ML20101N165
| ML20101N165 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 04/04/1996 |
| From: | Reid D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20101N168 | List: |
| References | |
| RTR-NUREG-1433 BVY-96-37, NUDOCS 9604080277 | |
| Download: ML20101N165 (5) | |
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I VERMONT YANKEE NUCLEAR POWER CORPORATION Ferry Road. Brattleboro, VT 05301-7002 ENGINEERING OFFICE 580 MAIN STREET BOLToN, M A 01740 (508) 779-6711 April 4,1996 BW 96-37 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
References:
(a)
License No. DPR-28 (Docket No. 50-271)
(b)
NUREG-1433 Rev.1, Standard Technical Specifications for General Electric Plants, BWR/4 (c)
W Final Safety Analysis Report, Section 7.7.4.2
Subject:
Proposed Change No.183 Control Rod Over-Travel Indication Surveillance Pursuant to Section 50.90 of the Commission's Rules and Regulations, Vermont Yankee Nuclear Power Corporation hereby proposes the following change to the facility Operating License [ Reference (a)].
ProDosed Chanae This proposed change revises the existing requirements for control rod and drive mechanism coupling verification per Specification 4.3.B. The current requirements include specific methodology not only for the performance of the verification of rod and drive mechanism coupling, but also for testing the indication of over travel which is used to determine coupling. The specific testing methodology is proposed to be removed from the Technical Specifications and administratively controlled. This change is consistent with both the General Electric - Standard Technical Specification (GE-STS) 3.4.1.3.6, "Contromed Drive Coupilng" (Revision 4), and the improved STS (Reference b) Surveillance Requirement 3.1.3.f,.
Specifically, the changer proposed are as follows:
(1)
Page 83, Speci'.icallon 4.3.B.1(b). The requirement forverification of coupling after uncoupling is revised to be consistent with the other requirements for verification of coupling, i.e., the first time a rod is fully withdrawn following a refueling outage (a time during which activities that may affect coupling are most probable). This verification is identified as observing that the rod does not go to the over-travel position. An additional Specification to require verification that the over travel indicating light is working properly by withdrawing an uncoupled rod to the over-travel position is Inconsistent and unnecessary.
(2)
Page 89 & 90, Bases for Specification 3.4.B.1 and 4.3.B.1. Revised Bases to incorporate additionalinformation consistent with the incorporation of item 1 above.
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U.S. Nuctrar Regulatory Commission VERMONT YANKEE NUCLEAR POWER CORPORATION
' April 4,* 1996 Page 2 Reason / Basis for Chanae Coupilng verification is performed to ensure the control rod is connected to the control rod drive mechanism and will perform its intended function when necessary. The Surveillance requires verifying a control rod does not go to the withdrawn over travel position. The over-travel position feature provides a positive check on the coupling integrity since only an uncoupled control rod drive can reach l
the over-travel position. The verification is required to be performed when a control rod is fully withdrawn, after each refueling outage (since work on the control rod or CRD System may have affected coupling), and after each uncoupling.
Typically, the instrumentation used to determine that a specific parameter is within limits, or a component is operable, is not itself required by the Technical Specifications. The August 1995 revision to 10CFR 50.36 incorporated a specific set of objective criteria as guidance for determining which regulatory requirements and operating restrictions should be included in Technical Specifications.
These criterla also do not li.clude such secondary instrumentation as the over travel indication. Such instrumentation is typically controlled administratively to meet the requirements for 10CFR Part 50.
Appendix B,Section XI, " Test Control," and Section Xil, " Control of Measuring and Test Equipment."
These administrative controls are also considered to be adequate for the over travel indication.
The referenced Specification requires that "following uncoupling, each control rod drive and blade shall be tested to verify positive coupling and the results of each test shall be recorded. This test shall consist of checking the operability of the over-travelindicator circuit prior to coupling by withdrawing the drive and observing the over-travel light. The drive and blade shall then be immediately coupled and fully velthdrawn. The position and over-travel lights shall be observed."
