Information Notice 1999-01, Deterioration of High-Efficiency Particulate Air Filters in a Pressurized Water Reactor Containment Fan Cooler Unit

Deterioration of High-Efficiency Particulate Air Filters in a Pressurized Water Reactor Containment Fan Cooler Unit

ML031040519
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:	01/20/1999
From:	Matthews D, Teneyck E NRC/NMSS/FCSS, Office of Nuclear Reactor Regulation
To:
References
IN-99-001, NUDOCS 9901220109
Download: ML031040519 (6)

t UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 January 20, 1999 NRC INFORMATION

NOTICE 99-01: DETERIORATION

OF HIGH-EFFICIENCY

PARTICULATE

AIR FILTERS IN A PRESSURIZED

WATER REACTOR CONTAINMENT

FAN COOLER UNIT

Addressees

All holders of licenses for nuclear power, research and test reactors;

and fuel cycle facilities.

Purpose

The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice to alert addressees

to previously

unknown service life and service condition

limitations

of high efficiency

particulate

air (HEPA) filters that are used in ventilation

systems by licensees

of power, research and test reactors;

and certain fuel cycle facilites.

It is expected that recipients

will review the information

for applicability

to their facilities

and consider actions, as appropriate.

However, suggestions

contained

in this information

notice are not NRC requirements;

therefore, no specific action or written response to this notice is required.Descriotion

of Circumstances

On September

13, 1998, the operators

at Consolidated

Edison's (Con Edison's)

Indian Point 2 (IP-2) Nuclear Power Plant received a low-flow alarm on one of the five containment

fan cooler units (FCUs). Con Edison personnel

inspected

the FCU's internal components

and found that one of the HEPA filters in the bottom row had failed and clogged the fan intake screen. The FCU contains a bank of 64 HEPA filters, each 2 feet by 2 feet in size. Five other filters near the failed filter were badly damaged. To confirm the extent of the problem, Con Edison subsequently

inspected

the other 4 FCUs. One FCU had HEPA filters in which the urethane seal had pulled away from the filter frame and the filter medium had assumed an hour- glass shape. Con Edson concluded

that the problem had a potential

common-mode

failure mechanism

that could significantly

degrade both the cooling of the FCU and the filtering

by the HEPA filters.Discussion

The HEPA filters in the two affected FCUs were Series Model 8 manufactured

by Flanders Filter Corporation;

they are no longer made. The Series 8 filter consists of a square stainless steel frame and a convoluted

filter medium made of glass fibers held together by an acrylic latex binder and coated with a silicone waterproofing

agent. The filter medium is secured to all 990122 An c

IN 99-01 January 20, 1999 four sides of the filter frame by a urethane coating and, unlike many other HEPA filter designs, does not have internal stiffeners

or corrugated

separators

to support the glass fibers. These HEPA filters were installed

in 1991 and, due to being located in the normal air flow, have been in almost continuous

use since then; many other FCU designs have the filters in service only during testing or an accident.Con Edison identified

many causes contributing

to the unexpected

failure and degradation

of the HEPA filters, such as (1) excess water (from condensation

as well as carryover

from the upstream de-misters, which had plugged or partially

plugged drain lines) which Increased

filter loading and distortion, (2) inadequate

surveillance

for detecting

filter degradation

or determining

when HEPA filters should be replaced, and (3) no established

service life. A technical

report prepared for Con Edison following

testing of samples of new and used HEPA filter media provided quantitative

support for this root cause determination.

While inherent weaknesses

in the FCU design (such as having the HEPA filters in the normal flow stream) and poor preventive

maintenance

practices (such as not monitoring

the condition

of the upstream FCU de-mister

drains) were noted, previously

unknown limitations

regarding

HEPA filter service life and the effect of service conditions

were revealed.HEPA filters used in the FCUs at IP-2 are required by Technical

Specifications

to be surveillance

tested every refueling

outage. Such testing involves (1) visual inspection

in accordance

with ANSI Standard N510-1975 for indications

of filter damage (e.g., filter medium tears, cracks, or bums, and damage to seating gaskets) and excessive

dirt loading, (2) a check for filter bypass by a dioctylphthalate (DOP) aerosol efficiency

test, and (3) measurement

of air flow and differential

pressure across the filter bank. This testing does not check for evidence of current or prior media wetting. The initial qualification

testing of the HEPA filters, as specified

in Military Specification

F-51068, did subject the filter to a continuous

water spray during the resistance-to-pressure

test performed

at higher than accident condition

flows. However, the filters were not subsequently

subjected

to any type of testing to demonstrate

that they remain capable of performing

their intended function.

