ML20084N150
| ML20084N150 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 09/14/1972 |
| From: | Coughlin J FLORIDA POWER & LIGHT CO. |
| To: | Kruesi F US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084M989 | List: |
| References | |
| 10CFR50.55E, NUDOCS 8306020538 | |
| Download: ML20084N150 (2) | |
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FLORIDA POWER & UGHT COMPANY September 14, 1972 Mr. Frank E. Kruesi, Director Directorate of Regulatory Operations U.
S. Atomic Energy Commission Washington, D. C. 20545
Dear Mr. Kruesi:
Re: Docket Nos. 50-250 and 50-251 Turkey Point Units 3 and 4 In accordance with 10 CFR 50.55(e), a design deficiency in motor operated residual heat removal (RHR) valves 750 and 751 in Turkey Point Plant Units 3 and 4 is hereby reported. This report is somewhat behind the schedule given in 10 CFR 50.55(e) because until an on-site meeting of September 12, 1972, we were unable to obtain information from the valve supplier (Westinghouse, the nuclear steam supply system vendor) that the valve manu-facturer (the Copes-Vulcan Division of the Blaw-Knox Company) had agreed that a design change was in order and had supplied a proposed design change to Westinghouse in the form of preliminary drawings.
The design deficiency was found when RHR valve 4-751 (a Unit No. 4 valve) was dismantled for installation of a stainless steel gland follower and associated studs and nuts on June 15, 1972 as replacements for carbon steel parts. This was part of a valve upgrading program having the objective of reducing corrosion of valve parts in systems containing boric acid.
When valve 4-751 was disassembled, two cracks were found in the valve lower disc retainer, a stainless steel Type 410 part meeting an ASTM-A-240 material specification.
The subject valves (750 and 751) are unusual 14-inch motor operated gate valve assemblies in the suction side of the RHR system. These valves have a gate made of two parallel discs held apart by a spring. This is in contrast to the typical wedge shaped gate and "V" seat in common gate valves. The two parallel discs are held in alignment by "E" shaped upper and lower disc re-tainers, with the outer legs of the "E" fitted into notches in the disc edges, and the center leg of the "E" fastened to the disc holder by a cap screw.
It was obvious from inspection of the valve parts that the disc assembly had
" bottomed" and that the retainer had cracked when it pressed against the concave bottom of the valve body. By June 30, 1972 it was determined that the lower disc retainer in 3-750, 4-750 and 4-751 had been cracked and that 3-751 was not cracked. On June 30, 1972 the Region II Office of the Directorate of Regulatory Operations was advised by telephone that Florida Power & Light Company considered this to be a design deficiency, as defined I
in 10 CFR 50.55 (e).
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Mr. Frank E.
Kruesi September 14, 1972 It was determined that the valve motor operator controls were wired in accordance with the drawings supplied by Westinghouse. However, this did not meet the Copes-Vulcan requirements.
As originally connected, valve closure travel was stopped by a torque switch. Obviously, this did not prevent over-travel. After the failure, the motor operator controls were rewired so a limit switch stops the disc when it is concentric with the seat (about 1/4 inch from contact with the bottom of the valve body), with the torque switch set as a back-up to the limit switch. A torque switch is set to stop opening travel when the valve backseats.
The revised controls are satisfactory for motor operation, but do not take care of the case of manual operation (i.e. use of handwheel). There fore, FPL in-stalled a temporary mechanical stop to limit closing travel of the valve stem.
On September 12, 1972 Westinghouse advised FPL that Copes-Vulcan has designed a modified lower disc retainer that will prevent overtravel, that will not break on " bottoming" and that will transmit forces to the stem in the event of
" bottoming". Redesigned parts will be on site soon and will be installed as soon as practicable.
If failure of the valves had occurred in operation it is probable that no parts would have entered the reactor coolant system and caused difficulty, but leakage to the RHR system would have been an operating difficulty, probably leading to a cold shutdown for valve repair.
It is believed the design deficiency has been solved.
Your inspectors are cordially invited to look at the valves, failed parts, drawings, etc. at the site as usual.
burs ve y truly,
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Mr. John G. Davis, Director Region II, Directorate of Regulatory Operations
~ Atlanta, Georgia Mr. Richard DeYoung, Assistant Director for Pressurized Water Reactors Directorate of Licensing Washington, D. C.
Mr. Jack Newman Newman, Reis & Axelrad Washington, D. C.
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MONTHLY REPORT JULY 1972 Florida Power and Light Company (Turkey Point 3 and 4) - The licensee informed Region II (Atlanta) by telephone on July 7 and 20 of the following:
1.
Three of four 14-inch stainless steel isolation valves in the residual heat removal system were found to have cracked gate alignment plates.
The cracking was attributed to overstress caused by overtravel of the valve motor driver.
The valve fabricator (Copes-Vulcan) replaced the cracked plates and will modify the valve motor driver to prevent overtravel.
