Information Notice 2004-06, Loss of Feedwater Isokinetic Sampling Probes at Dresden Units 2 and 3
| ML040711214 | |
| Person / Time | |
|---|---|
| Issue date: | 03/26/2004 |
| From: | Beckner W NRC/NRR/DIPM/IROB |
| To: | |
| Hodge, CV, NRR/DIPM/IROB, 415-1861 | |
| References | |
| TAC MC1970 IN-04-006 | |
| Download: ML040711214 (6) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 March 26, 2004 NRC INFORMATION NOTICE 2004-06: LOSS OF FEEDWATER ISOKINETIC SAMPLING
PROBES AT DRESDEN UNITS 2 AND 3
Addressees
All holders of operating licenses for nuclear power reactors except those who have permanently
ceased operation and have certified that fuel has been permanently removed from the reactor
vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to recent experience in which feedwater isokinetic sampling probes were broken off
and lost in feedwater spargers. It is expected that recipients will review this information for
applicability to their facilities and consider actions, as appropriate. However, suggestions
contained in this information notice are not NRC requirements; therefore, no specific action or
written response is required.
Background:
In 1971, to expand its water chemistry program, the Dresden licensee installed three sample
probes in each of the Unit 2 and 3 feedwater and condensate systems. In each unit, the probes
were installed at the discharge of the condensate pump (condensate sample probe), at the
suction of the condensate booster pump (condensate demineralizer effluent sample probe), and
at the discharge of the feedwater heaters to the feedwater spargers in the reactor vessel
(feedwater sample probe). These probes were designed for isokinetic sampling, in which the
water sample drawn in the probe is representative of the fluid in the process stream.
Each stainless steel probe was joined to the condensate or feedwater pipe by a carbon steel
collar. The collar was joined to the probe by a weld on the outside of the collar and to the
condensate or feedwater pipe by a weld to a carbon steel weldolet on the pipe. The collar
allows welding of dissimilar materials in the shop; field welding then only needs to be done on
similar materials. The crevice made by a small clearance between the collar and outside
diameter of the probe is exposed to water flow. Typically, these probes are about 0.3 meter
(1 foot) long and about 2 centimeters (3/4 inch) in diameter.
In 1977, the nuclear steam supply system vendor, General Electric (GE), issued a generic
communication ("Improved Feedwater Sample Probe," Service Information Letter (SIL) No. 257, December 30, 1977) to report failures at two boiling water reactor nuclear power plants in which
feedwater probes broke and lodged in downstream valves. The failure mechanism was
determined to be transgranular stress corrosion in the crevice between the collar and the probe.
GE recommended an improved probe design in which a seal weld would protect the crevice
from the water flow.
In 1990, GE issued a generic communication ("Improved Recirculation Water Chemistry
Sample Probe," SIL No. 518, August 6, 1990) to document potential failure of a recirculation
system sample probe due to mechanical, high-cycle fatigue induced by flow vibrations.
Description of Circumstances
In 2001, the Dresden licensee became aware of GE SIL 257 and planned inspections of the
Unit 2 and Unit 3 feedwater sample probes.
Dresden Unit 2:
During the refueling outage in 2001 (D2R17), the licensee found the feedwater sample probe
missing. The licensee evaluation determined that the missing probe was most likely in a
feedwater sparger and did not present a safety concern. Another probe was installed to replace
the missing probe in accordance with GE SIL 257.
During the refueling outage in 2003 (D2R18), the licensee found three holes in the N4C 240E
sparger nozzle and a sample probe resting in the sparger. The licensee inferred that the probe
was the missing feedwater sample probe and that the probe apparently caused the sparger
damage, although the physical phenomenon acting on the probe that could cause such damage
to the sparger was (and still is) unclear. The licensee removed the resting probe and repaired
the sparger. During a forced outage in December 2003 (D2F40), ultrasonic testing indicated
that the probe installed in 2001 was missing. Based on a GE evaluation, the licensee
determined that the probes apparently failed from mechanical, high-cycle fatigue induced by
flow vibrations during their respective service periods. The licensee evaluation determined that
the potential for lost parts in the reactor vessel did not compromise reactor safety.
Also during pre-outage work to support D2R18, the licensee found the condensate
demineralizer effluent sample probe in a condensate booster pump casing. The licensee
evaluation determined that pieces missing from this probe presented a moderate risk of fuel
fretting but no fuel or control rod drive safety concerns.
