Information Notice 1995-06, Potential Blockage of Safety-Related Strainers by Material Brought Inside Containment

Potential Blockage of Safety-Related Strainers by Material Brought Inside Containment

ML031060375
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, Three Mile Island, 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
Issue date:	01/25/1995
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-95-006, NUDOCS 9501190091
Download: ML031060375 (9)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 January 25, 1995 NRC INFORMATION NOTICE 95-06: POTENTIAL BLOCKAGE OF SAFETY-RELATED STRAINERS

BY MATERIAL BROUGHT INSIDE CONTAINMENT

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 (IN)to alert addressees to the potential blockage of safety-related

strainers by material brought inside containment. 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 April 28, 1994, with the reactor in cold shutdown, the licensee for the

Palisades Nuclear Power Station (Palisades) determined that plastic material

used inside containment could block the containment sump screens after a

design basis accident. The licensee declared the high-pressure safety

injection pumps and the containment spray system pumps inoperable and began

thoroughly cleaning the containment to remove unnecessary material that could

contribute to the blockage of containment sump screens.

In April 1994, at the Grand Gulf Nuclear Station (Grand Gulf), engineering

personnel evaluated whether plastic wrap and similar materials used inside

containment could block safety-related strainers. The evaluation specifically

addressed the potential for a thin plastic film used to cover the personnel

shielding platform and the dryer/separator strongback to become dislodged by

containment spray during a loss-of-coolant accident (LOCA) and enter the

suppression pool and eventually block the emergency core cooling suction

strainers. The plastic film had been used to cover the equipment to prevent

the spread of loose surface contamination.

On October 10, 1994, at Browns Ferry Unit 2, divers inspecting the underwater

surfaces of the Unit 2 torus found numerous pieces of cloth-like material on

the bottom of the torus and on the surfaces of the emergency core cooling

strainers. The pieces were typically 25 square centimeters [4 square inches]

in size, but smaller pieces were also found. The divers made a videotape of

the as-found condition of one half of the torus. This included two of the

four emergency core cooling suction strainers inside the torus. The videotape

9501190091 PDR ITE NOfCotQ 95t*°O4 9

'I'

IN 95-06 January 25, 1995 showed that about 15 percent of the surface area of one strainer was covered

and a lesser amount of the second strainer. The material was later found to

be pieces of absorbent paper towels sometimes used inside containment for

maintenance and cleaning purposes.

Discussion

The events described above illustrate that plastic or fibrous material brought

inside containment may become a concern after a design basis accident. In

general, the material met the plant guidelines for material allowed inside

containment and was intentionally brought inside the containment to reduce the

spread of loose contamination, identify plant equipment, or for cleaning

purposes. The materials involved and the actions taken by the licensees are

further described as follows:

Palisades

Palisades employs a pressurized-water reactor with a large dry containment.

The licensee evaluated the use of adhesive labels and double-sided tape to

affix signs to walls and equipment or piping inside containment. The licensee

recognized that the high temperature and humidity that may result from a

design basis accident could loosen or dissolve the adhesive. The licensee

concluded that, in a worst case scenario in which all of the material became

dislodged and entered the containment sumps, the material would cause blockage

of recirculation flow of containment sump water and, thereby, could affect the

functioning of safety systems.

The licensee thoroughly cleaned the containment and removed about 9 square

meters [100 square feet] of unnecessary signs and adhesives including

nonessential vendor labels, duct tape, double-sided tape used to affix signs,

"Dymo-tape" labels, and tape used to identify plant equipment. After the

cleaning, less than .9 square meter [10 square feet] of material remained.

The licensee did an engineering analysis and found that the area of greatest

concern extended radially about 1.5 meters [5 feet] from the containment sump

downcomer for plastic signs and labels and about 3 meters [10 feet] for duct

tape. The licensee plans to develop a checklist for containment cleanliness

that addresses sump blockage from signs, labels, and tags affixed by adhesive

materials. The licensee will also develop a labeling standard that considers

the possibility for sump blockage from materials secured by adhesives.

