ML20207G069
| ML20207G069 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/04/1999 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20207G066 | List: |
| References | |
| 50-346-98-21, NUDOCS 9906110010 | |
| Download: ML20207G069 (14) | |
See also: IR 05000346/1998021
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U. S. NUCLEAR REGULATORY COMMISSION
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Docket No: 50-346
License No: NPF-3
Report No: 50-346/98021(DRP)
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Licensee: Toledo Edison Company
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Facility: Davis-Besse Nuclear Power Station )
Location: 5501 N. State Route 2 i
Oak Harbor, OH 43449-9760 l
Dates: September 1 - December 1,1998 and
April 25 - May 13,1999
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, inspector: K. Zellers, Resident inspector
Approved by: Thomas J. Kozak, Chief
Reactor Projects Branch 4
Division of Reactor Projects
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9906110010 990604 *
PDR ADOCK 05000346
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EXECUTIVE SUMMARY
Davis-Besse Nuclear Power Station
NRC Inspection Report 50-346/98021(DRP)
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This inspection was a review of licensee maintenance activities associated with pressurizer
spray valve RC-2. This report covers the periods between September 1 - December 1,1998
and April 25 - May 13,1999.
Maintenance
The failure to ensure adequate material separation was maintained during pressurizer spray
valve RC-2 maintenance activities resulted in the installation of three carbon steel
body-to-bonnet (BTB) nuts on the valve. In addition, the licensee failed to take prompt, i
effective corrective actions commensurate with safety to identify and correct this condition once I
it was discovered that one of the eight RC-2 BTB nuts was missing. Two apparent violations
were identified (Section M1.1).
The degraded condition of RC-2 with orie nut partially corroded and two missing nuts required a
detailed evaluation to determine if it would have functioned under all design loads. Although
the licensee initially determined that the valve would not have functioned under extreme design ,
conditions, the results of a more detailed calculation indicated that it would have functioned l
under all design loads (Section M1.1).
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Once the licensee determined that boric acid corrosion (BAC) was the most likely cause for the
missing nuts on RC-2, a thorough evaluation of the condition was conducted and extensive,
effective corrective actions were developed. The inspectors noted a much greater sensitivity to
the effects of BAC on plant equipment and a recognition that some plant maintenance practices
required improvement, more oversight, and more assessment (Section M7.1).
The engineering plan to address the extent of condition for the two missing BTB nuts on
pressurizer spray valve RC-2 was comprehensive and detailed. The licensee completed the
extent of condition review during the recent mid-cycle outage. Additionally, the licensee
demonstrated a heightened sensitivity to boric acid corrosion effects on plant equipment
(Section M7,1).
The inspector determined that the licensee's boric acid control program was adequately
documented. However, a weakness was identified in the program concerning the verification of ,
materials subjected to boric acid corrosion which contributed to the failure to promptly identify ;
that the RC-2 valve components were not as specified in its design document (Section E3.1). !
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Report Details
ll. Maintenance
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M1 Conduct of Maintenance
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M1.1 Corrosion of Valve RC-2 Body-to-Bonnet Nuts j
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a. Insoection Scope (62707)
The inspectors reviewed the circumstances surrounding the licensee's identification of
missing body-to-bonnet (BTB) nuts on motor operated pressurizer spray valve RC-2.
b. Observations and Findinas
Background
Boric acid corrosion (BAC) of carbon steel reactor pressure boundary components in
pressurized water reactor (PWR) plants has been an NRC concern since at least 1979.
- Severalinformation notices and industry reports have described this problem. In 1988,
the NRC issued Generic Letter (GL) 88-05 which required PWR licensees to implement
BAC programs. Generic Letter 88-05 illustrated several examples where BAC corroded
carbon steel reactor pressure boundary components and either caused a failure of the
pressure boundary or significant degradation of the pressure boundary that required
repair before plant operation could continue.
Davis-Besse pressurizer spray valve RC-2 is a motor operated 2% inch globe valve.