This requires the following procedure: After the drive and/or blade is installed and the position indicating probe is re-installed, the over travel alarm is verified to be in for that drive. The operator then applies a withdraw signal to that drive. The 0.2 second Insert signal at the start of the withdrawal sequence, which uniatches the collet fingers, inserts the drive a short distance and clears the over-travel alarm but doesn't insert far enough to couple the blade. The directional control valves then shift to drive out the CRD and the over travel alarm is verified in again. If this occurs the drive is given an insert signal to couple the drive to the blade. The drive is then fully withdrawn (to notch position 48) and a standard coupling check is performed and the over travel alarm is verified to be clean.
This procedure. can be accompFshed, however, as described above, this entails attempting to insert a rod just far enough to pick up the coupled reed switch without actually coupling the rod. It is somewhat difficult to withdraw an uncoupled control rod drive without inadvertently recoupling the drive due to the Insert signal that is momentarily given by the Reactor Manual Control System to allow the CPO collet fingers to disengage the index tube [ Reference (c)). If the control rod and the drive mechanism are inadvertently recoupled during the withdraw signal, then the control rod must be uniatched and the surveillance re-initiated. This testing methodology resulted in a loss of approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of critical path time during startup from the last refueling outage. An audit of other plant's Technical Specifications identified no requirements for those other plants to perfctm this verification In this manner. Further, this methodology appears to provide no additional Information or obvious benefit.
1 Normal procedures provide for the drive to be fully withdrawn and uncoupled when a new drive or control blade is installed. The indication provided by the over-travel alarm will be verified at that time and recorded. This will remove the need to insert and withdraw each drive mechanism prior to coupling. The drive will then be inserted to couple the rod and drive mechanism, and the standard coupling check will be performed (i.e., observe and record that the over-travel alarm stays clear).
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l U.S.' Nuclear Regulatory Commission
' VERMONT YANKEE NUCLE AR POWER CORPORATION
' April 4,1996 Page 3
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Safety Con'siderations Coupilng verification is performed to ensure the control' rod is connected to the control rod drive mechanism and will perform its intended function when necessary. The S0rveillance requires verifying a control rod does not go to the withdrawn over-travel position. The over-travel position feature provides a positive check on the coupling Integrity since only an uncoupled CRD can re'ach the over-travel position. The actual verification of recoupling is not proposed to be revised. However, the Surveillance Requirement for verification of the over-travelindication is proposed to be removed from
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the Technichi Specifications. This change is consistent with General Electric - Standard Technical l
Specification (GE-STS) 3.4.1.3.6, " Control Rod Driv.e Coupling" (Revision 4).
l Control rod position Information is provided'primarily b'y the position Indicator probe (PIP) which contains switches,' mounted one on each side at 53 different levels. These switches transmit electrical l
signals to provide control room indication of control rod position. These switches are normally open l
and closelndividually during control rod drive mechanism operation only when a ring magnet (installed l
In the bottom of.the drive piston) passes in close proximity to the switch. Most are arranged in pairs at three Inch 1ntervals on the switch support to provide e control room digital display of rod position
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from "00" (control rod fully inserted into the core) to "48" (control rod fully withdrawn to the backseat posill6n). Additi'onal switches are installed on the op~posite side of the switch support from the normal switch at 00 to provide the control room with a signal for rod " full-In." Similarly, additional switches are installed near the bottom of the probe to provide the control room with a signal of rod " full-out."
Another swit,ch is' installed two inches below the normal full out position of the control rod drive mechanism. Since the noimallimit of the drive piston downward travelis provided by the backseat position ("48"), this switch is closed only when the control rod and the drive mechanism are uncoupled and the drive mechanism is withdrawn to the over travel position.
