ML20037B242
| ML20037B242 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 09/06/1977 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009090896 | |
| Download: ML20037B242 (1) | |
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'CENTRACFILEs SEP G 19D~
Loclect ::os. 50-10, 50-237, 50-249, 50-254,56-265, 50-2c5, 50-304, 50-373, 50-374,40-454, 50-455, 50-456, 50-457 i
Co: nonwealth Edison Cocpeny l
ATTN:
!!r. Syron Lee, Jr.
Vice President P. O. Box 767 Chica3o, IL 60690 l
Gentlece.n:
The uclosed IE Circular !!c. 77-11 is forwarded to you for infornation. If there are any questidas related to your under-i-
i standinC of the suggested actione, please cor.tccr. this of' ice.
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Sincerely, I
James G. T.cppler Director Euclocure:
IE Circular No. 77-11 cc v/cnc1:
Mr.
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.:wtic.n Superint.cnder.t 1:r. J. r,itel. Plant Superintendent
'tr. L. J. 2urke, Site Freject Stiperintendent Pr. Cunnn: Sorensan, Site Project Superintentient l
IIr. R. Cosaro, Project l
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IE Circular No. 77-!!
September 6, 1977 LEAKAGE OF CONTAlm!ENT ISOLATION VALVES WITil RESILIENT SEATS i
DESCRIPTION OF CIRCUMSTANCES:
Several licensees have reported difficulty in satisfying leakage test requirements on containment isolation valves with resilient valve seats.
The seat materials have been identified as neoprene and ethylene propylene. The licensecs reporting difficulty in satisfying the testing requircments had either a 36-inch or 42-inch butterfly valve manufactured by the Henry Pratt Company uith neo-prene seats or a 24-inch butterfly valve manufactured by the Allis Chalmers Company with ethylene propylene scats.
The cause of the excessive leakage has been determined to be either general degradation of the resiliency characteristics of the scal, cold temperatures and the associated " hardening" of the seal, or a combination of the two.
Testing of these isolation valves is required under 10 CPR 50, Appendix J on an interval defined as each reactor shutdown for refueling, but in no case at an interval greater than 2 years.
In all except one of these several cases described herein it uns the required testing which defined the les.hage path.
In these cases an examination of the resilient valve seat material indicated that the material had hardened and lost some resiliency I
and showed signs of wear due to valve cycling.
Exposure to various i
environmental conditions such as humidity and temperature have also, in some cases, apparently accclcrated the degradation or changed the perforcance characteristics of the seating material.
In one case, the valve was continuously pressurized ac part of a penetration pressurication cystem and it was determined that the valve leakage was cycling uitn the outside air temperatures. Mien the air temperature dropped at nicht, the valve seat uould con-tract away from the valve and leakage would begin. As temperature increased, the reverse would occur.
If this isolation valve had not been under constant pressure monitoring this phenomenon would not have been observed unicos a Type C local leak rate test had been performed to chech the leahage under both temperature conditions.
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IE Circular No. 77-11 September 6, 1977 The valven involved have been those associated with containnent purge and ventilation systenu.
l'rclininary informatica necms to indj cate that for the service these valves sec, a life expectancy of the resilient seats is at best about 3 years and may be less, dependent upon specific conditions to which they are subjected.
j Actions by the licensees have consisted of several differcut approaches to assure the continued nearly lech-tight behavior of 7
these large, butterfly isolation valves.. Scats are being replaced, seat materials are being tested for resiliency, local testing fre-quency has been increased, and for the facility where leakage was
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associated with temperature extremes, an external heat source has been provided.
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All holders of operating licenses or construction pernits should be aware of the possible limited useful life of the resilient valve seats for use on large, butterfly valves.
Certain steps can be taken to minimize the possibility of excessive valve leakage and measures can i
l be taken to quickly detect the leaks if they occur.
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l These actions may be implemented through the following considerations.
1.
Based on availabic data or =anufacturers recommendations, assess i
the acceptability of testing frequency and maintencnce schedules l
for existing valves of the type described.
If results of the review indicate the need for replacement, schedules for the replacement of resilient seat materials should be developed.
2.
Review of expected service conditions to provide assurance that temperature extremes will not adversely affect the leakage rates.
The need for shortened intervals of testing should also be considered.
3.
For those licensees who have plants under constructien, applicants sh'ould re-examine the specifications for the design and purchase of similar valves so that their characteristics in service are anticipated and the future maintenance program is considered prior to plant ccmpletion.
No uritten response to this Circular is required; houever, as needs or experience indicate there tay be further follow-up action.
If such follow-up is required the individual licensecs will bc con-tacted.
If you require additional information regarding this sub-jcct, contact the Director of the appropriate NRC Regional office.
Enclosure:
l List of IE Circulars Issued in 1977 t
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Enc 3nr.ure IE Circular 77-11 Date:
Septcu'aer 6,1977 LISTING OF IE CIRCULARS ISSUED IN 1977 CIRCULAR SUBJECT FIRST DATE OF ISSUED TO NO.
ISSUE l
77-01 Malfunctions of 1-4-77 All holders of Limitorque Valve Operating License Operators (OL) er Construc-tion permit (CP) l 77-02 Potential llcavy 2-15-77 All affected j
Spring Flooding holders of OLs I
77-02A Potential Heavy 2-16-77 All affected Spring Flooding holders of CPc 77-03 Fire Inside 2-28-77 All holders ci a Motor Centrol OLc and cps' Cer.tcr 77-04 Inadequate Lock 3-17-77 Safeguard Group Assemblies I, II, IV, V, Licensees 77-05 Liquid Entrapment 3-24-77 All holdeis cf in Valve Bonnets OLs and CFc 77-06 Effects of Hydraulic 4-1-77 All holders of Fluid on Electrical OL's and CPr Cable 77-07 Short Period During 4-12-77 11 elders of Reactor Startup BWR OLs 77-08 Failure of Fecduater 4-13-77 All hviders Sample Probe of OLc 77-09 Improper Fuse 5-25-77 All holders of Coordination In BUR BWR OLs or CPc Standby Liquid Control System Centrol Circuits 77-10 Vacuu Conditions 7-15-77 All ho]dern of Rcaultiq: in Dr :n e to hewie: 0; crat-Lic,uid Prvcece...utc i n,
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