The valve specifications stated that the valve was constructed of s'. winless steel with the
exception of the yoke which was carbon steel. Eight stainless steel nuts are specified to
seal the valve body to its bonnet. The work area around RC-2 with the reactor coolant
system (RCS) at normal operating temperature (NOT) was challenging to plant workers.
The room temperature was about 150 degrees at NOT, and poor lighting, cramped ,
quarters, and the valve being at knee level imposed additional difficulties for personnel l
doing work on the valve. Several flights of stairs inside containment had to be climbed
to access the valve. Additionally, the burden of wearing protective clothing and hauling
tools was present. Consequently, industrial safety personnelimposed a requirement
that the maximum stay time for work on valve RC-2 be 15 minutes from entering to .
exiting containment. l
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Event
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A sequence of events relating to the identification of two missing nuts on RC-2 is
included as an attachment to this inspection report. The following is a description of
these events.
On April 11,1998, the licensee began the eleventh refueling outage (RFO 11). During a
walkdown of the reactor pressure boundary while the plant was still at NOT, engineering
personnelidentified that RC-2 had a packing leak. The packing leak left a dry boric acid
residue on the valve that prevented engineering personnel from immediately performing l
a BAC assessment for the valve. On May 5, licensee personnel identified that the
RC-2 packing leak had caused severe BAC of its carbon steel yoke. No stainless steel
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l To install the yoke, the bonnet had to be removed and reinstalled; additionally new
packing material was used in an effort to stop the packing leak. A new motor operator
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was then installed, completing work activities on the valve. l
On May 19, the licensee was heating up the primary systems for the plant startup from
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RFO 11. During a containment walkdown, licensee personnel again observed a packing
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leak on RC-2, Maintenance personnel checked the packing nut torque up to 50 ft/lbs
with minimal movement and effect on the leak. Based on the characterization of the
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observed leakage, the BAC evaluation for the packing leak, and the assumption that the
remaining valve materials were configured in accordance with specifications (including
l the body-to-bonnet nuts), outage management personnel determined that the
consequences of operating with the packing leak would be minimal. Therefore, licensee
management decided not to repair the packing leak prior to resuming plant operations.
l As a precautionary measure, a maintenance work order was written with instructions to
perform a packing gland Furmanite injection to stop the leak if the leak rate increased or
if boric acid bui! dup resulted in corrosion of the yoke. In addition, plant engineering
personnel were tasked with conducting periodic valve inspections during plant
operations. On May 22, engineering personnelidentified that the flow of the leakage
down the side of RC-2 was confined to a 60 degree arc, that there was no increase in ;
leak rate, that there was no boric acid buildup on the valve or yoke, and determined that '
no action to stop the leak was necessary at that time.
On June 2, RC-2 was observed to have boric acid buildup on the valve yoke and
Donnet. Pictures were taken to document the as-found condition and the boric acid was
removed. The packing leak rate remained the same and the water from the leak
remained confined to the same 60 degree arc on the valve body. On June 27 during a
forced plant outage, additional boric acid buildup was cleaned off of RC-2. Minor ;
corrosion was noted on the yoke, but the packing leak rate remained the same. On j
- July 24, while the plant was at NOT, a Furmanite injection rig was installed onto the
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packing gland area of RC-2 for future use should the packing leak increase.
On September 1, during an inspection of RC-2, licensee personnelidentified that the
packing leak rate had increased and that there was boric acid buildup in the vicinity of
the Furmanite injection rig. After partially cleaning the buildup, maintenance personnel
discovered that one BTB nut was missing. A thorough evaluation of this degraded
condition was not initiated. Rather, because the location of the missing nut was in the
vicinity of the Furmanite injection device, maintenance personnel suspected that the
contractor had removed the nut to facilitate the Furmanite rig installation. Therefore,
station personnel proceeded to investigate this potential cause, and did not seriously
consider that the nut may have corroded away. Unknown to the licensee was the fact
that the missing nut was in all likelihood made of carbon steel and that it had corroded
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away due to BAC.