2.
During additional-hot functional testing, one of the reactor coolant pressurizer safety valves was retested by manually
" popping" the valve at a reactor coolant pressure of 2,400 psig and a temperature of 547 F.
The test demonstrated the adequacy of the valve discharge piping to withstand the forces exerted by the water seal being expelled during valve op'eration.
Fuel loading is scheduled to start on July 28.
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August 9, 1972 MOTE TO J. 3. H m mem PROBLEM WITH COPES VULCAN VALVgg. caemm1C CONSIDERATIONS This confires my understanding that the Reactor Construction Branch is following up on the RH1 valve problems at Turkey Point (80 Inquiry Report No. 50 250/72-1/CDs) including possible ganarie considerations.
Original signe'd g' J. G. Keppleg p J. G. Keppler, Chief, Beactor Testing and Operations Branch Directorate of aagulatory Operations ces M. S. Hildreth, 30 W. C. Saidle, 20:11 1
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UNITED STATES ATOMIC ENERGY COMMISSION
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REGION II - Su li E 818 230 P E AC HT R E E ST R E ET, NOR T H W EST Y t tr puca.c 1 (404,526 4503 trug e AT L ANT A, GEORGI A 30303 DIRECTORATE OF REGULATORY OPERATIONS July 7, 1972 J. G. Keppler, Chief, Reactor Testing and Operations Branch (2)
Directorate of Regulatory Operations RO INQUIRY REPORT NOS. 50-250/72-1/CDR AND 50-251/72-1/CDR FLORIDA POWER AND LIGHT COMPANY (TURKEY POINT 3 AND 4), LICENSE NOS.
CPPR-27 AND 28, DOCKET NOS. 50-250 AND 251, CRACKED GATE ALIGNMENT PLATES IN RESIDUAL HEAT REMOVAL (RHR) SYSTEM ISOLATION VALVES The attached inquiry report is forwarded for information.
Since modifications are required to limit the drive mechanism of these Copes-Vulcan valves, it would appear that generic problems are involved. The potential hazard is that debris from a destroyed align-ment plate could be drawn into the RHR pumps or could, conceivably,
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enter the reactor coolant loop through backflow.
On subsequent inspections, we shall follow progress on the modifications at Turkey Point.
The licensee has stated that a report of the failures will be issued in accordance with 10 CFR 50.55(e).
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' W. C.
eidle, Chief l
RO:II:JCB Reactor Operations Branch i
Enclosures:
R0 Inquiry Rpt. Nos.
50-250/72-1/CDR and 50-251/72-1/CDR (Lewis) cc w/ encl:
J. B. Henderson, R0 RS, AD For Safety and Security Stds. (3)
L Asst. Director For Boil. Water Reactors (2)
L Asst. Director For Press. Water Reactors (2)
L Asst. Director For Operation Reactors (3)
L Asst. Director For Site Safety (2)
R0 Office of Operations Evaluation RO Asst. Dir. for Procedures R0 Asst. Dir. for Inspection & Enforcement R0 Files DR Central Files TRANSMITTED VIA MAG CARD 7/7/72, 1:55 pm, kk l'x 3.
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U. S. ATOMIC ENERGY COMMISSION REGION II DIRECTORATE OF REGULATORY OPERATIONS RO Inquiry Report Nos. 50-250/72-1/CDR 50-251/72-1/CDR Subj ect : Florida Power and Light Company Homestead, Florida License Nos.: CPPR-27 and CPPR-28 Facilities: Turkey Point 3 and 4
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Descriptive
Title:
Cracked Gate Alignment Plates in Residual Ieat Removal (RHR) System Isolation Valves.
Prepared By:
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72 R. C. Lewis, Reactor Inspector Date Reactor Operations Branch J. Olmstead, Turkey Point Project Manager, telephoned R. C. Lewis on June 30, 1972, to report that three of the four RHR, inlet isolation valves were found to have a crack in the gate alignment plate.
The cracked gate alignment plates were visually detected on Jun'e' 19, 1972, when the valves were disassembled to replace carbon steel packing gland assemblies with gland assemblies of stainless steel. The gland assembly change was effected to install a material more compatible with the boric acid operating environment. There are two 14-inch RHR inlet isolation valves per facility (FSAR Figures 4.2-1 and 6.2-1).
Tlu t of the four valves contained cracked places (one on Unit 3 and both of the Unit 4 valves). Olmstead stated that Copes-Vulcan, Incorporated, fabricator of the valves, attributed the cracked plates to overstress caused by overtravel of the valve motor driver.
Olmstead stated that the cracked plates had been replaced on the three affected valves and that temporary administrative controls had been implemented to prevent overdriving the valves. A permanent modification to prevent overtravel of the valve motor driver is being fabricated by Copes-Vulcan.
Olmstead stated that a report of the alignment plate failures would be submitted in accordance with 10 CFR 50.55(e).
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