ML20012D821
| ML20012D821 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/20/1990 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-A-47, REF-GTECI-SY, TASK-A-47, TASK-OR 1783, GL-89-19, TAC-M74934, NUDOCS 9003280412 | |
| Download: ML20012D821 (4) | |
Text
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TOLEDO
%se EDISON A Cartenor f regy Ccrm Docket Number 50-346 DONALD C. SHELTON va.%
.u,way License Number NPF-3 Serial Number 1783
. March 20, 1990 United States Nuclear Regulatory Commission Document Control Desk Vashington,.D. C. 20555
Subject:
Response to NRC Generic Letter Number 89-19; Request for Action Related to Resolution of Unresolved Safety Issue A-47 " Safety Implication of Control Systems in LVR Nuclear Power Plants" Gentlemen This letter is submitted pursuant to 10CFR50.54(f) in response to NRC Generic Letter Number 89-19, " Request for Action Related to Resolution of Unresolved Safety Issue A 47" (Log Number 3091 dated September 20, 1989). Generic Letter Number 89-19 discusses that as a result of technical resolution of Unresolved Safety Issue (USI) A-47 it was determined that protection should be provided for certain control system failures and that selected emergency procedures should assure that plant transients resulting from control system failures do not compromise public safety.
As a result of this technical resolution, the NRC concluded that all Pressurized Vater Reactor (PVR) plants should provide automatic steam generator overfill protection and that plant procedures and technical specifications should include provisions to verify periodically the operability of the overfill protection and to assure that automatic overfill protection is'available to mitigate main feedvater (MFW) overfeed during reactor power operation. The NRC also concluded that certain Babcock & Wilcox plants should provide automatic initiation of auxiliary feedvater on lov steam generator level, or another acceptable-design, to prevent steam generator dryout on a loss of power to the control system.
The NRC provided specific control system design and procedure modification guidance in Enclosure 2 to Generic Letter Number 89-19.
Toledo Edison hereby provides the following in response to Generic Letter Number 89-19, Enclosure 2, Item 3, Babcock and.Vilcox - Designed PVR Plants.
It should be noted that, within the context of Generic Letter Number 89-19, Davis-Besse Nuclear Power Station, Unit 1 is a Group I plant and the response is based on this group categorization., Item 3(a), NRC Recommendation It is recommended that all Babcock and Vilcox plant designs have automatic steam generator overfill protection to mitigate MFV overfeed events.
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Docket Nuxb:r 50-346:
License Number NPF-3 Serial Number 1783 i
Page 2 The design for the overfill protection system should be sufficiently separate from the MFV. control system to ensure that the MFV pump vill trip on a steam
-generator high-water-level signal (or other equivalent signals) when required, even if a loss of power, a loss of ventilation, or a fire in the control portion of the MFV control system should occur.
Common failure modes that could disable overfill protection and the feedvater-control system, but still result in a feedvater pump trip, are considered acceptable failure modes.
Response
Davis-Besse Nuclear Power Station Unit I has in place a Steam and Feedvater Rupture Control System (SFRCS) trip on high Steam Generator (SG) level which closes the MFV isolation valves and the MPV control valves, and the Main Steam Isolation Valves (MSIV's), and initiates auxiliary feedvater (AFV). This is a
-safety-grade trip using.tvo actuation channels with a 2-out-of-2 per actuation channel initiating logic. The closure of the MSIV's removes the Steam Supply to the Main Feedvater Pump Turbines (MFPT's) and results in their shutdown.
The MPPT's are not tripped separately.
The design for the overfill-protection system is sufficiently separate from the MFV control system to ensure that MFV isolation occurs on a steam generator high-vater-level signal when required, even if a loss of power, a loss of ventilation, or a fire in the control portion of the MFV control system should occur., Item 3(b), NRC Recommendation It is recommended that plant procedures and technical specifications for all B&W plants include provisions to periodically verify the operability of overfill protection-and ensure the automatic MFV overfill protection is operableLduring reactor power operation.
The instrumentation should be demonstrated to be operable by.the performance of a channel check, channel functional, testing, and channel calibration, including setpoint verification.