The licensee performed an operability evaluation for RC-2 and, based on an evaluation
of seismic, thrust, and pressure loads, determined that the valve would remain
functional at design loads with one of the eight nuts missing. A plan was developed to
decontaminate the valve and replace the missing nut.
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A maintenance team was tasked with developing a plan to install a stainless steel nut in
. the missing location. On September 9, while decontaminating RC-2, a radiation
protection technician (RPT) discovered that a second BTB nut was missing. The
maintenance team continued with the plan to install the first missing nut. Plant
management was informed of the second missing nut once the maintenance workers
! completed installing the first missing nut. An action plan was developed to install the
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second missing nut, verify that the remaining nuts were not magnetic (which would
l provide assurance that they were stainless steel), and to perform the Furmanite injection
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into the RC-2 packing gland to stop the packing leak. On September 10, maintenance
workers installed the second BTB nut, performed the Furmanite injection which stopped
the packinc leak, and did not identify any other magnetic BTB nuts on RC-2. A
debriefing of the maintenance workers did not occur after these tasks were comoleted.
It would later be learned that the mechanic had difficulty installing the nut and, due to
the short stay time in the area, did not do a thorough inspection to determine if any other
nuts were magnetic.
l- On October 14, operators manually tripped the reactor due to a CCW rupture disk
failuro (previously reported in IR 50-346/98018). On October 16, with the reactor still
shutdown, workers identified that the RC-2 BTB nut installed on September 10 was not
flush against its bearing surface. It was determined taat its stud was not adequately
cleaned prior to the installation of the nut and that the cemains of a corroded nut were
below the new nut. In addition, the workers identified that two of the RC-2 BTB nuts
were magnetic. One of the magnetic nuts was carbon steel and was 30 percent
corroded. The other magnetic nut was magnetic stainless steel and was intact. At this
time, the licensee did a thorough evaluation of this condition. It was determined that
BAC of carbon steel nuts was the most likely cause of the two missing and one corroded
l nut. An action plan to replace all of the nuts was developed and implemented on l
l October 17. In addition, a root cause evaluation of this series of events was performed. l
- A detailed evaluation was required to determine if RC-2 was operable in the degraded
condition of having two nuts missing and one additional nut partially corroded. The
results of the licensee's operability evaluation indicated that RC-2 was not functional for i
design loads with two of the eight BTB nuts missing, which was reported to the NRC in
l Licensee Event Report (LER) 50-346/98-009, " Reactor Coolant System Pressurizer l
Spray Valve Not Functional with Two of Eight Body to Bonnet Nuts Missing." The
licensee contracted with a vendor to perform a more detailed calculation to determine
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whether valve RC-2 would have maintained its integrity under design basis conditions
with the most limiting BTB nut configuration. On April 23,1999, the licensee received
the more detailed calculation from the vendor, which indicated that the valve would have
been functional under design basis conditions.
10 CFR Part 50, Appendix B, Criterion Ill, " Design Control," states, in part, that ,
measures shall be established for the selection and review for suitability of application of I
materials, parts, equipment, and processes that are essential to the safety-related
functions of structures, systems, and components.10 CFR Part 50, Appendix B,
Criterion XVI, " Corrective Actions," states, in part, that measures shall be established to i
assure that conditions adverse to quality, such as failures, malfunctions, deficiencies,
deviations, defective material and equipment, and nonconfnrmances, are promptly
identified and corrected. Two apparent violations of these requirements were identified.
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Extent of Condition
l The licensee developed Engineering Department inspection Plan IP-M-02, "RC-2 Extent
of Condition, that addressed all of the American Society of Mechanical Engineers
(ASME) Class 1 reactor coolant system pressure boundary bolting, except specialty
bolting (e.g., once through steam generator man-ways, reactor coolant pump
body-to-bonnet bolting, reactor pressure vessel head bolting). As a result,50 ASME
Class 1 bolted connections were to be inspected for potentialimproper materials and
RCS leakage. This action plan was completed during the recent mid-cycle cutage.
