ML20217M714
| ML20217M714 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/29/1998 |
| From: | Bajestani M TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 50-327-98-01, 50-327-98-1, 50-328-98-01, 50-328-98-1, GL-91-18, NUDOCS 9805050090 | |
| Download: ML20217M714 (7) | |
Text
.
s Tennessee Valley Authority, Post Office Box 2000, Soddy Daisy, Tennessee 37379-2000 I
Masoud Bajestani Site Vice Presdent Sequoyah Nuclear Diant April 29, 1998 U.
S.
Nuclear Regulatory Commission 10 CFR 2.201 ATTN: Document Control Desk Washington, D.
C.
20555 Gentlemen:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT (SQN)
NRC INSPECTION REPORT 50-327, 50-328/98 REPLY TO NOTICE OF VIOLATION (NOV) 50-328/98-01-01 This letter provides our reply to the subject NOV dated March 30, 1998.
The NOV addresses the failure to perform a 10 CFR 50.59 evaluation for changes made to the 2A-A motor driven auxiliary feedwater pump.
The enclosure contains our response to the NOV.
There are no commitments contained in this response.
The NRC Inspection Report also requested a response to Unresolved Item (URI) 50-327,328/98-01-02, concerning an unverified FSAR Chapter 15 Accident Analysis assumption for 10-minute operator action on a main feedwater piping rupture.
A response to this URI will be provided under separate cover.
If you have any questions regarding this response, please contact me at extension (423) 843-7001 or Pedro Salas at i
extension (423) 843-7170.
Sincerely, 9,o\\
ou a'esta Enclos e
4 ~t
'""v ec:
e page 2 9905050090 990429 PDR ADOCK 05000327 G
PDR i
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U.S.
Nuclear Regulatory Commission l
Page 2 April 29, 1998 l
cc (Enclosure):
l Mr.
R. W. Hernan, Project Manager Nuclear Regulatory Comlaission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector l
Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 l
Regional Administrator U.S.
Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-3415 Ms. Eileen M. McKenna NRR/DRPM/PGEB Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Mr. David B. Matthews Deputy Director, NRR/DRPM Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Mr. Lawrence J. Chandler Associate General Counsel Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Me. Anne T. Boland RGN-II/ ORA /EICS Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739
ENCLOSURE 1 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN)
UNITS 1 AND 2 INSPECTION REPORT NUMBER 50-327, 50-328/98-01 REPLY TO NOTICE OF VIOLATION (NOV) 50-328/98-01-01 RESTATEMENT OF VIOLATION "10 CFR 50.59 (a) (1) allows the holder of a license to make changes to the facility and procedures as described in the Final Safety Analysis Report (FSAR) without prior Commission approval unless the proposed change involves a change to the Technical Specifications or an unreviewed safety question (USQ).
10 CFR 50.59 (b) (1) requires that the licensee shall maintain records of changes to the facility and that these records include a written safety evaluation which provides the bases for the determination that the change does not involve an unreviewed safety question.
Contrary to the above, in the following examples the licensee made changes to the facility as described in the FSAR without an adequate written safety evaluation which provides the bases for the determination that the changes did not involve f
an USQ:
A.
On October 13, 1987, work request B232398 documented that the rotating element on the 2A-A motor driven l
auxiliary feedwater pump (MDAFWP) was replaced.
Post maintenance testing identified that the pump performance characteristics changed such that the discharge pressure of 1660 pounds per square inch gauge (psig) at the 30 gallons per minute (gpm) i recirculation flow value e:cceeded the piping design pressure (1650 psig) and that there was a 100 psig increase in the pump shutoff head.
The parameter changes indicated that the pump performance curves were changed.
These were changes in the facility as described in the FSAR Table 10.6.7-2 which listed the AFW system design pressure as 1650 psig and the pump design head at 2900 feet at 440 gpm.
Also, the AFW pump composite curves in FSAR figures 10.4.7-6 and 10.4.7-7 were impacted.
The licensee's Problem Evaluation Report (PER) SQP 871598 dated October 29, 1987, included a technical evaluation which concluded that this was an accept-as-is condition.
