ML20211K503
| ML20211K503 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/30/1999 |
| From: | Miller H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tom Gurdziel AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML20211K506 | List: |
| References | |
| 50-220-99-06, 50-410-99-06, NUDOCS 9909080006 | |
| Download: ML20211K503 (7) | |
See also: IR 05000220/1999006
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August 30, 1999
Mr. Thomas Gurdziel
9 Twin Orchard Drive
Oswego, NY 13126
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' Dear Mr. Gurdziel:
I am responding to your letter to Chairman Dicus, dated July 6,1999, in which you expresseJ
concems involving the June 24,1999, Nine Mile Point Unit 2 (Unit 2) automatic reactor
shutdown. The NRC staff, shares your concem for the proper operation of Unit 2 and we have
pursued the answers to many of the same questions you raised in your July 6 letter. The NRC
resident inspectors were augmented by other NRC Region i inspectors to evaluate the Unit 2
equipment issues and to assess the overall performance of the Unit 2 staff and management
during and following this event. The inspectors' findings and conclusions are currently under
review and will be documented in NRC Inspection Report No. 50-220 and 50-410/99-06, by mid-
September 1999. A copy of this report will be forwarded to you, when available.
Prior to Unit 2 restart and retum to electrical generation, the NRC staff reviewed and discussed
. with Niagara Mohawk Power Corporation (NMPC) the various equipment failures, safety
systems responses, and operator actions associated with the June 24 automatic shutdown.
These discussions with NMPC were to ensure a common understanding of all of the issues and
to convey our expectation that corrective actions be thorough and complete prior to unit restart.
In general, the NRC staff found that the Unit 2 operators responded adequately to the failures
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and challenges encountered during the June 24 automatic shutdown. The two automatic
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shutdowns (June 24 and April 24,1999) within two months are above the current industry
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average (slightly less than one scram per unit per year) and were caused by unrelated
equipment failures or malfunctions. While it is true that both automatic shutdowns involved
offsite power problems, there does not appear to be any significant correlation either between
those two events or with the performance of other plants. The NRC staff is not aware of the
neighboring nuclear plants of Nine Mile Point Unit 1, James A FitzPatrick, or Ginna being subject
to any loss of offsite power events since the beginning of the year. We have been monitoring
the Unit 2 reactor core isolation cooling (RCIC) system performance in recent months, as
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documented in inspection Reports 50-220 and 50-410/99-04 and 99-05. Copies of these two
reports with our assessments of licensee performance and copies of the NMPC licensee event
. reports involving the two automatic shutdowns are enclosed for your information.
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0FFICIAL RECORD COPY
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99090e0006 990830
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ADOCK 05000220
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Thomas Gurdziel
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The items for which you requested a specific response in your July 6 letter have also been
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addressed in an enclosure to this letter. I hope that my staff and I have been responsive to your
. request. If you have any further detailed questions or concerns regarding the performance of
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Unit 2, please contact Michele' G. Evans, Chief, Branch 1, Division of Reactor Projects, Region I,
(610-337-5224) responsible for direct inspection oversight of the Nine Mile Point facilities.
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Sincerely,
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Original Signed'by:
J. T. Wiggins for
Hubert J. Miller
Regional Administrator
Docket No. 50-410
Enclosures: As stated
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Thomas Gurdziel
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Distribution w/encis:
~ D. Holody, ORA l
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R. Crienjak, DRP
_W. Lanning, DRS
B. Holian, DRS
M. Evans, DRP
W. Cook, DRP -
M. Oprendek, DRP
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G19990345
. CRC-00-0621
OCM #3812
. PUBLIC
Region i Public Document Room (w/ concurrences)
Nuclear Safety Information Center (NSIC)
Distribution w/encis: (VIA E-MAIL)
