ML20132C843

Deleted Tech Specs 4.4.9.2 & 4.4.9.3 Re Surveillance Requirements for Main Coolant Sys Structural Integrity

ML20132C843
Person / Time
Site:	Yankee Rowe
Issue date:	07/19/1985
From:	YANKEE ATOMIC ELECTRIC CO.
To:
Shared Package
ML20132C833	List: ML20132C831 ML20132C843
References
NUDOCS 8507310015
Download: ML20132C843 (3)

Text

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ATTACHMENT A

1. SHROUD TUBE INSPECTIONS Proposed Change Delete Technical Specification Surveillance Requirement 4.4.9.2 Reason and Basis for Change This Technical Specification Surveillance Requirement is not a Standard Technical Specification. It was adopted in 1972 in conjunction with a plant modification as a special surveillance requirement. Events since 1973 have led to the conclusion that this specification is no longer appropriate because its content is redundant to standard specifications added since 1973 and because the basis for its accelerated frequency has been satisfied.

The original configuration of the Yankee reactor core internals included a control rod shroud tube assembly which, after twelve years of operation, sheared some bolting, shifted position and slowed the control rod drop times. A new, simplified and unitized assembly was installed in 1973 and the USNRC (then AEC) approved Proposed Change No.106, reflecting this modification.

One of the provisions of Froposed Change No. 106 was to include in the Technical Specifica'.icas the surveillance requirement in question. The intent was to verify that the new design actually solved the original problem. During that same time frame, the American Society of Mechanical Engineer's (ASME)Section XI Inservice Inspection (ISI) Program grew from its infancy to full maturity.Section XI also recognizes the need and provides for inspection of all reactor core internals, including a control rod shroud tube package. Yankee Technical Specifications include ASME Section XI as Surveillance Requirement 4.0.5. Thus the surveillance of the control rod shroud tube assembly is covered by two Technical Specification requirements.

There are differences between the two requirements. The ASME Section XI inspections are conducted at least once per 40 months

, in situ and at least once per 120 months in detail with the assembly pulled out of the reactor. Meanwhile, the Proposed Change No. 106 version (T.S. 4.4.9.2) of these inspections is conducted once ,per 18 months, but in situ only. The former program provides less frequency but greater detail than the latter.

The basis for the ' accelerated (18 month) surveillance was to verify a valid fix to the original problem. The new assembly has been closely monitored for the ensuing thirteen years. With no indications contrary to a successful solution after thirteen years, the basis of the accelerated effort is accomplished.

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Therefore it is appropriate to rely on the ASME Section XI program requirements for continued assurance of the integrity of the reactor core internals.

2. PRESSURIZER INTERNALS INSPECTIONS Proposed Change Delete Technical Specification Surveillance Requirement 4.4.9.3.

Reason and Basis for Change During the early (1970-1974) development of the ASME Section XI i Inservice Inspection (ISI) Program, it was discovered that the cladding on the Yankee pressurizer walls was cracked.

Research of the vessel design revealed that the cladding had been applied with a stitch welding technique which produces a quilting effecc and that cladding cracks in this design are not only possible but normal. Further irvestigation involved ultra sonic testing from the outside to assure no propagation of the cracks into the base metal. None was found. Finally, as a conservative measure, Yankee adopted a Surveillance Requirement to monitor the cracks for change.

Since that time, ASME Section XI has dropped the inspection requirements. Meanwhile Yankee has monitored these cracks for over ten years with no significant change to report.

The cost of this monitoring is measured in high exposure of people in and near the pressurizer and in extended refueling time. Therefore, given that the results have shown no changes and that the cost in exposure and refueling time are the only significant effects, it is proposed that this Surveillance Requirement be deleted.

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