, measurements of most control and diagnostic chemistry variables were continuing to be made on grab sample The inspectors considered that the inline ion chromatograph system will afford the licensee a powerful analytical instrument for identifying trace amounts of organic and inorganic impuritie Both this instrument and the 11bench-top 11 ion chromatograph were being applied to resolving the cation/anion imbalance related to sodium 11throw 11 from condensate polisher (3)
Quality Control - Because of the increasing importance being placed on differences between very small concentrations of potentially corrosive species and the development and use of highly sensitive manual and inline analytical instrumentation, the Chemistry Department.was continuing _to upgrade its program for quality control of analytical result In addition to the programs previously reviewed by the inspectors, an outside vendor had been contracted to periodically provide standard
. solutions of control and diagnostic chemistry variables in concentrations consistent with those encountered in actual plant operatio The inspectors reviewed quality control charts that
~. were being used for manual procedures and discussed with the
~::;~::}c:iuality control coordinator means for applying quality control
- **-:',~t~*"to inline analytical instrumentatio The Chemistry
.:*_~):.Department's *qua 1 ity control program was consistent with SGOG
- guideline (4)
Primary Chemistry - Since the last inspection the licensee had made two changes in the primary chemistry control program in an effort to achieve two goals:
to minimize out-of-core radiation levels caused by activation products (principally cobalt-60 and cobalt-58); and to reduce the potential for primary-side stress corrosion cracking of steam generator tube..
?/Reduction of out-of-core radiation levels -
Much of the radiation exposure acquired by operation and maintenance personnel, especially during a refueling outage, can be attributed to radioisotopes of cobalt that are produced by neutron activation of trace amounts of cobalt and nickel that are removed from structural components of the primary coolant system and subsequently deposited on primary system piping wall As the result of recent investigations EPRI has published information that shows that plant radiation field buildup can be beneficially affected by maintaining the pH and lithium hyroxide concentration in the reactor coolant at higher levels than presently recommende (EPRI Report NP-4762-SR, PWR Primary Water Chemistry Guidelines, September 1986).
The inspectors observed that the Chemistry staff was attempting to achieve the benefit of keeping pH as high as possible during a fuel cycle while remaining within the coordinated band for boric acid - lithium hydroxide recommended by Westinghous The inspectors were informed that the use of further elevated lithium concentrations is under discussion with Westinghous The second change in primary chemistry control was reducing the hydrogen overpressure so as to achieve a concentration. of dissolved hydrogen of 25 to 35 cc/kg, as opposed to a previous upper limit of 50 cc/k This action had been taken to reduce the possibility for stress-induced corrosion in the primary side of steam generator tube Such cracks have been observed in steam generator tubes with residual stresses in the U bend and tube sheet region Recent investigations have shown that this 11pure-water 11 cracking mechanism is related to dissolved hydrogen and can be beneficially affected by reducing the hydrogen concentratio Although primary side tube cracking has been observed principally in Westinghouse steam generators other than the Model 51F at Surry, the licensee 1 s action is considered to be prudent and acceptabl (5)
Chemistry Audit Programs - During this inspection the licensee was a 1 so conducting an i nterna 1 audit of the Chemistry
_\\.,Pepartmen The inspectors discussed the scope of this audit
.,::.:;;,/with the auditor and other members of the Quality Assurance
'"*"staff. Although the auditor received guidance from a designated member of the Chemistry Department during the performance and evaluation of his review, the inspectors considered the review to be unbiased and to be addressing important elements of the chemistry program, especially those that were administrative in natur The inspectors were also shown an Evaluation Checklist that had been used by the licensee 1 s Corporate Chemistry Staff during an evaluation performed at Surry in December 198 The scope of this evaluation covered all aspects of the Chemistry Department 1s Quality Control program; e.g., calibration of
,.
instruments, standardization of procedures and quality control cha~t The inspectors considered this type of audit to be an important factor in maintaining the accuracy and credibility of control data acquired by the Chemistry staf Conclusions During this inspection no violations or deviations were identifie An audit of pertinent data showed that Technical Specifications related to reactor coolant chemistry control had been me The 1 i censee was considered to be cognizant of current tech no 1 ogy pertaining both to corrosion problems and possible solutions to these problems that have been recommended by SGOG, EPRI, and the nuclear power industr The 1 i censee I s chemistry program continued to benefit from the resources that had been made available through the steam generator agreement with Westinghouse; however, implementation of the i nl i ne sampling system and associated data management and alarm systems had not yet become functional.