ML20133H683
| ML20133H683 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/29/1985 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| EVY-85-93, FVY-85-93, GL-85-06, GL-85-6, NUDOCS 8510180068 | |
| Download: ML20133H683 (4) | |
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4 VERMONT YANKEE NUCLEAR POWER CORPORATION 5-93 RD 5. Box 169. Ferry Road, Brattleboro, VT 05301 ENGINEERING OFFICE N
/4.
1671 WORCLSTER RO AD F R AMINGHAM. MASSACHUSETTS 01701 Tf tf PHONE et r 812 8500 September 29, 1985 U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Attention:
Office of Nuclear Reactor Regulation Mr. Harold R. Denton, Director
References:
a)
License No. OPR-28 (Docket No. 50-271) b)
10CFR50.62, " Requirements for Reduction of Risk from Anticipated Transients Without Scram (ATWS) Events for Light-Water-Cooled Nuclear Power Plants" c)
Letter, USNRC to All BWR Licensees and Applicants, NVY 85-15, dated January 28, 1985, " Clarification of Equivalent Control Capacity for SLC Systems (Generic Letter 85-03)"
d)
Letter, USNRC to All Power Reactor Licensees and All Applicants for Power Reactor Licenses, NVY 85-71, dated April 16, 1985, " Assurance Guidance for ATWS Equipment that is not Safety-Related (Generic Letter 85-06)"
e)
Letter, BWR Owners Group to USNRC, BWROG 8527, dated July 16, 1985, "ATWS Technical Specifications - 10CFR50.62" f)
Letter, USNRC to BWR Owners Group, dated August 19, 1985
Dear Sir:
Subject:
Generic Letter 85 ATWS Compliance Schedule (10CFR50.62)
By Generic Letter 85-06, dated April 16, 1985 (Reference d)], NRC issued quality assurance guidance for ATWS equipment.
In accordance with the issuance of that guidance (considered the reference data for initiating the schedule in 10CFR50.62(d)], Vermont Yankee herein provides a proposed schedule for meeting the requirements of Paragraphs (c)(1) through (c)(5) of 10CFR50.62.
Items 50.62(c)(1) and (c)(2) are requirements for pressurized water reac-tors and do not apply to Vermont Yankee.
With respect to Item 50.62(c)(3), Vermont Yankee meets the requirement to have an Alternate Rod Insertion (ARI) System that is diverse (from the reactor trip system) from sensor output to the final activation device. Vermont
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Yankee's ARI System utilizes redundant scram air header exhaust valves; is designed to perform its function in a reliable manner; and is independent (from the existing reactor trip system) from sensor output to the final activation device. Attachment I to this letter provides a discussion of the Vermont Yankee ARI System with respect to 10CFR50.62(c)(3) requirements.
8510100068 850929 O
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PDR ADOCK 05000271 I I P
s VIII(MONT YANK 1515 NUCl.liAIl POWillt ColtI OltATION U.S. Nuclear Regulatory Commission September 29, 1985 Page 2 With respect to Item 50.62(c)(5), Vermont Yankee presently meets the requirement to have equipment to trip the reactor coolant recirculating pumps automatically under conditions indicative of an ATWS. Vermont Yankee's Recirculation Pump Trip (RPT) System is described in Attachment 1 to this letter.
Based on the above, Vermont Yankee's existing plant design is considered to fully meet the requirements of 10CFR50.62 Items (c)(3) and (c)(5).
With respect to Item 50.62(c)(4), Vermont Yankee will implement a design or operational modification of its standby liquid control system during its second refueling outage after July 26, 1984, to meet the requirements of 10CFR50.62(c)(4). As Vermont Yankee was in an outage on the July 26, 1984 date, implementation is scheduled for our planned spring 1987 outage (prior to the start of Cycle 13).
Based upon prior discussions with your staff, which sup-ported our interpretation that Vermont Yankee's 1984 refueling outage did not constitute the first refueling outage under the Rule, we trust this proposed schedule is acceptable.
Vermont Yankee is p;esently evaluating various compliance alternatives with the BWR Owners Group to satisfy the requirements of 10CFR50.62(c)(4).
The guidance provided by Generic Letter 85-03 [ Reference c)] will be used as the besis for determining the proper boron equivalent in control capacity and weight percent of sodium pentaborate solution for conformance with Item 50.62(c)(4) requirements. We will notify you of the SLC System design or operational modi-fication that will be implemented prior to startup from our scheduled 1987 outage.
We trust this information is satisfactory; however, should you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION h..
Warren P. Murphy V
Vice President and Manager of Operations
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ATTACHMENT 1 VERMONT YANKEE ALTERNATE ROD INJECTION AND RECIRCULATION PUMP TRIP SYSTEMS 10CFR50.62(c)(3) AND (5) REQUIREMENTS i
10CFR50.62(c)(3) specifically requires that:
a Each boiling water reactor must have an alternate rod injection (ARI) system that is diverse (from the reactor trip system) from the sensor output to the final actuation device. The ARI system must have redun-dant scram air header exhaust valves. The ARI must be designed to perform its function in a reliable manner and be independent (from the existing reactor trip system) from sensor output to the final actuation device.
The ARI System presently installed at Vermont Yankee fully meets this requirement. The ARI System is actuated from dedicated instrumentation which senses reactor vessel level and pressure and generates the relay contact clo-sures neces;ary to initiate an ARI. This instrumentation, although of the same type (i.e., Rosemount transmitters), is both electrically and physically separate from any other reactor trip system associated instrumentation and supplies an initiation signal to the ARI solenoid valves.
The ARI solenoid valves are installed in the scram air header such that they are redundant to each other and to other scram solenoid valves. These ARI solenoids are installed in such a way that initiation of either, or both, of these solenoid valves, will cause the scram air header to exhaust.
10CFR50.62(c)(5) specifically requires that:
Each boiling water reactor must have equipment to trip the reactor coolant recirculating pumps automatically under conditions indicative of an ATWS. This equipment must be designed to perform its function in a reliable manner.
The Recirculation Pump Trip (RPT) System at Vermont Yankee is a parallel system off of the ARI trip circuitry. Like the ARI circuitry, the RPT trip coils are installed in the recirculation pump motor generator sets in such a way that initiation of either or both trains of the vessel level or pressure cir-cuitry will cause a trip of both recirculation pumps.
This trip is accomplished by disrupting the generator field breaker which causes a virtually instan-i taneous stopping of its associated recirculation pump. To accommodate for this lack of "coastdown" on low reactor level, the RPT is delayed ten seconds to allow better core void sweeping as ECCS Systems begin their safety function.
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l The RPT/ARI Systems presently installed at Vermont Yankee are configured such that they are a 2-out-of-2/once systems. The systems are subdivided into l
four (4) channels, two channels per power division, i.e., SI or SII, and each
- r channel having a level and a pressure input from dedicated transmitters. The 1
low level setpoint, or the high pressure setpoint must be exceeded by both chan-j nels associated with a power division in order to trip the recirculation pumps j
and exhaust the air header.
To assure system reliability, the RPT/ARI Systems are powered from a IE, battery backed, ECCS power source rather than the usual RPS power.
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Based on the above, the design of Vermont Yankee's ARI and RPT Systems can j
be considered to be separate from normal reactor trip systems and fully meet 10CFR50.62(c)(3) and (c)(5).
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