ML20247A612
| ML20247A612 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/11/1989 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8905230218 | |
| Download: ML20247A612 (5) | |
Text
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BALTI M O RE GAS AND ELECTRI CHARLES CENTER P.O. BOX 1475 BALTIMORE, MARYLAND 21203 GEORCE C. CREEL Vict PRcerocur NucLt AR rNEROY (300 #60 4455 May iI,1989 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Auxiliary Feedwater System Reliability Improvement Plan
REFERENCES:
(a) Letter from Mr.
J.
T.
Wiggins (NRC) to M r.
G.
C.
Creel (DG&E) dated February 3,1989, NRC Region I Combined Inspection Report Nos. 50-317/88-32 and 50-318/88-32 (b) Letter from Mr. J. A. Tiernan (BG&E) to NRC Document Control Desk dated January 20, 1989, Request for Amendment Gentlemen:
This letter is in response to Reference (a). Inspection Report 88-32/32 expressed your concerns related to the Auxiliary Feedwater (AFW) System. We have evaluated the problems associated with the AFW and supporting systems. A system reliability improvement plan has been initiated. Enclosure (1) provides the details of our corrective action as you requested.
Reference (a) described various performance problems with the AFW system.
Specifically, problems with the steam-driven AFW pump governor and governor linkages were identified. Additional discussion was provided on the stroke time testing of the AFW steam admission valves. Many of these problems can be addressed by the Technical Specification change requested in Reference (b).
Reference (b) will allow a slower starting time for the AFW pump, thereby reducing dynamic shock and starting duty on the governor and associated linkages. An extended response time will also allow us to upgrade the steam admission valves and AFW pump governors, bOOI 18 890533
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Document Control Desk May 11,1989 Page 2 1
Should you have any questions regarding this matter, please do not hesitate to contact me.
Very truly yours,
,/
U(,
GCC/SRC/ dim cc:
D. A. Brune, Esquire J. E.
Silberg, Esquire R. A.Capra, NRC S. A. McNeil, NRC-W. T. Russell, NRC H. Eichenholz/V. L. Pritchett, NRC
- 1. Magette, DNR l
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ENCLOSURE (1)
REPLY TO NRC - INSPECTION REPORT 50-317/88-32: 50-318/88-32 AFW RELIABILITY IMPROVEMENT PLAN INTRODUCTION The performance of the AFW system will be enhrinced by:
o
' slowing AFW turbine start-ups, o
correcting material ' condition problems, o
correcting AFW ventilation / emergency ventilation design basis restrictions, o
eliminating overly restrictive Technical Specifications and FSAR limits.
RELIABILITY IMPROVEMENT PLAN
-The instability in the AFW turbine start-ups is caused by unrealistic expectations of our stee m admissian system. This is addressed in part by our requested Technical Specification change.
Material condition problems have been caused by component aging, excessive testing, excessive condensate build-up in steam admission lines, bearing degradation, and I
packing problems with the AFW pumps.
The AFW Pump Room emergency ventilation-system capabilities are being re-examined. The design margin for the system will not allow further enhancements to the steam admission system due to the unavoidable increase in heat load to the room that would result from 0
additional modifications.
The design temperature (130 F) for this room under equilibrium conditions during an accident is based on the need to ensure adequate cooling of the steam-driven pump bearings. The design. margin for emergency ventilation has decreased because of additional heat loads added in the form of system improvements to the original design and a re-evaluation. of the hest sink during accident conditions.
The bearing and pump manufacturers have been consulted on the 130 F FSAR limit. They stated that the limit is overly restrictive and can be elevated to 150 F with no degradation in bearirig perforinece. All other instrumentation in the room has been evaluated for~ the higher temperature and was found able to withstand the harsher environment.
Our AFW system Technical Specifications are overly restrictive, as discussed in
' Reference (b). The system response time required by the Technical Specifications is too short. Additionally, the train operability requirements need to be clearly defined so that' they are based on the availability of all components, not just the pumps alone.
Action is being taken to improve reliability. Our schedule is to complete all actions within the next two years. If the schedule or scope needs to be modified, we will inform you. The following steps are currently being investigated / planned to improve
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A ENCLOSURE (1)
REPLY TO NRC INSPECrlON REPORT 50-317/88-32: 50-318/88-32 AFW performance. Please note that for those actions scheduled to be completed during
-l the Unit 2 1989 Refueling Outage, many are under way and may have been completed at this time.
A.
Improvement of AFW Steam Admission Subsystem 1.
Install ' t.ew Steam Admission Check Valv' es in horizontal piping. Estimated
.completioa date: Unit 1. - 1990 Refueling Outage; Unit 2 - 1989 Refueling Outage.
j 2.
Install automatic bypass on ' CV-4070 ' and CV-4071 to allow roll of turbine prior to main valve opening and to quickly ' reduce. differential pressure
.across valve. disc. Estimated completion date: Unit 1 - 1990 Refueling Outage; Unit 2 - 1989 Refueling Outage.
3.
Install Steam Admission Line Isolation Valves to allow maintenance at 1990 Refueling outage; power. Estimated completion date: Unit 1
Unit 2 -1989 Refueling Outage.
]
4.
ixtend Technical Specification response time to allow slowing of turbine start. License amendment request currently at the NRC for review.
a.
Slow the opening of CV-4070 and CV-4071 by decreasing the air vent j
orifice size.
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b.
Change surveillance test procedure to allow slower start for time response testing and to permit measuring time response based on flow initiation to steam generators instead of the time to achieve desired discharge head of the pump in mini-flow conditions.
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c.
Install new Woodward governors on AFW turbine with slower j
acceleration bushings to de_ crease the rate of turbine acceleration between turbine speeds of 2000 and 4000 RPM.
NOTE:
Items a, b, and c above cannot be implemented until the Technical Specification change referenced in Item (4) is approved.
B.
Imorove Material Condition of AFW System J
1.
Upgrade AFW Pump packing and packing technique. Estimated completion date:
September 1989 (both Units).
2.
Evaluate a more modern design for the remote electric trip of the Trip / Throttle Valve. Estimated completion date: December 1990.
3.
Replace AFW Check Valves (AFW-129 and AFW-130) with improved design.
Estimated completion date: Unit 1 - 1990 Refueling Outage; Unit 2 - 1991 Refueling Outage.
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's ['l,,. Y ENCLOSURE (1)
REPLY TO NRC INSPECTION REPORT 50-317/88 50-318/88-32 l
4.-
Reroute AFW Turbine cooling recirculation flow path back to pump suction.
Present arrangement 'causes overpressure conditions in the cooling lines because the flow must return to No.12 Condensate Storage Tank. A shorter flow ' path to pump suction would allow necessary f*ow ' at a much lower
. driving head. - Estimated completion date: Unit' 1 - 1990 Refueling Outage;
' Unit 2 - 1991 Refueling Outage.
C.
Licensine ' Actions for AFW System 1.
Evaluate submitting license amendment request to change AFW System
. Technical -
Specifications to clearly define requirements. of train operability based on major. component availability instead 'of only considering-the AFW pumps. Estimated completion date of evaluation:
December 1989.
0
- 2. '
Raise' to 150 F the'130 F pump room temperature limit in FSAR.
D.
AFW Pumo Room Ventilation Enhancements 1.
Conduct AFW Pump Room equilibrium temperature test to determine automatic
. steam trap _ effects and pump bearing performance in higher temperature environment. Estimated completion date: Unit 1 - 1990 Refueling Outage; j
Unit 2'-
1989 Refueling Outage.
1 2.
Lag all steam lines in AFW Pump Room (complete).
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