A new condensate demineralizer effluent probe, modified in accordance with GE SIL 257, was
installed in Unit 2 during the D2R18 outage.
Dresden Unit 3:
During the refueling outage in 2002 (D3R17), the licensee likewise found the feedwater sample
probe missing. The licensee evaluation determined that the missing probe was most likely in a
feedwater sparger and did not present a safety concern. Another probe was installed to replace
the missing probe in accordance with GE SIL 257.
In response to the experience at Unit 2, the licensee planned internal and external inspections
of all Unit 3 spargers to locate the missing probe. During the Unit 3 outage for steam dryer
maintenance in 2003 (D3M10), the licensee conducted the planned inspections and found no
sparger damage but did find two probes resting in the N4B 150E sparger. Based on a GE
evaluation, the licensee determined that the probes failed from mechanical, high-cycle fatigue induced by flow vibrations during their respective service periods. The licensee evaluation
determined that the potential for lost parts in the reactor vessel did not compromise reactor
safety.
During maintenance outage D3M10, a new condensate demineralizer effluent probe, modified
in accordance with GE SIL 257, was installed in Unit 3 to replace the previous probe that was
found intact.
Discussion:
In reviewing related operating experience and conferring with GE, the Dresden licensee found
that similar probe failures had occurred at the Perry, Braidwood, Browns Ferry, and Grand Gulf
nuclear power plants during the years 1990-2001. In 1996 and 1997, the licensee for Quad
Cities Units 1 and 2 replaced the similarly located isokinetic feedwater sampling probes in
The GE evaluation, performed for the Dresden licensee, indicated that the natural frequency of
the initial unmodified feedwater sample probe was within the range to lock into the vortex
shedding frequency of the pre-EPU flow rate. The natural frequency of the SIL 257-modified
feedwater sample probe was within the range to lock into the vortex shedding frequency of the
post-EPU flow rate. The licensee found no indication of pre-installation design analysis for flow- induced vibration in the initial installation of the sample probes and the licensee reported that
the SIL 257-modified probe was not analyzed for the increased flow rates associated with EPU
prior to installation. The GE analysis indicated that the SIL 257-modified feedwater sample
probe natural frequency would not have locked into the pre-EPU flow rate vortex shedding
frequency had it been installed pre-EPU.
The BWR Owners Group is coordinating the overall industry response to potentially adverse
flow effects from power uprate operation, including sample probe performance.
This information notice requires no specific action or written response. If you have any
questions about information in this notice, please contact one of the technical contacts listed
below or the appropriate project manager in the NRCs Office of Nuclear Reactor Regulation.
/RA/
William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Maitri Banerjee, NRR Dr. C. Vernon Hodge, NRR
(301) 415- 2277 (301) 415-1861 E-mail: mxb@nrc.gov E-mail: cvh@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
ML040711214 OFFICE OES:IROB:DIPM TECH EDITOR PM:DLPM EMEB:DE
NAME CVHodge *see previous concurrence MBanerjee* DTerao*
DATE 03/25/2004 02/24/2004 03/15/2004 03/15/2004 OFFICE SC:OES:IROB:DIPM C:IROB:DIPM
NAME CJackson W.Beckner
DATE 03/25/2004 03/26/2004
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2004-05 Spent Fuel Pool Leakage to 03/03/2004 All holders of operating licensees
Onsite Groundwater for nuclear power reactors
(except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel) and for
research and test reactors, and
all holders of fuel storage licenses
and construction permits.
2004-04 Fuel Damage During Cleaning 02/24/2004 All holders of operating licenses
at a Foreign Pressurized Water for light-water reactors, except
Reactor those who have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.
2004-03 Radiation Exposures to 02/24/2004 All well-logging licensees.
Members of the Public in
Excess of Regulatory Limits
Caused by Failures to Perform
Appropriate Radiation Surveys
During Well-logging
Operations
2004-02 Strontium-90 Eye Applicators 02/05/2004 All U.S. Nuclear Regulatory
New Calibration Values and Commission (NRC) medical-use
Use licensees and NRC master
materials license medical-use
Permittees.
Note: NRC generic communications may be received in electronic format shortly after they are
issued by subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following
command in the message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit