ML19332D306
| ML19332D306 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/22/1989 |
| From: | Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NYN-89152, NUDOCS 8911300334 | |
| Download: ML19332D306 (8) | |
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1 NepHompsSre-y c,r.,_
- Senior Vice Pmident and :
,y Chief Operating Officer.
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l United States-Nuclear Regulatory Commission i
Washington ;DC 20555 j
LAttentions Document Control Desk
References:
-iL(a)U' Facility Operating License No. NPF-67, Docket No. 50-443 (b) JUSNRC. Letter dated August 21, 1989, " Inspection Report-
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No. 50-443/89-07", B. A. Bogeri o'E.'A.. Brown' t
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Subject:
..Responseito NRC Inspection Report No. 50-443/89-07 Gentlemen:
N' The NRC requested via Reference (b)' that New Hampshire Yankee (NHY) provide plans for resolving the. steam leakage concerne through the auxiliary a
feed pump turbine control valves (Unresolved item 50-443/89-07-01) and thel
, leakage through certain reactor coolant system pressure +1 solation valves
- (Unresolved iten 50-443/89-07-02). The NHY. responses to these unresolved ~
s litems are.;provided sis-Enclosures one (89-07-01) and two (89-07-02)' to this-q letter.
Should you have any. questions regarding this matter, please contact j
7-Mr. R..R.LBelanger at'(603) 474-9521, extension 4048.
i Very truly.yours,
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-8911300334 091122 PDR-ADOCK 05000443 10 PNV
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s New Hampshire Yonkee Division of Public Service Company of New Hampshire
- P.O. Box 300
- Seo'orook, NH 03874
- Telephone (603) 474 9521 A
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' United States Nuclear' Regulatory Commission November 22, 1989'.
' Attentions Document Control Desk-.
Page 2 ces.
Mr. William T. Russell V
Regional Administrator
. United States Nuclear Regulatory Commission i.:
. Region'I 475 Allendale Road-King of Prussia, PA -19406
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Mr.-Victor Nerses, Project Manager Project Directorate I-3' I
United'. States Nuclear Regulatory Coanission
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Division of Reactor Projects-Washington, DC '20555.
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Mr.'Antone C. Cerne i
NRC Senior Resident Inspector
- P.O.' Box 1149 Seabrook,.NH-'03874
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jY ENCLOSURE 1.TO NYN-89152
' E RESPONSE TO NRC INSPECTION REPORT'NO. 50-443/89-07 b
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t-New Hampshire Yankee-November 22, 1989 4 to NYN-89152 E
Steam Leakane Concerns Throuth the Auxiliary Feed Pumn Turbine Control
-Valves (Unresolved Item 50-443/89-07-01)
LBackaround The steam supply control valves for the emergency feedwater pump
. turbine-were modified.and subsequently tested in accordance with Procedure
=STP-101, " Turbine Driven Emergency Feedwater Start Verification Test".
This i
testing. identified steam leakage through the valves, which was determined to j
be. acceptable.
During-NRC Inspection 89-07, the inspector noted that steam leakage through valve MS-V394 was sufficient to cause cycling of the downstream
- check valve. Unresolved item 89-07-01 requires a reevaluation of the
- acceptability of leakage through the isolation valve.
Response ~
Prior to performance of' Low Power Testing, operability tests were iperformed on:the'EFW steam supply system to test the pilot plug design, verify the turbine overspeed setpoint, and confirm valve stroke time and time delays.
With high differential pressure across the seat (i.e., 1,000 PSID),
valves MS-V393~, V394 and V395 would not open. Modifications to the pilot
-plug, seal rings and valve opening spring provided satisfactory valve per-formance. Following successful completion of the start-up tests, operability of the system was declared.
Subsequently, some= leakage past normally closed MS-V394 was
' discovered.- Engineering Evaluation 89-021 was performed to assess the effects of this leakage on the availability and operability of the turbine-driven emergency feedwater pump. This evaluation concluded that the system was operable and recommended a maintenance inspection for MS-V394 and check valves'MS-V94 and V96. These recommendations were based on industry guidance (EPRI Report NP 5479) relative to premature wearing of check valve parts under continuous cyclic' conditions. Steam leakage past MS-V394 caused MS-V96 to; cycle approximately 2 to 3 times per second and, therefore, this Buidance was applicable to the observed conditions.
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i New Hampshire Yankee November 22, 1989 l
Isolation valves MS-V393 and V394 upstream of' valves MS-V94 and V96 L
have been specified with the lowest achievable 1 seat leakage criteria
'available for valves with metal to metal' seating surfaces. Class V-critoria as delineated in ANSI B16.104-1976 are-applicable.
