ML20247C456
| ML20247C456 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 05/12/1989 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20247C463 | List: |
| References | |
| BVY-89-11, NUDOCS 8905240474 | |
| Download: ML20247C456 (9) | |
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YERMONT YANKEE NUCLEAR POWER CORPORATION Proposed Change No. 147 RD 5, Box 169 Ferry Road. Brattleboro. VT 05301 BVY 89-44 MPLV TO ks ENGINEERING OFFICE 680M^'"S*EET May 12, 1989 BOLToN, MA 01740 (508)779-6711 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
References:
(a) License No. DPR-28 (Docket No. 50-271)
(b) Letter, VYNPC to USNRC, WVY 80-49, dated March 17, 1980 (c) Letter, USNRC to VYNPC, dated November 3, 1980 (d) Letter, USNRC to VYNPC, NVY 87-04, dated January 8, 1987 (e) Letter, VYNPC to USNRC, FVY 87-41, dated April 10, 1987
Subject:
Proposed Technical Specification Change Regarding ATWS Rule (10CFR50.62)
Dear Sir:
Pursuant to Section 50.90 of the Commission's Rules and Regulations.
Vermont Yankee Nuclear Power Corporation hereby proposes the following changes to Appendix A of the Operating License (Reference (a)).
Proposed Change Vermont Yankee proposes the following changes to the Technical Specifications associated with the ATWS Rule (10CFR50.62) regarding the Standby Liquid Control (SLC) and Alternate Rod Insertion (ARI) Systems:
Change 1. Reactor Standby Liquid Centrol System, Technical Specification Sections 3.4/4.4 A, B, C, D, E, F, and G Limiting Conditions for Operation and/or Surveillance Requirements (Pages 79, 79a, 80, 80a, 80b, and 80c) are revised and/or added; Figure 3.4.1 (Page 81) is deleted; and applicable Sections 3.4/4.4 Bases Sections (Pages 83, 83a, and 84) are revised to reflect the increased Boron-10 enrichment in the SLC System sodium pentaborate solution concentration.
Change 2. Protective Instrument Systems, Technical Specifications Sections 3.2/4.2.I (Page 34a) are revised; Table 3.2.1 (Pages 39a and 40) is revised; Table 4.2.1 (Page 53a) is revised; and applicable Section 3.2 Bases (Page 63) are revised to incorporate specific reference to the ARI system within the Technical Specifications.
The specific page changes and additions associated with this amendment request are listed in Attachment A and provided in Attachment B.
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United States Nuclear Regulatory Commission May 12, 1989
' Attention: Document Control Desk Page 2 Reason for Change on July 26, 1984, the Code of Federal Regulations (CFR) was amended to include Section 10CFR50.62 (ATWS Rule) which required specific improvements in l
the design and operation of nuclear power plants to reduce the likelihood of failure to shutdown the reactor following anticipated transients, and to mitigate the consequences of an ATWS event.
l By letter, dated January 8, 1987 (Reference (d)), NRC requested Vermont Yankee to provide plant-specific information sufficient to demonstrate the compliance adequacy of the systems addressed in Paragraphs (c)(3), (c)(4), and (c)(5) of 10CFR50.62 (ATWS Rule). Additionally, this letter requested Vermont Yankee to enclose an amendment request containing proposed Technical Specifications associated with the ATWS-related components. Accordingly, Vermont Yankee provided the information requested for the ARI, SLC, and Recirculation Pump Trip (RPT) Systems (Reference (e)), and committed to submit any Technical Specification changes in a subsequent submittal.
Change 1. Vermont Yankee's SLC System provides backup shutdown capability via manually initiated injection of sodium pentaborate solution, containing the neutron absorber Boron-10, into the vessel in the unlikely event that withdrawn control rods remain fixed in the rated power pattern following a scram signal. The SLC System provides the capability to bring the reactor from full power to a cold shutdown condition by the injection of a sodium pentaborate solution.
Parallel active components ensure high system reliability and explosive, zero leakage injection valves ensure the neutron absorber does not enter the vessel until the system is initiated. The sodium pentaborate solution is maintained above the saturation temperature by the normal ambient building temperature supplemented as needed by heaters and heat tracing to ensure precipitation does not occur.
