IR 05000346/1989021
| ML20005E363 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/29/1989 |
| From: | Miller H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Shelton D TOLEDO EDISON CO. |
| References | |
| NUDOCS 9001050128 | |
| Download: ML20005E363 (6) | |
Text
{{#Wiki_filter:y - > @b. ' ' g [ $ [ DEC 291989 ] Docket No. 50-346 -. ' Toledo Edison Company: ATTN: Mr.-Donald Shelton , Vice President- . Nuclear Edison Plaza- , 300 Madison Avenue _ Toledo, OH 43652 ~ Gentlemen: By ' letter dated December 8, 1989, we provided you a copy of NRC Inspection Report No. 50-346/89021(DRS)-regarding-acoustic emission monitoring. Enclosure.3 to the inspection report entitled " Investigation of Acoustic Leak Monitoring-for.
' Nuclear Regulatory Commission Region III" contains information which is considered. i proprietary by H.A.F.A. and which, therefore, should not_be in the public
' domain. Redacted pages 5, 17, 22, 23, and 24 with the confidential commercial .information deleted are enclosed.
-Please insert these pages in place of those pages contained in the report you received-(and in all copies you may have made) and destroy the originals.
Those who-are on distribution for this letter and'its enclosures should likewise
- take-this action.
Please call Duane Danielson at 708/790-5610 when this has i been accomplished.-~ Copies of this letter and enclosures have been sent to all other recipients of the inspection report.
Sincerely, ,. " Original Signed by R. W. Cooper IT , Hubert J. Miller, Director ' Division of Reactor Safety ' i TEnclosures: As stated e cc w/ enclosures: L. Storz, Plant Manager ! DCD/DCB (RIDS) Resident Inspector, RIII !
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- E A case in point is the treatment of AEIresponse of sensor No. 6 on main steam line A at Pausados,
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sibility was shifted to *an additional VT-2* which found no sign of leakage. Based on ec3 the VT-2 result, a cautionary suggestion of other NDE when convenient was made. The conclusion was that no through-wall leakage was apparent from any ot'er section of either main steam line, if a leak-like noise is present, but judged to be a non-rejectable conoition, the
. detection of additionalleaks in the same area is not possible, if visualinspection must
-; , j be invoked to detect leakage, then the reduced hold-time and reduced pressure allowed t-j the !!T method should be revoked.
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6. HAF.A FACIUTY VIStr
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6.1 GENERAL DISCUSSION General discussions with most of H.A.F.A management and engineering staff were led by Duane Danielson.
t 6.2 ACOUSTIC 1.EAK MONITORING OUES110NS ,, , ' My effort was concentrated on the question of the validity of the acoustic leak testing used on steam systems and water-pressurized piping' at Palisades and Davis-Besse. The records of testing at both plants were examined in detail. Some data were re-plotted from the logs to deternha the validity, of acoustic leak test analysis on Palisades. Ouestions about the rnethod of recording'RMS dataM'h " , ere discussed with Allen Wehrmeister and Rick Milke at l H.A.F.A. Questions and answers are listed below.
jI 1.
Why was no data recorded on EARS'.1, 2 and 3 while the pressure was increasing from less than 50 psi to 900 pui? , . - A1.
The power was off in containment where the three systems were located.
2.
On ears 1, channel 6, the RMS millivolts is recorded as 14.32. 14.28. 14.28.
' 14300.14300.14.35.14.30.14.30.14.35.14.30.14.30.14.30.14.30.1430.8000, 8000, 8000, 7.82, 7.85, 7.88, 5.02, 4.36, 4.01, 60, 110, 300, 350, 800.Is it possible that the underlined values all represent the same reao'ng with the decimal misplaced? , '
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.. ~. - ~.. . . . ' . ' , -'k > ; .. f 7. DESCRIPTK)N OF METHOD f I was shown how the RMS was taken from an analog output connected by a rotary switch to the 32 channels of the EARS (H.A.F.A's name for the Spartan). This. , J output was a DC voltage representative of the RMS voltage. A standard DVM was used , for the readout. The DC output was derived from a differential circuit which could have I a negative output when the DC voltage dropped below an intomal reference value.
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Allen Wehrmeister explained to me how the interpretation of the Spartan recorded data was used to determine the presence of a leak.M -. , . , . - ... ... .. , _ J ... ..... N _ ? _,........ ........9 g . - .. ~......... .,
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.. _ _ _. _ _ .... _ T 7.1 DEMONSTRATION OF llT 'A' laboratory demonstration of the llT method was performed.
A 20-foot length of 2-3 inch diameter pipe was outfitted with an inlet LMD and an outlet LMD to monitor the leakage from a throttle valve at the outlet. Acoustic sensors were connected to an EARS unit where the RMS output from each sensor could be monitored. At the suggestion of John Jacobson, a small valve near the inlet end was . used as a simulated extemal leak. The outlet valve sir.iutated an intemal leak. We found that the RMS output from the sensor mounted on the throttle valve increased b sharply when the external leak rate was increased to about 120 ml/ min (0.03 gpm).
These measurements were made while the simulated internal leak from the valve at t opposite end of the pipe was at 0.44 gpm indicated by the two LMDs. The LMD was not sensitive enough to detect the loss of 0.03 gpm t ough the simulated extemalleak while measuring 0.44 gpm flow through the pipe. _ . The demonstration showed that leaks could be detected when the leak signal exceeded the uncertainty of the ambient noise signal m y , $ g gy}gfy .ErthfWM AM ~ m i: ) i . _ _.,. _ . _ _.. - -.
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- t; '; ~[ 8. ANALYSIS OF METHOD i fj - , '~ . lt is clear that the signal-to noise ratio must be very high for Wehrmeister's leak identiucation criteria, ' ~ h _ _ .. _.__ - _ W Therefore, the sensitivity of the leak detection process depends on the-g background noise.
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No qualification testing was reported that defines the relation b< ! ween noise , and leak detection sensitivity.
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.The sensor spacing on water filled system tests where LMDs were used was i usually too great for acoustic leak detection, s The leak detection and location system described in Topical Report H.A.F.A.
f 135 P measures the input output flow to determine amount of leakage and uses acoustic leak monitoring to locate the region or component that is leaking. This process would facilitato the rapid inspection of a pressure boundary.
The acoustic leak monitor technique was not fully or properly implemented at Palisades or Davis Besse. The tests included in the topical report were not adequate to qualify the acoustic leak monitor technique because no calibration of the acoustic - , leak detection sensitivitp was performed. A functional check us;ng simulated leak was sometimes used. Another functional check using a pencil-lead break technique was performed. These tests give no evidence as to the leak detection sensitivity or the . distance over which a leak may be detected. Furtha, the degradation of leak detection sensitivity with increasing background noise is not addressed.
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