Technical specifications should include appropriate Limiting Conditions for
-Operation (LCOs). These technical specifications should be commensurate with the requirements of existing technical specifications for channels that initiate protective actions.
Response
-As stated in the Generic Letter, the intent of this recommendation is to modify the plant procedures to provide periodic testing of overfill protection and to consider inclusion of these requirements in future Technical Specification improvements.
At Davis-Besse the SFRCS high-level trip is subjected to surveillance testing similar to the safety-grade SFRCS low-level trip which includes channel check, channel functional test and channel calibration (including setpoint verification).
However, the high-level trip is not included in the Davis-Besse Technical Specifications. The Technical Specification issue for this trip has been referred to the B&V Owners Group Technical Specification Committee for review against the criteria specified in the NRC Interim Policy Statement on Technical Specification Improvements.
Toledo Edison vill evaluate the result of the B&W Owners Group Technical
p Dock 0t Numb;r 50-346.
+
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- License Number NPF-3
. Serial Number 1783 Page 3 Specification Committee's review and, if necessary, vill consider incorporating the recommended Technical Specification changes during a future upgrade., Item 3(c), NRC Recommendation It is recommended that plant designs with no automatic protection to prevent steam generator dryout upgrade their design and the appropriate technical specifications and provide an automatic protection system to prevent steam generator dryout on loss of power to the control system.
Automatic initiation of auxiliary feedvater on steam generator low-vater level is considered an acceptable design.
Other corrective actions identified in Section 4.3 (4) of NUREG-1218 could'also be taken to avoid a steam generator dryout scenario on loss of power to the control system. The staff believes that only three B&V
- plants, i.e.,
Oconee 1, 2, and 3, do not have automatic cuxiliary feedvater i
initiation on steam generator lov vater level.
Response
Davis-Besse has the SFRCS which provides automatic protection to prevent SG l
dryout by automatically initiating AFV on lov SG 1evel. Technical Specifications Section 3/4.3.2.2 contains operability and surveillance requirements. Therefore, this recommendation does not apply to Davis-Besse.
l In conclusion, Davis-Besse has in place a safety-grade SG overfill protection system.that isolates HFV and the steam source for the HFPT's. Toledo Edison believes that this most closely satisfies the Group I design criteria for j
overfill protection as delineated in Generic Letter Number 89-19.
The overfill protection system is included within the existing surveillance and i
operating procedures for.the SFRCS low-level trip, which assures proper operation. Toledo Edison has no plans to include a HFV pump trip circuit in the overfill scheme because the closure of HSIV's on an overfill event
. accomplishes shutdown of the HFV pumps by removing the steam to the HFPT's.
Inclusion of the high-level trip in the Technical Specifications is pending review and recommendation by the B&W Owners Group Technical Specification 4
Committee.
Should you have any questions or require additional information, please contact Mr. R. V. Schrauder, Manager - Nuclear Licensing, at (419) 249-2366.
Very truly yours, I \\..h JSL/ssg Enclosure cc:
P. H. Byron, DB-1 NRC Senior Resident Inspector A. B. Davis, Regional Administrator, NRC Region III T. V. Vambach, DB-1 NRC Senior Project Manager
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- Do:k:t No::ber 50-346 Licensa Nu:ber NPF-3 Serial Number 1783 t
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RESPONSE TO NRC GENERIC LETTER
" REQUEST FOR ACTION RELATED TO RESOLUTION OF UNRESOLVED SAFETY F
ISSUE A-47" FOR DAVIS-BESSE NUCLEAR POVER STATION UNIT NUMBER 1 This letter is submitted in conformance with Section 182a, Atomic Energy Act of-1954, as amended, and 10CFR50.54(f) in response to Generic Letter Number 89-19 " Request for Action Related to Resolution of Unresolved Safety Issue A-47."
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By:
D. C. Shelton, Vice President Nuclear f
l Sworn and subscribed before me this 20th day of March,1990 o
b kfh Notary P4ilic, State of Ohio EVELYN L DRESS NOTARY PUBUC, STATE 0F 0HIO i
MyComfruionDpiresJuly28,1994 s
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