Vermont Yankee committed to implement a design modification during the 1987 refueling outage to satisfy the ATWS Rule SLC requirement for minimum flow capacity and boron content equivalent in control capacity to 86 gpm at 13 weight percent sodium pentaborate solution for a 251" diameter reactor pressure vessel.
This requirement increased the required rate of Boron-10 delivery into the vessel.
There were three methods to meet the increased delivery rate requirement discussed in General Electric's Licensing Topical Report, NEDE-31096-P:
- 1) two-pump system operation; 2) increase the sodium pentaborate solution concentration; and 3) increase the Boron-10 enrichment of the sodium pentaborate solution. The enrichment alternative offered several advantages including maintaining system redundancy and requiring no system hardware modifications. By enriching the boron in the sodium pentaborate solution with the Isotope B-10, Vermont Yankee met the equivalent control capacity requirement. This design alternative maintains the current one-pump operation and existing solution concentration and volume. Accordingly, the equivalent control capacity requirement is met for the Vermont Yankee 205" diameter reactor vessel by enriching
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the boron content with a B-10 isotope to a percentage appropriate to the Vermont Yankee vessel size. Therefore, Vermont Yankee met the I
requirements of 10CFR50.62(c)(4) by implementation of the SLC alternative described above in conformance with an approved design alternative contained in NEDE 31096-P and the NRC staff conditions noted in Section 5.2.3 of the SER enclosed with NRC letter dated January 8, 1987 (Reference (d)).
By letter, dated April 10, 1987 (Reference (e)), Vermont Yankee committed that any Technical Specification sections requiring change as a result of the implementation of the enriched boron solution modification would be submitted for NRC approval as a separate license amendment request. Accordingly, this proposed change is submitted for approval.
Change 2. With regard to Vermont Yankee's conformance with the 10CFR50.62(c)(3) ARI requirements and objectives, Vermont Yankee's ARI System is in compliance with the conceptual design alternatives contained in the BWR Owners Group Licensing Topical Report (NEDE 31096-P) submitted January 14, 1986, and approved by NRC on October 21, 1986, and meets the requirements of 10CFR50.62(c)(3) in that it utilizes redundant scram air header exhaust valves; is designed to perform its function in a reliable manner; and, is independent (from the normal Reactor Trip System) from the sensor output to the final actuation device.
In addition, the ARI System is diverse (from the Reactor Trip System) from sensor output to final actuation device in that:
(a) The ARI System utilizes Solencid Operated Valves (SOVs) which are required to be energized to function, whereas the Reactor Trip System (RTS) utilizes SOVs which are required to be de-energized to function.
(b) The ARI System utilizes de-powered valves, whereas the RTS utilizes ac-powered valves.
(c) All instrument channel components including sensors, signal conditioning, and logic components are different from the existing components used for RTS.
Technical Specifications for the ARI System are essentially i
contained in the Sections 3.2/4.2 logic / actuation specifications for the RPT System approved by NRC in 1980 (References (b) and (c)).
Because ARI is not specifically identified in these sections, Vermont Yankee committed by letter dated April 10, 1987 (Reference (e)) to consider revising the RPT Technical Specification sections to provide a specific reference to the ARI System.
Accordingly, this proposed change is submitted for approval.
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United States Nuclear Regulatory Commission.
May 12, 1989
- Attention: Document Control Desk Page 4 Basis for Change
' Change 1. Sections 3.4/4.4 A, B, C, D, E, F, and G Limiting Conditions for Operation and/or Surveillance Requirements are revised, and/or added, and Figure 3.4.1 is deleted to: allow the sodium pentaborate solution to be used for recirculation testing; add a solution concentration equivalency to meet original design basis concentration, add a Boron enrichment testing interval; and add ATWS Rule equivalency requirements for determining the minimum 10CFR50.62 ATWS equivalency parameters.
Recirculation of the solution during testing as an option to using
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only demineralized water, as now required, will allow more operational latitude-to conserve the concentration of the sodium pentaborate solution trapped in the piping prior to testing. The trapped solution would normally be pushed into'the solution tank with demineralized water, thus reducing the solution concentration in the tank slightly each time testing is performed. Using the solution for recirculation testing would allow the solution to be pumped, to the greatest extent possible, into the solution tank before demineralized water is used to push the remaining solution into the tank. This reduces the amount of dilution to the solution tank.