Consequently, loss of structural

strength and deterioration

can go undetected

and can result in failure during design-basis

conditions

when the filters will be subjected

to a much higher temperature, much higher differential

pressure and much more entrained

moisture than during normal service conditions.

Filter media testing found a significant

loss of silicone waterproofing

agent from filter media samples that had seen a long service life -up to 7 years. This reduction

allowed the filter medium to absorb water readily; little or no observable

water absorption

was observed on new filter media. As the water is absorbed, the medium expands and closes the medium filter pores. However, since the differential

pressure is typically

measured across an entire bank of filters, local water loading in one or more filters does not enable the overall differential

pressure to rise sufficiently

to disclose a problem with the HEPA filters. Moreover, a damaged or failed filter could reduce the differential

pressure across the filter bank. Water absorption

also increases

the weight of the filter medium and can weaken it. The service life of a filter is highly dependent

upon HEPA service conditions, which includes high moisture content, entrained solids In the air, and elevated temperatures.

The Department

of Energy (DOE) recently sponsored

research into HEPA filter deterioration

when several HEPA filters in a ventilation

system at the Rocky Flats Environmental

Technology

Site failed. Those filters had been in service for more than 15 years and had been repeatedly

subjected

to wetting by an upstream fire protection

deluge system test. The testing conducted involved filter media from a variety of HEPA filter manufacturers, although most manufacturers

~1-IN 99-01 January 20, 1999 use similar filter media. This research also showed significant

losses in the tensile strength of HEPA filter following

the wetting of used filters; it also showed that the tensile strength was not recovered

fully restored after drying. Further water exposures

resulted in additional

losses in filter media tensile strength.

The results of this research were publicized

at the 25th DOEINRC Nuclear Air Cleaning and Treatment

Conference.

The DOE research data cannot be used to quantify the useful life of a HEPA filter, but the data do demonstrate

that there is a finite HEPA filter life and that wetting of the filter medium reduces its strength.In response to the research findings, Con Edison replaced the filters in the two affected FCUs with new Flanders Series F & W filters that incorporate

internal stiffeners

to help support the filter medium. Con Edison has limited the service cycle of the FCU HEPA filters to 6 years and implemented

inspections

to confirm the following:

(1) the integrity

of the urethane seal between the filter medium and filter housing, (2) proper drainage from the FCU, and (3) the extent of water condensation

and/or direct wetting of the filters.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, the appropriate

regional office, or the appropriate

office of Nuclear Reactor Regulation (NRR) Project Manager.Dire r Division of Fuel Cycle Safety and Safeguards

Office of Nuclear Material Safety and Safeguards

David B. Matthews, Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: Richard S. Barkley, Region I 610-337-5065 E-Mail: rsbl@nrc.gov

John J. Hayes, NRR 301-415-3167 E-Mail: hh@nrc.gov

John P. Segala, NRR 301-415-1858 E-Mail: jpsl@nrc.gov

Jerry Carter, NRR 301-415-1153 E-Mail: tjc@nrc.gov

Bill Troskoski, NMSS 301-415-8076 E-mail: wmt@nrc.gov

Attachments:

List of Recently Issued NMSS Information

Notices List of Recently Issued NRC I foation Notices#Vdss jaflon:a- A&\1 Attachment

IN 98-45 December 15, 1998 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject- Issuance Issued to 98-45 Cavitation

Erosion of Letdown Line 12/15/98 All holders of operating

licenses Orifices Result in Fatigue Cracking of Pipe Welds for nuclear power reactors, except those that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor.98-44 Ten-year Inservice

Inspection

12110/98 (ISI) Program Update for Licensees that Intend to Implement

Risk-Informed

ISI of Piping 98-43 98-42 Leaks in the Emergency

Diesel Generator

Lubricating

Oil and Jacket Cooling Water Piping 12/04/98 All holder of operating

licenses for nuclear power reactors, except those that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor All holder of operating

licenses for nuclear power reactors, except those licensees

that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel All holders of operating

licenses for nuclear power reactors All holders of operating

licenses for nuclear power reactors, except for those who have ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel Implementation

of 10 CFR 50.55a 12/01/98 (g) Inservice

Inspection

Requirements

98-41 Spurious Shutdown of Emergency

11/20/98 Diesel Generators

from Design Oversight OL = Operating

License CP = Construction

Permit

_ 99-01 January 20, 1999 use similar filter media. This research also showed significant

losses in the tensile strength of HEPA filter following

the wetting of used filters; it also showed that the tensile strength was not recovered

fully restored after drying. Further water exposures

resulted in additional

losses in filter media tensile strength.

The results of this research were publicized

at the 25th DOE/NRC Nuclear Air Cleaning and Treatment

Conference.

