U-600722, Interim Deficiency Rept 55-86-07 Re Broken Tack Welds on Valves 1G33F042A & B.Initially Reported on 860828.Anchor/ Darling Valves Found to Fail from Vibration Caused by Extreme Throttling Conditions.Investigation Continuing

Interim Deficiency Rept 55-86-07 Re Broken Tack Welds on Valves 1G33F042A & B.Initially Reported on 860828.Anchor/ Darling Valves Found to Fail from Vibration Caused by Extreme Throttling Conditions.Investigation Continuing

ML20210S684
Person / Time
Site:	Clinton
Issue date:	09/30/1986
From:	Hall D ILLINOIS POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
55-86-07, 55-86-7, U-600722, NUDOCS 8610080207
Download: ML20210S684 (5)

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U-600722 s

Ll4-86 ( 09 - 30) -L 1A.120 ILLIN0/8 POWER COMPANY CLINTON POWER STATION, P.O. BOX 678. CLINTON, ILLINOIS 61727 SEP 3 0 1986 Docket No. 50-461 Mr. James G, Keppler Regional Administrator l Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 l

Subject:

Potentially Reportable 10CFR50.55(e) Deficiency 55-86-07:' Broken Tack Welds on Valves

1G33F042A and 1G33F042B

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 i potentially reportable deficiency concerning broken tack welds between the valve disc and disc nut on valves 1G33F042A and IG33F042B. Preliminary investigation and evaluation of this matter has determined that the broken i tack welds are caused by vibration created by extreme

throttling conditions. Our investigation of this matter is continuing. This letter represents an interim report in i accordance with the requirements of 10CFR50.55(e).

Attachment A provides the details of our investigation to date.

l Illinois Power, Sargent & Lundy (S&L), and General Electric (GE) have evaluated the potentially affected valves for safety implication / significance with regards to plant modes 4 and 5. The results of these evaluations determined that a single or common mode failure of the affected valves would not impact the safe shutdown or the Technical Specification operability of plant systems during fuel load and up to the time of initial criticality. On this basis all actions required to resolve this issue will be completed prior to initial criticality.

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U-600722

' L14-86 ( 09-30 )-L 1A.120 We trust that this interim report provides you sufficient background information to perform a general assessment of this potentially reportable deficiency and adequately describes our overall approach to resolve this issue.

Sincerely yours,

. .all Vice President RLC/kaf Attachment cc: NRC Resident Office Illinois Department of Nuclear Safety INPO Records Center

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Attachment to

, s U-600722 ATTACHMENT A ILLINOIS POWER COMPANY CLINTON POWER STATION DOCKET NO. 50-461 Potentially Reportable 10CFR50.55(e) Deficiency 55-86-07:

Broken Tack Welds on Valves 1G33F042A and 1G33F042B INTERIM REPORT Statement of Potentially 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 1G33F042A and 1G33F042B. On valve 1G33F042A the disc nut and disc were disengaged and one half of the stem retaining ring was missing and had appeared to have entered the system. On valve 1G33F042B the disc was backed out of the disc nut approximately 1% inches.

Investigation Results/ Corrective Action Illinois Power's investigation into this matter has identified 60 Anchor / Darling Valves in use at the Clinton Power Station (CPS) having the same design as failed valves 1G33F042A and 1G33F042B. Anchor / Darling Valve Company was requested to evaluate the failure of valves 1G33F042A and 1G33F042B, The preliminary evaluation of this matter by Anchor / Darling determined that the tack weld failures resulted from repeated impact loads induced by vibration of the valve disc due to extreme throttling conditions, i.e.,

valve throttled to less than 20% of its open posi; ion.

Anchor / Darling's investigation and evaluation of the matter 1

is continuing to fully define the throttling criteria for these valves and determine required corrective actions to preclude recurrence of these failures.

Pending completion of Anchor / Darling investigation and

evaluation of this matter, IP has placed administrative controls on those valves determined to be potentially j impacting to Technical Specification operability of plant l systems. The administrative controls were implemented to l preclude throttling of these_ valves to less than 20% of l their open position until they can be repaired or determined l

by the valve vendor as not subject to this type failure.

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Attachmsnt to U-600722 ATTACHMENT A (continued)

Investigation Results/ Corrective Action (Continued)

Maintenance Work Requests (MWRs) were initiated to repair 1G33F042A and 1G33F042B in accordance with Anchor / Darling's recommendation which required a full circumferential weld between the valve disc and disc nut.

Complete corrective action needed to resolve the subject deficiency and to eliminate the root cause(s) to preclude recurrence will be addressed after Anchor / Darling has completed the investigation and evaluation of this matter.

Safety Implications / Significance Illinois Power's investigation of this potentially reportable deficiency is continuing. The safety implications and significance will be assessed after S&L, GE, and Anchor / Darling have completed their evaluation of this matter. It is anticipated that approximately thirty (30) days will be required to complete our investigation, determine reportability and to file a final report on the issue.

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