ML17263A434

Responds to 890920 GL 89-19, Safety Implication of Control Sys in LWR Nuclear Power Plants. Overfill Protection Provided Through Trip Bistables in Reactor Protection Racks Powered from A,B,C & D 120 Volt Ac Instrument Buses

ML17263A434
Person / Time
Site:	Ginna
Issue date:	10/27/1993
From:	Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	Andrea Johnson Office of Nuclear Reactor Regulation
References
REF-GTECI-A-47, REF-GTECI-SY, TASK-A-47, TASK-OR GL-89-19, NUDOCS 9311040085
Download: ML17263A434 (10)

Text

ACCELERATE DOCUMENT DISTRIBUTION SYSTEM REGULB~Y INFORMATION DZSTRZBUTIO YSTEM (RIDE)

ACCESSION NBR:9311040085 ,

DOC.DATE: 93/10/27 NOTARIZED: YES DOCKET FACIAL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION MECREDY,R.C. Rochester Gas 6 Electric Corp.

RECIP.NAME RECIPIENT AFFILIATION JOHNSON,A.R. Project Directorate I-3

SUBJECT:

Responds to 890920 GL 89-19, "Safety Implication Of Control Sys In LWR Nuclear Power Plants." Overfill protection provided through trip bistables in reactor protection racks D powered from A,B,C a D 120 volt ac instrument buses.

DISTRIBUTION CODE: A001D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: OR Submittal: General Distribution

/

NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). 05000244 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D PD1-3 LA 1 1 PD1-3 PD 1 1 JOHNSON,A 2 2 D INTERNAL: NRR/DE/EELB 1 1 NRR/DORS/OTSB 1 1 NRR/DRCH/HICB. 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 NUDOCS-ABSTRACT 1 1 C/LFDC 1 0 OGC/HDS1 1 0 REG FILE 01 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 D

D D

NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEl CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISIS FOR DOCUMENTS YOU DON'T NEEDI TOTAL NUMBER OF COPIES REQUIRED: LTTR 15 ENCL 13

~ I IIII III IZZV I@II IIIIIIIIIII ROCHESTER GAS AND ELECTRIC CORPORATION o 89 EAST AVENUE, ROCHESTER N. K 14649-0001 ROBERT G MECREDY TELEPHONE Vice President AREA COOE7ie 540-2700 Ginna Nuclear Production October 27, 1993 U.S. Nuclear Regulatory Commission Document Control Desk Attn: Allen R. Johnson Project Directorate I-3 Washington, D.C. 20555

Subject:

Generic Letter 89-19, "Safety Implication of Control System in LWR Nuclear Power Plants" (USI A-47)

R.E. Ginna Nuclear Power Plant Docket No. 50-244

Dear Mr. Johnson:

Generic Letter 89-19 dated September 20, 1989 requested licensees to respond within 180 days from the date of the Generic Letter detailing whether the recommendations of the Generic Letter will be implemented and to provide an implementation schedule if applicable. Our original response letter dated March 19, 1990 was based on the Ginna Station analog feedwater control system which was in use at that time. During the 1991 refueling outage, this system was replaced with an advanced digital feedwater control system (ADFCS).

Amendment No. 41 and NRC Safety Evaluation Report (SER) dated February 28, 1991 authorized a change to the Technical Specifications for installation of the new feedwater control system (ADFCS). The NRC staff concluded that the new ADFCS, using the median signal selector (MSS), met all the applicable guidelines and regulations. The NRC staff recommended testing actions proposed by RG&E for one cycle of operation, and these were completed.

On October 3, 1991 a conference call between NRC and RG&E was held to discuss the steam generator overfill aspects in'eeting the intent of Generic Letter 89-19 an'd its application to the new ADFCS. Subsequently, an NRC Request for Additional Information (RAI) dated October 18, 1991 was issued to RG&E to update its original response letter dated March 19, 1990 with, regard to the new ADFCS design. The request was to address the following issues:

1) The Feedwater Control System is not powered from the same source as overfill protection.

2) Overfill protection and feedwater control are not located within the same cabinets.

3) Overfill protection and feedwater control signals are routed such that a fire is not likely to affect both systems.

-Ann.n~

931"1'040085 931 027 PDR:,,ADOCN 05000244 PDR

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4) Plant procedures and Technical Specifications include requirements to periodically verify operability of overfill protection.

At Ginna Station, Steam Generator (SG) overfill protection is initiated on a SG high water level signal based on a 2-out-of-3 initiating logic. This instrumentation is safety grade but also is used for both SG level control and protection. The level control signals from each instrument channel are isolated from the protection functions, and input to a median signal selector (MSS) at the ADFCS. The overfill protection system isolates Main Feedwater (MFW) by closing the MFW control and bypass valves.

