ML20151L885

Forwards Supplemental Response to NRC Safety Evaluation of WCAP-10858, ATWS Mitigating Sys Actuation Circuitry Generic Design Package, Per Request During 871214 Telcon. Addl Info Will Be Provided Per Commitment in

ML20151L885
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	04/13/1988
From:	Rebecca Barr PORTLAND GENERAL ELECTRIC CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20151L889	List: ML20151L885 ML20265D528
References
NUDOCS 8804220177
Download: ML20151L885 (10)

Text

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M M N DM David W. Cockfield Vice President, Nuclear Apell 13, 1988 Trojan Nuclear Plant Docket 50-344 Licenso NPF-1 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555

Dear Sir:

Supplemental Responso to the Nuclear Regulatory Commission (NRC) Safety Evaluation of WCAP-10858, "Anticipated Transient Without Scram (ATWS)

Mitigating System Actuation Circuitry (AMSAC) Generic Design Packago"

REFERENCES:

1. NRC Letter to Portland Ceneral Electric Company (PGE)

Dated September 23, 1986 Transmitting Safety Evaluation of Topical Report (WCAP-10858), "AMSAC Concric Design Package".

2. PCE Letter to NRC Dated October 29, 1986, "Responso to NRC Safety Evaluation on AMSAC Ceneric Design Package".

3. PCE Letter to NRC Dated October 30, 1987, "Plant-Specific Response to the NRC Ssfety Evaluation of WCAP-10858, "Anticipated Transient Without Scram (ATWS) Mitigating System Actuation Circuitry (AMSAC) Cencric Design Package."

Attachment 1 to this letter provides additional clarification related to the Trojan-specific AMSAC design as requested by members of your staff during a December 14, 1987 telephone conference call. PGE will provido additional information upon request or by September 30, 1988 as committed to in Reference 3.

Sincerely, Attachment c: Mr. John B. Martin Mr. R. C. Barc Regional Administrator, Region V NRC Resident Inspector U.S. Nucicar Regulatory Commission. Trojan Nuclear Plant Mr. William Dixon State of Oregon [gh Department of Energy l' t l

8804220177 880413 /

PDR ADOCK 05000344 P DCD e E,'.Ca~nnEN-tPz m esgo rra

Trojan Nuclear Plant Document Control Desk Docket 50-344 April 13, 1988 Licenso NPF-1 Attachment 1 Pago 1 of 5 SUPPLEMENTAL RESPONSE TO NUCLEAR REGULATORY C0KMISGION (NRC)

SAFETY EVALUATION OF WCAP-10858, "ANTICIPATED TRANSIENT WITHOUT SCRAM (ATUS) MITIGATINC SYSTEM ACTUATION CIRCUITRY (AMSAC)

GENERIC DESIGN PACKAGE" Portland General Electric Company's (PCE) original response to the NRC Safety Evaluation of WCAP-10858 was provided to the NRC in a letter dated October 30, 1987. The supplemental information below is provided in response to a request by the NRC staff during a December 14, 1987 telephono conferenco call.

1. NRC Request - Diversity Insure that the output isolation relay is tested por Appendix A of the NRC Safety Evaluation.

PGE Responso - Diversity PGE does not yet know the specifics of the output isolation relay to be used. PGE will meet the requirements of Appendix A or resolve any iden-tified deviations that may occur with the NRC prior to installation of the AMSAC System.

2. NRC Request - Lor,ic Power Supplies The AMSAC power should not come from the same 480-V ac motor control. cen-ter (MCC) as the Reactor Protection System sourco. A common point at a 4160-V ac MCC is acceptable. If located on a common 480-V ac MCC, then redundant isolation from this MCC for AMSAC is necessary.

The AMSAC sourco does not have to be emergency dicsol generator backed if sufficient battery capacity exists to allow accomplishment of all initi-ating events.

PCE Response - Logic Power Supplies PGE has reviewed the NRC position related to the logic powcr supplies.

A.*.though the NRC does not requiro AMSAC to be emergency diosol backed, it is PGE's desire to do so iri order to ensuro maximum reliability. Without major modification 2, the current design of Trojan's Engineered Safety Features Electrical System does not allow for providing an emergency diesel-backed source of power without that source of power being common to the 480-V ac source for the Reactor Protection System. Therefore, PGE provides the following justification that the proposed AMSAC sourco of power [Y30 - Uninterruptibio Power Supply (UPS)] is provided sufficient isolation from the Reactor Protection System power (preferred instrument ac buses) by the electrical system design.

1

Trojan Nuclear Plant Document Control Desk Docket 50-344 April 13, 1988 License NPF-1 Attachment 1 Page 2 of 5 For reference, attached is a recent copy of the Trojan singlo-line diagram (E-1, Revision 15), which shows the Y30 UPS primary feed from MCC B22 and the bypass (backup) UPS input from MCC B26. This drawing also shows the Class IE 125-V de buses, and the preferred instrument buses.

There are two basic types of faults which could potentially affect both the Y30 UPS and the preferred instrument ac buses. The first would be a fault in the 480-V network, which could then be seen at both the battery charger inputs to the direct current buses and the inputs to the UPS.

The second instance is an actual fault on the preferred instrument buses (or their related battery buses), which, for discussion purposes, could feed through the battery buses and back through the charger into the 480-V network and, hence, to the UPS input.

For the first caso, it is not considered probable that any typo of a fault (overcurrent or overvoltage/undervoltage) on the 480-V bus network would reflect into the preferred instrument busos. The system has been design J such that faults or undervoltages will result in either a breaker tripping to isolato the fault, or the batteries taking over from the chargers to supply the inverters to the preferred Instrument buses.

