ML20235M301
| ML20235M301 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/10/1987 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| SL-2828, NUDOCS 8707170142 | |
| Download: ML20235M301 (6) | |
Text
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Georgia Power Company 333 Piedmont Avenue Atlanta. Georgia 30308 Telephone 404 526 6526 Maihng Address-Post Office Box 4545 Atlanta, Georgia 30302 b
Georgia Power L T. Gucwa f
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Manager Nuclear Safety and Ucensing 0400m X7GJ17-V600 July 10,1987 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 PLANT V0GTLE - UNIT 1 NRC DOCKET 50-424 OPERATING LICENSE NPF-68 TEMPORARY TECHNICAL SPECIFICATION RELIEF Gentlemen:
This letter documents Georgia Power Company's (GPC's) verbal request and the NRC's agreement in telephone conferences on July 9 and July 10, 1987 to temporarily extend the Technical Specification time limit for hot standby operation of VEGP Unit 1 with an inoperable Control Room Emergency Fil tration System train.
The action requirement of Specification 3.7.6 currently requires that, with one train inoperable while in Mode 1, 2, 3, or 4, the inoperable train be restored to operable status within 7 days or that the plant be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
GPC requested and received NRC approval for a one-time extension of the 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> time limit to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, applicable to the "B"
train inoperability which was declared on July 2, 1987.
This extension was requested to prevent an unnecessary thermal cycle and allow the plant to be maintained in hot standby while modifications are made to correct a single failure vulnerability in the "B"
train. provides details of the circumstances necessitating this relief request and our justification that no significant safety consequences result from the extension.
GPC also requested and received tjRC approval for startup and power operation for a period of up to 7 days after the "B" train is restored to operable status before removing the "A" train from service for similar modifications.
Justification for operation in this condition is addressed in Enclosure 2.
As discussed with NRC, GPC believes that the "A" train modifications can be completed within the 7 day limit of the Technical Specifications.
B70717034g 979,39 DR ADOCK 0500o424 A003 PDR fl 1
Georgia Power b U. S. Nuclear Regulatory Commission July 10,1987 i
Page Two If you have questions, please contact this office at any time.
Sincerely, WW L. T. Gucwa l
JH/im
Enclosures:
1.
Justification for LC0 Extension 2.
Justification for Plant Operation c: Georgia Power Company Mr. R. E. Conway Mr. J. P. O'Reilly Mr. G. Bockhold, Jr.
Mr. J. F. D' Amico Mr. C. W. Hayes GO-NORMS l
l Southern Company Services Mr. R. A. Thomas Mr. J. A. Bailey Shaw, Pittman, Potts & Trowbridge Mr. B. W. Churchill, Attorney-at-Law Troutman, Sanders, Lockerman & Ashmore Mr. A. H. Domby, Attorney-at-Law U. S. Nuclear Regulatory Commission Dr. J. N. Grace, Regional Administrator Ms. M. A. Miller, Licensing Project Manager, NRR (2 copies)
Mr. J. F. Rogge, Senior Resident Inspector-0perations, Vogtle Georgians Against Nuclear Energy hr. D. Feig Ms. C. Stangler 0400m i
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Georgia PowerI ENCLOSURE 1 PLANT V0GTLE - UNIT 1 l
NRC DOCKET 50-424 OPERATING LICENSE NPF-68' JUSTIFICATION FOR LC0 EXTENSION BACKGROUND The VEGP Unit 1 control room is provided with. two emergency filtration trains as described in FSAR Sections 6.4 and 9.4.1.
In _ the emergency (or pressurization) mode of operation, control room air is recirculated through one or both filter trains with sufficient outside air being taken in to maintain the ' control.' room 'at a positive pressure with respect to surrounding areas. _The emergency mode of operation is initiated automatically by a safety injection signal or the detection of high : radiation. in the control room outside air intake.. Upon automatic initiation, both emergency filtration trains are activated and the l
isolation dampers between the normal and emergency systems close.
The control room normal air handling units automatica11y' trip when the isolation dampers close.
After automatic activation of. both trains in the emergency mode, one train may be manually transferred to -the emergency standby mode from the control room, while the other' train continues to operate in the emergency mode.
i Technical Specification 3.7.6, Control Room Emergency Filtration System, requires that both trains be operable while in Modes 1, 2, 3, and 4.
With one train inoperable, the inoperable train is required to be restored to operable status within 7 days or the unit must be in at least hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
DISCOVERY OF DESIGN DEFICIENCY On July 2,1987, with VEGP Unit 1 operating at_ full power, GPC was notified of a design oversight' which, in certain event sequences, could potentially degrade the ability of the emergency filtration system to maintain the specified positive pressure in the control ' room.
.If electrical power to a filter ~ train operating in the emergency mode were lost, the isolation dampers (1HV-12118,12119,12128,12129,12130, ' and 12131,. shown in FSAR Figure 9.4.1-1 Sheet 3) for that train.would remain open..The other train can be assumed to be operable; however, the 'open dampers 'in the idle train would provide a path for control room air..to flow back to the outside air intake duct which is the ' source of makeup
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air for the operating train.
This could reduce the_ amount of ' positive pressure which could be maintained in the control room.. This potential degradation was brought to GPC's attention ' by' a contractor-employed engineer who had knowledge of a similar condition at another. nuclear power plant.
0400m El-1
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q Georgia Power b I
ENCLOSURE 1 (Continued)
JUSTIFICATION FOR LCO EXTENSION CORRECTIVE ACTIONS Calculations or tests to determine the extent of the potential degradation in control room pressurization have not been performed.
