ML20199F989
| ML20199F989 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/18/1997 |
| From: | Jeffery Wood CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2493, NUDOCS 9711250061 | |
| Download: ML20199F989 (11) | |
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8.601 N State MAe 2 419-249 7300 John K. Wood oah Hatttw.oH 43449 FAX: 419-3218337 Vce Presde<W Nuclear Davis-Besse Docket Number 50-346 License Number NPF-3 Serial Number 2493 November 18. 1997 United States Nuclear Regclatory Commission Document Control Desk Washington, D. C. 20555-0001
Subject:
Request for Exemption from 10 CFR 50, Appendix R, Section III.0, Oil Collection System for Reactor Coolant Pumps Ladies and Gentlemen:
This letter transmits Toledo Edison's request for an exemption from 10 CFR Part 50,
- Appendix R, Section 111.0 n:quirements regarding the oil collection system for reactor coolant pumps (RCPs). This exemption request pertains to the remote oil fill lines installed for the Davis Besse Nuclear Power Station (DBNPS) RCPs.
Information supporting this request is contained in the attachment. Toledo Edison has concluded that for the reasons specified in the attachment, special circumstances as defined m 10 CFR 50.12 exist and that the granting of the requested exemption will not present an undue risk to the I
health and safety of the public and is consistent with the common defense and security, f
The DBNPS eleventh refueling outage (11RFO) is scheduled to commence on April 11,1998.
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- Approval of this exemption request would preclude the need to perform plant modifications to /
1 the four RCP remote oil fill lines during 11RFO. It is estimated that approximately 3.2 man rem would be incurred oy personnel implementing the plant modifications. Absent either approval of this exemption request or implementation of the plant modifications, any future additions of oil to the RCP motor lower bearing reservoir during power operations would require a power reduction of sufficient magnitude to allow personnel local access to the oil reservoir. In order to support planning for the i1RFO, Toledo Edison reqests NRC approval of this exemption request by March 11,1998, 9711250061 97111e PDR ADOCK 05000346-kfl
- Docket Number 50-346 License Number NPF-3 Serial Number 2493 Page 2 Should you have any questions or require additional information, please contact Mr. James L. Freels, Manager - Regulatory Affairs, at (419) 321-8466.
Very truly yours, 4
MK aj Attachment cc:
A. B. Beach, Regional Administrator, NRC Region 111 S. J. Campbell, DB-1 NRC Senior Resident inspector A. O. Ilansen, DB-1 NRC/NRR Project Manager Utility Radiological Safety Board l
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a Docket Number 50-346 -
License Number NPF-3 Serial Number 2493 Attachment
'Page1 REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX R, SECTION IILO OIL COLLECTION SYSTEM FOR REACTOR COOLANT PUMPS in accordance with 10 CFR 50.12, Toledo Edison (TE) requests an exemption for the Davis-Besse Nuclear Power Station (DBNPS) from the requirements specified in 10 CFR Part 50, Appendix R, Section 111.0 regarding the oil collection system for reactor coolant pumps (RCPs). This exemption request pertains to the remote oil fill lines installed for the DBNPS RCPs.
llackcround 10 CFR 50.48," Fire Protection," requires nuclear power plants licensed prior to January 1,1979 to implement Section 111.0 of 10 CFR 50, Appendix R. Section 111.0 requires, in part, that the licensee have a seismically designed collection system capable of collecting tube oil from all potential pressurized and unpressurized leakage sites, including lift pump and piping, overflow lines, lube oil cooler, oil fill and drain lines and plugs, flanged connections on oil lines, and lube oil resen oirs.
At the DBNPS, remote oil fill lines were added in 1990 to each of the four RCP motors so that oil could be added to the lower oil reservoir of a RCP motor, if necessary, from a low-dose area during power operation. Use of the remote oil fill lines, in lieu of having personnel transport oil to the oil fill connection at the RCP motor and add it locally, also reduces the chance of spilling oil in the imme.diate area of the RCP during oil addition. In addition to reducing personnel dose, use of the remote oil fill lines also is advantageous from a personnel industrial safety (e.g., heat stress) standpoint.
The attached Figure I shows a schematic of the remote oil fill system, including the size and :ype of its components. The remote oil fill system is a non-pressurized, gravity-feed design. Each remote oil fill line consists of a fill pot located outsi& the secondary shield wall (or 'D-Ring') and stainless steel tubing and flexible hose from the fill pot to the RCP motor lower oil reservoir. The flexible stainless steel hose minimizes the effect of any translated vibration and thermal movement. The quantity of oil to be added is transported to the fill pot location in approved containers.
The remote oil fill line installations are designed to be leaktight and are sloped so as to not trap any oil as it gravity drains from the fill pot to the reservoir. Therefore, except during use, the fill pots and lines will contain no significant quantity of oil. The remote oil fill lines terminate inside of the existing oil colle ction enclosure for the lower oil reservoir, above the normal oil level of the lower oil reservcir, so that there is no potential for oil leakage from these lines during normal plant operation.
Docket Number 50-346 License Number NPF-3 Serial Number 2493 Attachment -
- Page 2 At the time of their design, the remote oil fill lines were considered a means to facilitate maintenance -
and were not viewed r s 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 10 CFR 50, Appendix R, Section 111.0. In early 1997, the DBNPS became aware that another licensee had submitted an exemption request regarding the lack of an enclosure on remote oil fill lines. On February 19,1997, a Potential Condition Adverse to Quality Report (PCAQR) was initiated by the DBNPS staff to track resolution of this issue. This condition was later reported to the NRC as a condition outside the design basis of the plant (Licensee Event Report 97-004-00 dated March 3,1997). The remote oil fill lines have since been disabled to prevent their use.