Grand Gulf

Grand Gulf uses a boiling-water reactor (BWR) with a Mark III containment that

has an open suppression pool separated from the drywell by a weir wall. The

licensee had formed a task force to inspect for materials inside the

containment that could block the emergency core cooling strainers. The task

force was concerned that plastic film covering some of the refueling equipment

could be dislodged and block the strainers. The licensee removed the plastic

film from the dryer/separator strongback and is having a cover fabricated for

the strongback that will withstand LOCA conditions. The licensee determined

that, because of the location, the plastic film covering the personnel

IN 95-06 January 25, 1995 shielding platform could not be washed into the suppression pool; therefore

the plastic film was left in place and securely fastened to the platform. The

licensee had previously painted the transparent plastic film to make the film

easier to locate.

The task force also considered whether step pads used inside containment could

block the strainers. The step pads are used to control contamination at exits

from radiological control areas inside containment and are taped to the floor

with yellow and magenta duct tape. The licensee does not consider it likely

that the step pads would be dislodged during a containment spray actuation;

however, to minimize this possibility, the radiation department removed step

pads not required for continuing work.

Browns Ferry

Browns Ferry uses a BWR with a Mark I Type containment that consists of a

steel drywell and toroidal suppression pool. Divers inspecting inside the

Unit 2 torus found pieces of paper towel and tape in the torus and on the

strainers. The licensee cleaned the torus and strainers of the paper towel

and tape, removing about 1 square meter [11 square feet] of material. The

total surface area of the four strainers is 3.7 square meters [40 square

feet]. If all of the material had become deposited on the strainers it would

have blocked about 25 percent of the strainer surface area. From videotape, about 15 percent of one of the two strainers examined was actually blocked

under normal operating and test conditions. The licensee calculated that the

strainers could be blocked up to 65 percent and still allow adequate core

cooling flow.

The licensee determined that material may enter the torus through any of three

ways: (1) personnel accessways, (2) vacuum breaker vents, or (3) the torus

downcomer vents inside containment. The licensee plans to place covers over

the vacuum breaker vents and the torus downcomer vents during maintenance

activities in those areas. Regarding the personnel accessways, the licensee

reviewed the foreign material control data from the last outage and found

weaknesses in the process. For example, an entry in the material control log

specified that a bag of towels was brought into the torus area but did not

specify the quantity of towels taken in or removed. The licensee issued a

site bulletin to alert plant personnel to the need to carefully implement

material control procedures and is reviewing the foreign material exclusion

procedures for revision.

Related Generic Communications

In NRC Bulletin 93-02 and Supplement 1, "Debris Plugging of Emergency Core

Cooling Suction Strainers," the staff discussed the potential for containment

sump screens and emergency core cooling strainers to become blocked by fibrous

material from piping insulation or air filters. The staff requested licensees

to identify sources of fibrous materials and to take immediate compensatory

actions to ensure the functional capabilities of affected safety systems. In

NRC Information Notice 93-34 and Supplement .1,"Potential for Loss of

Emergency Cooling Function Due to a Combination of Operational and Post-LOCA

Debris in Containment," the NRC staff discussed the problem of emergency core

II 1 .

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IN 94-xx

December xx, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Dave Skeen, NRR

(301) 504-1174 Joseph Birmingham, NRR

(301) 504-2829

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IN 95-06 January 25, 1995 cooling systems becoming blocked by a combination of operational and

postaccident debris including paint flakes, dirt and corrosion products, and

fibrous material from any source. In NRC Information Notice 94-57, 'Debris in

Containment and the Residual Heat Removal System," the staff discussed

additional examples of debris blockage of emergency core cooling systems.

These communications highlighted the need to consider dirt and debris and

fibrous material as sources of material capable of blocking containment sump

screens or emergency core cooling strainers.

This information notice discusses the potential for materials such as tape, labels, plastic film, and paper or cloth products intentionally brought inside

containment to collect on screens and strainers and block core cooling

systems.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Joseph L. Birmingham, NRR

(301) 504-2829 Richard M. Lobel, NRR

(301) 504-2865 Attachment:

List of Recently Issued NRC Information Notices

AA, XJ# 6

Attachment

IN 95-06 January 25, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

95-05 Undervoltage Protection 01/20/95 All holders of Construction

Relay Settings Out of Permits for nuclear power

Tolerance Due to Test reactors.