- W. Travers, OEDO
M. Knapp, OEDO
F. Miraglia, OEDO
P. Norry, OEDO
S. Shirley, EDO
M. Bridgers,' EDO
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S. Bums, OGC
S. Collins, NRR
R. Borchardt, OE .
E. Adensam, NRR.
D. Hood, NRR
G. Hunegs, SRI, Nine Mile Point 1 & 2
M. Fudge, ORA
DOCUMENT NAME: G:\\ BRANCH 1\\GURDZIELRESPONSE.WPD
To receive a copy of this document, indicate in the box: "C" = Copy without
attachment / enclosure
"E" = Copy with attachment / enclosure
"N" = No copy
OFFICE
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DATE
08/X/99
080#99
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08/,3799 ~
OFFICIAL RECORD COPY
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ENCLOSURE 1
Event Summary:
The cause of the Nine Mile Point Unit 2 reactor shutdown on June 24,199g, was an automatic
. trip signal on low reactor vessel level caused by the failure of a circuit card in the master
feedwater flow controller. The circuit card failure caused the control valves to go closed.
. Operators were unable to recover from the closure of the feedwater valves quickly enough to
prevent the reactor protection system actuation and there is no back up feedwater flow
controller. Unit 2 systems response to the automatic shutdown was complicated by a relay .
failure in the generator protection circuit which caused the 115KV Line #5 feeder breaker in the
facility's offsite switchyard to open. The loss of Line #5 resulted in the partial loss of normal
electncal (non-safety) power and the momentary loss of the Division I and 111 emergency buses.
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Both emergency buses were re-energized by their respective emergency diesel generators.
Due to the partial loss of normal uectrical power, operators manually started the reactor core
isolation cooling (RCIC) system and restored vessel level with the RCIC system controller in
' manual.' Operators controlled reactor vessel level with the RCIC system controller in ' manual'
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because of flow oscillations with the controller in ' automatic.' The RCIC system remained
functional, but was declared inoperable per Technical Specifications (reference Event Number
' 35859, dated June 24,1999) due to the inability of the controller to perform properly in
' automatic.' The electrical failure resulted in the loss of the non-safety condenser offgas system.
Wdh the offgas system unavailable, the main condenser lost vacuum and was not available as a
. heat sink. Per. procedure, operators closed the main steam isolation valves and dumped steam
to the torus, via the safety relief valves, to remove decay heat and control reactor pressure and
temperature.
Item 1
"All feedwater control does not receive power from just one UPS."
Response:
The feedwater control system is a balance-of-plant system. Although important to the reliable
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and efficient operation of the unit, it is not required to be powered by one or more of the safety
related divisional emergency power supplies. The power supply is a single non-safety related
uninterruptible power supply (UPS - 1VBS V101) which, by its design, ensures continuity of
power via attemate non safety related electrical power sources.
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" Adequate g;;eative maintenance is now being performed on all UPSs.' (This includes
confidence that the presently installed UPSs have manuals and drawings that are consistent
with their manufacture, all"little" batteries arefbeing replaced on a schedule that is appropriate
to any applied float-voltage and emblent panel temperature, the emergency diesel generators
are the default power supply to all UPSs, and all UPS capacitors are replaced based on age and
temperature requirements.)"
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Enclosure 1
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' Response:
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?The April 24,1999, automatic reactor shutdown was complicated by a blown fuse on the" power
Jsupply inverter to the 2VBB-UPS3B uninterruptible power supply (UPS)." NMPC's investigation
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, (documented in Licensee Event Report No. 50-410/99-005, dated May 24,' 1999) identified the
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. cause of the blown fuse to be a design deficiency in the maintenance bypass transfer switch.
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The blown fuse was replaced and the transfer switch design deficiency was bypassed prior to
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unit restart.' The root cause for the design deficiency is being investigated by the licensee.
Preventive maintenance does not appear to be a contributing factor to this fuse problem.
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' Item 3
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"If there are any pieces of the feedwater system that lock-up on loss of power, reactor operators .
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and their supervisors are trained in how to reset them."