The original design objective of the Standby Liquid Control System is met by injecting a quantity of boron, of which at least 19.8%
must be the isotope Boron-10, which produces a concentration of 800 ppm of boron in the reactor core in less than 138 minutes. The injection time is L set on a maximum solution volume in the tank of 4,830 gallons and a minimum injection rate of 35 gpm. This is based on a minimum amount of total boron in the solution storage tank.
Total boron is based on 19.8% of the total boron being the isotope Boron-10. By increasing the enrichment (Boron-10 percentage) more Boron-10 is available for each increment of concentration. An increase in enrichment can reduce solution concentration accordingly. By using the highest relative concentration, corresponding to the lowest solution volume, a conservative relationship between enrichment and concentration is obtained. An equivalent amount of Boron-10 is injected to satisfy original design reactor shutdown requirements by increasing the solution enrichment thus reducing the minimum solution concentration.
If the equation C 1 10.1%
- 19.8% / E is satisfied (where; C = tested concentration, 10.1% = reference concentration, 19.8% = natural enrichment (percentage of Boron-10 in total boron), and E = tested enrichment %) the original design objective of the Standby Liquid Control System is met.
Boron enrichment testing is performed at a frequency commensurate with the ability of enrichment to change. Enrichment testing of the solution is only necessary prior to an operating cycle to verify
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~* Attention:- Document Control Desk Page 5 system operability by ensuring that sufficient Boron-10 is available
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to meet ATWS shutdown requirements. Boron enrichment testing is performed on the chemicals to be used as make up to the solution tank. The combination of chemicals (boric ecid and borax) or sodium pentaborate used as make up must meet the minimum ATWS Rule enrichment equation specified in Section 3.4.D.
The ATWS equivalency requirements for determining the minimum ATWS equivalency parameters are accomplished by a formula using solution concentration, Boron-10 enrichment, and flow rate. Basing equivalency on the specified formula and its three variable parameters allows for compensation of a deficient parameter by changing one or more of the other parameters, thereby allowing a quicker. return to ATWS Rule equivalency requirements.
The Sections 3.4/4.4 Bases section are revised to reflect the above changes.
Change 2. Section 3.2/4.2 I is revised to include a specific reference to'the ARI System within the Protective Instrument Systems Specifications.
Table 3.2.1 is revised to add reference to specific limiting conditions of operation requirements for the ARI System.
Table 4.2.1 is revised to add specific reference to test and calibration frequencies for the ARI System.
The Section 3.2. Bases is revised to reflect the above changes.
Safety Considerations This proposed change does not present an unreviewed safety question, as defined in 10CFR50.59. The ATWS Rule required plant modification to meet ATWS conditions that are additional to those required for safe shutdown under the conditions addressed in the FSAR. Both the ARI and SLC System-related Technical Specification changes proposed reflect enhancements to safety that are in compliance with the conceptual design alternatives contained in the BWR Owners Group Licensing Topical Report (NEDE 31096-P) submitted January 14, 1986, and approved by the NRC in their Safety Evaluation Report contained in Reference (d).
This proposed change has been reviewed by the Plant Operations Review Committee and the Vermont Yankee Nuclear Safety Audit and Review Committee.
Significant Hazards Consideration The standards used to arrive at a determination that a request for amendment requires no significant hazards consideration are included in the Commission's regulations,10CFR50.92, which state that the operation of the
United States Nuclear Regulatory Commission May 12, 1989
' Attention: Document Control Desk Page 6 facility in accordance with the proposed amendment would not:
- 1) involve a significant increase in the probability or consequences of an accident previously evaluated; 2) create the possibility of a new or different kind of accident previously evaluated; or 3) involve a significant reduction in a safety margin. The discussion below addresses these standards and demonstrates that the proposed amendment involves no significant hazards considerations.
Change 1. Vermont Yankee has determined that the requested changes associated with the SLC System do not:
1)
Involve a significant increase in the probability or consequences of an accident previously evaluated because the increase in SLC System control capacity via Boron-10 enrichment effectively increasing the Boron-10 injection rate does not alter the function of the system, method of operation or dual train configuration; the system response time to an ATWS event has been reduced as the increased Boron-10 enrichment of the solution provides faster negative reactivity insertion thus reducing the consequences of the ATWS event; the SLC System is not credited in any of the design basis accident analyses and, as such, is considered to provide only an additional mitigative feature in the event of an accident; the SLC System sodium pentaborate solution concentration and flow rate required by the NRC for reactivity control independent of the control rods are not reduced from the values previously evaluated and presented in the Technical Specifications; the addition of enriched boron provides a shutdown margin greater than the previously calculated shutdown reactivity control capacity, and the change does not affect the possibility of an ATWS.
