ML19242D126
| ML19242D126 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/08/1979 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 534, NUDOCS 7908140527 | |
| Download: ML19242D126 (5) | |
Text
.
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%me EDISON Docket No. 50-346 LOWELL E. ROE vice Pres.cea.
License No. NPF-3 r,ca..
o-Serial No. 534 August 8, 1979 Director of Nuclear Reactor Regulation Attention:
Mr. Darrell G. Eisenhut Division of Operating Reactors United States Nuclear Regulatory Commission Washington, D. C. 20553
Dear Mr. Eisenhut:
This letter is in response to Mr. Stello's letter of May 25, 1979 related to the feedwater lines at Davis-Besse Nuclear Power Station, Unit 1 (DB-1).
The requested items relating to design information as well as the two asterisked items under f abrication history were submitted on June 19, 1979 (Serial No. 518).
The remainder of the information you requested is attached.
Yours,.very truly, LER:TJM Attachment cc:
J. G. Keppler, Regional Director Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 00l
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Docket No. 50-346 License No. NPF-3 Serial No. 534 August 8, 1979 INFORMATION REQUESTED ON PWR FEEDWATER LINES FABRICATION HISTORY Question 3: Provide the NDE performed during and af ter fabrication of the weld joints requested in Question 2.
Response
The information on NDE was provided in Actachments 12 and 13 of our letter No. 518 dated June 19, 1979.
Question 4: Provide the Code edition to which the feedwater piping system was fabricated.
Response
Feedwater piping from isolation valve to the feedwater ring header was fabricated to ASME Section III, 1971 Edition, including Summer 1971 Addenda.
Feedwater ring header and risers were fabricated to Power Piping Code, USAS B31.1.0-1967 with Errata dated March, 1969.
The feedwater spray nozzles which are bolted to the steam generator were fabricated to ASME Code Section III, 1968 Edition through Summer 1968 Addenda.
Question 5: State the fracture toughness requirements, if any, for the feedwater piping system.
Response
Feedwater piping from isolation valve to the feedwater ring header was charpy impact tested at 10 F.
The balance s f the piping did not receive any charpy impact testing.
PRESERVICE/ INSERVICE INSPECTION AND OPERATING HISTORY Question 1:
State whether the feedwater system welds received a preservice inspection in accordance with ASME B&PV Code,Section XI.
Response
Preservice examination was performed on the feedwater system per the applicable construction code to which the system was designed; pre-service inspection on Class 2 systems and components under ASME Section XI was not required to be performed when the plant was constructed.
Qucstion 2: Provide the extent of inservice inspection performed on the feedwater pipe to steam generator nozzle welds.
Include the results of the examinations, any corrective actions taken and causes of any f ailures.
Response
The steam generators at Davis-Berse Unit 1 do not have nozzles, as the main feedwater system attaches to the steam generator means of bolted connections. Auxiliary feedwater piping is contiected to the steam generator by a welded nozzle connection with an internal ring header used. Portions of the inservice inspection have been performed on the auxiliary feedwater and reported to NRC Regional Office with the remainder to be performed during the first refueling outage as specified by our reply to NRC IE Bulletin 79-13 (Serial No. 1-80, dated July 13, 1979).
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Docket 80. 50-346 License No. NPF-3 Serial No. 534 August 8, 1979 PRESERVICE/ INSERVICE INSPECTION AND OPERATING HISTORY (Continued)
Question 3: Provide the schedule and extent of inservice inspection for the feedwater system for the next inspection Laterval.
Response
The feedwater syates will be inspected in accordance with the ASME B&PV Code Sectied XI, 1977 Edition thru the Su=mer 1978 Addenda, to the extent that is practicable within design physical limitations and geometry of construction.
Question 4: Provide any history of water hammer or vibration in the feedwater system and design changes and/or actions taken to prevent these occurrences.
Response
The only water ha==er which has been observed in the feedwater system withht containment has occurred during startup under one specific condition.
This condi; ion occurs when a small feedwater flow (mini-feed) is used, bypassing the startup control valves, to keep the steam generator (SG) nozzles flooded, at a feedwater temperature of approximately 200 F, and when the reactor coolant system (RCS) temper-ature is less than 180 Fc In this instance,when a vacuum is applied to the main steam system, flashing occurs in the SG nozzles. To preclude this problem of water hammer, the small feedwater flow is now initiated only if thc RCS temperatgre is greater than 180 F.
