ML20058P784
| ML20058P784 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/14/1990 |
| From: | Papanic G YANKEE ATOMIC ELECTRIC CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| REF-PT21-90 BYR-90-114, NUDOCS 9008200081 | |
| Download: ML20058P784 (5) | |
Text
t
&^
YANKEEATOMIC ELECTRIC COMPANY "C"l,f0*]l'* V" o
. 3 580 Main Street, Bolton, Massachusetts 017401398
)
August 14, 1990 i
BYR 90-114 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Attention
.Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation Referencet (a) License No. DPR-3 (Docket No. 50-29)
Subject:
10CFR21 Report on Misapplication of Fluorolube FS-5 011 in Main Steam Line Pressure 9auges Dear Sirt Yankee has completed an evaluation under 10CFR21 which concluded that the failure of Weksler pressure gauges, Model SA243PR4LW(9, does not represent a substantial safety hazard to the operation of Yankee Nuclear Power Station.
However, because the failure mechanism is new to Weksler and Weksler is a commercial grade supplier of process instrumentation and not subject to the reporting requirements of 10CFR21, we also concluded that this should be reported to ensure that other plants are made aware of this situation. to this letter provides the necessary details of this altuation.
Should you have any questions regarding this matter, please contact us.
i Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY Georg
- apanic, Senior Project Engineer Licensing GP/tlp/WPP72/89 Enclosures cc USNRC Region I USNRC Resident Inspector YNPS l
l UJV
//// { )
M 9008200091 900814
- PDR ADOCK 03000029 S=
t PDC 7
,t j
e 3.
ENCLOSURE ~1 g
Company Informing the Commission g
Yankee Atomic Electric Company e
580 Main Street Bolton, Massachusetts 01740-
-Facility
~
Yankee Nuclear Power Station (YNPS)
Star Route
-Rowe, Massachusetts 01367 Component Main Steam Line Press v e Indicators for the Safe Shutdown System (SSS)
MS-PI-438, 439, 440, and 441 Firm Supplying, Component Weksler Instruments Corporation P.O. Box 808 80 Mill Road Freeport, NY 11520-0808 Nature of Defect One Weksler pressure gauge Model SA243PR4LWX9, is in service in each of the four Main Steam. Lines (MSL) upstream of the Nonreturn Valves (NRVs) to provide
. local MSL pressure'inu e tion for the SSS.
The SSS MSL pressure gaugis were installed in 1985. During a quarterly surveillance In' January 1988, it was noted that the pressure gauges were not tracking comparative to main control board indications. Due to concerns'with low' temperature operation, the manufacturer was requested to provide clarification 'of the capillary tube silicone oil temperature rating.
It-was identified that'the original SSS MSL pressure gauges purchased commercial grade under Purchase Order 105298 were filled with a high temperature fluid, 1 Dow Corning 210, rated at +30'F to 650'F.
The vendor reconnended replacing
-the Dow Corning'210 fill fluid with FS-5 Fluorolube, rated at -50'F to 500'F.
Five new SSS MSL pressure gauges with Fluorolube FS-5 oil fill were purchased as commercial grade by Purchase Order QA 40916 and received by Yankee on iNovember 6,.1989.
The original precsure gauges were replaced at various intervals. Original pressure gauge, MS-PI-439, was replaced on March 29, 1990 with a new pressure gauge with the Fluorolube FS-5 oil. fill.
Per NCR 90-011, the replaced (new) pressure indicator, MS-PI-439 developed a leak at the capillary tube at the ccnnection to the diaphragm seal within hours after installation.,=The pressure gauge was replaced on Apr'.1 6, L990 with a second new= gauge with 'the Fluorolube FS-5 oil fill. Althougu this pressure gauge was operational, it was. removed from service on July 11, 1990 while the plant was shutdown for analyzing the Fluorolube FS-5 oil.
n
.t_
j WPP72/89 l
,s-
,i 4-ENCLOSURE 1 (Continued)'
i On April 21', 1990, the original MS-PI-438 and MS-PI-440 pressure gauges were replaced with new ones with the Fluorolube FS-5 oil fill. Additionally, at this time, it was decided to replace MS-PI-441 such that all SSS MSL pressure gauges would have the Fluorolube FS-5 oil fill.
On May 5, 1990 MS-PI-438 and MS-PI-441 decrease: to zero indication with full steam pressure applied. MS-PI-441 was replaced with a spare original'(Dow Corning 210' oil fill) pressure gauge. The failed MS-PI-438 was not replaced and left in place due to removal problems from galling of the fitting, which connects it to the process. MS-PI-438 was removed from service while the plant was shutdown on June 27, 1990.
Occidental Chemical Corporation (OCC), the Fluorolube FS-5 oil manufacturer, was consulted regarding the use of this oil in the Weksler pressure gauge units-for the SSS MSL pressure indication application at the Yankee plant.
Per the telephone conversation the OCC representative indicated Fluorolube FS-5 oil is the thinnest and the most volatile of the Fluorolube oils. OCC's experience has noted that Fluorolube FS-5 volatilizes at approximately 300'F.
Additionally, it is possible that in our application at the normal temperature of 465'F, FS-5 could start to decompose to its basic elements, fluorine and chlorine. The above two conditions, volatilization and L
decomposition of the Fluorolube FS-5 oil, would create voids in the filled l
system which would impair the performance of the pressure indication f rom l
sluggish to no response. Furthermore, the presence of chlorine and fluorine l
would cause corrosion of the stainless steel components which would lead to oremature structural failure of the metal.
l On July 2, 1990, the three failed pressure gauge units, MS-PI-438, 439, and 441, were pressurized, disassembled, and inspected by Weksler in the presence of Yankee Atomic Electric Company personnel at Weksler's manufacturing facility.
