U-600824, Amended Final Deficiency Rept 55-86-09 Re Broken Tack Welds Between Valve Disc & Disc Nut.Initially Reported on 860828. Caused by Vibration Created by Extreme Throttling.Valves Will Be Replaced W/Valves Designed for Extreme Throttling

Amended Final Deficiency Rept 55-86-09 Re Broken Tack Welds Between Valve Disc & Disc Nut.Initially Reported on 860828. Caused by Vibration Created by Extreme Throttling.Valves Will Be Replaced W/Valves Designed for Extreme Throttling

ML20210U476
Person / Time
Site:	Clinton
Issue date:	02/09/1987
From:	Hall D ILLINOIS POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
55-86-09, 55-86-9, U-600824, NUDOCS 8702180488
Download: ML20210U476 (8)

Text

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U-600824' L14-87( 02- 09)-L 1A.120 ILLINDIS POWER COMPANY CUNTON POWER STATION. P.O. BOX 678. CLINTON, tLLINOIS 61727 FEB 91987 Docket No. 50-461 Mr. James G..Keppler Regional Administrator Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Subject:

Reportable 10CFR50.55(e) Deficiency 55-86-07: Broken Tack Welds on Valves 1G33-F042A and 1G33-F042B

Dear Mr. Keppler:

, On August 28, 1986, Illinois Power Company (IP)-

notified Mr. F. Jablonski, NRC Region III (Ref: IP Record of Coordination Y-203106, dated September 2, 1986) of a potentially reportable deficiency concerning broken tack welds between the valve disc and disc nut on valves 1G33-F042A and 1G33-F042B.. Preliminary investigation and evaluation of this matter has determined that the broken tack welds were caused by vibration created by extreme throttling conditions. Administrative. controls;were implemented for Anchor / Darling throttling' valves having the same design and determined to be potentially impacting.to Technical Specification operability of plant systems. The administrative controls were implemented as an interim measure to preclude throttling of these' valves to less than c 20% of their open position until they could be repaired or determined by the valve vendor'to not have been degraded by

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their previous throttling history.

Subsequent to submittal of our final reaort on the subject deficiency, a concern was expressed by the NRC Resident Office regarding the adequacy of the justification to assure that following removal of the administrative controls, the throttling valves would not be subject to failure between now and the first refueling outage. Lifting of the administrative controls on the Shutdown Service Water System-(SX) valves is considered acceptable since Sargent &

Lundy (S&L) had determined that the failure of these valves.

would not impact safety, but a more detailed justification is needed for removing the administrative controls on General Electric (GE) designated valves because their failure would be significant to plant safety.

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1. ;U-600824 Ll4-87 ( 02- 09)-L ,

1A.120 ,,

.This letter represents an: amended final report

regarding the subject reportable deficiency (Ref: IP Letter U-600767, D.lP. Hall to J. G. Keppler: dated November 26, 1986).. This amended final report is being submitted to 4

- provide a more detailed justification for removal of the -

administrative controls on GE. designated valves which' perform a-throttling function. Attachment A provides the .i details of our_ justification for removal of these controls.

An evaluation for.the safety implication and significance. included single and common mode failures of the l valves manufactured by Anchor / Darling. Sargent &'Lundy's-  :

evaluation. concluded that the safety of the plant was not R

. - impaired by'the single or simultaneous failure'of S&L i

specified valves ~. Per.GE's evaluation, failure of the GE ,

supplied valves was determined 1to be significant to.the safe operation of Clinton Power Station (CPS) and,~ ' therefore ,

reportable under the provisions of 10CFR50.55(e). .;

'I

, We trust that this amended final report-provides you  !

i sufficient background information to perform a general assessment of-this reportable deficiency and adequately 1 describes our overall approach to resolve this issue.

Si re - yours, [

. P. Hall Vice President g RLC/bsa j Attachment cc: NRC Resident Office Illinois Department of. Nuclear Safety INPO Records Center-p i

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Attachm:nt to-

'U-600824 ATTACHMENT A

_ ILLINOIS POWER COMPANY

' CLINTON. POWER STATION 4

DOCKET NO. 50-461-Reportable 10CFR50.55(e). Deficiency 55-86-07:

Broken Tack' Welds on Valves ~IG33-F042A'and 1G33-F042B-AMENDED FINAL REPORT Statement'of Reportable Deficiency / Background On August 28, 1986, Illinois Power Company (IP) notified Mr. F. Jablonski, NRC Region III (Ref: IP. Record of Coordination Y-203106, dated September 2, 1986):of a-potentially reportable deficiency. concerning broken: tack -

welds between-the valve disc and disc nut on valves 1

1G33-F042A and.lG33-F042B. On valve 1G33-F042A the disc. nut l

and disc'were disengaged and.one half of_the stem. retaining ring was missing and had appeared to have entered the

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r system. On valve 1G33-F042B the disc was-backed out of.the disc nut approximately 1%. inches.

j Investigation Results/ Corrective Action

! -e l Illinois Power's initial investigation into this aatter

identified 60 Anchor / Darling Valves in use at the Clinton

j. Power Station 1(CPS) having the.same design as failed valves ,

[' 1G33-F042A and 1G33-F042B.-~However, during final assessment.  !

