ML20205C192
| ML20205C192 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/11/1986 |
| From: | Foster D GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-86-270-000 GN-990, PT21-86-270, PT21-86-270-000, NUDOCS 8608120275 | |
| Download: ML20205C192 (4) | |
Text
w ost f ce Box Waynesboro, Georgia 30830 Telephone 404 554-9%1, Ext. 3360 404 724-8114. Ext. 3360 GeorgiaPower D. O. Foster
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July 11,1986 United States Nuclear Regulatory Commission Region II File: X7BG03-M106 Suite 2900 Log:
GN-990 101 Marietta Street, Northwest Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 and 2; 50-424, 50-425; Dragon Needle Valves; Letter GN-896 dated May 5, 1986; Letter GN-931 dated June 19, 1986 Attention: Mr. J. Nelson Grace In previous correspondence on this subject, Georcjia Power Company indicated the one inch and three-quarter inch Dragcn valves would be upgraded.
Georgia Power Company has subsequently determined that these valves performed satisfactorily during testing and that no additional modifications are needed. Enclosed is an amended copy of our evaluation.
This response contains no proprietary information and may be placed in the NRC Public Document Room.
Yours truly, D. O. Foste PAH/D0F/tdm Enclosure xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 J. H. Miller R. A. Thomas L. T. Gucwa J. P. O'Reilly D. R. Altman C. W. Hayes G. F. Head P. R. Bemis G. A. McCarley R. E. Conway J. A. Bailey D. S. Read J. T. Beckham
- 0. Batum Sr. Resident (NRC)
R. H. Pinson G. Bockhold C. S. McCall (OPC)
P. D. Rice C. E. Belflower J. E. Joiner (TSLA)
- 8. M. Guthrie J. F. D'Amico D. C. Teper (GANE)
D. E. Dutton E. D. Groover NOM 4S s
. 8608120275 860711 DR ADOCK 05000424 PDR Zg
EVALUATION OF A POTENTIALLY REPORTABLE CONDITION DRAGON NEEDLE VALVES Initial Report:
On April 10, 1986, Mr. R. E. Folker Vogtle Project Quality Assurance Engineer, informed Mr. E. F. Christnot of the USNRC Region II of a potentially reportable condition concerning Dragon needle valves.
In subsequent correspondence to the NRC (letter GN-896 dated May 5, 1986), Georgia Power Company indicated the NRC would be informed of the results of the evaluation of this condition on or before June 20, 1986.
Background Information:
During the safety injection pre-operational testing in preparation for the cold hydrostatic testing, Dragon valves of 1-1/2" and 2" size experienced high noise and vibrational levels, leakage through the packing, and in one case (tag number 1-1204-U4-140), stem failure.
Vibration was evident as the valves were opened from a 1/8 turned position.
Vibration was also evident throughout the full range of stem travel to a near full open position.
Dragon needle valves are used in the following high pressure throttling applications.
To accomplish flow balancing or metering, a temporary flow or testing device is used to establish the correct setting or opening for the 1
valves.
A.
Cold leg injection from safety injection pumps Four 2" valves 1-1204-U4-139,140,141, and 142 One 2" valve is used in each of the four parallel flow paths to balance flow and limit the combined flow to preclude safety injection pump runout.
These valves are to be positioned, locked in place, and flow tested.
i B.
Hot leg injection from safety injection pumps Four 2" valves 1-1204-04-116, 117, 118, and 119 Two valves are used on each safety injection pump.
The valves balance flow in 2 parallel flow paths and preclude pump runout.
These valves are to be positioned, locked in place, and flow tested.
C.
Cold leg injection from centrifugal charging pumps Four 1-1/2" valves 1-1204-U4-022, 023, 024, and 025 i
One 1-1/2" valve is used in each of the four parallel flow paths to balance i
flow and preclude pump runout.
These valves are to be positioned, locked in place and flow tested.
D.
Reactor coolant pump seal injection Four 1" valves 1-1208-U4-414, 415, 416, and 417 Meters flow to the reactor coolant pump seals.
