IR 05000029/1985019

Insp Rept 50-029/85-19 on 851007-08.No Violations Noted. Major Areas Inspected:Licensee Action to Address Proposed Changes to Tech Spec Re Main Coolant Sys Structural Integrity Surveillance Requirements

ML20136D941
Person / Time
Site:	Yankee Rowe
Issue date:	11/13/1985
From:	Reynolds S, Wiggins J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20136D904	List: IR 05000029/1985019 ML20136D899
References
50-029-85-19, 50-29-85-19, NUDOCS 8511210394
Download: ML20136D941 (6)

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U.S. NUCLEAR REGULATORY COMMISSION

REGION I

Report N /85-19 Docket N License No. DPR-3 Licensee: Yankee Atomic Electric Company 1671 Worcester Road Framingham, Massachusetts 01701 Facility Name: Yankee Nuclear Power Station Inspection At: Rowe, Massachusetts Inspection Conducted: October 7-8, 1985 Inspectors: " !'3!8 f

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S. D. Reynolds, Jr., Lead Reactor Engineer date

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l C ief, Materials and Processes date

_ Approved by:USection, JA Wiggins B(,DRS

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-Inspection Summary: Announced Inspection conducted on October 7-8, 1985 (Inspection Report No. 50-029/85-19)

i Areas Inspected: Licensee's action to address proposed changes to Technical l Specification concerning Main Coolant System Structural Integrity surveillance l

requirements. The inspection involved 12 inspector-hours.at the Rowe plant

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Results: No violations were identifie PDR ADOCK 050 G

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DETAILS Persons Contacted Yankee Atomic Electric Company (YAEC)

• B. Drawbridge, Assistant Plant Superintendent-N. St. Laurent, Plant Superintendent

• G. Papanik, Senior Licensing Engineer

• G. Maret, Reactor Engineering

• T. Henderson, Technical Director B. Eklund, Reactor Engineering U.S. Nuclear Regulatory Commission W. Hazelton, MTEB, NRR (by phone)

• Denotes those present at exit intervie ' Review of Examination Results of Surveillance Testing of Control Rod Shroud Tube Structure The inspector examined the licensee's activities in evaluation of design changes made for the control rod shroud tube on service experience as determined by in situ TV optics visual examination. The results of these activities are a proposed change to Technical Specification PC18 ,

The inspector examined engineering documents related to the change in control rod shroud tube design and subsequent surveillance inspection results which showed that the new design solved the bolt loosening and subsequent loss of perpendicularity (with the lower support plate)

, proble Technical Specification (TS) Change #106 resulted in a modified design and installation of the Reactor Pressure Vessel (RPV) control rod shroud tube (CRST) assembly during 1973. The inspector reviewed Westinghouse Atomic Power Division (WAPD) Dwg 646J652 Sub 4 dated March 20, 1973 which showed the original design. The original design had the CRST's, individually bolted to the lh" thick lower core support bottom plate. The inspector also reviewed WAPD Dwg 646J692 Sub 12 dated February 16, 1975 which showed the modified design for the CRST bolted through the top and bottom plates of lower core support plat The inspection included an examination of the plant Reactor Engineering file for PC106 which included the following:

YAEC (Minnick to Directorate of Licensing) PC106 dated February 5, 1973

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This letter proposed a new stainless steel shroud tube structure-(in four sections) which consisted of 24 shroud tubes, a lower tie plate and upper support plate. This design change was required due to bolting failures and lack of shroud tube / support plate perpen-dicularity. The new design includes larger bolting and nominal clamping force (265,200 versus 201,300 pounds). It was reported that the new design results in essentially no change in flow dis-tribution or pressure dro *

YAEC letter to AEC dated March 16, 1973 and Proposed TS change 106 Supplement Number 1 which included the following:

• YAEC, Reactor Vessel Shroud Assembly -

Summary of Mechanical, Thermal and Hydraulic Evaluations -

March 1973 This document discusses the decrease in number of shroud tubes by 25%, increase in bolting capability and the recessed fit design change which maintains alignment even with loss of bolt preload. It includes an improved shroud tube flange to tube weld with a full penetration weld replacing the filled weld design. Mechanical and thermal / hydraulic evaluations were conducted. The design change to remove 8 shroud tubes is similar to that used in the Connecticut Yankee Model testing which showed that removing 8 shroud tubes decreases cross flow velocit *

Summary of Guides, Codes, and Standards Used in Design and Fabrication of the Shroud Tube Replacement Assembly (March, 1973). This document shows the new materials utilize * Reactor Vessel Shroud Assembly - Preoperational and Post Opera-tional Inspection of Surveillance Programs - March 1973

• AEC SER for PC106 (by A. Burger) dated March 30, 1973. The second to last paragraph of this document requires YAEC to perform an inspec-tion on at least one shroud tube in each quadrant (i.e. 4 of 24)

during each refueling outag * YAEC letter (Skovhalt to Minnick) dated March 30, 197 This letter indicates licensee's analysis of the original problem and reasons for improvement in new desig * YAEC letter (Heider to Directorate of Licensing) dated April 24, 1973. This letter discusses control rod drop exercises which indicate normal drop times and indicate lack of binding in the

, shrou * YAEC letter (Heider to Directorate of Licensing) dated May 7,1973.

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This letter discusses more rod surveillance testing data and l indicates rod drop times.