A plant modification is being designed to encapsulate the existing remote oil fill line with seismically supported stainless steel welded joint rigid pipe and stainless steel flexible hose. The existing fill pots mounted outside the 'D rings' would also be enclosed. The estimated cost to implement this plant modification is in excess of $30,000. In addition to the dollar cost. it is estimated that approximately 3.2 man rem will be incurred by personnel implementing the plant modification.
The lower oil reservoir for each RCP motor has an oil level switch to monitor oil level for high and low level computer alarms. The remote oil fill lines are only used when the low level computer alarm is received. Additions of oil to the RCP motor lower bearing reservoir are only required infrequently. A review of system performance records shows that since installation of the remote oil fill lines in 1990, they hae only been used three times, most recently in August 1994, and not more than three pints of oil was added on each occasion.
While an oil addition can be made durirg power operations without the use of the existing remote oil fill lines, this evolution requires a power reduction to approximately 20 to 30% of rated thermal power, in order to reduce dose levels low enough to allow personnel local access to the oil reservoir.
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Approval of this exemption request will allow future use of the remote oil fill lines, without incurring the dollar and man-rem expenditures to implement the planned plant modification.
Basis (br Exemption Reauest 10 CFR 50.12," Specific Exemptions," permi's the Nuclear Regulatory Commission to grant exemptions which are authorized by law, will not present an undue nsk to the health and safety of the public, and are consirc. at with the common defense and security, provided that special circumstances are present. Special circumstances are present when application of the regulation in the particular circumstances is not required to achieve the underlying purpose of the rule (50.12(a)(2)(ii)). Toledo Edison believes, for the reasons described below, that the installation of an oil collection enclosure around the remote oil fill lines is not required to achieve the underlying
Docket Number 50-346 License Number NPF-3
- Serial Number 2493 Attachment
- Page 3 purpose of Appendix R, Section 111.0, which is to ensure that leaking oil will not lead to a fire which could damage safe shutdown systems during normal or design basis conditions.
The type of oil used in the lower reservoir hzs a minimum flash point of approximately 400 degrees Fahrenheit. Any oil leakage would fall onto the top of the RCP insulation, onto the Reactor Coolant System (RCS) cold leg insulation, or ento the containment floor. The RCP and RCS cold leg insulation is metal reflective type insulation with a typical surface temperature below approximately 212 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. There are no other credible ignition sources present during normal operation.
Ilased on prior experience, the remote oil fill lines are likely to be required to be used on a very infrequent basis. In addition, under the compensatory measures described below, the maximum amount of oil that could be available for leakage is only four pints. Ilowever, assuming that significant quantities of oil leaked from the remote oil fill lines, and assuming 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 (other than small drips) would be funneled to the floor drains below each RCP. Consequently, an oil fire in one 'D-Ring' would not 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 fire would be detected by the two heat detectors over each RCP motor that individually alarm in the control room. If an indication of a fire is received, the operators would take appropriate actions in accordance with the existing pre-fire plans for each of the RCPs.
Fire Protection Features Two RCPs are located within each of the two Steam Generator compartment areas (rooms 216 and 218) within containment which comprise the secondary shield 'D-Rings'. As mentioned above, fire detection is provided by two heat detectors over each RCP motor. These eight detectors individually alarm in the ntrol room.
Fire suppression inside the containment relies on manual fire fighting action. Various fire suppressior. :quipment in the fonn of portable fire extinguishers and wheeled fire extinguishers equipped with fire hose is available to the station fire brigade, as shown on the attached Figures 2 through 5.
In addition, a 2-1/2 inch hose connection is available on the Ser ice Water System in containment that could be used for fire fighting. Three separate connections are provided on the 603' elevation near the personnel hatch.
Docket Numhr 50-346 License Number NPF-3 Serial Number 2493 Attachment
' Pege 4 Comnensatory Measures in order to minimize the potential for an oil fire due to a leak from the portions orthmmote oil fill line that are not enclosed by an oil collection system, the following actions will be taken each time oil is added through this system:
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Oil may be added only when a low oil level computer alarr.1 is received on an RCP motor.
Only a predetermined amount of oil necessary to clear the alami (approximately three pints based on prior experience) will be initially added to the reservoir via the remote oil fill line. A maximum total volume of four pints of oil may be added in an attempt to clear the alarm.
The oil fill pot will be verified empty prior to exiting the immediate area. Any spillage resulting
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e from adding oil to the remote oil fill pot will be cleaned up.
Personnel responsible for the oil addition evolution will be instructed to report to the control room any evidence of smoke during the oil addition process, if smoke is visually detected, the
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fire brigade will be immediately dispatched to the area.
A visual inspection will be conducted following refueling outages to confirm the integrity of the remote oil fill line system.
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Conclusions:==
l The remote oil fill lines are of a leak-tight design, and are only used infrequently. A hypothetical worst case oil spill and ignition will not impact post-fire safe shutdown capability. Administrative controls will be established to minimize the potential for an oil fire due to a leak from the portions of the remote oil fill line that are not enclosed by an oil collection system.
Based on the above, the underlying purpose of Appendix R,Section III.0, which is to ensure that leaking oil will not lead to a fire which could damage safe shutdown systems during normal or design basis conditions, is accomplished without the installation of an vil collection enclosure around the remote oil filllines.
The granting of this exemption request would have no impact on plant radiological or non-radiological efiluents and involves no significant radiation exposure.
llecause the underlying purpose of Appendix R is preserved, Toledo Edison concludes that the proposed exemption does not present an undue risk to the health and safety of the public and is consistent with the common defense and security.
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Docket Number 50-346 a
License Number NPF-3 l
Serial Number 2493 Attachment Page 5 Figure 1 Remote Oil-Fill System Schematic Typical of 4 '
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