ML20128B151
| ML20128B151 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 06/24/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20128B129 | List: |
| References | |
| NUDOCS 8507030143 | |
| Download: ML20128B151 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION g
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WASHING TON, D. C. 20666 o.....*
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 43 TO FACILITY OPERATING LICENSE NPF-12 SOUTH CAROLINA ELECTRIC & GAS COMPANY SOUTH CAROLINA PUBLIC SERVICE AUTHORITY I.
INTRODUCTION By letter dated April 9,1985, South Carolina Electric & Gas Company requested a revision to the Virgil C. Summer Nuclear Station Technical Specification 3/4.1.3 " Movable Control Assemblies." Technical Specifi-cation 3.1.3.1 sets forth those actions which must be taken when a full length movable control assembly is inoperable. This is applicable in Modes 1 and 2.
The proposed Technical Specification includes a new action statement to address the inoperability of the movable control rod assembly due to a rod control urgent failure alam or obvious electrical problem in the rod control system for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
II.
EVALUATION The rod control system (RCS) is used to compensate for fast short term reactivity changes such as those resulting from power changes and xenon peaking. The RCS utilizes the control banks in order to maintain a pro-gramed average temperature in the reactor system by regulating the reactivity in the core, but is not directly involved with the performance of any safety functions for mitigating the consequences of a transient or accident. As such, it is classified as a non-Class 1E system. The system actuates alams, governs control rod movement, and initiates rod movement in response to load changes. One of the annunciators displayed on the plant annunciator panel is the " Rod Control Urgent Failure" alam, which indicates that an internal failure has occurred in the full length rod control system. This inhibits automatic rod motion but permits manual movement of a selected bank if the logic cabinet and the two power cabinets associated with the selected bank are not in urgent alam.
The present action statement under the limiting condition for operation (LCO) addresses the situation where more than one full length rod is inoperable or misaligned from the group step counter demand position by more than 212 steps.
In this case, the unit must be in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The licensee has proposed to include a new action state-ment to address inoperability of the movable control rod assemblies due to a rod control urgent failure alam or obvious electrical problem in the rod control system. This would allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to perform any required maintenance to restore the system to an operable status. Other-wise the unit must be brought to hot standby within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
As justification for the proposed change in the Technical Specifications for operable control rod assemblies, the licensee provided a description O
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i of the rod control system, the diagnostic features of the rod control system and the process for identifying the root cause of rod control system malfunctions. One such diagnostic feature of the rod control system is failure detection. A " Rod Control Urgent Failure" alarm is i
actuated by five failure detectors (regulation failure, phase failure.
logic error, multiplexing error and card missing) in each power cabinet or by three failure detectors (slave cycler receives a GO pulse during i
a step, oscillating failure, card missing) in the logic cabinet. A rod control urgent failure alarm which is annunciated in the main control j
room stops automatic rod motion but permits manual movement of a l
4 selected bank under certain conditions, t
i Due to the types of failures which result in the rod control ur$ent failure alam, the licensee concludes that this condition is on y i
i indicative of problems associated with the rod control system and is not l
an indication that would preclude the capability for control rod inser-l tion on a reactor trip. Based on our review of this matter, we concur with the licensee's conclusion that the rod control urgent failure alam is an indication of a control system failure and is not related to con-j trol rods being untrippable.
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i Since the inoperability of the rod control system does not present an immediate concern with regard to the capability of safety systems, we t
conclude that it is prudent not to require actions which could lead to j
unusual operating circumstances.
4 The rod control system operates independently of the rod drive mechanisms.
A rod control urgent alarm is the result of a control system failure and is not related to a mechanically inoperable rod or rods. There tre failures that do not result in a rod control urgent failure alam that i
could prevent one or more rods from moving. In this regard, the Itcensee addressed the means available to distinguish whether the problem is in F
the control system or in the coil mechanism. Test points are located in the power cabinets for the rod control system which pemit monitoring of the electrical current to coils in the control rod mechanism. If the I
control system does not vary the currents to the mechanism coils, the i
problem is isolated to failures in the rod control system. In this case it would be obvious that the malfunction is due to component failures associated with the rod control system and not related to the control rod drive mechanism. Therefore, based on this review the staff concludes that where the inoperability of control rod assemblies can be positively identified as being associated with malfunctions internal to the rod control system. It is acceptable to allow adequate time far maintenance i
before requiring that the unit be placed in hot standby.
l Therefore, the staff concludes that the proposed changes to the Technical Specifications are acceptable.
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!!!. ENVIRONMENTAL CONSIDERAT!ON This amendment involves a change in the use of a facility component located within the restricted area as defined in 10 CFR Part 20. The 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 Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR Sec. 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 this amendment.
IV.
CONCLUSION The Comission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (50 FR 20989) on May 21, 1985, and consulted with the state of South Carolina. No public comments were received, and the state of South Carolina did not have any coments.
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regula-tions and the issuance of this amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributors: Jon B. Hopkins, Licensing Branch No. 4. DL Narinder K. Trehan, Instrumentation and Control Systems Branch, DSI Dated: June 24, 1985 l
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