There was no documented 50.59 evaluation / screening until September 7,
195J, and this screening incorrectly concluded that the change did not impact the information in the FSAR.
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B.
On October 19, 1996, work order 96-038636 increased the impeller / casing wear ring clearance on the 2A-A MDAFWP to resolve excess thrust conditions.
During the maintenance activity, the licensee identified that the pump casing tolerances exceeded the vendor specifications and initiated PER SQR962756, dated October 29, 1996.
This PER corrective actions included procuring a new pump and providing an interim, accept-as-is evaluation for the pump with the
-changed impeller dimensions.
The impeller dimension change was a compensatory action to address the pump thrust problems due to the casing / impeller clearance deficiency, until the pump was replaced in December, 1997.
On November 1, 1996, PER SQ962788 identified that the design control process was not implemented for this maintenance activity which resulted in changes to the pump performance characteristics.
A technical evaluation in the PER stated that the new impeller and old impeller did not share the same pump curve, the new impeller would drive the full system flow upwards on the system resistance curve, and the additional flow from the stronger new impeller was Aculated to require additienal horse power (hp) for e
a total of 555 hp.
This 555 hp value_was greater than E
the 544 hp value listed in the Shutdown Board load listing in FSAR tables 8.3.1-1 and 8.3.1-2.
The impeller clearance change also impacted the AFW pump composite curves in FSAR figures 10.4.7-6 and 10.4.7-7.
The PER did not include or require a 50.59 l
evaluation / screening.
This is a severity Level IV Violation (Supplement IV)."
TVA's REPLY TO THE VIOLATION l
- 1. Reason For The Violation Example A:
The reason we did not document the problen in a 50.59 evaluation / screening was our interpretation that, as far as the auxiliary feedwater (AFW) system pressure is concerned, the SON FSAR treats " design pressure" and " maximum operating pressure" differently.
The recorded prer-ure difference relates to design pressure and code all;wances.
A design pressure requires evaluation encompassing the provisions of the related code.
The FSAR design value and the applicable code together provide guidance on how to evaluate and treat a temporary increase in pressure.
Design pressure, in light of the code, is not a system maximum value.
The code of record for the AFW system, as described in Table 3.2.2-2 of our FSAR, is USA Standard B31.1.0-1967, " Power Piping Code."
This code states that the piping system shall E-2
be considered safe for occasional operation for short periods at higher than the design pressure.1 In this example, the system went above the design pressure value, and an engineering evaluation was performed which determined the condition would not exceed the design pressure incorporating code allowances.
The limitations of this allowance are that the design pressure can be exceeded up to 15 percent increase above the S-value (design pressure at design temperature) durjng 10 percent of the operating period.
This allows the AFW system to be operable and FSAR compliant at 1897 psig for up to 10 percent of the plant life.
The highest value determined in postmaintenance testing was a recirculation flow measurement of 1660 psig, which is an increase of 0.06 percent.
The increased pressure was seen only during the recirculation flow measurement.
Therefore, the system would be exposed to the higher than the design pressure during two operating modes:
(1) during recirculation conditioa with no flow going to the steam generators and suction aligned to the condensate storage tanks, and (2) during conditions with low or no flow to the steam generators and suction aligned to the emergency raw cooling water system which is an abnormal operating condition.
Taking into account both of these operating modes and accident operation, it was conservatively estimated the plant could see this pressure 1.7 percent of.;he operating period (this accounts for use of this pump for the remaining 32-year life of the plant).
This percentage is below the code allowance of 10 percent of the operating period.
Therefore, as concluded in 1987, the AFW design pressure listed in the FSAR was not impacted and no change had been made to the facility as described in the FSAR.
In light of these circumstances, we considered it unnecessary to change l
'USAS B31.1.0-1967, "Pownr Piping Code" states in paragraph 101.2.2,
" Internal Design Pressurn," that The internal design pressure shall not be less than the maximum sustainert fluid operating pressure within the piping, and shall include allowances for pressure surges, except as these conditions may be modified by the provisions cf Pars.102.2.4, 102.2.5, 102.3.2 and 102.3.3.
