ML19340A955
| ML19340A955 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 10/08/1976 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009100824 | |
| Download: ML19340A955 (1) | |
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UNITEo STATES NUCLEAR REGULATORY CONIMISSION CENTRAL FILES REGION til 799 ROOSEVELT RO AD GLEN ELLYN ILLINOIS 60137
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.a Conanonwealth Edison Company Docket Nos. 50-295, 50-304, ATTN:. Mr. Byron Lee, Jr.
50-10, 50-237, 50-249 Vice President 50-254, 50-1!65, 50-456, Post Office Box 767 50-457, 50-454, 50-455, Chicago, Illinois 60690 50-373, 50-374 Gentlemen:
The enclosed Circular No. 76-05 is forwarded to you for action.
If there are any questions related to your understanding of the actions required, please contact this office.
Sincerely, James G. Keppler Regional Director Enclosure IE Circular No. 76-05 cc w/ enc 1:
Mr. R. Cosaro, Project Superintendent Mr. B. B. Stephenson Station Superintendent Mr. Gunnar Sorensen, Site bec w/ enc 1:
Project Superintendent
\\CentralFiles Mr. L. J. Burke, Site IE Files Project Superintendent PDR 1
Mr. N. J. Kalivianakis Local PDR Station Superintendent Anthony Roisman, Esq.,
Mr. J. Bital, Plant Attorney Superintendent WTIOS
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IE Circular No. 76-05 October 8, 1976 i
HYDRAULIC S110CK AND SWAY SUPPRESSORS, - MAINTENANCE or BLEED AND LOCK-UP VELOClTIES ON ITT GRINNELL'S MODEL NOS. - FIG. 200 AND FlG. 201, CATALOG PH-74-R DESCRIPTION OF CIRCUMSTANCES:
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Recent information has become availabic related to improper lock-up and. bleed rates of certain ITT Grinnell shock and sway suppressors (snubbers). The control block or valve block on the snubbers involved is one which contains the mechanisms for a " dual orifice type" maobbar valve arrangement. These control bloths or valve blocks can be identified by four locking nuts on the surface of the block. These 1
nuts lock the stem of the valve control into position. Rotation of the stem modifies the orifices which control the lock-up and bleed rates. The units in questions, at this time, are those snubbers which have control block or valve block serial numbers from B-0001 through B-2000.
These snubbers include 1 1/2 inch diameter (3 kip capacity) through 6 inch diameter (72 kip capacity) units.
ITT Grinhell first identified this problem in connection with their own testing program during the last two weeks of August 1975. The origin of the Problem was traced by Grinnell to November of 1974 when a design cha'ge 'anown as Ravision B) was initisted on Model Nos. - Figura n
200 and Figure 201, Catalog PH-74-R snubbers, along with the addition c,f i
a Crinnell design specification for lock-up and blaed velocities. These new rates were to be 8 in/ min, plus or minus 2 in/ min. for loch-up and 4 in/ min plus or minus 1 in/ min. for bleed. At that time production testing of completed snubbers included within the above series of serial numbers was completed on the basis of "go" or "no-go" testing and did not specifically determine the lock-up and bleed rates for each snubber.
Crinneil has determined that all snubbers involved should lock under seismic events as designed, but perhaps at a lower velocity.
Additionally, the bleed rate has been determined to exist at a value as low as 1/8 in/ min.
This,could result in increased piping stresses depending on the specific design. With the uncertainty of specific lock-up and bleed rates, there is the possibility of adverse effects on the piping systems or components the snubbers were designed to protect.
It has been stated, however, that to the best of Grinnell's knowledge, there were no lock-up and bleed criteria defined by their customers for the plants identified as having utilized snubbers from the B-0001 through B-2000 series.
Even through lock-up and bleed rates on snubbers with adjustable orifices are now determined prior to shipment from the manufacturer, there is always the possibility that subsequent removal or tightening of the locking nuts on the control block or valve block will modify the orifice setting, thus affecting lock-up and bleed rates. At least two models of Grinnell's 1
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IE Circular No. 76-05 October 8, 1976 snubber control valves use some type'of seal on the locking washers and in some cases these may have been replaced in the field to change the seal material or correct small leaks.
