ML20129F791
| ML20129F791 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/30/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20129F779 | List: |
| References | |
| NUDOCS 9610070036 | |
| Download: ML20129F791 (3) | |
Text
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4, UNITED STATES y
j NUCLEAR REEULATCRY COMMISSION I 2 WASHINGTON, D.C. =a =1
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.149 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271
1.0 INTRODUCTION
By letter dated April 4, 1996, the Vermont Yankee Nuclear Power Corporation (the licensee) submitted a request for changes to the Vermont Yankee Nuclear Power Station (VYNPS) Technical Specifications (TSs). The proposed changes would remove the requirement in Specification 4.3.B.l(b) to check the operability of-the control rod over-travel indicator circuit prior to coupling each control rod. The licensee will continue to monitor the operability of the overtravel circuit by observing the position and overtravel lights during a coupling check following de-coupling. The Itcensee proposed to maintain testing of the over-travel indication function using the current methodology in administrative 1y controlled documents. The actual requirement in Specification 4.3.B.l(b) to verify control rod drive coupling would not be changed.
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The safety objective of control rod drive coupling verification is to ensure that the control rod is connected to the control rod drive mechanism and will perform its intended function when necessary. As discussed in the TS Bases for the control rods, control rod dropout accidents can lead to significant core damage. Consequently, in order to eliminate the possibility of a rod dropout accident, the TS require maintaining control rod drive coupling integrity.
i The purpose of the control rod drive over-travel indication instrumentation is to provide a positive check on the integrity of the control rod drive coupling. This check is based on the design of the control rod drive mechanism and control rod which prevents a coupled drive from reaching the over-travel position. That is, an uncoupled drive may be withdrawn until the over-travel annunciator indicates an over-travel position has been reached-but a coupled drive cannot actuate the over-travel annunciator when fully withdrawn.
i 2.0 fyALUATION TS 4.3.B.1(b) requires verifying control rod drive. coupling integrity (1) when a rod is fully withdrawn by observing that the rod does not go to the over-travel position, and (2) prior to startup following a refueling outage by continuously withdrawing each rod to observe that the rate of withdrawal is t
9610070036 960930 PDR ADOCK 05000271 P
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proper and that the rod does not go to the over-travel position. These provisions are not proposed to be changed. However, this TS also states, i
"Following uncoupling, each control rod drive and blade shall be tested to verify positive coupling and the results of each test shall be recorded."
It then prescribes how to perform this test:
"This test shall consist of checking the operability of the over-travel 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 withdrawn. The position and over-travel lights shall be observed."
The licensee proposed to remove the operability verification of the over-l travel circuit from this specification by deleting the portions of the preceding text indicated by italics. The specification would then require the licensee, following uncoupling and subsequent re-coupling, to check the operability of the overtravel circuit by observing both the position and overtravel lights.
An attempt to withdraw a fully-withdrawn control rod past the backseat position will result in one of the following displays:
For a coupled drive, the control rod will not withdraw past the backseated position as indicated by the control rod position indicator probe (PIP) displays of "48" and " full-out" and the over-travel indicator not 4
displayed.
3 For an uncoupled drive, the control rod will withdraw past the backseated position as indicated by display of the over-travel indicator, but no PIP 4
displays.
If neither the PIP displays nor the over-travel display appear, then the drive may be either (a) coupled with both PIP displays inoperable, or (b) uncoupled with the over-travel display inoperable.
If the "48" and " full-out" indicators are no longer displayed, but the i
over-travel indicator is also not displayed, this is indicative of a probable over-travel indication problem and should be investigated prior to continuing or declaring the control rod and drive mechanism " coupled."
This is why the current Specification requires observing both "the i
position and over-travel lights." This type of redundant indication makes the required additional specific surveillance of the over-travel indication unnecessary and redundant. On this basis, the changes to surveillance testing of the overtravel circuit and corresponding TS and TS bases are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Vermont State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes requirements with respect to installation or use of facility components located within the restricted area as defined in 10 CFR 1
Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (61 FR 20860). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0. CONCLUSION The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
C. Harbuck Date:
September 30, 1996 l
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