Information Notice 1993-59, Unexpected Opening of Both Doors in an Airlock

Unexpected Opening of Both Doors in an Airlock

ML031070240
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	07/26/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-059, NUDOCS 9307200123
Download: ML031070240 (10)

K>

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555

July 26, 1993

NRC INFORMATION NOTICE 93-59: UNEXPECTED OPENING OF BOTH DOORS IN AN AIRLOCK

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to a potential problem that may result when

interlocks which prevent both airlock doors being open at the same time are

not in use or not operable. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. However, suggestions contained in

this information notice are not NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

On February 25, 1993, when the plant was operating at 100-percent power, personnel at River Bend Station inadvertently had both airlock doors open at

the same time. The airlock at River Bend is a pneumatic airlock that was

designed for either automatic operation actuated by a pushbutton or manual

operation using handwheels located on the doors. The original intent was to

operate the airlock in the automatic mode, which incorporated both electrical

and mechanical interlocks. However, operation in the automatic mode was not- reliable and, since 1985, the airlock was operated in the manual mode.

The manual mode incorporates only the mechanical actions associated with

turning the handwheel.

The electrical interlocks, which had been identified

as being for "personnel safety," were not being used, and the licensee did not

believe that they were necessary. An operable mechanical interlock-allows

only one handwheel at a time to be in the open position.

Operation of the

handwheel (1) positions two pins into keepers, (2) repositions two 3-way ball

valves used to inflate/deflate the pneumatic seal, (3) operates a valve that

equalizes pressure across the door, and (4) actuates the mechanical interlock.

On February 25, 1993, a licensee employee entering containment closed the

outer door (not completely) and turned the handwheel to the closed position.

By placing the outer door handwheel in the closed position, the mechanical

interlock was satisfied, thereby permitting the handwheel on the inner door to

9307200123 flrOA-

9 3 &0

At

tt9O~t&2-sq

N'

IN 93-59 July 26, 1993 be subsequently turned to the open position.

This subsequent action deflated

the door seal and air rushed from the containment past the employee in the

airlock. A supervisor outside the airlock sensed the air flow out of the

airlock and alerted the employee in the airlock, who promptly re-inflated the

seals on the inner door and then properly (fully) closed the outer door. A

second instance on the same day that involved different people nearly resulted

in a repeat opening of both doors.

An engineer leaving the containment nearly

opened the inner door while the outer door was not fully closed. A technician

in the airlock had previously turned the handwheel on the outer door to the

closed position.

In both instances, the lack of an operable door position

interlock permitted the handwheel to be turned to the open position.

The licensee has modified the interlock system on the airlocks to incorporate

the door closure switch into the circuit to prohibit manual operation of the

handwheel when the associated door is not fully closed.

Discussion

There have been a number of other instances at other facilities when both

doors of a containment airlock were opened; however, only a small fraction

occurred during power operation.

Nevertheless, each instance represents a

potential for a large leak path.

Most of the known at-power occurrences were

attributed to failure to properly seat the door (due to rebound) or to

component failure. -In-most-instances,--the

time-both-doors were open was very- short.

Thus, the actual safety significance was low.

The effects of changing the operating mode of an airlock from automatic to

manual may not be limited to a change from the pushbutton operating the

handwheel to manually operating the handwheel.

Operation in the manual mode

may also eliminate some of the design interlock features, such as those that

would prevent having both doors open at the same time and assuring that there

is no significant pressure differential across an airlock door before it is

opened.

Of particular concern in the River Bend event is that part of the interlock

system was removed from service, apparently without a fundamental

understanding of the function of the electrical interlocks in assuring the

integrity of the containment boundary.

The safety significance of positive

verification of door closure via functioning door position switches was not

recognized.

K>

IN 93-59 July 26, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact: J. Carter, NRR

(301) 504-1153 Attachment:

List of recently Issued NRC Information Notice

2 Z

c0

-n -n

O'9

>cn>

-4--

mZ

C )

(a)

(a

0

e>

2 C:

0-4 O(n

-.51 z ;

Attachment

IN 93-59

July 26, 1993

Page I of 1

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

93-58 Nonconservatism in Low-

07/26/93

All holders of OLs or CPs

Temperature Overpressure

for pressurized-water

Protection for Pressurized- reactors.

Water Reactors

,93-57 Software Problems

07/23/93

All holders of OLs or CPs

Involving Digital

for test and research

Control Console Systems

reactors and nuclear power

at Non-Power Reactors

reactors

93-56 Weakness in Emergency

07/22/93

All holders of OLs or CPs

Operating Procedures

for pressurized water

Found as Result of

reactors.

Steam Generator Tube

Rupture

93-55 Potential Problem with

07/21/93

All holders of OLs or CPs

Main Steamline Break

for pressurized water

Analysis for Main Steam

reactors.

Vaults/Tunnels

93-54 Motor-Operated Valve

07/20/93

All holders of OLs or CPs

Actuator Thrust

for nuclear power reactors.

Variations Measured

with A Torque Thrust

Cell and A Strain Gage

93-53 Effect of Hurricane

07/20/93

All holders of OLs or CPs

Andrew on Turkey Point

for nuclear power reactors.