In these cases, if proper pro-cedures were not followed to maintain the stem portion in its original position, the orifice setting could change.
The tightening of a lock nut itself could rasult in a change to the orifice.
ITT Grinnell makes the following statement in the printed material furnished with each snubber assembly:
" Adjustment of snubber valve requires equipment capable of measuring rate and load. DO NOT ATTEMPT TO RESET ADJUSTMENTS IN THE FIELD."
The recommended corrective action outlined by ITT Grinnell is to replace the entire valve assembly (2 required per snubber) known as the " barrel" in the case of the lock-up control, and the pins or stems (2 required per snubber) used to control the bleed rate.
ITT Grinnell has prepared documents which prescribe the replacement procedures. The replacement parts are precalibrated. Therefore, field calibration of the entire snubber unit will not be necessary if the replacement parts are installed /
in accordance with the prescribed procedures.
The tolerances on the precalibrated pins or stems associated with the bleed mechanism will exceed the original value of 4 in/ min, plus or minus 1 in/ min.
The new b1'.-d rate,'will be 4 in/ min plus or minus 2 in/ min.
Corrective action could also consist of recalibration of the existing snubbers with adjustments made to bring the operating characteristics of the units back within the tolerances specified by ITT Grinnell. Monitor-ing of relative rotation of the lock washer and stem could it. the future be carried out if position marks were provided on the parts af ter calibration.
ITT Grinnell has identified the following f acilities which have licenses under 10 CFR 50 which received snubbers within the group defined by the bounding serial number.
Number of Grinnell Snubbers Plant Model Nos.-Fig. 200 & Fig. 201 Farley Nuclear Plant 239 Millstone Point Unit 2 185 North Anna 155 Davis Besse Unit 1 111 D. C. Cook 78 Calvert Cliffs 66 Beaver Valley 53 Diablo Canyon 41 Ginna 6
Kewaunee 2
Peach Bottom 2
Browns Terry 1
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IE Circular No. 76-05 October 8,1976 ITT Grinnell has also informed the utilities who own these facilities 4
regarding this matter; however, some of the series may be in use or intended for use at other reactor facilities as a r.esult of utilities loaning or selling units to other utilities or by the fact that sub-contractors or other suppliers might be involved.
ACTION TO BE TAKEN BY LICENSEE:
For all power reactor facilities with an operating license or a con-struction permit using or intending to use the above described snubbers on safety related systems or components:
1.
Determine if any of the subject snubbers are installed or scheduled to be installed in safety-related systems at your facility.
a.
Provide a list containing each snubber identified and indicate the piping system or component with which it is associated.
f b.
Indicate for each snubber its history of testing and test results as well as its maintenance history.
c.
For each snubber list the current required lock-up and bleed rates and what rates the snubbers were specified to meet by the original construction / purchase specification.
Indicate the organization, by name, that was responsible for the preparation of the construction / purchase specification.
d.
If replacement parts are utilized instead of recalibration of the snubbers, provide an assessment of the effect of a bleed
- rate of 2 in/ min. which represents the new lower bound.
2.
For snubbers within the above described series that do not have documentation available defining the lock-up and bleed velocities, provide a description of the actions to be taken to substantiate these. characteristics.
Also, provide the schedule to complete these verifications and modifications, if needed.
3.
Review mai 1tenance and modification procedures - for the above described series of snubbers where such actions could affect the performance characteristics of the snubbers.
Such actions include but are not limited to the disassembly of snubbers, replacement of seals, changiag nydraulic fluid and,the changing of any valve springs. F.oiify the procedures, as appropriate, to assure that any future maintenance or modifications will not change the performance charactericcies.
4.
Provide a report which contains the responses to items 1, 2 and 3 above within 90 days of the date of this Circular.
Reports should be submitted to the Director of the NRC Regional Of fice.md a copy i
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IE Circular No. 76-0'5 October 8, 1976 should be forwarded to the NRC Office of Inspection and Enf orectnent,
Division of Reactor Inspection Programs, Washington, D. C. 20555.
Approval of NRC requirements for reports concerning possible generic problems has been obtained under 44 U.S.C. 3152 from the U.S. General Accounting Office.
(CAO Apprpval B-180255 (R0062), expires 7/31/77).
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