United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9411150165

TVA

Tennessee Valley Authority, Post Office Box 2000,
Spring City, Tennessee  37381


NOV 07 1994

CDR-50-390/87-10                                   10 CFR 50.55(e)
CDR-50-391/87-10

U.S. Nuclear Regulatory Commission
ATTN:  Document Control Desk
Washington, D.C.  20555

Gentlemen:

In the Matter of the Application of      )         Docket Nos. 50-390
Tennessee Valley Authority               )                     50-391

WATTS BAR NUCLEAR PLANT (WBN) - UNITS 1 AND 2 - MATERIALS PROGRAM
DEFICIENCY - FAILURE OF CATEGORY C DEVICES MAY ADVERSELY AFFECT
CATEGORY
A DEVICES - CONSTRUCTION DEFICIENCY REPORT CDR-50-390/87-10 AND CDR-50-
391/87-10 - SUPPLEMENT TO FINAL REPORT

The purpose of this letter is to supplement TVA's final report for CDR-50-
390/87-10 and CDR-50-391/87-10 with a similar condition documented in
Finding Identification Report (FIR) WBA890571001.  CDR-50-390/87-10 and
CDR-50-391/87-10  were initially reported to NRC Region II Inspector
Gordon Hunegs on April 2, 1987, as SCRWBNEEB8680 and SCRWBNEEB8684.  An
interim report was submitted on April 30, 1987, and a final report on
March 21, 1988.  A supplement to the final report is provided in the
enclosure.

If there are any questions, please telephone P. L. Pace at (615) 365-1824.

Sincerely,


Dwight E. Nunn
Vice President
New Plant Completion
Watts Bar Nuclear Plant

Enclosure
cc:  See page 2


U.S. Nuclear Regulatory Commission
Page 2

NOV 07 1994

cc (Enclosure:
      NRC Resident Inspector
      Watts Bar Nuclear Plant
      Rt. 2, Box 700
      Spring City, Tennessee  37381

      Mr. P. S. Tam, Senior Project Manager
      U.S. Nuclear Regulatory Commission
      One White Flint North
      11555 Rockville Pike
      Rockville, Maryland  20852

      U.S. Nuclear Regulatory Commission
      Region II
      101 Marietta Street, NW, Suite 2900
      Atlanta, Georgia  30323


                                ENCLOSURE

                  WATTS BAR NUCLEAR PLANT UNITS 1 AND 2
                   CDR-50-390/87-10, CDR-50-391/87-10
                       SUPPLEMENT TO FINAL REPORT

DESCRIPTION OF DEFICIENCY AS PROVIDED IN TVA'S FINAL REPORT

"The subject Significant Condition Reports (SCRWBNEEB8680 and
SCRWBNEEB8684) identify a condition in which failure of environmental
qualification (EQ) Category C electrical devices may result in EQ Category
A devices being unable to perform their safety functions.  Category C
devices are defined as equipment which will experience design basis
accident (DBA) environments but are not required to function for
mitigation of the DBA which created the adverse environment.  This
condition is in violation of 10 CFR 50.49, which states that nonsafety-
related equipment failure because of postulated environmental conditions
should not prevent satisfactory performance of safety-related equipment.

Some specific examples of devices which would have adverse interaction
because of DBA harsh environment are as follows:

      A ground fault in a Category C handswitch resulting in the inability
      of several isolation valves (Category A devices) to function for
      post accident monitoring (reactor coolant, containment sump, and
      containment atmosphere sampling).

      A short circuit in a Category C valve limit switch resulting in
      failure of a letdown containment isolation valve (Category A device)
      to close.

      A short circuit in a Category C valve limit switch resulting in the
      inability to open emergency gas treatment suction valve (Category
      A device.)

The root cause of this deficiency is attributed to the fact that at the
time these components were designed, the environmental qualification
program was less stringent than the requirements contained in 10 CFR 50.49
and TVA's current environmental qualification program."

FINDING IDENTIFICATION REPORT (FIR) WBA890571001

Watts Bar Design Criteria WB-DC-40-54, Environmental Qualification to 10
CFR 50.49, now specifies that the following must be considered to
determine if a device is Category C:

      (a)  Affects on a Category A or B device, including interconnection
           of power supplies and control logic;

      (b)  Affects on devices in mild environments which must function to
           mitigate a design basis accident;

      (c)  Affects on Class 1E power systems.

                                   E-1


Categories A, B, and C are defined in NUREG 0588.  A device is categorized
with an A, B, or C based on the environmental conditions of the design
basis accidents for which they must (A) function, (B) need not function
but must not fail, or (C) whose failure is deemed not detrimental to plant
safety or accident mitigation.

Contrary to the above, FIR WBA890571001 identified examples of Category
C devices that have been added or relocated by design changes/calculations
since December 1986, without addressing the potential interactions as
noted above.

This deficiency occurred because of deficient procedures and the lack of
training for existing procedures.

SAFETY IMPLICATIONS

The condition potentially would adversely affect the capability of
essential safety-related equipment to mitigate the consequences of a
design basis accident (DBA).

CORRECTIVE ACTIONS

In addition to the corrective actions provided in TVA's final report dated
March 21, 1988, for SCRs WBNEEB8680 and WBNEEB8684, TVA has taken the
following steps to resolve FIR WBA890571001:

System Category and Operating Time (C&OT) calculations, Design Change
Notices (DCNs) and Engineering Change Notice (ECNs) Modification Packages
that have been issued since December 1986 have been evaluated for
potential impacts to calculation WBPEVAR8603005, Failure Analysis of
Category C Devices Utilized in Class 1E Power Systems.

These evaluations identified the need for detailed failure modes and
effects analysis (FMEA) for a number of DCNs.  FMEA have been performed
and documented for these DCNs in new and/or revised interaction
calculations.

Unacceptable component interactions have been corrected by Design Change
Notice M-20561-A.  This design change added isolation fuses to the 480
volt shutdown boards for eight ventilating system flow switches.  These
modifications have been completed.

Engineering Administrative Instruction (EAI)-7.05, "Watts Bar 10 CFR 50.49
Program Requirements For Environmental Qualification of Electrical
Equipment," has been revised to require impact reviews for C to A
interaction calculations.  Changes that add or delete devices, or changes
the category of a device require an impact review.

EAI-3.19, "Change Review Checklist For Electrical Calculations," has been
revised to include questions which will help identify any impact to
WBPEVAR8603005 when modifications are made to circuits containing Category
C devices.

Affected personnel have been retrained to the requirements of the above
procedures.

                                   E-2


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