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Procedure No. OP-1703 for Shroud Tube and Vessel Inspection:

Revision For Core # Completion Date 6 XVII 4/27/84 5 XVI 10/2/82 4 XV 6/21/81 3 XIV 11/8/78

Procedure No. OP-4706 for Shroud Tube Inspection for Core X-XI Refueling 6/8/74

Memo: 3/15/73 - Installation of new lower internals (shroud tube)

Memo: 3/22/73 - Baseline inspection of new shroud tube installation

Westinghouse {W) Shroud Tube Assembly Replacement Field Assembly:

this included W DWG 616A408

Memo: Autio to Moody dated May 25, 1978. This indicates results of surveillance inspection and suggestion to relax frequency of inspec-tion The inspector _noted that there was inconsistency between the Revision dates of OP-1703 where some of the Revision dates were when the revision was made and some were when the next revision was required. The comple-tion dates of the inspections were, however, found to be satisfactory such that the Technical Specification requircments were met. It was also noted that the record copy of OP-4706 dated 6/5/74 was completed in penci The inspector observed the most current video tapes which indicated uniform gaps between the bolted joints which is indicative of maintenance of the necessary perpendicularity between the CRST and lower core plate assembl Review of the control rod drop times also indicated no problems due to loss of perpendicularit The in;pector examined the applicable edition and addenda of ASME Section XI IWB-2000, Table IWB 2500-1 category B-N-1 which the licensee interprets to require 40 month in situ examination and a 120 month examination with the structure removed from the RPV. The inspector concurred that this inspection program is satisfactory and poter ially a more sensitive inspection than the current inspection required by TS 4.4. No violations were identifie .. .

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.4 Pressurizer Cracked Cladding Surveillance The inspector examined the licensee's activities in monitoring cracks in the applied liner cladding on the pressurizer and reviewed its proposal to eliminate further inspection as indicated on PC 186 to the T The pressurizer was fabricated by B&W and utilizes a resistance spot welded applied lining (cladding) of 304 stainless steel. In the early 1970's, at the inception of the ISI program, it was determined that there were cracks in the applied lining as reported in Southwest Research Institute Final Report SWRI Project 17-2935 Summary of Test Results (first paragraph).

Technical discussions conducted by the inspector with NRR MTEB personnel

. involved in the cladding cracking problem in the 1965 - 1970 era indicated the cause of the cracking was intergranular stress corrosion cracking (IGSCC). In the process of manufacturing the pressurizer, the liner (cladding) was furnace sensitized and, in all probability high levels of residual stress were introduced due to dissimilarity in thermal expansion coefficients. It was the opinion of NRR that early service experience which employed relatively high oxygen in the water chemistry was respon-

-sible for the corrodant in the stress corrosion cracking (SCC) reactio Upon reduction of the corrodant, the SCC would be expected to diminish or sto The inspector also held further discussions with W PAD materials engine-ering personnel associated with the use of the spot welded applied liners for early military prototype pressure vessel Information obtained from this conversation indicated that cracks in the weld nugget were related to lack of delta ferrite in the 304 to carbon steel spot weld and cracks in the cladding material were due to IGSCC in early operation with oxygenated water. The weld nugget should be below the liner surface except for welds with excessive amperage. Thorough NDE examination and in some cases destruc-tive examinations following' service indicated that cracks in the applied liner did not propagate in the backing steel pressure boundary materia The licensee conducted visual In Service Inspection (ISI) surveillance inspections at each 18 month outage by use of a TV optics system in accordance with procedures YA-VT-11 and OP-4712 to meet TS requirements'

4.4.9.3. In 1974 the ifcensee utilized a 45 engle shear wave ultrasonic examination (UT) of a two foot square area containing known liner cracking to insure that cracking of the liner (cladding) did not propagate into the pressure boundary material. No base metal cracks were observe ~

The inspector observed the results of video tape inspection conducted to OP-4712 on May 22, 1984; September 21,1982; July 10,1981; November 28, 1978; August 2, 1977; and a memorandum to file written in 1975. Video tapes from the most current inspections were viewed along with early video tapes. The inspector concurred with the licensee's interpretation that these tapes did not show indication of a noticeable increase in cracking

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level in these time periods. .However, it was also noted that the quality of the inspection increased as the licensee had more experience with the TV camera set up resulting in a more detailed inspection in recent year The inspector also inspected a portion of the October 1974 ISI Interval I report by Mr. T. Henderson which related to the pressurizer liner cracking and the Magnaflux corporation UT shear wave disposition sheets referenced in the ISI repor Also the inspector examined the changes to ASME SC XI which were made

. subsequent to the licensee implementating the liner inspection progra This review found that the Summer 1976 Addenda eliminated the Table IWB-2500 Category B-I-2 examination requirement for the interior clad surfaces of vessels other than reactor vessel The overall results of the inspection were that there is no indication that the cracking of the applied liner is increasing and that the cause of crack-ing and lack of propagation from the applied lining to backing steel (pres-sure boundary) is consistent with materials engineering evaluations and the basis for the elimination of the SCXI requirement to monitor cladding crack No violations were identifie . Exit Interview The inspector met with the licensee representative at the conclusion of the inspection on October 8, 1985. The inspector summarized the scope and findings of the inspection. No written information was given to the licensee by the inspector during the course of the inspection.

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