The following items address each SG overfill protection criterion in the context of the Ginna Station ADFCS design requested in the October 18, 1991 RAI and updates and supersedes our original response dated March 19, 1990:

1~ S stem Power Overfill protection is provided through trip bistables in the reactor protection racks, which are powered from A, B, C and D 120 VAC instrument buses. Upon bistable actuation, the 120 VAC protection relays (normally powered by the bistable) are de-energized, and the relay contacts (configured in a 2-out-of-3 matrix) open, de-energizing the vent solenoids from Train A and Train B 125 VDC power, resulting in closure of the main feedwater control and bypass valves.

The ADFCS receives power from both the A and C 120 VAC instrument buses via an uninteruptible power transfer feature.

Failure of both A and C instrument bus feeds to the ADFCS is required to cause a loss of feedwater control. Loss of the A and C buses will also result in fail safe actuation of the overfill protection system thus overriding any actions of the ADFCS. The design of overfill protection is considered to be adequate because of the fail safe design, and actuation will override any actions of the ADFCS.

2. Location Overfill protection and feedwater control are physically located in separate cabinets.

3 ~ Routin Overfill Protection The SG level transmitters are located inside containment.

Level signals from four of the transmitters exit containment in the Auxiliary Building Intermediate Floor (ABI). Two of the level signals exit containment in the Intermediate Building Basement (IBB). The trip bistables are located in protection racks in the Control Room. The basic relay

contacts for solenoid actuation are located in the SIA & SIB racks in the Relay Room. Routing from the penetration to the valve is illustrated on Table l.

Routin Feedwater Control The feedwater control system is located in the ADFCS Rack in the Relay Room. The SG level signals are taken from LT-461, 462, 463 (SG-A) and LT-471, 472, 473 (SG-B) channels via isolators located in the Control Room protection racks and supplied to median signal selectors in the ADFCS Rack. The feedwater valve control signals are routed from the ADFCS Rack to the control valves as illustrated on Table 1.

Overfill protection and feedwater control circuit share common fire areas, but are not routed within the same cable jacket.

A review of Ginna's safe shutdown capability in the event of any credible postulated fire (which include the common areas) was documented in our fire protection and Appendix R conformance reviews, and approved by the NRC in Safety Evaluation Reports dated 02/14/79 (Fire Protection) and 02/27/85 (Appendix R). Also, RG&E has documented contingency actions in the event of fires in specific areas (e.g., SC-3.30 series procedures and other plans covering fire-fighting strategies for safety-related fire areas). Therefore, based upon the routings shown on Table 1 and the above discussion, it is considered that all required situations involving safe shutdown in the event of a fire have been addressed, and no additional changes are warranted.

4 ~ Technical S ecifications Surveillance Technical Specification 3.5.2 requires SG overfill protection to be operable and specifies limiting conditions for operation should the system or portions of the system become inoperable.

Technical Specification Table 4.1-1 requires SG level to be tested monthly. Therefore, Technical Specifications require periodic verification of system operability.

Procedures are in place that implement the Technical specification requirements. Also, functional logic tests are performed that verify valve response.

Based upon Technical Specification surveillance requirements, power supply configuration, fail-safe design of overfill protection, separate cabinets and adequate cable routing (fires have been addressed in Appendix R reviews), the Ginna design provides sufficient separation to ensure automatic SG overfill protection to

mitigate a main feedwater overfeed event. No system modifications are planned as a result of this Generic Letter.

Very'truly yours, Robert C. Mecredy Subscribed and sworn to before me on this 27th day of Oct., 1993 f

MARIE C. Vlt.lENEUVE GAH)304 Nolary, Public, State ol Hew Yor~

Attachment Monroe CountY 19

>~iyeissioft gxpirez Octobe( 31<

xc: Mr. Allen R. Pohinson (Mail Stop 14Dl)

Project Directorate I-3 Washington, D.C. 20555 U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Ginna Senior Resident Inspector

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TABLE 1 CABLE ROUTING OVERFILL PROTECTION Protection SIA Level Containment Rack SIB Sicinal Penetration R~outin Location Location Routinca LT-461 & LT-472 (AE10) ABI, CT, CR CR RR, AHR, TB, Valve ABI LT-463 & LT-471 (AE11) ABII CT I CR CR RR, AHR, TB, Valve ABI LT-462 & LT-473 (CE4) IBB, CR CR RR, AHR, TB, Valve IBB FEEDWATER CONTROL SYSTEM Signal ADFCS Level Pickup Rack Sicina1 Location Location Routine[

LT 461 I 462 I 463 CR RR, AHR, TB, Valve LT 471 g 472 I 473 CR RR, AHR, TB, Valve Leceend ABI Auxiliary Building Intermediate Floor AHR Air Handling Room IBB Intermediate Building Basement CT Cable Tunnel CR Control Room RR Relay Room TB Turbine Building

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