2)
Create the possibility of a new or different kind of accident than previously evaluated because the proposed changes involve a system whose function is to provide an additional mitigative shutdown capability and no system modifications are made; the addition of enriched boron does not effect any system or component which could initiate an accident; and there are no systems or subsystems that interact with the SLC System which could initiate an accident.
Thus, no new or different unevaluated accident is created.
3)
Involve a significant reduction in a margin of safety because the addition of enriched boron to the SLC System tank solution concentration actually increases the capability of the SLC System to achieve cold shutdown, thus no margin of safety is reduced.
Change 2. Vermont Yankee has determined that the requested changes associated with the ARI System do not:
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' United States Nuclear Regulatory Commission May 12, 1989 Attention:- Document Control Desk Page 7 1)
. Involve a significant increase in the probability or consequences of an accident previously evaluated because the addition of a specific reference to the ARI System in the Technical Specification does not result in any system hardware modification or new plant configuration for operation.
Thus no FSAR accident consequences previously evaluated are impacted.
Further, the ARI System is not postulated to initiate any accident scenarios, thus this change does not affect the probability of previously evaluated accidents.
2)
Create the possibil'.2y of a new or different kind of accident than previously evaluated because no new plant configuration for operation results from this change. The ARI System is a parallel to the RPT System and is actuated by the same trip circuitry and utilizes the same logic arrangement and sensors.
Thus'no new or different unevaluated accident is created by incorporating a specific reference to the ARI System within the Technical Specifications.
3)
Involve a significant reduction in a margin of safety because this change involves no physical or procedural modifications.
The change provides specific reference in the Technical Specifications to the ARI System by incorporating limiting conditions for operation and-surveillance requests consistent with those previously approved for the RPT System, thus no margin of safety is reduced.
Additionally, because these proposed amendments to the Vermont Yankee Technical Specifications are directly associated with compliance with the ATWS Rule, they are similar to Example (vii) provided by the Commission (51FR7751, dated March 6, 1986) as one of the types of amendments not likely to involve a significant hazards consideration. Example (vii) denotes an amendment to make a license conform to changes in the regulation when the license change results in very minor changes to facility operations clearly in keeping with the regulations. Additionally, the changes proposed herein also resemble Example (ii), which denotes an amendment that constitutes an additional limitation, restriction or control not presently included in the Technical Specifications, in that stricter operating and surveillance requirements reflect additional conservatism. Based on the above, Vermont Yankee has determined that the proposed amendment involves no significant hazards considerations.
Schedule of Change This proposed change will be incorporated into the V'ermont Yankee Technical Specification within thirty days following receipt of your approval.
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' Attention: ' Document Control Desk Page 8.
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We trust that the information above adequately supports our requests; however, should you have any questions in this matter, please contact us.
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Very truly yours.
VERMONT YANKEE CLEAR POWER CORPORATION l
$d /$ M W. P.Mu ph l
Vice Presid t a d Manager of Operations l
l WPM /0046w Enclosure cc: Vermont Department of Public Services
. 120 State Street Montpelier, Vermont 05602 Attention:
Mr. G. Sterzinger, Chairman USNRC Region I USNRC Resident Inspector, VYNPS STATE OF VERMONT ).
)ss OF WINDHAM COUNTY)
Then personally appeared before me, Warren P. Murphy, who, being duly sworn, did state that he is Vice President and Manager of Operations of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execute and file the foregoing document.in the name and on the behalf of Vermont Yankee Nuclear Power Corporation that the statements therein are true to the best of his knowledge and lief.
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Notary Public Diane McCue My Commission Expires
' February 10, 1991
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ATTACHMENT A Summary of Technical Specification Changes l
Delete the Following Pages Insert the Following Pages 34a 34a 39a 39a 40 40 53a 53a 63 63 79 79 79a 79a 80 80 80a 80b 80c 81 81 83 83 83a 84 84
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