Since some leakage is acceptable per this standard, it is not realistic that a' leak tight condition can be achieved'and/or maintained. This leakage as it
-influences check valve cycling must, therefore, be accommodated.
A drain / trap arrangement will be installed on each steam supply-
. header between the isolation valve MS-V393 (V394) and the check valve MS-V94
.(V96).
A steam trap will-be installed in each drain line to vent / drain the section of' piping upstream of-MS-V94 and V96.
Upon opening of the steam admission valve, the increased flow of steam to the trap will cause it to-close, preventing steam discharge to the pipe chase sump. A normally open maintenance isolation valve and. safety class-flow restriction orifice will l'
.be installed' upstream of each trap. This modification will-be completed Lprior to entry into Mode 3.
l In addition to preventing pressure build-up and check valve cycling, the drain will provide constant condensate drainage of this section of pipe.
Continuous drainage of the piping segment between MS-V393 (V394) and the
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downstream check valve MS-V94 (V96) will eliminate constant cycling of the check valve due to the steam isoletion valve leakage. This will reduce the possibility of premature check valve failere.. The drain, in addition to
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ensuring continuous condensate drainage -also reduces the potential for water hammer damage, l
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' ENCLOSURE:2'TO NYN-89152~
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s RESPONSE TO NRC INSPECTION REPORT NO. 50-443/89-07 3
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L New Hampshire Yankee November 22, 1989 b
l Leakane through certain Reactor Coolant System' Pressure Isolation Valves (Unresolved Item-50-443/89-07-02)
Background.
On June 19, 1989, while performing the RHR A pump surveillance test in Mode 2, where the RHR pump was operating on recirculation flow, leakage f
past the RHR to Safety Injection (SI) cold leg injection check valves (RH-V15 RH-V29. RH-V30, and RH-V31) was observed by New Hampshire Yankee. This leakage was apparently due to a reduced differential pressure across the i
check valves while running the RHR pump, allowing flow into the RHR system from.the SI accumulators. During this time, the RHR system was pressurized-above the RHR pump suction relief valve set pressure of 450 PSIG.
This relief valve lifted _and approximately 500 gallons of water waa drained from the four SI accumulators. Pressure in the system wae. subsequently vented off through the SI test line header to the P.efueling Water' Storage Tank (RWST) via RH-V28, SI-V62 and SI-V70.
In order to perform the RHR pump survaillance (0X1413.01) a procedure change was made to maintain the SI
' test header vent path to the RWST open for the duration of the test.
Unresolved item 89-07-02 requires an evaluation of the ability of the-
, Reactor Coolant-System Pressure Isolation Valves (RCS PIVs) installed to effectively isolate lower pressure Emergency Core Cooling System (ECCS) piping at lower differential pressures.
Recoonse A Request for Engineering Services (RES-89-381) was issued to request that an evaluation of the long term use of the SI test header line for the venting of the RCS and associated system and to seat the RCS PIVs, and to evaluate the ability of the present RCS-installed PIVs to effectively i.
l 1solate lower pressure ECCS piping at lower differential pressures (less than 2,235 psid) that are seen during plant operations.
New Hampshire Yankee, after consulting the check valve supplier, Westinghouse, has completed the response to RES89-381, and determined thats l.
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The 6-inch RHR cold leg injection check valves that interface with E
the accumulator discharge line should be inspected to ensure proper seating characteristics of the valves.
It is acceptable to open a single low head ECCS check valve test l.
line to facilitate check valve seating or to facilitate RHR pump L
surveillance testing.
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New Hampshire Yankee November 22, 1989 a
Response -(Continued).
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' ' Leakage from the; accumulators into the RHR system during a:small break loss of coolant accident or a steamline break event does not degrade _the ECCS function beyond that considered in the FSAR. 'The t'
FSAR Chapter'15 analyses remain the bounding analyses.
Valves RH-V15,;V29, V30 and-VS1 were disassembled and inspected.- A?
distortion of the-valve seat-for the six inch check valves'was identified by
blue dye-testing".
The distortion was corrected by relapping the seat :and
-proper seating was verified by successful " blue dye testing"._
To further confirm that'the check valve leakage was' corrected, post maintenanceLtesting-will be_ performed. All four valves will be leak rate
. tested by subjecting.the valves to the same type conditions (low
. differential pressure) under which leakage _had-previously occurred.
This testing will be performed following plant heatup to normal operating _
pressure and temperature when the accumulators are placed into. service.
/t Pressure isolation valvas in other RCS systems were reviewed-for'similar seat leakage conditions,'and where necessary, corrective maintenance was-
- performed.
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