ML20235H440

Summary of 870911 Meeting W/Util in Arlington,Tx Re Failure of Plant Circulator S/N C-2101 & Licensee Program to Recover from Failure.Licensee Rept, Preliminary Rept of Helium Circulator S/N C-2101 Damage & Justification... Encl

ML20235H440
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/21/1987
From:	Heitner K Office of Nuclear Reactor Regulation
To:	Calvo J Office of Nuclear Reactor Regulation
Shared Package
ML20235H443	List: ML20235H440 ML20235H473
References
TAC-65992, NUDOCS 8710010052
Download: ML20235H440 (3)

Text

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Docket No. 50-267 MEMORANDUM FOR: Jose A. Calvo, Director Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects FROM: Kenneth'L. Heitner, Project Manager-Project Directorate - IV ,

Division.of Reactor Projects - III,.

IV, V and Special Projects

SUMMARY

OF' MEETING WITH PUBLIC SERVICE COMPANY OF COLORADO TO DISCUSS FAILURE OF FORT ST. VRAIN CIRCULATOR C-2101 - SEPTEMBER 11, 1987 Re: 1) Licensee Event Report 87-018 dated August 28, 1987 (P-87300)

2) Preliminary Report of Helium Circulator S/N C-2101 Damage and Justification for Returning to Power Operation (Attachment 1)

The purpose of this meeting was to discuss the failure of Fort St. Vrain i circulator S/N C-2101, and the licensee's program to recover from this -i failure. This failure was reported to the NRC in Reference 1. The licensee's preliminary report on this f ailure is Attachment 1 to this meeting summary.

The attendees at this meeting are listed in Attachment 2. This meeting was i held at the NRC Region IV office in Arlington, Texas. l The licensee reviewed the background of the Fort St. Vrain helium circulators. i The four circulators each consist of a single stage helium' compressor on a (

single shaf t' driven by a- steam turbine or a pelton wheel. The circulators were originally designed for a 30 year wear free life. The original machine used a number of stainless steel materials in its design; in particular, in some of the bolting that has now failed. In order to perform its safety.

function, the machine must be capable of starting and continued operation on boosted firewater.

In the transient that led to discovery of the failure, the machine apparently tripped when the plant protective system sensed an "over speed" condition and tripped the circulator. When it was discovered.that the secondary penetration seal was leaking excessively, the licensee decided to replace this circulator with the spare. , ,

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8710010052 B70921 POR ADOCK 05000267

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Jose A. Calvo At the time of removal, hardware ejected from the machine was found in the circulator steam discharge and exhaust piping. These findings are discussed fully in Attachment 1. Subsequent to removal of the machine and partial disassembly at GA Technologies in San Diego, California has clarified some of the failures. The failures include bolting that holds in place the steam labyrinth and attaches the steam scroll to the bearing assembly.

The licensee has performed metallurgical analysis of parts from the failed circulator. The presentation material from this analysis is Attachment 3 to this meeting summary. The key conclusion from this analysis is the stress corrosion cracking was found in the failed bolting materials. However, the contaminant (s) leading to the failures have not been identified. The licensee stated that the steam scroll to bearing assembly (3/4 inch) bolts were of a high strength material and had a preload of about 120,000 psi. This preload was based on tightening tongue, and was within code allowables. In further discussion, the staff noted that tightening torque is not always accurately reflected in preload, and that highly stressed components, such as these bolts would likely be sensitive to this type of failure. The staff also requested detailed photographs of these failures be provided.

The licensee is continuing to perform evaluations of the failure and related questions: This includes

- A failure effects analysis for the failed bolting

- An analysis of consequences of loose parts ejected from the machine

- A review of the history and previous problems with all 5 circulator machines, and

- A more detailed review of previous materials problems.

These evaluations are underway, and other supplemental evaluations are planned.

The licensee stated that continued operation of Fort St. Vrain was justified, even though the failure found in circulator S/N C-2101, were likely to occur eventually in the other circulators.

The basis for continued operation was based on the following:

1) The failed circulator had been replaced. The results of the failure analysis to date had been presented to the staff.

2) A more thorough evaluation was being carried out with the goal of having a final evaluation in 120 days from this meeting date.

3) Increased on-line monitoring of the circulator wobble output on a daily basis, or on significant speed increases. Other performance parameters would also be trended.

4) Operation above 35% power would be on all 4 circulators.

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5) If another circulator failure is discovered, the licensee would shutdown the reactor.

' Jose'A. Calvo '

6) When the. evaluations noted above are completed, the licensee would prepare a specific plan of action to correct the condition in all circulators. At this time, another meeting would be held with the staff, to review these proposed actions.

7) Following the above evaluation, the licensee would reevaluate the current' circulator surveillance requirements, and propose a suitable amendment to the plant's Technical Specifications.

Based:on the above, the staff stated'that they concurred with the licensees proposal to continue reactor operation until all of' the necessary evaluations were complete. .However, the staff noted that.it's concurrence would only be for the.next-six months, and the licensee should make every effort to maintain the above schedule. The staff, also requested that the licensee provide a summary of its commitments to the staff, and the staff would respond with a' l written Safety Evaluation. The staff stated that the reactor may be returned to power operation (above 30% power) as'soon as the restart commi'mentsc are complete.

SSl Kenneth L. Heitner, Project Manager l Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects

Enclosures:

1 As stated DISTRIBUTION Docket File NRC & Local PDRs PD4 Reading File l KHeitner OGC-Bethesda EJordan JPartlow ACRS (10)

NRC Participants PD4 HH KHeitner: sr 09/Q/87

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