ML20236Q417
| ML20236Q417 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/06/1987 |
| From: | Ebneter S NRC OFFICE OF SPECIAL PROJECTS |
| To: | White S TENNESSEE VALLEY AUTHORITY |
| Shared Package | |
| ML20236Q418 | List: |
| References | |
| NUDOCS 8711200007 | |
| Download: ML20236Q417 (5) | |
See also: IR 05000327/1987048
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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WASMNGTON, D. C. 20555
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November 6,1987
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Docket Nos. 50-327/328
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Tennessee Valley Authority
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ATTH:
Mr. S. A. White
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Manager of Nuclear Power
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6N 38A Lookout Place
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1001 Market Street
Chattanooga, Tennessee 37402-2801
Dear Mr. White:
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SUBJECT:
SEQUOYAH UNIT 2 INTEGRATED DESIGN INSPECTION (IDI.)
The NRC committed at the July 8, 1987 entrance meeting'for the Integrated Design
Inspection, that the IDI report would be issued on or before November 6, 1987.
In keeping with our committed schedule, this letter conveys the results and
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conclusions of the Integrated Design Inspection of the Sequoyah Nuclear Power
Plant, Unit 2.
The inspection focused on the essential raw cooling water (ERCW) system,
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although other areas were covered as delineated in the enclosed inspection
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report.
Activities included examination of design, design bases, design
procedures, records, and inspection of the systems as installed at the plant.
Emphasis was placed on reviewing the adequacy of design details as a means of
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measuring how well the design process had functioned for the selected samples.
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The IDI uncovered several areas of programmatic weaknesses in the Sequoyah
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design process.
As discussed previously, in Mr. J. G. Keppler's letter of
October 9, 1987, the major programmatic weakness discovered by the IDI team
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relates to the technical adequacy of the structural calculations for safety-
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related buildings.
The team found these calculations. deficient for the
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following reasons:
(1) the calculations contained simplifying assumptions
for which there was no apparent technical basis, (2) the dimensional data
used in the calculations doas not agree with detailed structural drawings,
and (3) the calculations available for review during the IDI did not evaluate
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certain fundamental design considerations or design loading conditions.
Further, the team was concerned with the placement of rebar in reinforced
concrete and the seismic analysis of the steel containment vessel.
As a
result of these concerns, the IDI team could draw no conclusions regarding
the structural capacity of the plant to withstand design basis. events based
on the structural calculations reviewed during the inspection.
At.our
September 11, 1987 exit meeting and in Mr. J. G. Keppler's October 9, 1987
letter, you were requested to conduct additional independent technical-
reviews in this area.
8711200007 871106
ADOCK 05000327-
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Mr. S. A. White
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November 6, 1987
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The IDI team also identified a major programmatic deficiency with TVA's review
of vendor seismic qualification documents.
Nine examples were found where
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vendor supplied components were not seismically qualfied in accordance with the
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In addition, the IDI team identified a potential generic concern regarding pipe
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support design.
Of a sample of eight pipe supports reviewed, the IDI team
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found that three of the pipe support analyses contained nonconservative assump-
tions and incorrect dimensional data.
The team notes, however, that these
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three pipe support calculations were scheduled to be regenerated.
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Other areas of concern identified by the IDI team include inconsistent
application of the piping design code of record, inadequate environmental
qualification of equipment located in mild environments and the improper
specification of the ERCW system design pressure.
Across all disciplines, the IDI team found examples that indicated that TVA
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had reduced much of the design conservatism that normally exists in nuclear
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power plants.
The sense of the IDI team was that TVA traded-off design margins
for increased engineering analysis.
While this apparent design philosophy is
not unacceptable, the reduced design margins result in a diminished capacity
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to accommodate initial design errors without requiring plant modification.
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Several general observations can be made regarding TVA as a result of the
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in-depth IDI review.
One item observed by the team was an apparent lack of
timely corrective action in the Division of Nuclear Engineering (DNE).
For
example, the problems discussed above regarding the seismic analysis of the
steel containment vessel and the unrelated issue of the ERCW design pressure
were known to TVA in 1985 and 1986 respectively; however, up to the time of
the IDI, DNE had not resolved these items.
A second observation can be made regarding design verification.
In view of
the problems previously discussed regarding the adequacy of the structural
calculations, the use of incorrect dimensional information on pipe support
and equipment calculations and the improper use of the piping codes of record,
the IDI team concluded that weaknesses existed in TVA's design verification
process during the initial plant design.
Design verification, as required by
10 CFR 50, Appendix B, if properly implemented, should have detected these
types of errors.
A third area that needs the attention of TVA management is the lack of timely
implementation of changes to station operating procedures resulting from design
changes made by the Division of Nuclear Engineering.
For example, a " temporary
change" made in 1982, disconnected the wiring and logic for the automatic
operation of the ERCW traveling screen.
However, for the next five years TVA
did not have a procedure for manually operating the ERCW traveling screens to
remove debris.
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Mr. S. A. White
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November 6, 1987
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Finally, the IDI team as a group discussed the overall findings of the
inspection.
