ML18054B343
| ML18054B343 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/29/1989 |
| From: | Miller H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 9001050139 | |
| Download: ML18054B343 (6) | |
See also: IR 05000255/1989026
Text
Docket No. 50-255
Consumers Power Company
ATTN:
David P. Hoffman
Vice President
Nuclear Operations
1945 West Parnall Road
Jackson, MI
49201
Gentlemen:
- DEC' 2 9 198S
By letter dated December 8, 1989, we provided you a copy of NRC Inspection
Report No. 50-255/89026(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
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 enclosures should likewise
take this action.
Please call Duane Danielson at 708/790-5610 when this has
been accomplished.
Copies of this letter and enclosures have been sent to all
other recipients of the inspection report.
Enclosures:
As stated
cc w/enclosures:
Mr. Kenneth W. Berry, Director
Nuclear Licensing
Gerald B. Slade, General Manager
DCD/DCB (RIDS)
Resident Inspector, Rill
Sincerely,
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Hubert J. Miller, Director
Division of Reactor Safety
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A case in point is the. treatment of AE response of sensor No. 6 on main
steam line A at Palisades. ********************
- The respon-
sibility was shifted to *an additional VT-2* which found no sign of leakage. Based on
the VT-2 result, a cautionary suggestion of other NOE when convenientwas made. The
conclusion was that no through-wall leakage was apparent from any other section of
either main s.team line.
If a leak-like noise is present, but judged to be a non-rejectable condition, the
detection of additional leaks in the same area is not possible. If visual inspection must
be invoked to detect leakage, then the reduced hold-time and reduced pressure allowed
the !IT method should be revoked.
5
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6. HAF .A FACUJTY VISIT
6.1
GB-JERAL DISCUSSION
General discussions with most of H.AF.A management and engineering staff
were led by Duane Danielson.
6.2
ACOUSTIC LEAK MONITORING QUESTIONS
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 Oavis-
Besse. The records of testing at both plants were examined in detail. Some data were
re-plotted from the logs to determine the validity, of acoustic l~ak test analysis on i;_,
Palisades.
Questions about the method of recording RMS data
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- ere discussed with Allen Wehrmeister .and Rick Milke at
H.A.F.A. Questions and answers are listed below.*
1.
Why was no data recorded on EARS* 1, 2 and 3 while the pressure was
increasing from less. than 50 psi to 900 psi?
A 1.
The power was off in containment where the three systems were* locate.d.
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, aooo: 7.82, 7.85, 7_ga, s.02, 4.36, 4.01, 60, 110, 300, 350, 800. Is it
possible that the underlined values all represent the same reading with the
decimal misplaced?
17
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7. DESCRIPTION OF METHOD
I was shown how the RMS was taken from. an analog output connected by
a rotary switch to the 32 channels of the EARS (HAF .A's name for the Spartan). This .
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
a negative output when the DC voltage dropped below an internal reference value.
Allen Wehrmeister explained to me how the interpretation of the Spartan
recorded data was used to determin~ the presence of a leak.********
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7.1
DEMONSTRATION OF UT
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* out.let.
Acoustic sensors were
connected to an EARS unit where the RMS output from each sensor could be
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monitored. At the suggestion of John Jacobson, a small valve near the inlet end was
used as a simulated external leak. The outlet valve simulated an internal leak. We
found that the RMS output from the sensor mounted on the throttle valve increased
sharply when the external leak rate was increased to about 120 mljmin (0.03 gpm).
These measurements were made while the simulated internal leak from the valve at the
- 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 through the simulated external leak
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. ************
23
8. ANALYSIS OF METHOD *
It is clear that the signal-to-noise ratio must be very high for Wehrmeister's
leak identification criteria *********lllilll*********
Therefore, the sensitivity of the leak detection process depends on the
background noise.
No qualification testing was reported that defines the relation between noise
and leak detection sensitivity.
The sensor spacing on water filled syst~m tests where LMDs were used was
usually too great for acoustic leak detection .
The leak detection and location system described in Topical Report H.AF.A.
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 facilitate the rapid inspection of a pressure boundary.
The acqustic 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 sensitivitY was performed. A functional check usiAg 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. Further, the degradation of leak detection *
sensitivity with increasing background noise is not addressed.
24