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The execution of the plan resulted in several body-to-bonnet fasteners that had to be
visually inspected for integrity, several bolted connections that required torquing to stop
body-to-bonnet leakage, and five body-to-bonnet nuts (out of 564 nuts that were
inspected) that were made of material different than that prescribed by plant
specifications. None of the body-to-bonnet fastening material experienced corrosive ,
degradation. Two body-to-bonnet nuts on valve RC-33 were made of boric acid
corrosion resistant 410 series stainless steel. These nuts were replaced with the correct
material. Two body-to-bonnet nuts on valve MU-1B were made of 304 Nickel based
stainless steel versus 316 nickel based stainless steel. Plant personnel determined that
this condition was acceptable to use-as-is by determining negligible differences in
properties between the two materials; plans were to change the specifications to reflect
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this disposition. One body-to-bonnet nut on valve HP-57 had previously been
! determined to have magnetic properties. This was dispositioned as being temporarily
acceptable by performing an engineering calculation to demonstrate that the valve
would be able to perform its design basis function with one body-to-bonnet nut missing.
The orientation of the nut was such that it would not be subject to aggressive boric acid
corrosion because hot reactor coolant from a postulated packing leak would not flow
over the nut. Additionally, during the mid-cycle outage, the licensee conducted a
previously unplanned deep drain of the reactor coolant system in order to replace the
corroded yokes of three RCS cold leg drain valves (RC-32, RC-38, RC-40) instead of
evaluating them as degraded but operable.
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As a result of the findings, the licensee determined with a 99 percent confidence factor
l that bolted connections in remaining safety systems were acceptable. The inspectors
l determined that the licensee's corrective actions were adequate by either correcting the
l condition or by demonstrating that the condition was acceptable until the next available
oppor1 unity to correct the situation (the next refueling outage). The inspectors reviewed
l the bounding calculation for one nut missing on valve HP-57 and determined that the
l valve would still perform its design basis function in the unlikely event that it would
l corrode away.
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l Maintenance Practices
Instructions were incorporated into plant procedures to require a material type
evaluation for ASME Class 1 and 2 components in boric acid systems. Training was
planned to ensure the craft has tools available to aid in identifying material by markings,
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use of a magnet, and other types of testing or materialidentification equipment.
The mechanical maintenance staff was trained en this event and the consequences of
not torquing nuts as required in work documents. Expectations for stopping work when i
unanticipated conditions occur were included in the training sessions. In addition, the
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The first violation was for the failure to establish adequate design control
measures for the materials associated with pressurizer spray valve RC-2
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(eel 50-346/98021-01(DRP)). The second violation was for the failure to promptly '
identify and correct this condition once sufficient information was available to identify
this condition (eel 50-346/98021-02(DRP)).
c. Conclusions
The failure to ensure adequate material separation was maintained during pressurizer
spray valve RC-2 maintenance activities resulted in the installation of three carbon steel
BTB nuts on the valve. In addition, the licensee failed to take prompt, effective
corrective actions commensurate with safety to identify and correct this condition once it
was discovered that one of the eight RC-2 BTB nuts was missing. Two apparent ]
violations were identified. I
M7.1 Pressurizer Sprav Valve RC-2 Corrective Actions
a. inspection Scope (62707) )
The inspectors reviewed the corrective actions taken and planned to address the root
causes of the RC-2 event.
b. Observations and Findinas 1
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In response to this event, corrective actions were taken in the following topical areas: l
Boric Acid Corrosion Awareness
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The effects of boric acid corrosion on carbon steel, the importance of maintaining
material compatibility, the advantages and limitations on the use of on-line leak sealing,
the importance of proper segregation and identification, the use of a magnet, and I
material composition determination were covered during plant-wide stand-down training.
Boric Acid Corrosion Procedure Enhancements
individual responsibilities were clarified and actions better defined within the Boric Acid
Corrosion Procedure Section. The material verification process was expanded and now i
provides an additional level of confidence that the materials in contact with a boric acid I
leak are not susceptible to the effects of boric acid corrosion.