One central theme that emerged from this discussion was that
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the Division of Nuclear Engineering appeared to lack a systems integration
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function.
The design of a nuclear plant is complex in that many systems and
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components have multiple functions and interact with each other in ways that
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are not always obvious.
These subtle interactions, if not understood and
evaluated can cause severe safety problems.
In reviewing a number of the
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findings, it appeared to the team that systems interactions were not always
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considered.
The IDI team believes that TVA would benefit from the establish-
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ment of a multi-discipline review group, composed of senior technically
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oriented people, familiar with systems design, plant operations and the-
accident analyses methods and assumptions contained in the FSAR.
This
group could then assess the impact of future design changes on plant safety.
The attached report contains all of the deficiencies identified in Mr. J. G.
Keppler's letter of October 9,1987 as restart items as well as the remainder
of the team's findings.
In reviewing the findings initially categorized as
non-restart items, the IDI team has identified three additional deficiencies
that are required to be addressed before Sequoyah restart.
These items appear
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in the IDI report as Deficiencies D2.3-1, D2.4-1 and D4.3-9 and have been
discussed with your staf f by telephone.
None of the restart items previously
identified in Mr. J. G. Keppler's October 9,1987 letter have been changed in
the final report,
The enclosed IDI report identifies deficiencies regarding errors, procedural
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violations and inconsistencies.
Unresolved items are identified where more
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information is needed to reach conclusions.
Other observations are identified
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where it was considered appropriate to call your attention to matters which are
not deficiencies or unresolved items, but which are recommended for your con-
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sideration.
You are requested to respond in writing to the deficiencies and
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unresolved items within 60 days after receipt of this letter.
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In your assessment of individual deficiencies identified in the inspection -
report, you are requested to address the cause, the extent to which the
condition may be reflected in the unreviewed portion of the design, action to
correct the existing condition, action to prevent recurrence, and any other
information you consider relevant.
For unresolved items, the response should
provide information needed to reach conclusions concerning acceptability of the
specific feature or practice involved.
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We have received your response of October 29, 1987 addressing the restart
issues transmitted to you in Mr. J. G. Keppler's letter of October 9,1987.
During the IDI follow-up inspection, the week of November 2,1987, the team
will assess your responses by reviewing the supporting documentation such as
new calculations, revised drawings, etc.
We will notify you of any changes
regarding our request that you conduct independent reviews of structural cal-
culations or changes to any other restart issue as a result of our inspection.
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Mr.! S. A. White :
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November 6','1987,.
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In accordance'with'10'CFR'2.'790(a),'a copy of thist. letter and the enclosures
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will be'placed.in.the NRC,Public Document. Room.
Should you have any; questions concernin'g thisiinspection,.please contactTme:
at.(301):492-9663.
Sincerely,
Original signed by-
-Stewart D. Ebneter,-Director
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TVA Projects Division-
Office of.Special Projects
Enclosure:
Inspection Report.
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50-327/87-48, 50-328/87-48
cc w/ enclosure: See next page
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Mr.cS.'A. Whike ..
Sequoyah Nuclear Plant
Tennessee Valley Authority
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cc:
General Counsel
_ Regional Administrator, Region 11
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Tennessee Valley Authority.
U.S.. Nuclear RegulatoryLCommiss. ion
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400 West Summit Hill-Drive-
'101 Marietta Street, N.W.
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Atlanta,. Georgia' 30323
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Knoxville,, Tennessee 37902
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Resident. Inspector /Sequoyah NP
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Mr. R. L. Gridley
- c/o'U.S.' Nuclear Regulatory, Commission
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Tennessee Valley Authority
.2600 Igou Ferry Road:
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SN 1578 Lookout Place
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Soddy. Daisy,. Tennessee..'37379-
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Chattanooga, Tennessee 37402-2801
Mr. H. L.: Abercrombie:
c/o U,S.'GA0
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Tennessee Valley Authority-
1111 North Shore Drive
Sequoyah Nuclear Plant'
Suite 225, Box'194.-
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P.O. Box 2000.
Knoxville',lTennessee .37919
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Soddy Daisy, Tennessee 37379
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Tennessee Department of
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Mr. M.
R.. Harding
'Public Health
Tennessee Valley Authority
-ATTN:
Director, Bureau of.
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Sequoyah. Nuclear. Plant
Environmental Health. Services
P.O. Box 2000
Cordell> Hull. Building"
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Soddy Daisy, Tennessee 37379
Nashville', Tennessee 37219
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Mr. D. L. Williams
Mr.' Michael H.'Mobley, Director.-
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Tennessee Valley Authority
' Division of' Radiological Health
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400 West Summit Hill Drive
'T.E.R.R.A. Building..
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W10 B85
150.9th Avenue North
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Knoxville, Tennessee 37902
Nashville, Tennessee 37203
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County Judge
Dr. Henry Myers. Science Advisor
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Hamilton County Courthouse
. Committee. on_ Inte'rior
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Chattanooga, Tennessee 37402
and Insular' Affairs
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U.S. House of Representatives
Washington, D.C.
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