Rather, GPC chose to take corrective actions based on the conservative l
assumption that backflow through an idle, unisolated filter train would prevent control room pressurization to that pressure specified in the Technical Specifications.
At 4:22 p.m. on July 2,1987, the "B" filter I
train was isolated and declared inoperable by closing dampers 1HV-12119, 12129, and 12131 to preclude the postulated degradation.
Pursuant to Technical Specification 3.7.6, a limiting condition for operation (LCO) was entered.
The LC0 requires that the inoperable filter train be restored to operable status within 7 days or that the plant be in at least hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Work was immediately begun to develop a design change to correct the deficiency.
Installation of backdraft dampers was chosen as a solution.
These dampers, which are designed to limit reverse flow, will be installed in ducts 004 and 006 of train "A" and in ducts 003 and 007 of train "B".
Design work was completed and parts located by July 5.
Physical modifications to the "B" train were begun that day.
NEED FOR RELIEF REQUEST VEGP Unit 1 is currently in hot standby following a reactor trip on July 8,1987.
GPC has installed the "B" train backdraft dampers and will perform the testing required to demonstrate operability prior to startup.
We estimate that the "B"
train will be declared operable by July 12,1987.
The LCO, however, expired at 4:22 p.m. on July 9, which l
would require that the plant be in cold shutdown within the following 30 l
hours.
Placing the plant in cold shutdown would increase the duration of I
the current forced outage and would impose a thermal cycle on plant equipment which GPC believes would not be justified from a safety perspective.
GPC therefore requested an extension of the 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> time limit for placing the plant in cold shutdown to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
This extension allows the plant to remain stable in the hot standby mode until the "B" filter train can be declared operable and startup commenced.
0400m El-2 7/10/87 SL-2828 700775 i
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.t Georgia PowerA ENCLOSURE 1.(Continued)
JUSTIFICATION FOR LC0 EXTENSION JUSTIFICATION FOR LC0 EXTENSION GPC. has requested a one-time extension of the time limit for. hot standby operation of VEGP Unit 1 with an inoperable. control room emergency filtration train from 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> to 72. hours.
An : evaluation l
l using' PRA techniques has been performed and shows that 'the risk associated with this extension is acceptably low.
The probability of a realistic need (demand) and failure of. the operable filter train is calculated to be 4.5 X 10-8 during hot standby for a 3 day period.. This probability - is based on the. assumption that-fuel damage would need to occur as a result of the accident.
Based on the 'present level ' of radioactivity in the primary system, 'this assumption is reasonable.
In other words, there is about one chance. in 22 million that the operable' train will be needed to maintain control room habitability and fail.
Furthermore, backdraft damper installation in the "B"
train is complete and functional testing is currently being performed.
Even though this train has not yet been declared operable, it could realistically be placed in service in the remote event that the "A" train was needed and failed.
An evaluation has determined that if a demand occurred and neither emergency filter train was available, radiation doses to control room operators would be well within acceptable limits, assuming the release of the current inventory of iodine in the primary coolant and a conservative rate of-inleakage into the control room.
Finally, taking the plant to cold shutdown and almost immediately returning to power operation represents a needless plant transient and would thermally stress the boundaries which would protect-against 'a release of radiation to the control room.
In conclusion, since the risk from ' an inoperable control room emergency filtration train while in hot standby has been shown to be negligible, and since the " inoperable" filter train could likely function as a backup if required, operation of the plant in hot standby is justified ' for up to three additional days beyond the current Technical Specification limit.
0400m El-3 7/10/87 SL-2828 700775
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- Georgia Power b
. ENCLOSURE 2 PLANT V0GTLE - UNIT 1
.l NRC' DOCKET-50-424 OPERATING LICENSE-NPF-68.
' JUSTIFICATION FOR PLANT OPERATIOT
~ PLANT OPERATING CONDITION GPC has requested that,- following restoration of the "B" train-of the control room emergency ventilation system _to operable' status, startup and power operation be permitted'for a period not to exceed 7 days before the i
"A" train is L removed from service for modification.
During this period of time there is a possibility that' emergency-mode operation of. the system could be required and that backflow through the "A"
filter train-
.could degrade pressurization capability.
GPC has evaluated operation of the ' plant in this condition and concludes. that 'significant safety consequences would not result.
JUSTIFICATION FOR PLANT OPERATION The initiating ' events, while in startup or power' operation,. which take credit for emergency mode operation of the control' room emergency filtration system are loss-of-coolant accidents, main steam line breaks, steam generator tube ruptures, 'and ejection' of a control rod ' assembly.
The probability, during a 7 day period, of any of these events followed by a loss of electrical poyer resulting in the dampers remaining open, is calculated to be 2.2 X 10-c.
In the remote event that it became necessary, compensatory action could be taken to mitigate the consequences of the design. deficiency.
This action requires the operator to manually close;. the intake and l-exhaust dampers.for the affected filter train should a power failure.
occur while it is in operation.
The dampers for both. trains ' are. located in the radiochemistry laboratory which is adjacent.to the control room.
Access to the dampers requires use.of a ladder and removal of false ceiling panels.
The ladder will be left in place and the ceiling panels-removed during the subject 7 day period.
Since the calculated probability of the ; control room emergency filtration. system to fail to operate for Lthe events of' concern is so. low as to be considered negligible, ' and compensatory actions could be taken_
should-a' failure occur, no.significant risk is-involved in operation-during the subject 7 day' period.
0400m E2-1 7/10/87 '
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