Two attachments have been added to the procedure. An inspection cleanliness sheet
was added to track a leak from its discovery through decontamination and clean up for
inspection. The second attachment is an inspection checklist which guides individuals
through the inspection and material verification process to ensure that all aspects of
potential corrosion damage are investigated. The intention of adding these two
attachments was to enhance the tracking of open items and to provide documentation
that boric acid leaks have been analyzed for the potential to cause damage to
associated components.
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need to consider plant conditions, work site conditions, contingency plans,
communication requirements, and the need to pre-designate when a post work critique
is needed were also discussed.
c. Conclusions
Once the licensee determined that BAC was the most likely cause for the missing nuts
on RC-2, a thorough evaluation of the situation was conducted and extensive, effective
corrective actions were developed. The inspectors noted a much greater sensitivity to
the effects of BAC on plant equipment and a recognition that some plant maintenance
practices required improvement, more oversight, and more assessment.
The engineering plan to address the extent of condition for the two missing
body to-bonnet nuts on Pressurizer Spray Valve RC-2 was comprehensive and detailed.
The licensee effectively completed the extent of condition review during the recently
completed mid-cycle outage. Additionally, the licensee demonstrated a heightened l
sensitivity to boric acid corrosion effect. i
M8 Miscellaneous Maintenance lasues (92902)
(Closed) LER 50-346/98-009 and IFl 50-346/98014-01(DRP): Reactor coolant system
pressurizer spray valve not functional with two of eight body-to-bonnet nuts missing.
The details of the inspector's review of this issue are included in this inspection report. 1
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111. Enaineerina
E3 Engineering Procedures and Documentation
E3.1 Boric Acid Corrosion Proaram Procedure Content
a. Inspection Scope (IP 37551)
The inspectors reviewed the station program for boric acid corrosion control, which was
documented in procedure NG-EN-00324 Rev 01, " Boric Acid Corrosion Control."
b. Observations and Findinas
Generic Letter 88-05 requested PWR licensees to provide assurance that a program
was implemented consisting of systematic measures to ensure that boric acid corrosion
does not lead to degradation of the assurance that the reactor coolant pressure
boundary will have an extremely low probability of abnormalleakage, rapidly
propagating failure, or gross rupture. The generic letter specified that four elements
should exist in the licensee's program. The program was to include the following:
(1) Determination of the principal locations where leaks that are smaller than the TS
limits could cause degradation of the primary pressure boundary by boric acid
corrosion. Particular consideration should be given to identifying those locations
where conditions exist that could cause high concentrations of boric acid on
pressure boundary surfaces, i
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(2) Procedures for locating small coolant leaks that were less than the TS limits. It
! is important to establish the potential path of the leaking coolant and the reactor
pressure boundary components it is likely to contact. This information is
important in determining the interaction between the leaking coolant and reactor
coolant pre.sure boundary materials.
(3) Methods for conducting examinations and performing engineering evaluations to
establish the impact on the reactor coolant pressure boundary when leakage is
i located. This should include procedures to promptly gather the necessary
l information for an engineering evaluation before the removal of evidence of
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leakage, such as boric acid crystal buildup.
(4) Corrective actions to prevent recurrences of this type of corrosion. This should
include any modifications to be introduced in the present design or operating
procedures of the plant that: (a) reduce the probability of primary coolant leaks
at the locations where they may cause corrosion damage, and; (b) entail the use
of suitable corrosion resistant materials or the application of protective
coatings / claddings.
