ML20195E437
| ML20195E437 | |
| Person / Time | |
|---|---|
| Issue date: | 06/04/1986 |
| From: | Baker E, Trottier E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML20195E434 | List: |
| References | |
| REF-QA-99900049 NUDOCS 8606090031 | |
| Download: ML20195E437 (8) | |
Text
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ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.
SALEM, MASSACHUSETTS REPORT INSPECTION INSPECTION NO.: 99900049/86-01 DATE: 2/10-11/86 ON-SITE HOURS: 16 CORRESPONDENCE ADDRESS: Atwood & Morrill Company, Inc.
ATTN: Mr. S. N. Shields Vice President, Engineering 285 Canal Street Salem, Massachusetts ORGANIZATIONAL CONTACT:
Frederick W. Wilson, QA Manager TELEPHONE NUMBER:
617-744-5690 NUCLEAR INDUSTRY ACTIVITY: Atwood & Morrill provides special main steam isola-tion valves (Y-pattern globe), turbine extraction steam valves -(bleeder trip),
and general product line valves for gas and fluid systems.
4JY h(o ASSIGNED INSPECTOR:
E. H. Trottier, Reactive Inspection Section (RIS)
Date OTHERINSPECTOR(S): Bruce E. Miller, Consultant Brookhaven National Laboratory APPROVED BY:
M
[
f E. T. Baker, Acting Chief, RIS, Vendor Program Branch Date INSPECTION BASES AND SCOPE:
k.
BASES:
10 CFR 50 Appendix B and 10 CFR Part 21 B.
SCOPE: This inspection was conducted to determine whether appropriate consideration was given to the design, sizing, and location of the Atwood
& Morrill check valves purchased to replace and add to the feedwater system check valves at the San Onofre Nuclear Generating Station, Unit 1.
In addition, this inspection sought general information on check valve design, application, and recommended location in fluid systems.
PLANT SITE APPLICABILITY:
San Onofre Nuclear Generating Station, Unit 1, (50-206).
8606090031 860604 cojp9 EWA
ORGANIZATION: ATWOOD&MORRILLCOMPA5Y,INC.
SALEM, MASSACHUSETTS REPORT INSPECTION NO.: 99900049/86-01 RESULTS:
PAGE 2 of 6
' A.
VIOLATIONS:
None.
B.
NONCONFORMANCES:
None.
C.
BACKGROUND:
In the early morning hours of November 21,1985, Unit 1 of San Onofre Nuclear Generating Station (SONGS-1) experienced a temporary loss of inplant and offsite ac power.
(Plant emergency diesel generators were available to restore power within one minute, bu! operating instructions in effect at the time of the incident gave priority to restoring power to the plant from offsite sources.)
In the 21 seconds between the loss of inplant and offsite ac power, only one ac powered feed pump was available for both feedwater trains that supply all three steam generators. The suction piping of the non-running ac feed pump (low pressure feedwater heater train "B") should have been protected from over pressurization by the still-running "A" feed pump.
It was not. The 12-inch check valve at the discharge of feed pump "B" had failed to close on reverse flow. Thus, the "B" feedwater flash evaporator failed due to overpressurization.
Subsequent investigation found the "A" feed pump discharge check valve also stuck open, two 10-inch check valves stuck open in lines feeding two steam generators, and the 10-inch check valve broken apart in the line feeding the third steam generator.
As part of the measures taken by the utility (Southern California Edison) to prevent recurrence of this incident, Atwood & Morrill check valves were purchased to rcplace the failed feedwater check valves, plus other existing feedwater system check valves.
(In addition, the plant is adding three check valves to the feed system. These also wi'i be supplied by Atwood & Morrill.)
This inspection sought to review the design and operating history of the valves being purchased by San Onofre Nuclear Generating Station, Unit 1, as well as engineering (application) assistance and customer support programs (bulletins, maintenance advice, etc.) provided by Atwood & Morrill.
ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.
SALEM, MASSACHUSETTS REPORT INSPECTION NO.: 99900049/86-01 RESULTS:
PAGE 3 of 6 D.
O'.<ER FINDINGS AND COMMENTS:
1.
Design of SONGS-1 Atwood & Morrill Check Valves All eleven SONGS-1 Atwood & Morrill check valves purchased by SONGS-1 are of essentially the same design. However, the new 12-inch A and B feed pump check valves have a 7/32-inch hole drilled in their disks for pressure release. This was found to be required so that automatic valve alignment upstream (feed pump suction source) could occur in a timely fashion to support actuation of the required engineered safety feature systems.
The basic design features of the Atwood & Morrill check valve that differ from other check valves are:
disk arm, disk arm swing stop and disk is a one piece c& sting valve seat offset 20 from vertical The method used to limit disk travel (and thus set the full open angle) is to build up the disk arm swing stop.
In this check valve design, the disk arm swing stop strikes the inside of the valve body at the curved surface between the bonnet and valve outlet.
2.
Application to SONGS-1 Feed System The inspector interviewed the Atwood & Morrill Project Engineer for the SONGS-1 contract. He discussed the many conversations held with SCC staff engineers concerning important variables to be addressed when considering application of a particula" valve to a system. The system variables to be considered are:
flow velocity and valve location.
System flow velocity increases at the check valve because the a.
valve's seat bore (minimum flow passage) is usually somewhat smaller than system nominal pipe diameter, and system mass flow rate is a constant.
