ML20010C480
| ML20010C480 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/13/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NCR-CEB-79-19, NUDOCS 8108200121 | |
| Download: ML20010C480 (6) | |
Text
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^*4 TENNESSEE VALLEY AUTHORITY CHATTANOOGA, TENNESSEE '37401
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August 13, 19_81_ _
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. 7 Mr.: James P. O'Reilly, Director:
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-101 Marietta Street Atlanta,. Georgia 30303 ID\\
Dear Mr. O'Reilly:
SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 - DESIGN BASIS ACCIDENT MOVEMENTS
-0F STEEL CONTAINMENT VESSEL - NCR CEB 79 REVISED FINAL REPORT y
The subject deficiency was initially reported to NRC-OIE Inspector T. E.:Burdette on May 11, 1979 in accordnnce with 10 CFR 50.55(e).
Interim reports were. submitted on June 11 and.Jul.y '18,- 1979; a final report was submitted on-October 15, 1979; and a supplemental report was submitted on June 18, 1980. Enclosed is our revised final report.
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This report has been revised to reflect the current status of this -
. deficiency.
If you have any questiens, please get in touch witti D. L. Lambert at FTS 857-2581.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure cc:
Mr. Victor Stello, Director (Enclosure)
Office of Inspection and Enforcement U.C, Nuclear Regulatory Commission Wachington, DC 20555 N
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Au*mwoung PDR~~
An Equal Opportunity Employer.
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i ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DESIGN BASIS ACCIDENT MOVEMENTS OF STEEL CONTAINMENT VESSEL NCR SQN CEB 79-19 10 CFR 50.55(e)
REVISED FINAL REPORT Descriotion of Deficiency
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Piping which penetrates the steel containment vessel with rigid penetrations or is rigidly attached to steel containment vessel was analyzed and designed without adequate consideration for design basis accident (DBA) movements of the steel containment vessel. Specifically, due to possible inadequaciec
'.n piping analyses procedures, earlier analysis and design of piping systems penetrating the steel vessel incorrectly accounted for the following.
1.
Most piping systems which penetrate the steel vessel are supported by rigid pipe supports, springs, and/or by mechanical seismic supports (snubbers). However, the containment and piping -esponse to earthquake motion is rapid enough to cause the snubbers to lock up thereby preventing movement of the pipes. In the original analysis of the piping, it was assumed that the snubbers would not lock up during the accident ccndition.
2.
The displacement of the vessel wall and attached piping (at the point of attachment) was incorrectly assumed to be only outward for the analysis and design of certain piping systems where movement of the vessel wall was considered. However, inward movement of the containment vessel must also be considered where vessel wall movement is important.
3 In the original analysis of Sequoyah and Watts Bar piping systems, TVA's analysis approach was to conservatively analyze for containment vibratory motion during a DBA inside containment using static displacements. This analysis has consistent with the analysis approach and philosophy which was used at that time for free standing steel esntainment buildings and was judged to be adequate to encompass I
i inertial effects. It has recently been determined that acceleration l
effects due to the rapid vibratory movement of the containment vessel may not be adequately considered by the static analysis.
The attached table lists the piping systems by penetrations which have been reanalyzed to correct this nonconformance. All piping systems listed have been reanalyzed to account for the incrtial effects. This reanalysis enveloped any corrective action for the displacement problem. Piping
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systems which have been reanalyzed for snubber lockup are identified in the table.
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' Safety' Implications Statement' Had this condition gene uncorrected,1certain piping systems would have been
-overstressed during a>DBA and could, as a consequence,' result in a breach.
?in containment integrity. : This could have adversely affected the safe ~
1 operation of the plant.
Corrective' Action TVA has generated time history and response s;ectra data at each containment nozzle location for each of the ~ six primary. system DBA's.
Using this information, all piping systems' having -rigid penetrations through'the steel containment vessel were reanalyzed givingLfull~
consideration for the DBA event. ;Also, the new DBA movements were examined -
with respect to bellows type penetrations by both TVA and the bellows penetration vendor. AllLbellows type penetrations have been qualified for
'the DBA movements.
.TVA previously reported an oversight which occurred in the reanalysis of the residual heat removal (RHR) spray header piping. The RHR spray header
. piping attached to the steel containment vessel was within a lapped region contained in two separate analyses. Because of-some confusion over responsibility with a contractor, only one of the two analyses was reanalyzed in the original DBA reanalysis effort. TVA completed'the
. reanalysis of the RHR spray header piping under LECN 5282 which was issued in June 1980. The reanalysis showed that -new supports and changes to existing supports were required. The required new support installations and changes to existing supports have been made.
TVA has also checked all other systems for any similar _ oversight. There are no additional lines where TVA and contractor analyses join that were not completely reanalyzed in accordance with NCR SQNCEB79-19 The total analysis effort and final documentation for unit 1 is complete.
The piping reanalysis effort and its final documentation for unit 2 is also complete. The only unit 2 item remaining to be completed is qualification of the steel containment vessel nozzles and support pads for the new loads obtained from the piping reanalysia. This qualification effort will be completed by Au6uat 20, 1981. fbo loads a a presently expected to be acceptable with no reinforcement modifications required. Should any such modifications be required, they will be completed before initial criticality. To prevent recurrence of this deficiency, TVA has incorporated the proper DBA methods 1,nto their piping analysis orocedures.