E.
Makeup to RCP seal standpipe Four 3/4" valves 1-1208-U4-022, 371, 372, and 373 These valves meter nuclear cooling water to the reactor coolant pipe standpipe.
4
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Page two smaller size Dragon valves are also used at the Vogtle Electric Generating Plant in various other low pressure throttling and instrument isolation applications.
Dragon Valve has indicated that a unique needle valve design was furnished for each of the above applications.
This unique design is not optimum for the intended service in the safety injection system.
The features of this unique valve design included a union bonnet and a rotating stem with an unguided disc affixed to the stem by a stem disc retaining nut.
The disc was tapered and had a blunt or flat bottom.
The disc was designed to be loose on the stem.
Flow was designed to be from beneath the seat.
In high pressure drop applications, turbulent flow could induce the disc to move in relation to the stem thus setting up high frequency vibration and/or bending moments on the stem.
During testing of these valves, extreme vibration was observed.
It is the judgement of our architect engineer that these vibrations could have led to valve failure under normal operating conditions which could have prevented the valve from performing its safety function.
Desian Requirements of ECCS System:
The emergency core cooling system (ECCS) components.are designed such that-i a minimum of three accumulators, one charging pump, one safety injection (SI) 2 pump, one residual heat removal (RHR) pump, and one RHR heat exchanger, together with their associated valves and piping, will ensure adequate core cooling 2
in the event of a design basis accident (DBA).
The redundant onsite emergency i
diesels ensure adequate emergency power to at least one train of electrically operated components in the event that a loss of offsite power occurs simultaneously with an accident, even assuming a single failure in the emergency power system.
i l
The two safety injection pumps have the capability of supplying borated water 2
to either the cold or hot leg connections on all four RCS loops.
During the cold leg injection phase following a LOCA, the safety injection pumps take borated water from the RWST and deliver it to the reactor vessel through a comon header and four branch lines via the RHR injection line and the accumulator discharge lines connected to the reactor cold legs, once the RCS pressure has decreased below the shutoff head of the pumps.
Throttling valves are provided in each branch line for adjustment to limit safety injection pump runout and thus maximize flow conditions with one pump delivering through four lines and to equalize flow through all four lines such that the amount of coolant loss is minimized if one of the injection lines spills to containment.
The safety injection pumps are started automatically on an "SI" signal.
Engineerina Evaluation:
The evaluation indicates that had the described condition of these Dragon needle valves gone uncorrected, it could have impacted the safety of the plant.
If I
the stem of the valve fails, thus allowing the disc to become dislocated from its preset position, flow in the respective parallel paths will become unbalanced and may increase to a value which exceeds pump runout conditions.
Secondary effects of stem failure could include damage to the interior of the valve body, i
excessive valve and pipe vibrations and generation of metallic fragments being carried into downstream piping and components.
i
Page three
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Conclusion:==
Georgia Power Company has reviewed this condition and determined that a reportable condition as defined by the reporting criteria of Parts 10CFR50.55(e) and 10CFR21 does exist.
Based upon guidance in NUREG-0302 Revision 1 and other NRC correspondence, Georgia Power Company is reporting this condition pursuant to the reporting requirements of Part 10CFR50.55(e).
Corrective Action:
1.
Affix the valve disc solidly to the valve stem since these valves are not to be used as shut-off valves but as metering valves to be locked partially open.
2.
Replace stems on 1-1/2" and 2" valves since the stem threads extended into the top ring of packing.
3.
Replace the existing blunt nose unguided disc with a new disc design reconsnended by Dragon.
A mockup of this new design was successfully tested at VEGP on February 20, 1986.
The new disc incorporates a conical nose of 120* with body guiding and is rigidly attached to the stem.
4.
Corrective action for Unit I has been completed.
Corrective action for Unit 2 is expected to be completed within six months.
The modification for the Unit 2 valves are shown on memorandum of Change 31 to purchase order PAV-03412 to Dragon Valves.
Delivery of the modified valves has been requested and promised for August 30, 1986.
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