4 of the.60 valves documented in the interim repo'rt U-600722  :

dated September 30, 1986, it was identifiedLthat three (3)

of the valves were of a different configuration. These i three (3) Anchor / Darling valves (by design) have the disc j staked to the disc nut rather than tack welded. Although

! these valves are staked rather than tack welded, they. ,

'- experience similar degradation _when subjected to extreme

throttling conditions in that the staking becomes l ineffective allowing the' disc to back out of the disc nut.

! -On this basis, these three (3) valves have been included in thiscreport. Anchor / Darling _ Valve Company was. requested to

. evaluate the failure of valves 1G33-F042A and 1G33-F042B. '

! The preliminary evaluation of1this matter by' Anchor / Darling ,

determined that the tack weld failures resulted from:

repeated impact loads induced by'. vibration of theLyalve disc due to extreme throttling conditions, i.e., valve. throttled-

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to less than 20% of its open position.

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- Attachm:nt.to - '

U-600824 l

ATTACHMENT A (continued)

As an interim measure,'pending completion of Anchor /  !

. Darling. investigation and evaluation of this m'atter, IP.

3 alaced-administrative controls _cn those valves determined to f ue potentially impacting ~ to Technical Specification.

- operability of plant systems. 1Due administrative controls were implemented to preclude throttling of these valves 1to less than 20% of their open position until they:could be i c ' repaired or determined by the valve vendor to not have been degraded by their previous throttling history. 3 L Based on vendor recommendations, Plant Modification-

RT-14 was issued to provide a 360* weld between~the disc'and' disc nut'of valves 1G33-F042A and'lG33-F042B. This work was

< performed under Maintenance Work Requests (MWRs)-C-09332 and C-14484.

1111nois Power furnished: Anchor / Darling with. operating j data which_ included inlet pressure, temperature, flow rate,  !

! and pressure drop across the valves. .This data was'used-by.

i Anchor / Darling to evaluate the remaining _ valves for-a potential failure or degradation of_the. tack welds.

a >

On October 3, 1986, Anchor / Darling completed their. .

initial evaluation of the affected. valves and concluded that l the past operating conditions should not have caused any

damage to the valves. However, Anchor / Darling recommended .

l inspection of the tack welds on valves lE12-F021 and l lE21-F012 for-further assurance.that these valves had not  :

degraded or failed, because the_ Operating data for these l'

valves was not conservative enough to totally exempt them from possible degradation or failure. Maintenance. Work i Requests (MWRs) C-11753 and C-31433 were initiated to

perform an inspection of these. valves to verify the tack weld integrity. Valve lE21-F012.was inspected on October 15, 1986, under MWR C-31433. Linear indications (cracks)'

were found on both of the tack welds. ~These cracks.were

. documented on Nonconforming Material Report..(NCMR) No.

02-0989. Plant Modification M-34 was issued which' replaced

!. the tack welds with a full 360* circumferential. weld between-the disc and' disc nut. No linear _ indications wereifound on '

. the tack welds of-valve lE12-F021.

Of the 57 valves identified as having the'same' design as failed valves 1G33-F042A and 1G33-F042B,_35Eare used in

. throttling applications'. To date, 3 of these 35' valves have been repaired (lG33-F042A, 1G33-F042B,tand IE21-F012).- To:

, . provide additional assurance of-the integrity.of the discLto

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-disc nut tack welds during future operation of the plant,

'the remaining 32 valves performing a throttling function will be' inspected at the first refueling outage.. These valves ~~are expected to function without; degradation'until the first refueling outage based on~the.following:

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' Attachment to .

U-600824-ATTACHMENT A (continued) l Anchor / Darling'has performed-an' evaluation of-thel past throttling history ~ associated with these valves:

- and has' determined that the. valves are not1 degraded.

• Sixteen-(16).of.Ithe valves'are. monitored _by CPS In-Service Testing:(IST)l program.

• Anchor / Darling has reporte'd no failures ofIglobe valves supplied to other plants except the failure- .

of:a 24" globe valve in the RHR system in Chi Chan' Plant (Taiwan) and at the Susquehanna Plant.

Anchor / Darling has stated.that the globe' valves may be throttled for short periods of time-to less than

.20%.of the open position without any-potential.for i cracking of the tack welds.,

Subsequent to submittal of.our. final report on this reportable deficiency, a concern was' expressed by:the NRC 4 Resident Office lregarding the adequacy.of the justification to assure that following removal of the administrative -

j controls, the 32 remaining throttling-valves would not'be L subject to failure between now and the first refueling-outage when the valves will be inspected.. Lifting'of the administrative controls on the 9 Shutdown Service Water-  !

L System (SX) valves is considered-acceptable by the NRC since Sargent & Lundy (S&L) has determined'that the failure of these valves would not impact. safety. Lifting of:the l

administrative controls for the remaining throttling valves'-

! is considered acceptable based:on Anchor / Darling's evaluation.

