ML20129H585
| ML20129H585 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 10/30/1996 |
| From: | Miller H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Feigenbaum T CONNECTICUT YANKEE ATOMIC POWER CO. |
| Shared Package | |
| ML20129H586 | List: |
| References | |
| EA-96-440, FACA, NUDOCS 9611050291 | |
| Download: ML20129H585 (4) | |
See also: IR 05000213/1996080
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October 30, 1996
Mr. Ted C. Feigenbaum
Executive Vice President - Nuclear
c/o Mr. Terry L. Harpster
P.O. Box 128
Waterford, Connecticut 06385
SUBJECT:
NRC AUGMENTED INSPECTION TEAM REVIEW OF THE UNDETECTED
INTRODUCTION OF NITROGEN GAS INTO THE REACTOR VESSEL DURING
PLANT SHUTDOWN REPORT NO. 50-213/96-80
Dear Mr. Feigenbaum:
On October 2,1996, the NRC completed an Augmented Inspection Team (AIT) at the
Connecticut Yankee Atomic Power Company. The enclosed report presents the results of
that inspection.
The AIT was chartered to review the events surrounding the inadvertent decrease in
reactor vessel water level during plant shutdown conditions. The team also reviewed other
decay heat removal system challenges and equipment failures. The team developed a
sequence of events, determined the safety significance of the events, and assessed the
quality of response by the plant staff and management.
For approximately four days, control room operators were unaware that nitrogen gas was
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leaking into the reactor vessel and causing level to decrease. By September 1,1996,
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reactor vessel level had decreased to approximately 3 feet below the reactor vessel flange,
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The decrease in reactor vessel level was potentially significant because a further decrease
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in level could have challenged the function of the operating decay heat removal system,
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While there were no actual public health and safety consequences of this event and
adequate decay heat removal was maintained, the situation involving an unintended
decrease in reactor water levelin combination with the unavailability of decay heat removal
equipment was safety significant.
The team identified several areas where operations performance was inadequate. Several
operations procedures failed to provide adequate details or contained incorrect information.
The absence of acceptable procedures was a contributing cause for both the nitrogen gas
intrusion going undetecMd and for the inadvertent diversion of water from the reactor
coolant system (RCS). Goveral of the events were exacerbated by plant operators failing to
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follow p51t procedures, conducting activities without procedural guidance, or making
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inapproper 9 decisions. A lack of a questioning attitude resulted in the failure to promptly
identify W 'itrogen gas accumulation in the reactor vessel. The failure by more senior
operators a convey expectations to less experienced field operators during pre-job
briefings resulted in inappropriate equipment manipulation that either directly caused or
contributed to these events.
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Mr. Ted C. Feigenbaum
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The team concluded that the timeliness of maintenance activities in restoration of the
inoperable residual heat removal (RHR) pump to service and in support of maintenance of
severalisolation valves was inadequate. While the RHR pump repair activities were
generally methodical and conservative, the unavailability of quality parts and vendor
specifications, and repeated post maintenance test failures resulted in having only a single
RHR pump available for more than 3 weeks. The team also noted that the poor material
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condition of several isolation valves was a contributing cause of these events. Leaking
valves allowed nitrogen gas to inadvertently enter the reactor vessel and water from the
RCS to be diverted to the containment sump.
The support of plant operations provided by engineering and technical support (E&TS)
activities was not timely or effective. The condition of the temporary reactor head vent
system was significantly degraded. Over the past several years, management failed to
provide an effective response to previous plant staff concerns by not improving the vent
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header design. The failure to establish a functional reactor head vent allowed nitrogen gas
to accumulate in the reactor vessel. The absence of a direct means of monitoring reactor
vessel water level complicated the situation for the operators.
The failure by plant management and staff to fully appreciate the significance of these
events as they occurred resulted in a poor event response and in a delay in initiating an
integrated event recovery plan. The team determined that the actions taken during and
following the event to establish actual reactor vessel level and to provide fer continuing
decay heat removal from the reactor coolant system (RCS) were not timely. Delays were
also experienced in reestablishing control room reactor vessel level and temperature
indications and in aligning a reactor coolant pump for service. The actions implemented to
monitor the operating RHR pump, following the "B" RHR pump failure also were not
comprehensive or timely. Further, an effective event review and recovery team was not
established in a timely manner.
The AIT was not tasked with determining enforcement actions regarding the findings of
this inspection. You will be notified in a future correspondence as to our decision on any
possible enforcement actions.
You established an independent review team on September 3,1996, and issued a final
report after the AIT concluded on-site activities. The review of your overall corrective
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actions was beyond the scope of the AIT. The NRC will review your lessons learned and
corrective actions and will document our results in a separate inspection report. Our initial
review will focus on those actions that are associated with core offload and other refueling
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activities. The NRC also is reviewing the nitrogen intrusion event for potential generic
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communication.
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Mr. Ted C. Feigenbaum
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In accordance with 10 CFR 2.790 of the NRC's " Rules of Practice," a copy of this letter
and its enclosures will be placed in the NRC Public Document Room (PDR).
Sincerely,
ORIGINAL SIGNED BY
Hubert J. Miller
Regional Administrator
Region i
Docket No. 50-213
License No. DPR-61
Enclosure:
NRC Integrated Inspection Report No. 50-213/96-08
cc w/ encl:
F,. D. Kenyon, President and CEO - Nuclear Group
D. Goebel, Vice President - Nuclear Oversight
J. Thayer, Vice President - Nuclear Engineering and Support Recovery Office
F. C. Rothen, Vice President - Nuclear Work Services
J. J. LaPlatney, Haddam Neck Unit Director
L. M. Cuoco, Senior Nuclear Counsel
J. E. Van Noorde, Licensing Manager - Haddam Neck
H. F. Haynes, Director - Training
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J. F. Smith, Manager, Operator Training
W. D. Meinert, Nuclear Engineer
State of Connecticut SLO
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Mr. Ted C. Feiger
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Distribution w/ench
Region i Docket Room (with concurrences)
D. Screnci, PAO (2 ) AIT Reports
J. Rogge, DRP
NRC Resident inspector
M. Conner, DRP
D. Bearde, DRP
Nuclear Safety Information Center (NSIC)
PUBLIC
B. Letts, 01
Distribution w/enci (VIA E-MAIL):
W. Dean, OEDO
P. McKee, NRR/PD l-4
R. Jones, NRR
R. Bhatia, DRS, SALP Coordinator
R. Correia, NRR (RPC)
R. Frahm, Jr., NRR (RKF)
Inspection Program Branch, NRR (IPAS)
Distribution w/ encl: AIT Reports Only
Chairman Jackson
Commissioner Dicus
Commissioner Rogers
Commissioner Diaz
Commissioner McGaffigan
F. Maraglia, NRR
J. Taylor, EDO
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A. Chaffee, NRR/ DORS /EAB
M. Markley, ACRS
E. Jordan, AEOD
K. Raglin, Director, TCC
DCD (OWFN P1-37) (Dist. Code #lE10)
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DOCUMENT NAME: A: HN9680.lNS
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To receive a copy or this document. Indicate in the box: "C" = Copy without attachment / enclosure
"E" = Copy with attachment / enclosure
"N" = No copy
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DATE
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