Paragraph 102.2.4, " Ratings: Allowance for Variations from Normal Operation,"
further describes that It is recognized that variations in pressure and temperature inevitably occur, and therefore the piping system shall be considered safe for occasional operation for f.hort periods at higher than the design pressure or ternperature. Either pressure or tensperature, or both, may exceed the design values if the stress in the pipe wall calculated by the formulas j
using the maximula expected pressure during the variation by riore than the following allowances for the periods of duTation indicated (1) Up to 15 per cent increase above the S-value during 10 per cent of the operating period.
(2) Up to 20 per cent increase above the S-value during 1 per cent of the operating period.
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m I
the FSAR to increase the design pressure for the AFW I
l system.
Insofar as the AFW pump composite curves are concerned, Figures 10.4.7-6 and 10.4.7-7 are both pump performance curves comprised of the manufacturer test data on the original AFW' pumps.
These plots are representative only, and as such, have remained unchanged since the original issuance of the SON FSAR.
Figure 10.4.7-6 is a composite of two turbine driven auxiliary feedwater pumps; therefore, it is unrelated to the motor driven pump in question.
The motor driven auxiliary feedwater (MDAFW) pump curve, Figure 10.4.7-7, is labeled as a " Composite of four test curves."
This figure is comprised of the manufacturer test data on the' original four MDAFW pumps.
The l
figure is a representative _ depiction of MDAFW pump characteristics.
Pump replacements, even like-for-like replacements, are slightly different due to inherent manufacturing tolerances and result in small pump performance changes.
As such, we did not l
consider that the increase in the individual MDAFW-pump curve constituted or warranted a change in the FSAR composite test curve.
Example B:
The reason that we did not include a 10 CFR 50.59 evaluation / screening for this PER was 4
because of our interpretation that if a licensee intends to restore a nonconforming condition back to 1
its previous condition (as described in the SAR), then the corrective action should be performed in accordance with 10 CFR 50, Appendix B (i.e.,
in a timely manner commensurate with safety), and that a 10 CFR 50.59 safety evaluation is not required.
We documented the condition in our corrective action program, and despite the inaccurate accept-as-is designation, we did not intend to permanently accept the condition described in the example, and decided to rectify the condition with replacement at the first available opportunity.
The decision to replace the pump was made upon discovery of the pump casing tolerances exceeding the vendor specifications, and we shipped the replacement pump to the manufacturer for refurbishment prior to SON startup.
We completed an engineering evaluation for interim use of the pump and confirmed it was acceptable.
Interim acceptance of the degraded pump was not intended as a permanent modification or an indefinite acceptance.
The accept-as-is designation for the pump condition, including the horsepower rating, constituted a temporary acceptance until the first available opportunity to replace the pump.
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In fact, we made the decision to replace the pump as mentioned above prior to discovering the 555 hp value.
We replaced the pump as scheduled during the subsequent refueling outage -- the first available opportunity.
The temporary acceptance of the pump condition should have been described as a nonconforming condition, not an accept-as-is condition.
Since we did not intend to accept this nonconforming condition (i.e.,
casing tolerances outside of vendor specification, casing to impeller clearances at maximum value, and hp rating), we did not modify the licensing and design basis and make a permanent change or modification to the plant.
2.
Corrective Steps Taken And Results Achieved We corrected the nonconforming condition when MDAFW Pump 2A-A was replaced in 1997.
3.
Corrective Steps That [Have Been Or) Will Be Taken To Prevent Recurrence We revised the corrective action program in May 1997 l
to address degraded / nonconforming conditions related l
Additionally, we l
supplemented this guidance recently relative to the i
advent of Generic Letter 91-18, Revision 1.
The revision to the corrective action program ensures that degraded / nonconforming conditions are resolved commensurate with safety significance.
If the i
resolution of the condition cannot be corrected within one operating cycle, then appropriate justification must be prepared to support the proposed schedule.
If an interim compensatory action is taken to address the l
condition, a 10 CFR 50.59 evaluation must be pe r f oriaed.
- 4. Date When Full Compliance Will Be Achieved With respect to the violation cited, SON is in full compliance, i
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