The DOE research data cannot be used to quantify the useful life of a HEPA filter, but the data do demonstrate

that there is a finite HEPA filter life and that wetting of the filter medium reduces its strength.In response to the research findings, Con Edison replaced the filters in the two affected FCUs with new Flanders Series F & W filters that incorporate

internal stiffeners

to help support the filter medium. Con Edison has limited the service cycle of the FCU HEPA filters to 6 years and implemented

inspections

to confirm the following:

(1) the integrity

of the urethane seal between the filter medium and filter housing, (2) proper drainage from the FCU, and (3) the extent of water condensation

and/or direct wetting of the filters.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, the appropriate

regional office, or the appropriate

office of Nuclear Reactor Regulation (NRR) Project Manager.orig IsI'd by orig Is! 'd by Elizabeth

0. Ten Eyck, Director David B. Matthews, Director Division of Fuel Cycle Safety Division of Reactor Program Management

and Safeguards

Office of Nuclear Reactor Regulation

Office of Nuclear Material Safety and Safeguards

Technical

Contacts:

Richard S. Barkley, Region I John J. Hayes, NRR 610-337-5065

301-415-3167 E-Mail: rsbl@nrc.gov

E-Mail: jjh@nrc.gov

John P. Segala, NRR Jerry Carter, NRR 301-415-1858

301-415-1153 E-Mail: jpslnrc.gov

E-Mail: tjc~nrc.gov

Bill Troskoski, NMSS 301-415-8076 E-mail: wmt@nrc.gov

Attachments:

List of Recently Issued NMSS Information

Notices List of Recently Issued NRC Information

Notices DOCUMENT NAME: g:\TJC\HEPA2AIN.WPD

To receive a coDv of this document, indicate in the box C=Coov wlo attachment/enclosure

E=Copy with attachment/enclosure

N = No copyr \ I _[OFFICE PECI I Rl1 I PERB D:NMSS PECB I lPEC Il ['NAME J Carter* _RBarkely*

JCMiller*

_ETen Eyck* IRDennig*

JStolz* DMatthew[ DATE 1 12/23/98 l 12/24/98 1 12/28/98 1 01/11/99 I 12/24/98 1112/99 I 014/99 OFFICIAL RECORD COPY

IN 98-xx December xx, 1998 use similar filter media. This research also showed significant

losses in the tensile strength of HEPA filter following

the wetting of used filters; it also showed that the tensile strength was not recovered

fully after drying. Further water exposures

resulted in additional

losses in filter media tensile strength.

The results of this research were publicized

at the 25th DOE/NRC NuclearAir

Cleaning and Treatment

Conference.

The DOE research data cannot be used to quantify the useful life of a HEPA filter, but the data do demonstrate

that there is a finite HEPA filter life and that wetting of the filter medium reduces its strength.In response to the research findings, Con Edison replaced the filters in the two affected FCUs with new Flanders Series F & W filters that incorporate

internal stiffeners

to help support the filter medium. Con Edison has limited the service cycle of the FCU HEPA filters to 6 years and implemented

inspections

to confirm the following:

(1) the integrity

of the urethane seal between the filter medium and filter housing, (2) proper drainage from the FCU, and (3) the extent of water condensation

and/or direct wetting of the filters.Con Edison has also applied for a Technical

Specification

amendment

that would delete the requirement

for HEPA filters and the downstream

charcoal beds from the containment

FCUs.This amendment

is based on analyses that show the equipment

can be removed without significantly

affecting

the radiological

consequences

of a design-basis

loss-of-coolant

accident at IP-2.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.Elizabeth

Q. Ten Eyck, Director Jack W Roe, Acting Director Division of Fuel Cycle Safety Division of Reactor Program Management

and Safeguards

Office of Nuclear Reactor Regulation

Office of Nuclear Material Safety and Safeguards

Technical

Contacts:

Richard S. Barkley, Region I John J. Hayes, NRR 610-337-5065

301-415-3167 E-Mail: rsbl@nrc.gov

E-Mail: jh@nrc.gov

John P. Segala, NRR Jerry Carter, NRR 301-415-1858

301-415-1153 E-Mail: jps1@nrc.gov

E-Mail: tjcenrc.gov

ta~h~merS

List of Recently Issued NRC Information

Notices DOCUW NT NAME: To receive a copy of this document, Indicate In the box C=Copy w/o attachment/enclosure

E=Copy with attachmentfnclosure

N= No copy OFFICE 1IECB I I RI, Gl IPERB I JI D:NMSjz II l E it lPECB I IADDRP NAME JlFfer I Wlarke1 I CMillerNtkkETEN

EfCK I F ia9' I l6t7- L e D --98- k ilts -- I I 1..9. /OFFICIAL RE 9 COPY