Nuclear Generating

Station and Lessons

Learned

-

93-52 Draft NUREG-1477,

07/14/93

All holders of OLs or CPs

Voltage-Based Interim

for pressurized water

Plugging Criteria for

reactor (PWRs).

Steam Generator Tubes'

93-51 Repetitive Overspeed

07/09/93

All holders of OLs or CPs

Tripping of Turbine- for nuclear power reactors.

Driven Auxiliary Feed- water Pumps

OL - Operating License

CP - Construction Permit

C

(

0U .

1

0 Co -,

Z Z Z

.

0 -11 Z Z Z>

0 3' 0 i

al 'i

A,

IN 93-59 July 26, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

original signed by

A. E. Chaffee

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact:

J. Carter, NRR

(301) 504-1153 Attachm-ent:

List of recently Issued NRC Information Notices

• See previous concurrence

OFC

OEAB:DORS

SC/OEAB:DORS

PUB:ADM

C/OEAB:DORS

NAME

JCarter*

RDennig*

Tech Ed*

AChaffee*

DATE

05/14/93

05/17/93

04/22/93

05/17/93 OFC

• PDIV-2:ADR4-5

• OGCB:DORS

• C/OGCB:DORS

lD/DR ,

NAME

EBaker

MHarper

GMarcus

BGrimes

DATE

06/08/93

06/08/93

07/

/93

1

07/,.b/93l

[OFFICIAL RECORD COPY]

DOCUMENT NAME:

S:\\DORSSEC\\93-59.IN

IN 93-XX

June xx, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact:

J. Carter, NRR

(301) 504-1153 Attachment:

List of recently Issued NRC Information Notices

• See previous concurrence

OFC

OEAB:DORS

_

SC/OEAB:DORS

PUB:ADM

l C/OEAB:DORS

NAME

JCarter*

RDennig*

Tech Ed*

AChaffee*

DATE

05/14/93

1.05/17/93

04/22/93

05/17/93 OFC

• PDIV-2:ADR4-5

• OGCB:DORS

C/OGCB:DORS

D/DORS

NAME

EBaker

MHarper

GMarcus

BGrimes

DATE

06/08/93

06/08/93

0;1// /93

06/ /93

[OFFICIAL RECORD COPY]

DOCUMENT NAME:

S:\\DORSSEC\\AIRLOCK.IN

I

K>

IN 93-XX

June xx, 1993 s1

.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

I

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact:

J. Carter, NRR

(301) 504-1153 Attachment:

List of recently Issued NRC Information Notices

• See previous concurrence

OFC

l OEAB:DORS

SC/OEAB:DORS

PUB:ADM

l C/OEAB:DORS

NAME

JCarter*

RDennig*

Tech Ed*

AChaffee*

D

05/14/93

05/17/93

04/22/93

05/17/93 OFC

PDIV-2:ADR4-5 OGCB:DORS

C/OGCB:DORS

D/DORS

NAME

EBake

MHarper

GMarcus

BGrimes

l DATE J 06/0'/93

06/08/93

06/

/93

06/ /93

[OFFICIAL RECORD COPY]

DOCUMENT NAME:

S:\\DORS_SEC\\IN_25195

IN 93-XX

May xx, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact:

J. Carter, NRR

(301) 504-1153 Attachment:

List of recently Issued NRC Information Notices

OFC

O

R

-

SC

DUi

iRS

PUB:ADM X

C/OEAB:DORS

NAME

JrWter

R en

__Tech Ed

AC lfee

.DATE

______93

_

• '/f)/93

1

/;AA93

5/i7/93 OFC

PDIV-2:ADR4-5 C/OGCB:DORS

D/DORS

NAME

EBaker

GMarcus

BGrimes

DATE

/

/93

/

/93

/

/93

[OFFICIAL RECORD COPY]

DOCUMENT NAME:

G:\\TJC\\IN_25195

[

OFC

OEAB:DORS

_

SC/OEAB:DORS

PUB:ADM

j C/OEAB:DORS

NAME

JCarter

RDennig

Tech Ed /

AChaffee

[/

/93

1 / /93

14 / 793

1 / /93 J

OFC

PDIV-2:ADR4-5 C/OGCB:DORS

D/DORS

NAME

EBaker

GMarcus

BGrimes

DATE

/ /93

/ /93

/ /93 ii

[OFFICIAL RECORD COPY]

DOCUMENT NAME:

G:\\TJC\\IN_25195

IN 93-XX

May xx, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactors Support

Office of Nuclear Reactor Regulation

Technical contact:

J. Carter, NRR

(301) 504-1153 Attachment:

List of recently Issued NRC Information Notices

• See previous concurrence

OFC

OEAB:DORS

SC/OEAB:DORS

PUB:ADM

C/OEAB:DORS

NAME

JCarter*

RDennig*

Tech Ed*

AChaffee*

DATE , 05/14/93

1

05/17/93

04/22/93

1

05/17/93 J

OFC

PDIV-2:ADR4-5 C/OGCB:DORS

D/DORS

NAME

EBaker

GMarcus

BGrimes

D

/

/93

/

/93

/

/93

[OFFICIAL RECORD COPY]

DOCUMENT NAME: S:\\DORSSEC\\IN_25195