The inspectors determined that for the most part, procedure NG-EN-00324 incorporated-
the GL 88-05 recommendations either explicitly or by referencing other plant
procedures. However, procedure NG-EN-00324 did not provide detailed information on
the methods for conducting examinations and performing engineering evaluations to
establish the impact on the reactor coolant pressure boundary when leakage was
located. Specifically, the procedure did not require that the materials subject to boric
acid be verified to be corrosion resistant in the field. Consequently, engineering
personnel assumed that the RC-2 BTB nuts were made of boric acid corrosion resistant
stainless steel, as per plant specifications, instead of verifying that the materials were
actually as specified. The licensee indicated that a review of this procedure was
ongoing and that the procedure would be revised as necessary to address weaknesses
in the boric acid corrosion control program identified during the evaluation of this event.
c. Conclusions
The inspectors determined that the licensee's boric acid control program was
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adequately documented. However, a weakness was identified in the program
concerning the verification of materials subjected to boric acid corrosion which
contributed to the failure to promptly identify that the RC-2 valve components were not
as specified in its design document.
V. Manaaement Meetinas
X1 Exit Meeting Summary
The inspectors presented the inspection results to members of licensee management at the
conclusion of the inspection on May 13,1999. The licensee acknowledged the findings
presented. The inspectors asked the licensee whether any materials examined during the
inspection should be considered proprietary. No proprietary inforrt. ion was identified.
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PARTIAL LIST OF PERSONS CONTACTED
Licensee
M. C. Beier, Manager, Quality Assessment
G. G. Campbell, Vice President Nuclear
R. B. Coad, Jr., Superintendent, Radiation Protection
S. A. Coakley,~ Manager, Work Management
L._ M. Dohrmann, Manager, Quality Services
D. L. Eshelman, Manager, Operations
J. L. Freels, Manager, Regulatory Affairs
G. W. Gillespie Superintendent, Chemistry
P.. R. Hess, Manager, Supply
J. H. Lash, General Manager, Plant Operations
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D. H. Lockwood, Supervisor, Compliance
J, L Michaelis, Manager, Maintenance
S. P. Moffitt, Director, Nuclear Support Services
C. A. Price, Manager, Business Services
J. W. Rogers, Manager, Plant Engineering
G. A. Skeel, Manager, Security l
H. W. Stevens, Jr., Manager, Nuclear Safety & Inspections
F. L. Swanger, Manager, Design Basis Engineering
G. M. Wolf, Engineer, Regulatory Affairs
L. W. Worley, Director, Nuclear Assurance
NRC
K. S. Zellers, Resident inspector, Davis-Besse
INSPECTION PROCEDURES USED
IP 37551: Onsite Engineering
IP 62707: Maintenance Observation
IP 92902: Followup - Maintenance
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, ITEMS OPENED, CLOSED, AND DISCUSSED
Opened
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50-346/98021-01 (DRP) eel Failure to establish adequate design control measures for
the materials associated with valve RC-2
l 50-346/98021-02 (DRP) eel Failure to promptly identiff and correct incorrect use of
l carbon steel instead of stainless steel nuts on valve RC-2,
a significant condition adverse to quality
Closed
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i 50-346/98-009 LER Reactor coolant system pressurizer spray valve not
functional with two of eight body-to-bonnet nuts missing
50-346/98014-01(DRP) IFl Reactor coolant system pressurizer spray valve not
functional with two of eight body-to-bonnet nuts missing
Discussed
None
LIST OF ACRONYMS USED
-ASME American Society of Mechanical Engineers
BAC Boric Acid Corrosion
BTB Body-to-Bonnet
CFR Code of Federal Regulations
CR Condition Report i
ESF Engineered Safety Feature
GL Generic Letter
l&C Instrumentation and Controls i
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IR Inspection Report
LER Licensee Event Report
MWO Maintenance Work Order
NCV Non Cited Violation
NOT Normal Operating Temperature
NRC Nuclear Regulatory Commission
PCAOR Potential Condition Adverse to Quality Report
PDR Public Document Room
PWR Pressurized Water Reactor
RPT Radiation Protection Technician
RFO Refueling Outage
VIO Violation
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SEQUENCE OF EVENTS
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04/11/98 Start RFO 11.
04/22/98 RC-2 limit torque removed for replacement.
05/05/98 Severe corrosion of RC-2 yoke identified (PCAOR 1998-0915).
