ML17261B015

Responds to Generic Ltr 89-19, Safety Implication of Control Sys in LWR Nuclear Plants (USI A-47). Overfill Protection Provided Through Trip Bistables in Reactor Protection Racks Powered from 120-volt Instrument Buses

ML17261B015
Person / Time
Site:	Ginna
Issue date:	03/19/1990
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 9003270120
Download: ML17261B015 (6)

Text

I ACCELERATED DISTBJBUTION DEMONSTPA,TION SYSHM I

REGULATORY-. INFORMATION DISTRIBUTION SYSTEM (RI DS )

ACCESSION,,NBR:9003270120 DOC.DATE: 90/03/19 NOTARIZED: YES DOCKET FACIL: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 R

SUBJECT:

Responds to Generic Ltr 89-19, "Safety Implication of Control Sys in LWR Nuclear Plants."

DISTRIBUTION CODE A001D COPIES RECEIVED:LTR ENCL SIZE: D TITLE: OR Submittal: General Distribution S 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 PD1-3 LA 1 1 PD1-3 PD 1 1 D JOHNSON,A 5 5 D'

INTERNAL: NRR/DET/ECMB 9H 1 1 NRR/DOEA/OTSB11 1 1 NRR/DST 8E2 1 1 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 NRR/DST/SRXB 8E 1 1 NUDOCS-ABSTRACT 1 1 0 1 0 OGC/HDS2 ~

.1 0 1 1 RES/DSIR/EIB 1 1 EXTERNAL: LPDR 1 1 NRC PDR 1 1 NSIC 1 1 D

A D

D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEI CONTACT THE.DOCUMENT CONTROL DESK, ROOM PI-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISIRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEEDI TOTAL NUMBER OF COPIES REQUIRED: LTTR 21 ENCL 19

I'lÃlllll/f/ EIFIE EIaI (h la ROCHESTER GAS AND ELECTRIC CORPORATION o 89 EAST AVENUE, ROCHESTER, N Y. 14649.0001 TELEPHONE March 19, 1990 AREA COOE 715 546.2700 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 required licensees to respond within 180 days of the Generic Letter detailing whether the recommendations of the letter will be implemented and an implementation schedule applicable.

if The Generic Letter addresses concerns about .Steam Generator (SG) overfill protection. At Ginna, overfill protection is initiated on a SG high-water-level signal based on a 2-out-of-3 initiating logi'c. This instrumentation is safety grade but one of the three channels is used for both control and protection. The system isolates Main Feedwater (MFW) by closing the main feedwater. control and bypass valves.

In terms of USI A-47, this design is concluded to be acceptable if:

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

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

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

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

The following address each criterion in the context of the Ginna design:

5'003270i20 9003i9 PDR ADOCK 05000244 PDC 001 MjA

)py4o$ 5 ~P

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 Feedwater Control System receives power from the A and C 120 VAC instrument buses. Separate- breakers are used to provide power to the protection racks and the feedwater control system except Feedwater Loop A and Level Loop 461 share a common instrument Bus A breaker and a common regulator (TWINCO-MQ400A). Failure of the common breaker or regulator would cause a loss of Loop A feedwater control and. makeup of the LT-461 portion of overfill protection logic. Loss of any other breaker or regulator would only affect its associated level channel or Feedwater Control Loop B. Since overfill protection is fail safe, actuation of overfill protection will vent the feedwater control valve thus overriding any actions of the Control System. The design of overfill protection is considered to be adequate because of the fail safe design and actuation will override any actions of the feedwater control system.

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 lo'cated 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 1.

Routin Feedwater Control The Feedwater Control System is located in the feedwater rack in the Relay Room. The SG level signal is taken from LT-461 and, LT-471 channels via isolators located in the protection racks in the Control Room and supplied to the feedwater rack.

The valve control signal is routed from the feedwater rack to the control valves as illustrated on Table 1.

Overfill protection and feedwater control share common fire areas but are not routed in the same cable. 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). Thus, 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 be tested monthly.. There'fore, 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.

Ver truly yours, Robert C. c d Division Manager Nuclear Production Subscribed and sworn to before me on this 19th da of March, 1990.

g~ l, HAUCK

~~~&&aedNc York RWE/091 MONROEcoU~

Attachment xc: Mr. Allen R. Johnson (Mail Stop 14D1)

Project Directorate I-3 Washington, D.C. 20555 U.S. Nuclear Regulatory Commission Region 475 I

Allendale Road King of Prussia, PA 19406 Ginna Senior Resident Inspector

TABLE 1 CABLE ROUTING OVERFILL PROTECTION Protection SIA Level Containment Rack SIB Sicpal Penetration R~outin Location Location Routine[

LT-461 6 LT-472 (AE10) ABI, CT, CR CR RR, AHR, TB, Valve ABI LT-463 G LT-471 (AEll) ABI, CT, CR RR. RR, AHR, TB, Valve ABI LT-462 & LT"473 (CE4) IBB, CR CR RR, AHR, TB, Valve IBB FEEDWATER CONTROL SYSTEH Signal Feedwater Level Pickup Rack Sicgial Location Location ~Routin LT-461 CR RR, AHR, TB, Valve LT-471 CR RR RR, AHR; 'TB, Valve

~Le enu:

ABI Auxiliary Building Intermediate Floor IBB - Intermediate Building Basement CT Cable Tunnel CR Control Room RR Relay Room TB Turbine Building

V>

~

g

/ C

.r