A required surveillance of the over-travel position is unnecessary since an attempt to withdraw a control rod past the backseat position will result in one of the following conditions. (1) The control rod Will not l
withdraw past the backseated position'as indicated by the "48" and " full-out" indicators continuing to be displayed and the over-travel indicator not displayed. This is the expectsd response for a i
coupled control rod and drive mechanism. (2) The control rod will withdraw past the backseated j
position'as indicated by the "48" and " full-out" indicators no longer being displayed (since the ring magnet is no longer in close proximity to these switches) r nd the over-travel indicator will be displayed.
This is the expected response for an uncoupled control rod drive mechanism. (3) The control rod will i
i withdraw past the backseated position _, and the Indication will be inconclusive. If the "48" and " full-out" indicators are no longer displayed, but the over-travel indicator is also not displayed, this is Indicative of a probable over travel indication problem and should be investigated prior to continuing i
or declaring the control rod and drive mechanism " coupled." This is why the current Specification L
requires observing both "the position and over-travellights." This type of redundant indication makes
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the required additional specific surveillance of the over-travelindication unnecessary and redundant.
This redundant indication also allows the specific surveillance to be omitted with no significant safety consequences.
This Proposed Change has been reviewed by the Vermont Yankee Plant Operations Review Committee and the Vermont Yankee Nuclear Safety Audit and Review Committee.
Sionificant Hazards Consideration The Standards used to arrive at a determination that a request for amendment involves no significant i
hazards are included in the Commission's regulations (10CFR 50.92) which states that the operation
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t U S. Nuclear' Regulatory Commission
- VERMONT YANKEE NUCLEAR POWER CORPORATION April 4,' 1996 Page 4
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of the facility in accordance with the proposed amendment would not: (1) involve a significantincrease in the probability or consequences of an accident previously evaluated; (2) create the possibility of a new or differerit kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a trargin of safety. In addition, the Commission has provided guidance in the practical application.of t')ese c-iterie in 51FR7751, dated March 6,1986.
The discusslori below addresses each of 'there criteria ~ and demonstrates that the proposed amendment involves no significant hazards consideration.
(1)
The control rod drive mechanism over travel indication is not considered to be the initiator of
.any previously analyzed accident. Verification of coupling of the control rods and drive mechanisms is performed by other means and. continues to be required in this same manner, so there is no significant increase in the probability of a rod drop accident. The over travel indication is also no't considered in the mitigation of consequences of any previously analyzed
' accident, and the removal of a specific surveillance of the indication will not affect the response
' of the control rods or the reactor protection system to these accidents. Therefore, this change will.not significantly increase the probability or consequences of any previously analyzed
' accident;.
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(2)~
The proposed change does not necessitate a physical alteration of the plant (no new or
' ' different type of equipment wifl be installed) nor changes in parameters governing normal plant operation. The proposed change will. continue to provide effective methods to assure the control rods and their drive mechanisms are coupled and. preserve the sa_fety functions assDciated with the prevention or automatic mitiga.tlon of design basis accidents. Thus, this change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
(3)
The proposed changes continue to provide an appropriate method for verification of the capability of the over-travel indication to perform its function. Therefore, this change will not significantly reduce a margin of safety.
Based on the above discussion, we have determined that this change does not constitute'a significant hazard consideration as defined in 10CFR 50.92(c).
Schedule of Chanae The proposed change will be incorporated into Vermont Yankee Technical Specifications as soon as practicable following receipt of your approval.
U.S. Nucitar R!gulatory Commission VERMONT ANKEE NUCLEAR POWER CORPORATION
' April 4,' 1996 Page 5 - '
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We trust that the informa'tlon provided above adequately supports our request. However, should you l
have any question in this matter, please do not hesitate to contact us.
l Sincerely, 1
i Vermont Yankee Nuclear Power Corporation L
Donald A. Reid Vice President, Operations cc:
- USNRC Region 1 Administrator
~ USNRC Resident inspector - WNPS USNRC Project Manager - WNPS i
STATE OF VERMONT
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)ss WINDHAM, COUNTY
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Then personally appeared before me, Donald A. Reid, who, being duly sworn, did state that he is Vice President, Operations, of Verrnont 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, and that the statements therein are true to the best of his knowledge and belief.
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