Should the RCS tempersture be lesa chan 180 F at the time that the flow is to be initiated the miaifeed is delayed until the RCS reaches 130 F.
Therefore the feedwa'.cr hammer problem is minimized by pro-cedure through proper spplica' loa and sequencing of feedwater flow, c
RCS heatup, and condenser vacuum.
Question 5: Provide a description of feedwater chemistry controls and a summary of chemistry data.
Response
The limitations on secondary feedwater cation conductivity minimizes the degradation of the steam generator tubes and the potential for steam genecator tube leakage or failure due to stress corrosion.
Contamination of the steam generator secondary coolant increases the potential of tube degradation and impairment of tube integrity.
Generally, two major sources of contamination exist. One source of contamination results from condenser in leakage of impurities that may enter the secondary side of the steau generators if break-through of the condensate polishing demineralizers occurs. Continuous monitoring of the secondary feedwater by catien conductivity at Davis-Besee is an effective means of monitoring condensate polishing demineralizer breakthrough and minimizing the introduction of contami-nants to the steam generator.
During operation, the most common contaminants found in the demineralizer effluent will be at concentra-tions sufficiently low to be soluble in the superheated steam and will not accumulate or concentrate in the steam generators.
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Docket No. 50-346 License No. NPF-3 Serial No. 534 August 8, 1979 PRESERVICE/ INSERVICE INSPECTION AND OPERATING HISTORY,(Continued)
Question 5:
(continued)
Response
Another major source of secondary feeduater contamination results from concentration of impurities in the feedwater due to the moisture separator drains being pumped forward in the cycle, bypassing the condensate polishing demineralizers.
This problem is overcome at Davis-Besse by breaking the " concentration loop" by routing 50%
of the moisture separator drains to the condenser, and hence the condensate polishers, 100% of the time during operation.
The minimum quality specification to which feedwater should conform during normal power operation are given below:
Max total solids (dissolved and suspended), ppb 50 Max cation conductivity, umho/cm 0.5 Max dissolved oxygen, ppb 7
Max total silica (as Sio9), ppb 20 Max total iron (as Pe), ppb 10 Max total copper (as Cu), ppb 2
pH at 77F (adjusted with ammonia) 9.3 to 9.5 Total hardness (a)
Organics (b),
Lead O(c)
(a) Care is taken to eliminate hardness constituents due to possible steam generator deposition probless.
(b) Organic contamination is avoided in condensate polished systems to prevent possible resin fouling.
(c) Lead contamination of the feedwater is avoided in view of reported problems with Inconel 600 in water containing lead.
Maintaining the secondary feedwater within the limits of this specification will control the introduction of potentially corrosive impurities into the steam generators and minimize tube degradation.
Typical operating chemistry data for Davis-Besse, based on the operation to date, is listed below and is seen to be within the limits noted above.
pH 9.4 Cat.Cond.
0.25 umhos/cm Sodium 2 ppb Silica 5 ppb Iron 10 ppb 0xygen 5 ppb Hydrazine 40 ppb Copper 0 ppb
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Lead 0 ppb s
Docket No. 50-346 License No. NPF-3 Serial No. 534 August 8, 1979 PRESERVICE/ INSERVICE INSPECTION AND OPERATING HISTORY (Continued)
Corrosion of the steam generators, as well as other condensate and feedwater system components is limited by the addition of hydrazine to maintain a controlled residual of hydrazine af ter the last set of feedwater heaters.
Further, an alkaline pH of the feedwater is maintained to inhibit corrosion of the condensate and feedwater system materials of construction by the addition of ammonia to maintain pH within controlled limits.
Continuous and/or scheduled grab samples, obtained from selected system sample locations are analyzed to assure the control limits of these chemical additions are maintained. This monitoring provides reasonable assurance that t m conditions in the steam t
generators minimize the potential for rube degradation during all conditions of operation and postulated accidents, as a measure of protectica of the steam generator tubing which is an essential part of the reactor coolant pressure boundary.
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