Prior to disassembly for inspection of the diaphragm seat internal components and status of the Fluorolube FS-5 oil, a calibration of each unit was performed.
The calibration resulted with the indicators indicating 0 psig with 1,500 psig applied to the process side of the diaphragm seal. Subsequent calibration of the pressure indicators, once removed from the diaphragm seal / capillary tube, proved the indicators were functional, within the acceptable tolerance of + 1% of span. The disassembly of the diaphragm seal indicated the stainless steel diaphragm was intact, but scorched due to steam impingement. The Teflon gasket between the two flanges of.the diaphragm seal was still sealing, but partially deformed due to the steam temperature. The fill fluid port plug of the diaphragm seal was removed, and several drops (an insignificant amount compared to system volume capacity) of discolored (opaque) as opposed to translucent fill fluid were collected. The capillary tube was removed from the diaphragm seal.
Visual examinat.on of the diaphragm seal through the capillary tube port connection i
revealed a black viscous mass. Apparently, the Fluorolube in direct contact witn the diaphragm, exposed to the process temperatures, had decomposed and baked. The black color of the mass is an indication of carbon residue from the decomposition (stripping of chlorine and fluorine) of the carbon base Fluotolube FS-5 oil. WPP72/89
L 8-C ENCI.0SURE 1 (Continued)
Further inspection of the capillary tube once the armored cable was removed i
indicated the capillary tubes for MS-PI-439 and 441 were fully severed at a point just above the nickel chromium brazed weld to the fitting which threads into the diaphragm seal instrument port; and for MS-PI-438, a scission had developed half way around the capillary tube at the same location.
These breaches of the capillary tubes caused loss of hydraulic transmission of the pressure signal and, therefore, loss of pressure indication.
Initial examination by microscope, at 10X magnification of the exterior of the capillary tubes at the locations where they had failed, indicated the failures were due to a twisting and fatigue'of the tube.
Further examination by microscope of the interior walls of the capillary tube showed severe corrosion of the walls, with cracks in spiral form, typical of fatigue failure, from the inside wall toward the outside.
l Additional evaluations by Weksler of the failed capillary tubes included verifying the compounds of the nickel chromium flux material used-for the braze weld. This evaluation resulted in identifying that the nickel chromium flux manufacturer has modified their manufacturing process to include fluorides as a component of the flux material. The mndified flux material was used on the failed pressure gauges purchased by Purchase Order QA 40916, but not on the original pressure gauges purchased by Purchase Order 105298.
The.
I fluorides in the weld material, exposed to atmosphere, cause stress corrosion of stainless steel. Therefore.-the capillary tube failures are postulated to i
be resulting from the following conditions:
j f
(a) Capillary tube stress corrosion results from the fluorides in the nickel chromium flux.
(b) The Fluorolube FS-5 oil is decomposing on contact with the diaphragm due ta the extreme process temperature.
(c) The Fluorolube FS-5 oil decomposition into chlorine and fluorine causes q
the fluorine to react adversely with the stainless steel (note, chlorine reacts with stainless steel only when wet (i.e., water), causing corrosion. Once the integrity of the sealed system is breached due to a break, it is assumed condensation develops on the inside of the tube.
[
The condensation reacts with the uhlorine and fluorine to form hydrochloric and hydrofluoric acid which enhances the degradation of the stainless steel.
.(d) The diaphragm seal mounted on the 14" long by 3/4" pipe tap to the 2" steam line is exposed to excess vibration. The vibration on the weakened capillary tube, f rom Items (a) and (b) above, enhances the developed stresses causing the tube to break from fatigue.
(e) Additionally, the vibration results in an independent resonant frequency j
of the capillary tube armor. This is another mechanism which aids in the premature fatigue failure by causing the armor to bang into the capillary tube.
q 4
l 3-WPP72/89 1
,s.
ENCLOSURE 1 (Continued)
Although, Weksler has acknowledged capillary tube failures on other gauges.
those failures were attributed to poor handling during installation.
The failure of these capillary tubes with the Fluorolube FS-5 oil is a new occurrence which has not been observed before by Weksler.
To further confirm that the Fluorolube FS-5 oil is in fact deconposing,'on July 11, 1990, the installed operational MS-PI-439 pressure gauge was removed from service and inspected at the Yankee plant. The inspection revealed the pressure gauge was operational and the capillary tube intact. However, the capillary tube surface, at the immediate area adjacent to the weld of the fitting which threads into the diaphragm seal instrument port, showed signs of initial degradation similar to the failed units.
Visual examination of the diaphragm seal through the capillary tube port connection revealed a clean, dark yellow fluid. The dark yellow fluid was collected in a beaker, along with the clear colorless fluid from the capillary tube. The pH test, as recommended by 0C0, was performed on this fluid, and the results showed the presence of acidity, confirming oil decomposition.
Date of Incident MS-PI-439 failed on March 29, 1990. MS-PI-438 and 441 failed on May 5, 1990.
The failures were documented by Yankee NCRs 90-11 and 90-13.
Number of Components Yankee has four MSL pressure indicators for the SSS.
Corrective Actions Takt Yankee replaced all fo#r
_ tors with spare gauges which utilize the high temperature silicone oil.
l Related Advice Yankee's evaluation concluded that no substantial safety hazard currently l
exists at YNPS as the failure of the pressure gauges occurred on the non-nucicar side of the pressure boundary and that alternate MSL pressure indication would be available during operation of the SSS.
_4-WPP72/89