This is part of the normal Class IE design of theso circuits. In addi-tion, the UPS is designed to provido an uninterruptible output voltage for tFe conditions of faulted or improper input voltages. Even though Y30 is not Class IE, it is within its expected design operation to per-form this function of practical isolation from the 480-V bus to the output of the UPS. Therefore, it is not reasonable to assume that any type of a fault on the 480-V buses, or any of the upstream buses supply-ing them, would causo a power disruption to both the preferred instrument buses and the UPS.

For the second case, a potential fault on the preferred instrument buses and/or related battery buses would have to propagato through the appro-priato charger to the 480-V bus. Due to the Class IE design of the pro-tective breakers on both sides of the charger, and conaidering the design of the charger itself, it is not considered feasible that a fault would feed back through the charger onto the 480-V bus without opening a pro-tective device. Even if this would occur, the fault falls within the bounds of the first case (480-V bus faults), and the UPS itself is designed to protect against faults on its input which disrupt the output of the UPS.

The UPS does have a secondary input for the bypass condition. The UPS would only bo in bypass in instances of either UPS failure or if the normal rectifier input into the UPS has been de-energized for a long enough period that the UPS batteries can no longer ensure output of the UPS. Because these conditions are considered rare and are not part of the normal operation, it is not considered feasible that this would occur l

Trojan Nuclear Plant Document Control Desk Docket 50-344 Apell 13, 1988 License WPF-1 Attachment 1 Page 3 of 5 at the same time that faults on the 480-V buses would cause a de-energization of this bypass. Even if it did occur, the failure of numerous protective devices would have to occur before any faults could affect both the UPS output and the preferred instrument buses.

As can be seen from the previous discussion and Drawing E-1, a UPS (Y30) source should not be affected by any faults or failures on the following RPS sources:

1. Preferred instrument bus (Y22),120-V ac.

2. Control center bus (D20), 125-V de.

3. Charger No. 2 (D22).

4. Inverter No. 2 (Y26).

5. Battery No. 2 (D12), 125-V dc.

6. 480-V System.

3. NRC Request - Safety-Related Interface Reference the appropriate Final Safety Analysis Report (FSAR) section for isolation device (interface) criteria.

PCE Response - Safety-Related Interface FSAR Section 8.3.1.4.2 addresses the criteria for isolation devices.

4. NRC Request - Quality Assurance Has Appendix G to PGE-8010 been compared to the NRC Generic Letter 85-06, to ensure it meets or exceeds all requirements?

PGE Response - Quality Assurance PGE-8010. "Nuclear Quality Assurance Program", has been compared to NRC Generic Letter 85-06, and meets or exceeds all requirements.

5. NRC Request - Maintenance Bypasses Maintenance bypass must be indicated continuously on control room annunciators, even when acknowledged.

r--_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . - - - - - - - - - _ _ .- . - - - - - _ _ - - - - - - . - - - - - - _ . - - - - - - . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Trojan Nuclear Plant Document Control Desk Docket 50-344 April 13, 1988 License NPF-1 Attachment 1 Page 4 of 5 PCE Response - Maintenance Bypasses Maintenance bypass will be continuously indicated on the control room annunciator system when bypassed and ATWS actuation required (above C-20 setpoint). The maintenance bypass alarm may be assigned to the cathode ray tube (CRT) display portion of the new annunciator system, vice an annunciator window. The annunciator system design is not complete enough to determine the exact location of the alarm.

6. NRC. Request - Operating Bypasses (C-20)

Same as Item 5; however, it is better to annunciato this when power is below 40 percent.

PCE Response - Operating Bypasses The operating bypass permissive status (C-20) will be displayed on the bypass status panel. The status light still be on when power is below 40 percent. A status panel light will be used instead of an annunciator in order to eliminate the visual clutter associated with lighted annunci-ators when the reactor is shut down and the condition is normal.

7. NRC Request - Physical Separation from RPS Revise the response to reference FSAR Section 8.3 which covers the present separation criteria for Trojan and state that the existing separation criteria is not violated.

PCE Response - Physical Separation From RPS FSAR Section 8.3 covers the present separation criteria for Trojan. The existing separation criteria as defined in FSAR Section 8.3 will not be vlotated.

8. NRC Request - Environmental Qualif ication Discuss why isolators are acceptable (ie, Appendix A to Safety Evaluation is applicable),

pCE Response - Environmental Qualification The AMSAC isolation devices will comply with the environmental qualifica-tions (10 CFR 50.49) and with the seismic qualifications which were the basis for Plant licensing. These qualifications are consistent with the requirements of Appendix A to the NRC Safety Evaluation of WCAP-10858.

Trojan Nuclear Plant Document Control Desk Docket 50-344 April 13, 1988 License NPF-1 Attachment 1 Page 5 of 5

9. NRC Request - Testability at Power Commit to partial testability at power during a specific frequency (usually quarterly), and completion of end-to-end testing during each refueling outage. As a minimum, an administrative Plant procedure should be applicable to this commitment.

PCE Response - Testability at Power PGE will test all portions of the AMSAC circuitry which do not result in actuation of AMSAC function on a quarterly basis. This test will be con-ducted in accordance with a Plant Operating Manual Periodic Instrument and Control Test. End-to-end testing of the AMSAC circuitry will be com-pleted during each refueling outage in accordance with a Plant Operating Manual Periodic Instrument and Control Test.

10. NRC Request - Other Items The NRC requested a simple logic diagram for review and comment, showing Class IE and non-Class 1E interfaces with the appropriate time-delay settings.

PCE Response Attached Figures 1, 2, and 3 provide the requested diagrams. The actual time-delay settings have not been determined, and will be included in the final submittal.

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