Information Notice 1986-43, Problems with Silver Zeolite Sampling of Airborne Radioiodine

Problems with Silver Zeolite Sampling of Airborne Radioiodine

ML031250053
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	06/10/1986
From:	Jordan E NRC/IE
To:
References
IN-86-043, NUDOCS 8606040009
Download: ML031250053 (6)

SSINS No.: 6835 IN 86-43 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 June 10, 1986 IE INFORMATION NOTICE NO. 86-43: PROBLEMS WITH SILVER ZEOLITE SAMPLING

OF AIRBORNE RADIOIODINE

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This information notice is provided to alert licensees of the potential hazards

associated with sampling for radioiodines with silver zeolite (AgZ) in the

presence of hydrogen (H2) and oxygen (02). It is expected that recipients will

review the information for applicability to their radiation monitoring and

survey program and consider actions, if appropriate, to preclude similar

problems at their facility. However, suggestions contained in this notice do

not constitute NRC requirements; therefore, no specific action or written

response is required.

Description of Circumstances

During a recent surveillance test, the LaCrosse Boiling Water Reactor (BWR)

experienced a hydrogen ignition while sampling the plant offgas system. The

high H; concentration in the offgas system was caused by a faulty H2 -02 recombiner. An excerpt from the NRC regional followup inspection report in

Attachment 1 gives a detailed account of the event.

The licensee believes that the ignition source during this event was the AgZ

cartridge used in the .offgas sampling rig. The cartridge contained dehydrated

(less than 1% water content) AgZ. The heat of hydration released when the AgZ

absorbed moisture from the sample stream may have added enough heat to allow

catalytic recombination of H2 and 02. Catalysis also releases heat that would

have rapidly increased the temperature of the AgZ to the H2 ignition point.

Discussion:

Silver zeolite cartridges are used for sampling radioiodines in radioactive gas

mixtures. The AgZ chemically traps the iodines while letting the noble gasses

(which would interfere with subsequent radioanalysis) pass through. The

LaCrosse event highlights the following two properties of AgZ that are appar- ently not well understood by the industry.

Copies to: SWithers, YundtF Letitsch, Orser, Steele, E. Burton, E. Jordan, A. Holm, LIS, C. A. Olmstead, S. Hoag, S. Satitter, TNP:GOV REL F:NRC CHRONO,

TNP:GOV REL F:NRC IE Information Notice 86-43 PGE Action - M. H. Malmros (Due 8/12/86)

NSRD Action - M. H. Malmros

IN 86-43 June 10, 1986 1. Hydration State

The noble gas retention efficiency of AgZ is a function of its water

content (hydration). Dehydrating AgZ activates its surface, freeing-up

sites for noble gas adsorption. Data presented in NUREG/CR-3445 (March,

1985), "A Comparison of Iodine, Krypton, and Xenon Retention Efficiencies

for Various Silver Loaded Adsorption Media," show that the retention

efficiency for bound noble gas (gas not residing in the void fraction of

AgZ) of dehydrated AgZ is an order of magnitude higher than AgZ hydrated

to 9% by weight. Because AgZ is used to minimize noble gas retention and

interference, the use of dehydrated AgZ is self-defeating.

The heat of hydration can also effect AgZ's iodine retention. Heat

released, if dehydrated AgZ is used to sample humid air, increases its

temperature. This elevated temperature can reduce the retention effici- ency for iodine.

For the above reasons, when sampling for airborne radioiodine in the

presence of noble gases, use of dehydrated or activated AgZ is not

appropriate.

2. Catalytic Properties

Silver zeolite will act as a catalyst to recombine H2 and 02 into H2 0

(water). One manufacturer's study, run with 2% H2 in moderately dry (10%

humidity) air, indicated a threshold temperature at 1500 F before the

catalytic reaction becomes significant. Although the dependence of this

threshold temperature on such parameters as moisture content and H2 concentration are not known, it is assumed that higher H2 concentration

will lower the threshold temperature. This catalytic property of AgZ

makes its use in sampling from explosive or potentially explosive atmo- spheres (such as BWR offgas or waste gas storage tanks) unadvisable.

Note that for sampling the offsite environment or other onsite areas where

there is no possibility of having a significant H2 concentration, the catalytic

properties of AgZ are of no concern.

In addition to returning the offgas recombiner to an operable state, the

licensee is considering the following actions:

° using only charcoal cartridges for sampling the offgas radionuclides

o using a portable H2 analyses and checking for H2 concentration before

sampling the offgas

° using only partially hydrated (or noncatalyzing cartridges) for

post-accident sampling of stack effluents

o not using AgZ for post-accident containment sampling unless H2 concentration is less than 4 percent

IN 86-43 June 10, 1986 by this information notice.

No specific action or written response is required contact the Regional

If you have any questions about this matter, please

or this office.

