05000413/LER-1950-412, Forwards Rept Summarizing Review Results of Interunit Electrical Interfaces,Which Was Part of Corrective Action for LER 50-412/85-51.Item Also Identified in Insp Repts 50-413/85-35 & 50-414/85-32

Forwards Rept Summarizing Review Results of Interunit Electrical Interfaces,Which Was Part of Corrective Action for LER 50-412/85-51.Item Also Identified in Insp Repts 50-413/85-35 & 50-414/85-32

ML20140B912
Person / Time
Site:	Catawba
Issue date:	03/13/1986
From:	Tucker H DUKE POWER CO.
To:	Harold Denton, Youngblood B Office of Nuclear Reactor Regulation
References
NUDOCS 8603250026
Download: ML20140B912 (3)

LER-2050-412, Forwards Rept Summarizing Review Results of Interunit Electrical Interfaces,Which Was Part of Corrective Action for LER 50-412/85-51.Item Also Identified in Insp Repts 50-413/85-35 & 50-414/85-32

Event date:
Report date:
4132050412R00 - NRC Website

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March 13, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.. 20555 Attention: Mr. B. J. Youngblood, Project Director PWR Project Directorate No. 4 RE: Catawba Nuclear Station Docket Nos. 50-413 and 50-414 Review of Electrical Interfaces LER 413/85-51

Dear Mr. Denton:

The attached report summarizes the results of our review of interunit electrical interfaces, which was part of the corrective action for LER 413/85-51. This item was also identified by the NRC Resident Inspector as an Unresolved Item in Inspection Report 413/85-35, 414/85-32.

This completes our commitment to evaluate our susceptibility to a recurrence of this problem elsewhere in the plant.

Very truly yours, s

]8. D e Hal B. Tucker LTP: sib Attachment 03250026 R 860313 g ADOCK 05000413 PDR I \ .1e7)

'Mr. Harold R. Denten, Director March 13, 1986 Page Two cc: r. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission.

Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Dr. K. Jabbour Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. P. H. Skinner

-NRC Resident Inspector Catawba Nuclear Station Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station i

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Review of Electrical Interfaces Between Catawba Unit 1 and Unit 2 During the incident described in LER 413/85-51, a loss of power on a Unit 1 bus resulted in a loss of control power to some Unit 2 components. As part of the corrective action for this LER, Duke Power has performed a detailed design review of electrical interfaces between Unit I and Unit 2. The results of this review are summarized below.

Catawba has two 600V safety-related motor control centers (MCC's) IEMIG and 2EMXH, which are provided to supply power to safety-related loads which are shared between the two units. These MCC's and other buses subfed from them are the only shared safety-related buses at Catawba. Train A shared loads are fed from MCC IEHXG and Train B shared loads are fed from MCC 2EMXH.

Each of these MCC's has two manually interlocked incoming breakers fed from opposite units. MCC 1EMIG subfeeds 120V panelboard IEKPG and MCC 2EMXH subfeeds 120V panelboard 2EKPH.

As stated in the report of this incident, MCC 2EMXH was correctly aligned to its Unit I alternate source at the time of this incident. The Unit 1 Train B blackout therefore resulted in MCC 2EMXH and panelboard 2EKPH being de-energized. This caused the NV (Chemical and Volume Control System) valves 2NV189B and 2NV253B, with controls powered from 2EKPH, to reposition.

As a result of this incident, we have reviewed the loads powered from these MCC's and panelboards. The NV valve control circuits (1 and 2NV188A, 252A, 189B and 253B) are the only unit related loads supplied from these buses.

These control circuits will be moved to unit related power sources from the same unit as the associated valves. This was an' isolated case in which the NV control circuits were not assigned to the proper unit panelboard.

We have also reviewed non-safety-related shared buses and have found no unit related loads improperly assigned to these buses.

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