05000346/LER-1997-004, :on 970203,RCP Motor Oil Piping Was Not Protected from Leakage as Required Per 10CFR50 App R.Caused by Personnel Not Realizing Pressurized Piping in Area. Mods Made to Contain Piping as Necessary
| ML20136B596 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/03/1997 |
| From: | Lash J, Wolf G TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-97-004, LER-97-4, NP-33-97-004, NP-33-97-4, NUDOCS 9703110053 | |
| Download: ML20136B596 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) |
| 3461997004R00 - NRC Website | |
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TOLEDO
%mm EDISON A Centerlot Energy Company EDISON PLAZA 300 MADISON AVENUE TOLEDO. OHIO 43652-0001 NP-33-97-004 Docket No. 50-346 License No. NPF-3 March 3, 1997 United States Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 Ladies and Gentlemen:
LER 97-004 Davis-Besse Nuclear Power Station, Unit No. 1 Date of Occurrence - February 3, 1997 Enclosed please find Licensee Event Report 97-004, which is being submitted to provide 30 days written notification of the subject occurrence. This LER
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is being submitted in accordance with 10CFR50.73(a)(2)(ii)(B).
j very truly yours, 01-l s H. Lash Plant Manager Davis-Besse Nuclear Power Station GMW/dle Enclosure cc Mr. A. B. Beach Regional Administrator USNRC Region III j
Mr. Stan Stasek l
DB-1 NRC Sr. Resident Inspector I
l Utility Radiological Safety Board I
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9703110053 970303
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MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
DiviS-Besse Unit Number 1 05000 - 346 1 OF 6 TITLE (4)
RraCtor Coolant Pump Motor Oil Piping Not Protected From Leakage As Required Per 10CFR50 Appendix R EVEN I DAl E (5)
LER S UhlBER (6)
REPORI SUhlBER (7)
OlllER FACILillES IM OLVED (8) htQUENTIAL RE\\ blON F ACILITY hAML DuCRET NUMBER MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY YEAR 05000
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OPER TING THIS REPORIIS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR (: (Check one or more) (11) l MODE (9) 1 20.402(b) 20.405(C) 50.73(a)(2)(iv) 73.71(b)
I POWER 20.405(a)(1)(i) 53 36(C)(1) 50.73(a)(2)(v) 73.71(C)
LEVEL (10) 100 20.405(a)(1)(ii) 50.36(C)(2) 50.73(a)(2)(vu)
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NAME TELEPHONE NUMBER (include Area Code)
G:rald M. Wolf, Engineer - Licensing (419) 321-8114 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
CAUSL hY SILM COMPUNENT MANUFACTURLR ktJ'ORI AbLh
CAUSE
SYhfLM COMPONENT MANUFACTURER REPORIABLE TO NPRDS TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH OAY YEAR SUBMISSION YES X
NO DATE (15)
(d yes, complete EXPECTED SUBMISSION DATE) g ABSTRACT (Limit to 1400 spaces, i.e.,
approximately 15 eingle-spaced typewritten lines) (16)
On January 31, 1997, with the plant in Mode 1 operating at 100 percent power, it was discovered that a portion of the oil piping for each Reactor Coolant Pump (RCP) motor was outside the oil collection system that is required per 10CFR50, Appendix R.
This piping is the source connection for three pressure switches and a pressure gauge for the lift oil pump system, which is only pressurized when the lift oil pump is operating. On February 19, 1997, after reviewing pictures of the RCP motors as part of the corrective actions for this issue, more piping was found outside the RCP oil collection system.
This additional piping included lower bearing remote oil fill connections, which are not pressurized; and piping for the lower bearing oil reservoir drains, which is exposed to only two feet static head pressure. The lift oil pumps are currently not operating, and the remote oil fill connections have not been used this operating cycle.
This condition is considered outside the plant design basis and is being reported in accordance with 10CFR50.73 (a) (2) (ii) (B).
Plant modifications are being developed to contain or modify the piping as necessary to ensure compliance with 10CFR50, Appendix R.