4 General Electric (GE) and Sargent & Lundy were requested to provide the following information:

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a) Duration of throttling time from the system process i ' diagrams for the period between now and the-first refueling outage. (Furnished by GE) i

. b) Flow conditions - flow rate, inlet pressure, pressure' drop across the valves.and temperature. . (Furnished by

S&L) j The above data was. forwarded to Anchor / Darling.for ,

' their evaluation to determine the extent of valve. L degradation / failures during the first.18; months.. Based upon:

Anchor / Darling's evaluation, the valves are expected to function without failure until the first' refueling outage.

However, Anchor / Darling has recommended that valve 11E51-F022 i be monitored for excessive. vibration while being throttled. '

' The line'containing valve 1E51-F022 will.be l Page 3-of:5-

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'Attechm:nt to-4 U-600824 ATTACHMENT A (continued).

tested for vibrations-and the Nuclear Station Engineering

. Department (NSED) will reviewLthe test results. If the

, testing identifies. excessive-vibrations,. appropriate-corrective action will be taken to correct this, condition.

Centralized Commitment Tracking System Item No. 43942:has. '

been initiated to track this action to completion.

- Based upon Anchor / Darling's. detailed evaluation-(Ref:- 1 Anchor / Darling' letters dated January 2, 1987 and January 5, 1987), the-23 valves identified.in Attachment 1 will

' function without failure between:now.and theffirst-refueling outage. On this basis, the administrative controls-established at.the beginning of this investigation will be' removedLfo110 wing-review and concurrence-by the Clinton

-Power Station NRC Resident Office.

The three (3) Anchor / Darling 1 valves.which have their-disc staked rather than tack welded were also reviewed and evaluated as follows:

Valve 1E22-F010: The. failure of this. valve was documented by NCMR No. 01-1960. In accordance with the i-- disposition of'this.NCMR, staking of the' .

[ disc to the disc nut was revised to' apply ,

I three (3) one-inch long-tack welds to

[ preclude recurrence of this deficiency.

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[ Valve lE22-F011: The throttling limitations.for this valve were evaluated by GE. -GE'sLevaluation included the flow characteristics;from

Anchor / Darling letter dated March.17,.

! 1986, and the High Pressure' Core Spray (HPCS) system-pump curves to establish.a  ;

limiting throttling flow rate.offnot less than 4800.GPM. -This limitation was-procedurally implemente6.(Ref: CPS

., Procedure No. 9051.01). to. preclude ,

degradation of-the disc to disc nut-stake-caused by extreme throttling conditions.  ;

, Valve 1E22-F023: Inspection of this valve determined that this valve was'not degraded.. CPS.

procedures do not require.this valve to-perform a--throttling function, therefore, ,

no further corrective action was required.

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Attechment-to U-600824 ATTACHMENT 4 (continued)

Root Cause Illinois Power's root cause investigation of this ratter determined that the stake and tack weld failures resulted from extensive throttling of the valves between 0%

and 20% of the open position. To preclude recurrence,.all replacement or spare valves designated for extreme throttling duty (less than 20% of valve's open position) will be procured from Anchor / Darling under Specification-K-2866A. These valves will be designed for extreme throttling duty applications.

Safety Implication / Significance An evaluation of the safety implications and significance included an evaluation of single and common mode failures of the valves supplied by Anchor / Darling.

Sargent & Lundy's evaluation concluded that the safety of the plant was not impaired by the single or simultaneous failure of S&L supplied valves. Per GE's evaluation, failure of the GE supplied valves was determined t:o be adverse to the safe operation of Clinton Power Station (CPS) and, therefore, reportable under the provisions of 10CFR50.55(e).

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-Attechm:nt.to U-600824' ATTACHMENT [

Valves Performing Throttling Function Valve Number. System-

1. 1E12-F003A Residual ~ Heat R'emoval

-2, 1E12-F003B' Residual Heat Removal:

3. 1E12-F021 Residual Heat-Removal.-

4. 1E12-F023 Residual Heat: Removal ,

5. .lE12-F037A. Residual Heat Removal ,

6. lE12-F037B Residual Heat' Removal- 'I

'7 . lE12-F040 . Residual Heat Removal .]

!- 8. .lE12-F048A Residual Heat Removal-

9. 1E12-F048B Residual Heat Removal.

10. 1E12-F052A Residual Heat' Removal .

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11. 1E12-F052B Residual ~ Heat Removal

12. 1E12-F053A Residual Heat. Removal.

13. lE12-F053B Residual Heat Removal- -

14. 1E12-F087A Residual Heat Removal' r L 15. 1E12-F087B Residual Heat Removal-

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16 .- 1E32-F012 MSIV Leakage' Control:

17. 1E32-F013 MSIV Leakage Control ~

18. lE51-F022. Reactor Core 11 solation Cooling' .;

19. 1G33-F031 Reactor Water Clean-up

20. 1G33-F044 Reactor Water Clean-up:

Reactor. Water Clean-up-

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21. 1G33-F103  ;

L22. 1G33-F104 Reactor: Water Clean-up

. 23. 1G33-F107 Reactor: Water Clean-up.  :)

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