ML20050D158

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History of VT Yankee Feedwater Sparger Mods & Future Plans
ML20050D158
Person / Time
Site: Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date: 04/01/1982
From:
YANKEE ATOMIC ELECTRIC CO.
To:
Shared Package
ML20050D157 List:
References
NUDOCS 8204120085
Download: ML20050D158 (15)
v • d • e


Text

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HISTORY OF VERMONT YANKEE FEEDWATER SPARGER MODIFICATIONS AND FUTURE PLANS l

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19Zfi LIQUID PENETRANT INSPECTION OF N0ZZLES REVEALED CLAD CRACKS AT' BLEND RADIUS PRIMARILY AT THE 1800 (BOTTOM) LOCATION AFTER FOUR (4) YEARS OPERATION NO BORE CRACKS MAXIMUM DEPTH AT ANY GRINDOUT =.3125" TOTAL DEPTH AT 175 LOCATION SHALLOWEST DEPTH OF ANY BWR WHICH EMPLOYED A LOOSE FIT SPARGER CRACKS GROUND OUT NEW INTERFERENCE FIT FEEDWATER SPARGERS INSTALLED ALONG WITH JUNCTION BOX TEE INTERFERENCE FIT THERMAL SLEEVE SEATING SURFACE IS INCONEL WITH A.010"

.013" INTERFERENCE STAINLESS STEEL CLADDING WAS NOT REMOVED STARTUP OPERATING PROCEDURES MODIFIED TO REDUCE FEEDWATER '

FLOW CYCLING AND MINIMIZE OPERATING TIME AT LOW FEEDWATER TEMPERATURES

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1977 IN VESSEL LIQUID PENETRANT EXAMINATION PERFORMED ON INNER BLEND RADIUS OF EACH N0ZZLE WITH SPARGERS IN PLACE EXAM EXTENDS ABOUT 5" INTO BORE AT 00 AND 1800 SECTORS NO INDICATIONS FOUND J

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1980 NUREG-0619 ISSUED FOR COMMENT VERMONT YANKEE STATES DISAGREEMENT WITH NUREG CONCLUSION THAT INTERFERENCE FIT SPARGER THERMAL SLEEVE IS NOT A LONG TERM SOLUTION TO N0ZZLE CRACKING PROBLEM e

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JANUARY, 1981 NUREG-0619 ISSUED INTERFERENCE FIT FEEDWATER SPARGERS ARE NOT CONSIDERED A LONG TERM FIX AND SHOULD BE REPLACED BY 7/83 IN INTERIM, CONTINUE BIENNIAL OR 30 STARTUP SHUTDOWN IN-VESSEL LIQUID PENETRANT EXAMS 4

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APRIL 1981 FOLLOWING TELECON WITH NRC STAFF, VERM0 T YANKEE SUBMITTED DATA SUPPORTING OUR POSITION THAT THE INTERFERENCE FIT SPARGER WAS PERFORMING VERY WELL AND DID NOT REQUIRE REPLACEMENT i

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BASIS FOR JUSTIFICATI0l1 PTINSPECTIONSINDICATEDNOCRACKINGANbTHEREFORELITTLE OR NO BYPASS LEAKAGE WHICH IS NEEDED TO INITI ATE CRACKING LOWER RADIATION EXPOSURE BY INSPECTING THAN REPLACING SPARGERS OPERATING PROCEDURES WHICH MINIMIZE FEEDWATER FLOW CYCLING AND TRANSIENTS MUCH REDUCED NUMBER OF CRACK PROPAGATING STARTUP - SHUTDOWN CYCLES SINCE PLANT " MATURED" NO RELEVANT CLAD CRACKING HAS OCCURRED IN BWRS WITH ORIGINAL INTERFERENCE FITS l

INSTALLATION OF BYPASS LEAK DETECTION SYSTEM TO MONITOR DELETERIOUS LEAKAGE IN GENERAL, THE INTERFERENCE FIT DESIGN HAS SOLVED THE N0ZZLE CRACKING PROBLEM AT VERMONT YANKEE AND INSUFFICIENT JUSTIFICATION EXISTS TO REPLACE SPARGERS AND EXPOSE PERSONNEL TO SIGNIFICANT RADIATION O

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FEEDWATER TEMPERATURE COMPARISON BETWEEN I

GEllERAL ELECTRIC GENERIC AND VERMONT YANKEE HRS /YR IFW ( F)

GENERAL ELECTRIC VERMONT YANKEE (MATURE OPERATION) i 350 - 380 0

7073 300 - 350 5545 312 200 - 300 2354 14 100 - 200 116 53 100 28 16*

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~I REACTOR FEED! VATER HRS /YR db VERMONT YANKEE GENERAL ELECTRIC 450 28 4

400 16 98 350 21 19 300 36 2354 250 14 5545 200 561 8

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i JANUARY 1982 LETTER SENT TO NRC STAFF PROVIDING INSPECTION RESULTS AND 4

INITIAL LEAK DETECTION SYSTEM READINGS 4

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FUTURE PLAN CONTINUE TO MONITOR LEAKAGE WEEKLY ON LdAKAGE MONITORING SYSTEM PERFORM IN-VESSEL PT EXAMS AT THE CYCLIC INTERVAL (30 STARTUP -

SHUTDOWNS) SPECIFIED IN NUREG-0619 CONTINUE TO OBSERVE STARTUP PROCEDURES WHICH REDUCE CYCLING OF FEEDWATER FLOW AND TEMPERATURE CONTINUE TO OPERATE WITH INTERFERENCE FIT SPARGERS AND CLAD IN PLACE 4

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