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TEXT CONTINUATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U 8 NUCLEAR REGutAroRy COMMISSION, WASHINGTON. DC 205654001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF y
MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 FACluTY NAME (1)
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SEQUEN TIAL REVISION Divis-Besse Unit Number 1 05000-346 97
- - 004-00 2OF6 TEXT (If more space is required, use addiuonal copies of tlRC Form 366A) (17)
Descrintion of occurrence, On October 20, 1996, the AC powered lif t oil pump for Reactor Coolant Pump (RCP) 2-2 (AB-RO) was started in an attempt to reduce high motor up thrust bearing i
operating temperatures. On January 31, 1997, with the plant in Mode 1 operating at 100 percent power, low pressure alarms were received for RCP 2-2 lift oil system, and the AC powered lift oil pump was subsequently shut down.
In an attempt to discover the cause of the alarms, the spare RCP motors located in the turbine building were examined. Based on,this examination, it was theorized that the coupling for the lift oil pump has failed. However, during this examination, it was discovered that a portion of each RCP motor oil piping was outside the enclosure designed to contain oil from potential leak sites in the oil system. This piping is the source connection for three pressure switches and a pressure gauge for'the lift oil pump system, and is only pressurized when a lift oil pump is operating. On February 3, 1997, after determination that this piping is not in compliance with 10CFR50, Appendix R, Section III.0, this condition was reported.to the NRC via the Emergency Notification System in accordance with 10CFR50.72 (b) (1) (ii) (B). This condition is being reported in accordance with 10CFR50.73 (a) (2) (ii) (B) as a condition outside the design basis of the plant.
On February 19, 1997, after reviewing pictures of the RCP motors via a surrogate tour program as part of the corrective actions for this issue, two more sections of piping were found for each RCP motor that are not in compliance with 10CFR50, Appendix R, Section III.O.
The piping for the lower bearing oil reservoir drain appears to extend outside of the oil collection enclosure. This piping consists of a short section of line and a valve. Also, the lower bearing reservoir remote oil fill lines do not appear to be adequately protected against leakage. These conditions were reported to the NRC via the Emergency Notification System in accordance with 10CFR50.72 (b) (1) (ii) (B), and are also being reported in accordance with 10CFR50.73 (a) (2) (ii) (B) as conditions outside the design basis of the plant.
r In 1975, while Davis-Besse was under construction, Toledo Edison integrated an oil leakage collection system into the RCP motor design. At the time of incorporation, the NRC had not yet imposed any criteria or regulations concerning the design or requiring the installation of a RCP oil collection system.
The purpose of the oil collection system was to minimize any potential for oil leakage or high pressure oil spray from coming into contact with hot surfaces that could ignite the oil.
In August 1976, Appendix "A"
to Branch Technical Position 9.5-1 was issued requiring fire protection for primary and secondary containment areas including lubricating oil for the RCPs.
Toledo
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REcutATORv COuuissiON. wAsHiNcTON. DC 20555 0001. AND TO THE PAPERWORK REDUCTON PROJECT (31504104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 j
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SEQUENTIAL REVISDN l "U""
Divis-Besse Unit Number 1 05000-346 97
- - 004-00 3OF6 TEXT (If more space is required, use additional copoes of NRC Form 366A) (17)
Description of Occurrence: (Continued)
Edison's response to Appendix "A"
indicated that the oil collection system, in conjunction with the fire detection installed over each RCP motor, afforded equivalent protection to that of a fixed fire suppression system.
When Appendix R to 10CFR50 was issued in 1981, the contracted architect /
engineering firm for Davis-Besse reviewed the RCP oil collection system for the Davis-Besse Nuclear Power Station (DBNPS) and documented that the system met
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10CFR50, Appendix R, Section III.O with the exception that the system was only capable of holding the oil volume from one RCP motor per Reactor Coolant System loop rather than two motcrs. An exemption request was submitted to the NRC and was approved on August 20, 1984.
Apparent cause of occurrence:
The intent of the RCP oil collection is to collect oil from any leak or pipe break. No documentation could be found justifying the exclusion of the lift oil pump pressure switches, the lower bearing oil reservoir drain piping, or any other piping or component in the RCP oil system from being subjected to oil collection requirements. Drawings show the area where the lift oil pump pressure switches are located as an electrical panel.