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Response:
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Review of the Unit 2 Updated Safety Analysis Report and operator training documentation
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' identified that there are feedwater control system interlocks (e.g, flow control valves LV10A, B,
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and C fail"as-is" and lock in position upon a loss of control signal; LV10A, B, and C have a 50
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percent open clamp on turbine trip and low feedwater pump suction) and associated reset
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' functionsJ Review of the training curriculum learning objectives identifed that proper operator
response to the actuation of these interlocks is included in the classroom training. .
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Item 4
- There are no "open" items associated with either IN 91-64, Supp #1, or the Public Meeting of
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October,18,'1991.
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. Response:
N' C Information Notice (IN) 91-64, Site Area Emergency Resulting From a Loss of Non-Class
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1E Uninterruptible Power Supplies (UPS), dated October 9,1991, and Supplement 1, dated
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- October 7,1992, described the UPS maintenance oversights highlighted by the August 13,
1991, event at Nine Mile Point Unit 2. Licensee disposition of NRC Information Notices are not
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tracked by th6 3RC staff and do not require a licensee response. A review of the inspection
reports which documented the NRC staff's review of the August 13,1991, event (Inspection
Report Nos. 50-410/91-81,91-19, and 91-23) and of the associated Confirmatory Action Letter
' (CAL) 91-13 correspondences identified no outstanding issues or concems.
Item 5
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. Probable root 'causes associated with Event Number 35627 were determined before the plant
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went back on line."
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Enclosure' 1 -
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' Response:
As documented in Licensee Event Report (LER) No. 99-05, dated May 24,1999, and reviewed
in inspection Report Nos. 50-220 and 50-410/99-04 and 99-05, the causes for the problems
encountered were identified and corrective actions taken or planned prior to Unit,2 restart.
Item 6
"When circuit breakers to offsite power are open, the resulting phase difference is not more than
that allowed by control permissives."
Response:
At Unit 2, the ' fast' transfer (of non-safety related loads) from the unit auxiliary transformer to the
offsite 115KV electrical power source, by design, ensures a negligible phase angle difference
between the sources. When the unit is operating and connected to the offsite electrical grid the
phase angles are identical. The ' slow' or ' residual' transfer design at Unit 2 is protected by a
calibrated residual voltage protection relay. This voltage protection relay limits load residual
voltage to less than 25 percent, such that the combination of running voltage and residual
voltage (when transferred < 125 percent) does not exceed the capability of the connected
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equipment. (Note: the safety related buses are normally contwH:ted to the offsite 115KV power
source and do not automatically transfer on unit trip.)
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Item 7
"Any instrumentation / control cabinets provided with heavy steel doors to reduce the possibility of
electromagnetic interference are operated with their doors closed."
Response:
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. A preliminary inspector's review of the design of instrumentation and control cabinetry.and
' discussion with responsible plant staff at Unit 2 has identified that there are no such applications
of heavy steel doors to reduce the potential for electromagnetic interference (EMI) to the
enclosed equipment. The most typical methods of EMI reduction at Unit 2.are either cable
shielding or administrative controls to prohibit the use of portable radios or other electromagnetic
frequency (EMF) generating devices in the vicinity of sensitive equipment. The inspector
performed a sample verification of the adequacy of posted placards in areas containing EMI
sensitive equipment. No discrepancies were noted.
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EDO. Principal Correspondence Control
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FROM:
DUE:
EDO CONTROL: Gl9990345
DOC DT: 07/06/99
' FINAL REPLY:
Thoman Gurdziel
0;w:gs, New York
TO:
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Chairman Dieus
FOR' SIGNATURE OF :
- GRN
CRC NO: 99-0621
Collir.;, liRR Miller, R1
DESC:
ROUTING:
NINE MILE POINT -- PLANT PERFORMANCE
Travers
Knapp
Miraglia
Norry
Blaha
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Burns
DATE: 07/12/99
Collins, NRR
ASSIGNED TO:
CONTACT:
RI
Miller
SPECIAL. INSTRUCTIONS OR REMARKS:
PRIORITY ROUTING
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