This increase in velocity through the seat bore is an important variable, along with disk size and l
weight, in holding the valve disk fully open.
In a given fluid system, Atwood & Morrill recommends a seat bore diameter that will produce a flow rate between 10 feet per second (minimum) and 40 feet per second (maximum) during normal, extended system operation.
(Ten to 30 feet per second is considered an ideal l
l l
l
r ORGANIZATION: ATWOOD & MORRILL COMPAN'Y, INC.
SALEM, MASSACHUSETTS REPORT INSPECTION N0.: 99900049/86-01 RESULTS:
PAGE 4 of 6 range of flow velocity). The importance of minimum flow velocity is that it must be sufficient to hold the disk in the full open
(" pinned") position. Maximum flow velocity is important because it signifies a value above which excessive flow turbulence and pressure drop can occur.
Atwood & Morrill engineers worked with Southern California..
Edison (SCE) engineers to provide check valves whose seat port velocities and flow characteristics were expected to be adequate for the application.
Based on preliminary data supplied by SCE for 100% power operation, Atwood & Morrill predicted a seat velocity of approximately 25 feet per second through each of the three 10-inch check valves.
(The flow rate through each 12-inch check valve was expected to be similar because of a higher mass flow rate through two, slightly larger valves.)
Final rystem calculations yielded approximately 19.3 feet per second through each 10-inch check valve and 20.5 feet per second through each 12-inch check valve. As stated above, these valves are well within the ideal seat bore velocity range recommended by Atwood &
Morrill.
b.
Valve location is not a variable that is easily controlled by a company providing replacement valves in an existing plant.
In pursuing this issue with Atwood & Morrill engineers, the inspector was advised that Atwood & Morrill supports industry recommendations of locating check valves in piping runs such that the nearest system device capable of altering the' fluid flow profile is at least five pipe diameters downstream and ten pipe diameters upstream of the check valve, where possible.
Atwood & Morrill engineers cautioned that these are ideal con-ditions and are seldom found in application.
Beyond making SCE aware of industry recommendations, piping configuration in a plant already constructed is usually beyond the control of the valve manufacturer.
Further, Atwood & Morrill's experience has shown that while the ten pipe diameters upstream - five pipe l
diameters downstream arrangement may be ideal, Atwood & Morrill check valves have performed satisfactorily in decidedly less than optimum conditions for many years.
1 f
0 ATWOOD&MORRILLCOMPAdY,INC.
ORGANIZATION:
SALEM, MASSACHUSETTS REPORT INSPECTION N0.: 99900049/86-01 RESULTS:
PAGE 5 of 6 3.
Performance History of SONGS-1 Atwood & Morrill Check Valves The inspector established that while Atwood & Morrill has an adequate Part 21 procedure (Procedure No. 20-67.10, " Reporting of Defects and Noncompliances Under 10 CFR Part 21"), it has not had occasion to put its requirements inte effect since 1979.
Further, Atwood & Morrill has no formal method or procedure for processing or evaluating field deficiencies.
In defense of their seemingly non-existant Part 21 notifications (none in seven years), the inspector was advised that Atwood 6 Morrill has issued and will continue to issue information notices informing customers of difficulties encountered with valves supplied. These information notices (three since 1980) are sent in lieu of Part 21 notifications, because Atwood & Morrill seldom knows if a valve's application is-safety-related.
In August and November, 1983, tour nuclear customers were notified that NDE had not been performed on valves shipped to them.
In March, 1984, six nuclear plants were notified of cracked valve shafts in main steam isolation valves manufactured since 1976.
In December, 1984, one nuclear util-ity was advised that an Atwood & Morrill air-operated plug valve shipped to them could be defective.
In addition, Atwood & Morrill noted that almost all Atwood & Morrill valve problems brought to their attention turn out to be, on examination, plant installation related.
improper maintenance (pressure disturbances elsewhere in the system For example:
flow or to valve); improper size for application.
4.
Maintenance Recommendations Provided by Atwood & Morrill The inspector reviewed examples of instruction manuals shipped with each valve order. The manuals were found to contain a preventive maintenance section, a general maintenance section, and pressure y
seal ring precautions.
Preventive maintenance consists of an inspec-tion of bonnet and bearing cover gaskets for deterioration and obvious leaks to be performed, "...during any period of shutdown,...;" while general maintenance is to be performed at valve disassembly.
For valves with bolted bonnets, 12 steps for disassembly and 7 steps for reassembly are provided.
For valves with pressure seal bonnets, 29 steps for disassembly and 16 steps for reassembly are provided.
Valve I
seat inspection, lapping, and cleaning instructions are found in the disassembly steps. Torque values are provided for pressure retaining bolting and detailed instructions on how to tighten them are provided (typical bolting pattern sequence).
I
)
i ORGANIZATION: ATWOOD & MORRILL COMPANY, INC.
SALEM, MASSACHUSETTS REPORT INSPECTION NO.: 99900049/86-01 RESULTS:
PAGE 6 of 6 5.
10 CFR 50 Appendix B Program The inspectors reviewed the Atwood & Morrill Appendix B Quality Assurance Program as found in the Atwood & Morrill Quality Assurance Manual.
Its content and implementing procedures appeared to te adequate.
E.
CONCLUSIONS:
Based on the information reviewed during this inspection, the replacement Atwood & Morrill check valves are properly sized and designed for the in-tended application.
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