05/08-10/98 MWO 1-98-0463-00 written to replace yoke. Yoke made of carbon steel and no l
stainless steel yoke available for replacement. The bonnet, stem, disk, and
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packing was removed from valve so that the yoke could be installed. Work on
the valve completed on 5/10/98 (MWO 1-98-0463-00).
05/19/98 With the reactor coolant system at normal operating pressure and temperature,
a packing leak was identified on RC-2. Maintenance personnel checked the
packing nut torque at 22 ft/lbs with no movement noted. The valve was stroked
twice. The packing nut torque was checked again at 24 ft/lbs with no movement
noted. Valve was left stillleaking (MWO 1-98-0463-00).
05/20/98 Torqued packing nuts to 35 ft/lbs with only one flat movement on one of the two
nuts observed. (work history entry in 1-98-0463-00) l
05/20/98 Torqued packing gland nuts to 50 ft/lbs. Only one half flat movement on one of
the two nuts observed (MWO1-98-0463-00). Even with the increase in torque to
the packing gland nuts to 50 ft/lbs, no increase in the stem friction was
determined. Subsequently, the licensee determined that the possibility that the
packing gland was misaligned in the stuffing box which prevented mechanical i
movement of the packing gland. I
05/20/98 (1) Decision made by outage management to continue startup with RC-2 packing
leakage. Valve leakage was minor and hard to estimate due to liquid boil-off on
the horizontal surface of the valve yoke, very little of the leakage was running off
of the valve. Leakage was reduced to one area, about a 60 degree arc on the
outside diameter of the packing gland on the east side of the valve.
(2) MWO 1-98-0558-00 was written to perform a seal injection of the stuffing box
if the leak rate increased or boric acid buildup / corrosion of the carbon steel yoke
became a problem.
(3) Plant engineering to perform periodic inspections of the valve to determine if
conditions would change and warrant any further action. PCAOR 1998-1130
written to document packing leakage and provide the engineering evaluation of
potential boric acid corrosion concerns (SE LOG).
05/22/98 Containment entry to inspect RC2 packing leak. No change in leak rate was
observed. No boric acid buildup on the valve or yoke was determined. The
licensee determined no need for further actions at that time (SE LOG).
05/23/98 The plant was connected to the grid which completed RFO 11 activities.
06/02/98 Containment entry to inspect RC-2 packing leakage inspected RC-2 and found
small boric acid buildup on the valve yoke and bonnet. Boric acid was cleaned
off and removed with screwdrivers and a rag. Polaroid pictures were taken to
document the as-found condition. Packing leakage rate appeared to remain the
same as before, no increase in flow. Leakage still confined to the OD of the
gland in an area of 60 degrees of the circumference. There was no visible
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evidence of any corrosion on the valve yoke due to the boric acid buildup.
l Based on the packing leakage rate remaining steady and the fact that there was
no visible evidence of corrosion on the yoke, the licensee decided not to inject
the packing gland at that time and the inspection interval was increased to
30 days. (SE LOG)
06/24/98 Plant trip due to tornado and damage to the switchyard.
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l 06/27/98 Containment entry to inspect RC-2 packing leakage. The valve had a ball of
boric acid buildup around the east side of the yoke and bonnet. Used a portable
spray and water to rinse off the valve. Minor corrosion noted on the horizontal 3
surface of the yoke Packing leak rate was unchanged. Based on findings the
next inspection was scheduled for late August, approximately 60 days.