It is possible that the personnel reviewing the oil system did not realize that there was pressurized piping in this area.
It is also possible that the personnel felt that the probability of a leak or break at the lift oil pump pressure switches was very low since they did provide discussion in their 10CFR50 Appendix,R review that the lift oil system is normally only pressur; zed for approximately three minutes during startup.
The remote oil' fill lines were added in 1990 to each RCP motor so that oil could be added to the lower oil reservoir of a RCP motor, if necessary, from a low-dose area during power operations. A temporary remote oil fill line was also installed on RCP 2-1 motor upper bearing in May 1995, due to a small leak that resulted in a low oil level alarm. This temporary oil fill line was removed during the tenth refueling outage in April 1996.
All of the remote oil fill line installations were designed to not trap any oil after use.
The remote oil fill lines were considered a means to facilitate maintenance and were not viewed as part of the RCP oil system, therefore they were not designed to meet the requirement that any potential oil leakage would be collected as specified by 10CFR50, Appendix R, Section III.O.
These lines reduced the chance of spilling oil in the area of the RCP during oil addition while reducing dose received during power operations.l
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SEQUENTIAL REVISION
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Davis-Besse Unit Number 1 05000-346 97
- - 004-00 4OF6 TEXT (11more space is required, use addit 5al coptes of NRC Form 366A) (17)
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Analysis of Occurrence:
The lift oil pumps are normally operated for only a few minutes during each RCP startup, and during the prolonged coastdown of the last RCP during a plant shutdown.
The lift oil pump piping would be depressurized at other times, therefore there is minimal chance of oil spray when the lift oil pumps are not operating. Any leakage from the tubing movated outside the existing enclosure when the lift oil pumps are not operating wc.uld be contained by the lip around the top of the motor. The lif t oil pumps are not required during operation of the RCPs. With the lift oil pumps not in operation, the existing oil collection system is adequate for the lift oil pump piping that is outside the existing enclosure.
With the lift oil pumps operating, if an oil leak developed, this leakage would result in a low oil level, which would be detected by the control room operators via computer alarms, and they would then secure the lift oil pumps.
If this leakage resulted in a fire, either of the two heat detectors over each RCP motor would alert the operators in the control room to the situation.
Additionally, a fire may be detected by an increase in the Containment Air Cooler inlet temperature, which is currently being monitored once per hour by a roving fire watch.
Guidance has been provided to the operators not to start the lift oil pumps until this issue is resolved, unless directed by procedure in order to prevent equipment damage.
The remote oil fill lines consist of a fill pot located outside the 'D-Ring' and stainless steel tubing from the fill pot to the RCP motor lower oil reservoir.
Except during use, the fill pots and lines contain no oil. These lines terminate inside of the existing oil enclosure for the lower oil reservoir above the normal oil level so there is no potential for oil leakage from these lines during normal plant operation. A temporary remote oil fill line, made of high temperature flexible hose, was installed on RCP 2-1 upper motor bearing during operating cycle 10.
This temporary remote oil fill line was added during a plant downpower to add oil to the upper bearing oil reservoir. The remote oil fill lines are not pressurized, and are only used when a low oil level alarm is received on a RCP motor. A predetermined amount of oil is added via the remote oil fill lines to clear the alarm.
To ensure that the oil went into the bearing reservoir, the low level alarm is verified to clear after adding the predetermined amount of oil.
The remote oil fill lines have not been used this operating cycle, and guidance has been provided to prohibit the use of these lines until this issue is resolved.,
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TEXT CONTINUATION AR RECORDS MANAGEMENT BRANCH (MNB8 7714), U S. NUCLEAR REcuLATORY COMMISSION, WASHINGTON, DC 205554001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON. DC 20503.