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s 1 D SEQUOYAUNuCLEARLPLANb Piping Penetrations _Affected by UCR CEB179.,1 s:
Penetration Pipe AffcetedLby' Sys Reqd for;
__L.imber Sveten*
Size Service Snuhber Lockup-fSafe"Shutdoun' 16
.CVCS (Supply) 3 Normal charging to Regen Hx X.
29
.CCS (Disch) 6 R. C.
Pump 011 Cooler
-35 CCS (Disch) 6 Excess Le td own ~ Hx X-i**
39A WDS 1
N2 to Accumulators X
39B WDS
.75 H2 to Pressure Relief Tank X
40A
-AFW (Supply).
4
-Auxiliary Feedwater X
'X.
403~
AFW (Supply)~
X 40D CSAS (Supply) 3 Air supply for U2 Purge
~X 41 WDS.
3 Floor Sump Pump Discharge
-X 42 PWS 3
Pressurizer Relief. Tank Makeup X
(43A CVCS (Sup ply) 2 Sealvater Inj ec tion - RC. Pump 43B CVCS-(Supply) 2 Scalvater Inj e c t io n ~-- RC Pump'
/ 3C CVCS (Supply) 2 Scalwa ter. Inj ection - RC Pump 43D CVCS (Supply) 2 Sealva te r Injection - RC Pump' 44 CVCS (Disch)
.4 Sc alwa te r Return - RC Pump H
48A Containment Spray 12 Spray Header X
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'4~4 Containment Spray 12 Spray Header X'
cX 49A RHR Spray 8
Spray "cader X
-X 49B RHR Spray 8
Spray Hender X
cX SOA CCS (Disch) 3 RC Pump Theriaal Barrier 50B CCS (Supply) 3 RC Pump Thermal Barrier 51 FPS
.4 S e rv ic e to Standpipe Sys inside Cranewll-
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52 CCS (Supply) 6 RCP, CRDM, Louer Cont Vent Cooler
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-CCS' (Supply) 6 Excess-Letdown Hx X
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56 ERCW (Supply) 6 RCP, CRDM' Lower Cont Vent Cooler
.X 57 JERCW (L ;Jch) 6
- RCP, CRDM,Louer Cont Vent Cooler X
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58 ERCW'(Supply) 6 RCP, CRDM, Lower Cont Vent Cooler X
59 ERCW (Disch) 6 RCP, CRDM, Lownr Cont. Vent Cooler X
j 60
. ERCW. (Sup ply).
6 RCP, CRDM, Lower Cont Vent Cooler X
'j 61
.ERCW (Disch) 6 RCP, CRDM,-Lower; Cont Vent 1 Cooler X-
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62
.ERCU-(Supply) 6 RCP, CRDM, Lower Cont.-Vent. Cooler.
X 63 ERCW (Disch)'
6 ~ RCP, CRDM, Lower. Cont Vent Cooler.
~X 1
64
.ACS 2
Instrument Room Vent Cooler 1X 1
65" ACS 2
. Instrument Room Vent'Co'oler X
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SEQUOYAH NUCuEAR PLANT 1
Piping Penetrations Affected by NeR 623 79-19 f
Penetration Pipe Affected-by Sys Reqd for Nu'mber System
- Size Service Snubber Lockup Safe' Shutdown'
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66 ACS 2
Instrument Room Vent Cooler X
67
'ACS 2
Instrument Room Vent Cooler
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<6 8 ERCW (Supply) 2-Upper Containment Vent Cooler X
69 ERCW (Supply) 2 Upper Containment Vent Cooler X
70 EliCW (Disch) 2 Upper Containment Vent Cooler X
71 ERCW (Disch) 2 Upper Containment Vent Cooler X
72
'ERCW (Disch) 2 Upper Containment Vent Cooler.
X 73-ERCW (Disch) 2 Upper Containment Vent Cooler X
74 ERCW (Supply) 2 Upper Containment Vent Cooler X.
75 ERCW (Supply) 2 Upper Containment' Vent Cooler X
76 CSAS 2
Service Air 77 DWS 2
Demineralized Water X
78 FPS 4
Service to RCP Spray Coverage 82 Fuel Pool Cooling 6
From Refueling Cavity X
83 Fuel Pool Cooling 4
To Refuleing Cavity X
110 UHI-(supply) 2 UHI Valve Test Line 114 ICS 2
Clycol Floor Cooling X
115 ICS 2
Glycol Floor Cooling X
- For description cf acronyms, see next page.
coThe CCS piping between the excess letdown heat exchanger and the steel containment vessel is.
TVA Class.B and is required.to f unction as a containment boundry (i.e.,
a closed system).- ItLis for this reason that it is indicated as required for safe shutdown.
The f unction of supplying and discharging CCS vater to and from the heat exchanger is net required.for' safe shutdown.
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SEQUOYAll NUCLEAR PLANT.
4 Piping Penetrations Affecte<l by-NCR'CEB 79-l'9 l'
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. Ac ro nvin s S y s t en_
CVCS Chemical Volume and Control System
- CCS Component Cooling' System UDS Wastc~ Disposal System AFW Auxiliary Feedwa ter Sys tem PWS Primary Water System ICS Ice. Condenser _ System FPS Fire Protection System ERCW Essential Raw-Cooling System UWS Demineralized Water System UllI Upper Head Injection System ACS Air-Conditioning / Chilled Water System Y
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