ML20198E805
| ML20198E805 | |
| Person / Time | |
|---|---|
| Issue date: | 05/08/1986 |
| From: | Bosnak R NRC |
| To: | Crutchfield D NRC |
| Shared Package | |
| ML20151L176 | List: |
| References | |
| FOIA-86-266 NUDOCS 8605280271 | |
| Download: ML20198E805 (8) | |
Text
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p p nes'o, UNITED STATES y
NUCLEAR REGULATORY COMMISSION E
o O
y WASHINGTON, D. C. 20555 h@66 MEMORANDUM FOR:
Dennis Crutchfield, Assistant Director for Safety Assessment Division of Licensing FROM:
Robert J. Bosnak, Acting Assistant Director for Components and Structures Engineering Division of Engineering
SUBJECT:
TRANSMITTAL OF PROPOSED IE INFORMATION NOTICE RE:
MAIN STEAM SAFETY VALVES Please find attached our draft of a proposed IE Infonnation Notice entitled
" Main Steam Safety Valve Test Failures and Ring Setting Adjustments" for your transmittal to the Office,of Inspection.and Enforcement. The basis for the Notice was discussed at the Operating Reactors Events briefing of July 23, 1985.
The specific wording of the Notice has been coordinated with Mr. Caruso of ORAB, DL.
I Robi.rt J. Bosnak, Acting Assistant Director for Components and Structures Engineering Division of Engineering
Attachment:
As stated cc:
J. Knight
. F, Cherny W. Hammer H. Thompson G. Holahan R. Wessman i
M. Caruso H. Nicolaris V. Nerses E. Jordan, IE R. Oller, IE R. Baer, IE J. Durr, R I H. Gregg, R I 8605280271 860508 PDR FOIA MURPHY 86-266 PDR
UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 AUGUST
, 1985 IE Information Notice No.: 85-xx MAIN STEAM SAFETY VALVE TEST FAILURES AND RING SETTING ADJUSTMENTS Addressees:
All PWR nuclear power reactor facilities holding an operating license (0L) or a construction permit (CP)
Purpose:
This Infonnation Notice is being provided as a notification of a potentially significant problem pertaining to spring-actuated main steam safety valves (See Figure 1), that may possess less than the full rated flow capacity required for overpressure protection of the secondary cooling system in PWRs.
It is expected that recipients will review the information for applicability to their facilities and consider actions, if appropriate, to preclude a similar problem at their facilities. However, suggestions contained in this Infomation Notice do not constitute NRC requirements; therefore, no specific action or written response is required.
Description of Circumstances:
Between October 16, 1984, and December 1, 1984, Wyle Laboratories conducted several full flow steam tests on two separate main steam safety valves (MSSVs) manufactured by Crosby Valve and Gage Company. These Crosby 6R10 MSSVs are to be installed by Public Service of New Hampshire on the Seabrook main steam system. The tests were conducted in order to detennine the adequacy of various MSSV discharge piping arrangements. During the tests the valves were instrumented to measure valve disk lift. The valves were installed on the i
test facility with the settings of the valve adjusting rings as received from the valve vendor. With these ring settings the valve achieved about 50% of the full disk lift required to develop full. steam flow capacity within the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code required 3% accumulated overpressure limit. Adequate lift was not achieved for either valve with these ring settings, even for the largest diameter (least flow 1
i resistance) vent pipe tested. The guide ring of both valves was subsequently adjusted a significant amount (150 notches) during the course of testing and l
full disk lift was subsequently achieved.
1 i
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l IN 85-XX August
, 1985 Page 2 of These types of full flow tests are normally not performed by either Reactor Owners or the valve vendor on MSSVs, nor are such tests required for capacity certification according to the ASME Code,Section III.
In general, these valves are capacity certified by tests on much smaller size valves, and the capacities then extrapolated to larger size valves. The MSSYs on most PWRs, while not necessarily the same model or supplied by the same vendor, are like those at Seabrook in that these valves are generally at the upper end of the valve size range. This raises the concern that full flow functional demonstra-tion of these type valves may never have been performed.
A related MSSV problem which has occurred at several PWRs in the past few
.,...,, 3 g,. 4, years pertains to excessive blowdown of main steam system pressure during o g,. 4 transients which ha0e actuated some MSSVs. On separate occasions at the r enZ l. t Oconee, Salem, Trojan, and Davis-Besse nuclear facilities, MSSVs have remained /,ntvu1>ess-open below the correct reseat pressure and have blown down excessive amountsj dredfeshi.
e,.e,_,of steam. The design blowdown,value is usually 5% of setpoint pressure *5EM i:
b also dependent on the specific valve ring setting adjustments. Some valves at these facilities have exhibited as much as 10% blowdown. This raises the concern that some MSSVs may remain open too long, relieving excessive quantities of steam possibly adversely affecting cooling of the primary system and causing excessive thermal stresses on primary system components.
No specific action or written response is required by this Information Notice.
If you have any questions about this matter, please contact the Regional Administrator of the appropriate regional office or this office.
Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement
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