Equipment Harmonics

95-04 Excessive Cooldown and 01/19/95 All holders of OLs or CPs

Depressurization of the for nuclear power reactors.

Reactor Coolant System

Following a Loss of

Offsite Power

95-03 Loss of Reactor Coolant 01/18/95 All holders of Ols or CPs

Inventory and Potential for nuclear power reactors.

Loss of Emergency Mitiga- tion Functions While in

a Shutdown Condition

95-02 Problems with General 01/17/95 All holders of OLs or CPs

Electric CR2940 Contact for nuclear power reactors.

Blocks in Medium-Voltage

Circuit Breakers

95-01 DOT Safety Advisory: 01/04/95 All U.S. Nuclear Regulatory

High Pressure Aluminum Commission licensees.

Seamless and Aluminum

Composite Hoop-Wrapped

Cylinders

94-90 Transient Resulting in a 12/30/94 All holders of OLs or CPs

Reactor Trip and Multiple for nuclear power reactors.

Safety Injection System

Actuations at Salem

94-89 Equipment Failures at 12/28/94 All U.S. Nuclear Regulatory

Irradiator Facilities Commission irradiator

licensees.

94-88 Inservice Inspection 12/23/94 All holders of OLs or CPs

Deficiencies Result in for pressurized water

Severely Degraded Steam reactors.

Generator Tubes

OL - Operating License

CP = Construction Permit

IN 95-06 January 25, 1995 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

op¶IAn Ad by Bean K.Grimes

rrianr . Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Joseph L. Birmingham, NRR

(301) 504-2829 Richard M. Lobel, NRR

(301) 504-2865 Attachment:

List of Recently Issued NRC Information Notices

• See revious concurrence

OFFICE OECB:DOPS SCSB:DSSA C/SCSB:DSSA D/DSSA:NRR

NAME DSkeen* RLobel* RBarrett* GMHolahan*

DATE 12/05/94 12/13/94 12/13/94 12/22/94 OFFICE ADM:PUB OECB:DOPS SC/OECB:DOPS OECB:DOPS

NAME JMain* JBirmingham* RDennig* RKiessel*

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IN 95-06 January 25, 1995 If

This information notice requires no specific action or written response.

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

nrrtinT1 ,ned byBrlan K.Grimes

Pri an K.'Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

, Technical contacts: Joseph L. Birmingham, NRR

(301) 504-2829 Richard M. Lobel, NRR

i (301) 504-2865 Attachment:

List of Recently Issued NRC Information Notices

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IN 95-XX

January xx, 1995 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Joseph L. Birmingham, NRR

(301) 504-2829 Richard M. Lobel, NRR

(301) 504-2865

• See previous concurrence

OFFICE OECB:DOPS SCSB:DSSA C/SCSB:DSSA D/DSSA:NRR

NAME DSkeen* RLobel* RBarrett* GMHolahan*

DATE 12/05/94 12/13/94 12/13/94 12/22/94 OFFICE ADM:PUB OECB:DOPS SC/OECB:DOPS OECB:DOPS

NAME JMain* JBirmingham* RDennig* WRKessel*

DATE 12/05/94 12/05/94 12/22/94 12/22/94 OFFICE C/OECB:DOPS D/DOPS _

NAME AChaffee* BGrimes

DATE 12/27/94 01/ /95 401 OFFICIAL RECORD COPY

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IN 94-xx

December xx, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

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Technical contacts: Dave 5Aeeri7T4RR

( 4 4-1174 , I

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(301) 504-2865 DOCUMENT NAME: S:\DOPSSEC\DBRISIN.JLB

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NAME DSkeen* RLobel* RBarrett* GMHolahan*

DATE 12/05/94 1113/94 1 212/13/94 12/22/94 OFFICE ADM:PUB OECB:DOPS SC/OECB:DOPS OECB:DOPS

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NAME AChaffee* BGrimes (1k

DATE 12/27/94 12/ /94 OFFICIAL RECORD COPY

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IN 94-xx

December xx, 1994 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: Dave Skeen, NRR

(301) 504-1174 Richard Lobel, NRR

(301) 504-2865

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• See previous concurrence

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