ML20199H960
| ML20199H960 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 06/19/1986 |
| From: | Foster D GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-86-256-000 GN-954, PT21-86-256, PT21-86-256-000, NUDOCS 8607080021 | |
| Download: ML20199H960 (4) | |
Text
h h*ic Bo P "Y Waynesboro. Georgia 30830 Telephone 404 554 9961, Ext. 3360 404 724-8114. Ext. 3360 h
s a ogog';,,,
., p 01 aS'. O Georgia Power the southern electic sys?em Vogtte Project June 19, 1986 United States Nuclear Regulatory Commission Region II File: X7BG03-M112 Suite 2900 Log:
GN-954 101 Marietta Street, Northwest Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 and 2; 50-424, 50-425; Anchor Darling Model 5500 Mechanical Shock Arrestors Letter GN-907 dated May 12, 1986 Attention: Mr. J. Nelson Grace In previous correspondence on the above referenced subject, Georgia Power Company indicated the NRC would be informed of the results of our evaluation of this condition by June 20, 1986.
Georgia Power Company has completed its evaluation and concluded that a reportable condition as defined by the reporting criteria of Parts 10 CFR 50.55(e) and Part 10 CFR 21 does exist.
Based upon guidance in NUREG-0302 Revision 1 and other NRC correspondence concerning duplicate reporting, Georgia Power Company is reporting this condition per the reporting criteria of Part 10 CFR 50.55(e). A summary of our evaluation is attached.
This letter contains no proprietary information and may be placed in the NRC Public Document Room.
Your tr 1, D.' O. Fost[r Attachment xc:
U. S. Nuclear Regulatory Commission Document Control Desk l
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)
B. M. Guthrie J. F. D'Amico D. C. Teper (GANE)
D. E. Dutton E. D. Groover NORMS
/
I L 8607080021 860619 PDR ADOCh 05000424
EVALUATION OF A P0TENTIALLY REPORTABLE CONDITION ANCHOR DARLING MODEL 5500 MECHANICAL SH0CK ARREST 0RS Initial Report: On April 18, 1986, Mr.
R.
E.
Folker, Vogtie Project Quality Assurance Engineer, informed Mr.
E.
F.
Christnot of the U:NRC-Region II of a
potentially reportable condition concerning Anchor Darling Model 5500 Mechanical Shock Arrestors.
In subsequent correspondence to the. NRC, Georgia Power Company indicated the NRC would be informed of the results of this evaluation by June 20, 1986.
Background Information: During power ascension testing at another nuclear power plant, it was found that some Anchor Darling Industries (ADI) shock arrestors (snubbers) on the feedwater system had not moved to their expected positions relative to plant power levels.
An evaluation by ADI concluded that the units had defective ball screw assemblies because the torque required to move the ball screw assembly in tension was significantly greater than that required in compression.
ADI isolated the cause of this deviation to the ball screw assembly and met with their ball screw manufacturer.
It was verified that a condition existed at the entrance and exit of the ball return tubes that could cause the balls to skid rather than roll during operation.
This condition could not be traced to particular batches.
The mechanical shock arrestor, manufactured by ADI, is a device which protects piping systems during dynamic loading caused by a seismic event, water hammer, or other sudden shock distrubances.
During normal plant startup the shock arrestor allows unrestrained gradual movement of the supported piping due to thermal expansion.
The model series 5500 design translates external linear motion of a telescoping load-supporting assembly into internal rotational motion through the use of a ball screw assembly.
The rated load capacity of the model series 5500 arrestor is 55,000 lbs.
The maximum allowed force for gradual thermal movement is 2%
of rated load, or 1100 lbs.
Engineering Evaluation: In their letter of notification Georgia Power Company (GPC), ADI identified eighty-two (82) shock arrestors for Units 1 and 2 which were shipped to the Vogtle jobsite (see Table 1).
Fifty of these eighty-two suspect shock arrestors are in safety related systems, including seventeen in ASME Code Section III, Class 1 systems (reactor coolant and safety injection).
~
ADI requested that GPC return all identified shock arrestors for testing and repair of any deficient assemblies.
ADI initiated an in-house program which included testing of each shock arrestor and repair if the test showed that the drag force exceeded 2% of rated load.
Seven of the first eight shock arrestors tested, failed to meet the 2% limit.
The drag force exceeded 3%
of rated load on one of the failed shock arrestors and 12% on the remaining six units.
As a result, ADI decided to eliminate the preliminary evaluation test, rework the ball screw assembly and requalify every shock arrestor by test to ensure that the specification requirement of 2% maximum drag is met.
The six unacceptable units are considered inoperable based on the following:
1.
At a drag force greater than 3%, but equal to or less than 5% of rated load, the shock arrestor is considered operable only if engineering evaluation determines that the piping system is not adversely affected.
1 One of the deficient shock arrestors falls in this category, i
2.
At a drag force greater than 5% of rated load the shock arrestor is considered inoperable.
Five of the deficient units fall in this category.
At the Vogtle Electric Generating Plant, supported piping systems are designed on the basis that there is not more than a 1,100 lb. load which resists gradual thermal growth.
However, because the pipe would not move until the higher resisting force of the snubber is exceeded, the material stresses in the pipe wall would increase.
The higher pipe wall stresses could exceed the code allowables.
Since the possibility of exceeding the pipe wall stresses does exist, Georgia Power Company has concluded that a reportable condition exists.
Evaluation of Quality Assurance Program: This condition has been reviewed and it has been determined that there was not a significant breakdown in the Anchor Darling Industries quality assurance program.
==
Conclusion:==
Georgia Power Company has concluded that a reportable condition as defined by the reporting criteria of Parts 10CFR50.55(e) and Part 10CFR21 does exist.
Based upon guidance in NUREG-0302, Revision 1 ana other NRC correspondence, Georgia Power Company is reporting this condition per the reporting criteria of Part 10CFR50.55(e).
Corrective Action:
1.
Eight (8) Unit 1 shock arrestors were tested by ADI, repaired where necessary, requalified, and returned to the VEGP site.
2.
Thirty-seven (37) Unit 1 and Unit 2 shock arrestors were repaired without pretest, requalified, and returned to the VEGP site, 3.
The remaining thirty-seven (37) Unit 2 shock arrestors are being repaired and requalified by ADI and are scheduled to be returned to the VEGP site by June 30, 1986 (PCW #1F-1085 and 2F-1000).
I I
i t
i e
1 TABLE 1 QUANTITY OF ANCHOR DARLING 5500 SNUBBERS AT VEGP JOBSITE PROJECT QUANTITY SYSTEM CLASS UNIT 1 UNIT 2 Reactor Coolant (1201) 111 2
7 415 2
0 Nuclear Service 313 2
2 Cooling Water (1202)
Safety Injection (1204) 111 2
6 Main Steam (1301) 212 13 12 i
424 4
18 Main Feedwater (1305) 212 0
1 313 0
3 424 8
0 1
TOTALS 33 49 82 a