(SE LOG)
07/14/98 Engineering suggested to maintenance to have leak sealant hardware installed
on RC-2 during a scheduling a down power / outage to perform fill / soak and drain
of OTSGs. i
07/24/98 Containment entry to install Furmanite rig on packing for RC-2. Due to heat
stress surveys on 7/23/98, temp in PORV room was 150 F, which allowed {
15 minutes allotted times for moderate level work. RC-2 was drilled, tapped, and j
a 5/16 shutoff adapter was installed. All work was done in one entry with one RP
tech and one Furmanite tech. Furmanite tech received 15 mrem and was in a
209 mrem /hr dose rate field. RP tech received two mrem. No compound
injection was done at this time. Inspection of the valve showed no change in the
packing leak rate.(MWO 1-98-0558-00, Radiation Protection Work-In-Progress
Tracking Sheet, SE LOG) j
09/01/98 (1) A BTB nut was determined missing on RC-2 after the bonnet area had been 1
cleaned of boric acid. The licensee determined that with seven nuts remaining,
RC-2 remained operable based on preliminary evaluation of seismic, thrust and ,
pressure loads. Subsequently, engineering calculations supported this J'
determination. The location of the missing nut was the same place as the
Furmanite injection plug. The nut could not be located in CTMT. The licensee
suspected that the Furmanite contractor had removed the nut in order to install
the Furmanite injection device even though it appeared that the injection device
could be installed with the nut in place.
(2) Inspection of RC-2 indicated that leakage on the valve appeared to have
increased. (PCAQR 1998-1642, Radiation Protection Work-in-Progress Tracking
Sheet)
09/09/98 During decontamination and inspection of RC-2, a second nut was determined
missing. Maintenance supervision continued with the plan to install the first
missing nut without first telling the rest of the organization that a second nut was
found missing. Maintenance installed the first missing nut and torqued to
80 ft/lbs. Checked the torque of the remaining nuts. Did not find any movement
on the remaining BTB nuts. An engineering evaluation was planned to
determine the operability of RC-2 for two missing nuts. About 20 pounds of boric
acid was removed from the valve during the decontamination process
(MWO 1-98-0558-00, PCAOR 1998-1681).
09/10/98 (1) Maintenance worker installed the second missing nut. The nut went on hard,
and he torqued it past the required value (greater than 100 foot pounds). He did
not inform his management of this action, and maintenance management did not
become aware of this condition until October 27, when he was questioned as to
what he did.
(2) The maintenance worker was to verify that the remaining nuts were not
magnetic (implying that they were not carbon steel) by using a magnet on the
end of an extension. However, due to this action being performed at the end of
his allocated stay time in the hazardous environment, he conducted the magnetic
check very quickly and missed finding two other nuts that were magnetic (these
were found on 10/16/98)
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(3) Drilled and injected packing gland on RC-2, stopping the packing leak. The
online leak sealing was performed as an infrequently performed evolution.
(MWO 1-98-0558-00, SE LOG) '
09/18/98 Engineering determined that RC-2 had not been functional for design condition
. loads with two of eight nuts missing. LER followed (PCAOR 1998-1716).
10/14/98 Manual reactor trip due to CCW rupture disk failure. l
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10/16/98 With the plant shutdown, maintenance personnel performed a search for other
nuts in the vicinity of RC-2, again using a magnet to discriminate between
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stainless steel and carbon steel nuts, to determine if during some prior i
maintenance activity, that BTB nuts from RC-2 and some other equipment had
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been swapped. During this activity, a maintenance worker decided to again
check RC-2 BTB nuts and then determined that two other nuts were magnetic y
nuts. One of the nuts was 30 percent corroded. Additionally, the maintenance
person who over torqued the replacement nut on 9/10/98, determined that the
replacement nut was not fully engaged with the bonnet.
10/17/98 (1) All RC-2 BTB nuts were replaced with stainless steel nuts and torqued to
80 foot pounds (this elevated temperature torque value was provided by
Mechanical Design Engineering).
(2) A small scope extent of condition review to determine if other RCS pressure
boundary valves had magnetic nuts was conducted and determined that valve
HP-57, a stop-check valve for HPI line to RCS loop 2-1 had a magnetic nut. This
determination was not communicated to plant management until November 12.
(3) A small fragment of a carbon steel nut was found under the replacement nut
that was over torqued on 9/10/98.
10/20/98 Re-injected packing gland on RC-2 to stop a small leak where the injection
device penetrated the packing stuffing box.
4/23/99 Received detailed calculation from vendor indicating that the valve would have
functioned under design loads.
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