Administrator of the appropriate regional office

L. Jordan, Director

" Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Technical Contacts: Roger L. Pedersen, IE

(301) 492-9524 Edward F. Williams, IE

(301) 492-7611 Attachments:

1. Hydrogen Ignition in an Offgas Sampling Rig

2. List of Recently Issued IE Information Notices

Attachment 1 IN 86-43 June 10, 1986 HYDROGEN IGNITION IN AN OFFGAS SAMPLING RIG

(Excerpted from Referenced Inspection Report, Edited Version)

On March 6, 1986, a senior health physics technician at the LaCrosse Boiling

Water Reactor set up a portable sampling system to sample particulate and

radioiodine activity in the operational offgas line both upstream and down- stream of the on-line offgas system final high-efficiency particulate air

(HEPA) filter and charcoal adsorber bank. The sampling was being conducted to

test the collection efficiency of the HEPA filter and charcoal adsorber using a

differential radionuclide concentration method.

The sampling equipment consisted of new tygon tubing, a flow meter, an aluminum

filter paper holder containing an acetate filter paper, and a dual cartridge

holder containing two plastic cartridges containing silver zeolite (AgZ). The

AgZ had been dehydrated by the manufacturer to less than 5 percent moisture.

Past sampling of the offgas line was performed using two standard 2-inch

charcoal cartridges instead of AgZ cartridges. AgZ cartridges were substituted

because they adsorb less noble gaseous activity than charcoal cartridges and, therefore, reduce sample analysis interferences.

Two minutes after starting the sampling equipment (flow rate of 0.6 cfm), the

technician noted that water droplets had formed on the inside of the tygon

tubing downstream of the filter holders. One minute later, the technician

heard a loud bang and saw a bluish flash inside the sample tubing. The techni- cian then turned off the sampling pump, isolated the sampling lines, and

inspected the sampling equipment. The tygon tubing was a burnt brown color;

the inside of the flow meter was covered with a brown-colored oil film; the

cartridge holder was hot, difficult to open, and had a burned odor when opened;

plastic parts of the zeolite filters and holder displayed some melting and were

fused; the plastic retaining screens in the zeolite holders were no longer

intact; and the HEPA filter had disintegrated.

The licensee believes that an ignition began in the sample holder and that

sufficient H2 must have been present in the sample lines to sustain an

ignition. Sufficient H2 could be present if the offgas system catalytic

recombiner, located upstream of the filters being tested, were not operating

optimally. There is no H2 monitor downstream of the catalytic recombiner. The

licensee's Radiation Protection Engineer discussed the potential of H2 and 02 recombination catalysis by AgZ at ambient temperatures with two outside sup- pliers. It was determined that dehydrated AgZ will absorb moisture from the

sample stream until it reaches hydration. During this hydration, which creates

a slightly exothermic reaction, the AgZ granules will heat up. During this

heating, additional H2 and 02 alignment with the AgZ molecules may occur, and

some controlled catalytic recombination also may occur, which may further

150 0F, the AgZ will reach its

increase the AgZ granules' temperature. At about

threshold temperature for H2 and 02 catalytic recombination. At this threshold

temperature, the AgZ may cause a rapid recombination (ignition) of H2 and 02 if

the H2 concentration is above 4 percent.0 This may rapidly generate temper- atures inside the AgZ in excess of 1065 F.

Attachment 1 IN 86-43 June 10, 1986 ignition. There were fluctua- The offgas system continued to operate after the for several hours after

tions in effluent noble gas, particulate, and halogens The licensee noted an

the ignition; however, no alert setpoint was reached.

tanks and the catalytic

increase in the temperature of the offgas storage returned to near normal

recombiner (monitored parameters). The system slowly

and particulate effluent

except that an identifiable increase in halogena possible degradation of the

remained. These remaining increases indicate

plans to inspect the

final HEPA filter and charcoal adsorber. The licensee as necessary during

filter bank for damage and replace the HEPA and charcoal

this outage.

Reference:

50-409/86003 (DRSS), March

LaCrosse Boiling Water Reactor Inspection Report No.

28, 1986.

Attachment 2 IN 86-43 June 10, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-42 Improper Maintenance Of 6/9/86 All power rector

Radiation Monitoring Systems facilities holding

an OL or CP

86-41 Evaluation Of Questionable 6/9/86 All byproduct

Exposure Readings Of Licensee material licensees

Personnel Dosimeters

86-32 Request For Collection Of 6/6/86 All power reactor

Sup. 1 Licensee Radioactivity facilities holding

Measurements Attributed To an OL or CP

The Chernobyl Nuclear Plant

Accident

86-40 Degraded Ability To Isolate 6/5/86 All power reactor

The Reactor Coolant System facilities holding

From Low-Pressure Coolant an OL or CP

Systems in BWRS

86-39 Failures Of RHR Pump Motors 5/20/86 All power reactor

And Pump Internals facilities holding

an OL or CP

86-38 Deficient Operator Actions 5/20/86 All power reactor

Following Dual Function Valve facilities holding

Failures an OL or CP

86-37 Degradation Of Station 5/16/86 All power reactor

Batteries facilities holding

an OL or CP

86-36 Change In NRC Practice 5/16/86 All power reactor

Regarding Issuance Of facilities holding

Confirming Letters To an OL or CP

Principal Contractors

86-35 Fire In Compressible Material 5/15/86 All power reactor

At Dresden Unit 3 facilities holding

an OL or CP

OL = Operating License

CP = Construction Permit