ML20129H585

Forwards NRC AIT Insp Rept 50-213/96-80 on 960903-1002.AIT Chartered to Review Events Surrounding Inadvertent Decrease in Reactor Vessel Water Level During Plant Shutdown Conditions

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: IR 05000213/1996080 ML20129H585
References
EA-96-440, FACA, NUDOCS 9611050291
Download: ML20129H585 (4)

See also: IR 05000213/1996080

Text

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October 30, 1996

EA No.96-440

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 j

leaking into the reactor vessel and causing level to decrease. By September 1,1996, l

reactor vessel level had decreased to approximately 3 feet below the reactor vessel flange, i

The decrease in reactor vessel level was potentially significant because a further decrease j

in level could have challenged the function of the operating decay heat removal system, l

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

l follow p51t procedures, conducting activities without procedural guidance, or making

! 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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9611050291 961030

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Mr. Ted C. Feigenbaum 2

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  ;

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RHR pump available for more than 3 weeks. The team also noted that the poor material

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 j

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 I

actions was beyond the scope of the AIT. The NRC will review your lessons learned and l

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 '

activities. The NRC also is reviewing the nitrogen intrusion event for potential generic

l communication.

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Mr. Ted C. Feigenbaum 3

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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 1

!

Hubert J. Miller

Regional Administrator l

Region i 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

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H. F. Haynes, Director - Training

J. F. Smith, Manager, Operator Training

W. D. Meinert, Nuclear Engineer

State of Connecticut SLO

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Mr. Ted C. Feiger om 4

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

OE (2) EA PACKAGES ONLY

B. Letts, 01

Distribution w/enci (VIA E-MAIL):

W. Dean, OEDO

P. McKee, NRR/PD l-4

S. Dembek, PM, NRR

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 j

A. Chaffee, NRR/ DORS /EAB

M. Markley, ACRS

E. Jordan, AEOD

K. Raglin, Director, TCC

DCD (OWFN P1-37) (Dist. Code #lE10) l

INPO l

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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

0FFICE RI/DRS lN Rl/DRS ,

j Rl/R V l RI/ l RI/ l

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NAME JTrapp W/ JWiggins V bilpfller

DATE 10/18/96 V 10/ $0/96 f

10/ 3196 10/ /96 10/ /96

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0FFICIAL RECORD COPY

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