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SEQUENTIAL REVISION Divis-Besse Unit Number 1 05000-346 97
- - 004-00 5 OF 6 TEXT (11more space is required, use additronal copes ofIVRC Form 366A) (17)
Analysis of Occurrence: (Continued)
The lower bearing oil reservoir drain piping is of substantial construction, and it is unlikely that they would leak. This piping is not pressurized, and is exposed to only the static head of approximately two feet of oil. A leak in the reservoir drain line that is outside of the enclosure, while extremely remote, would allow the oil in the lower reservoir to leak. This leak would be detected by a low oil level alarm that would actuate af ter approximately 2 to 3 pints of oil had leaked from the lower reservoir.
U on receiving this low oil level p
alarm, the operators would take appropriate actions to determine the cause and location of the leak. The type of oil used in the lower reservoir has a minimum flash point of approximately 400 degrees Fahrenheit. Any oil leakage would fall onto the top of the RCP insulation, into the RCP seal cavity, onto the Reactor Coolant System cold leg insulation, or the containment floor. The RCP and cold leg insulation is metal reflective type insulation with an expected surface temperature below 200 degrees Fahrenheit and, therefore, would not serve as an ignition source. The construction of the insulation is such that the oil would tend to be diverted away from hot surfaces, and would not be retained as in the case of fibrous insulation. The RCP seal cavity is also expected to be below 200 degrees Fahrenheit. There are no other credible ignition sources present during normal operation.
. Assuming that significant quantities of oil leaked from any of the sources listed above, and that an ignition source was present, the effects of the resulting fire would be localized to within one 'D-Ring'.
The grading of the containment floor is such that any oil released would be funneled to the floor drains below each RCP.
Consequently, an oil fire in one 'D-Ring' would not i
spread to the other 'D-Ring'.
The Appendix R safe shutdown analysis assumed an all consuming fire within one 'D-Ring' and determined that adequate separation exists between redundant circuits to achieve safe shutdown. Any significant j
fire would be detected by the two heat detectors over each RCP motor that l
individually alarm in the control room, or possibly by an increase in containment Air Cooler inlet temperature that is currently being monitored once l
per hour by a roving fire watch.
If an indication of a fire is received, the operators would take appropriate actions in accordance with the existing fire
' pre-plans for each of the RCPs to extinguish the fire and safely shut down the l
plant. Therefore, the condition described is considered to be of minimal safety significance.
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NRC FORM 386A (5-92) 5
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NRC FORM 344A U.S. NUCLEAR REaULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 4584 EXPlRES 5/31/96 4
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MANAGEMENT AND BUDGET, WASHINGTON. DC 20503.
FA(,luTY NAME (1) 00Cnmi NUMBER (2)
LER NUMBER (4)
PAGE (3)
SEQUENTIAL REVISION Davis-Besse Unit Number 1 05000-346 l
97
--004-00 6 OF 6 TEXT (If more space as requtred, use addit >Onal copies ofIVRC Form 366A) (17)
Corrective Actions
A Standing Order was issued on February 20, 1997, to provide guidance to not start the oil lift pumps unless directed by procedure, and to prevent the use of i
the remote oil fill lines.
1 New enclosures are being designed for the RCP lift oil system piping.
These
,j' enclosures will be installed during the next plant shutdown of sufficient duration for implementation, provided the engineering design work is complete and the necessary materials are available. These enclosures will be installed no later than the next refueling outage, 11RFO, which is currently scheduled for spring, 1998.
The RCP lower bearing oil reservoir piping and the remote oil fill lines will be evaluated and modified, as necessary, to ensure they are in compliance with 4
10CFR50, Appendix R requirements. These actions will be completed by the end of the next plant shutdown of sufficient duration for implementation, provided the f
i-engineering design work is complete and the necessary materials are available.
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These changes will also be completed no later than the next refueling outage.
Failure Data LER 96-006 also documents a condition with the RCP oil collection system that was considered to be outside the design basis of the DBNPS.
This condition j
d involved a missing lip around the top of the motor, which was required per 1
10CFR50 Appendix R, that was overlooked during fabrication of the new motor.
The corrective actions taken in response to this previous event were to verify the lip around the top of each RCP motor was installed as originally designed, i
The current event deals with a deficiency in the original design of the RCP oil collection system. The previous corrective actions would not have been expected to have prevented or discovered the current event.
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