Information Notice 1992-14, Uranium Oxide Fires at Fuel Cycle Facilities

Uranium Oxide Fires at Fuel Cycle Facilities

ML031200616
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:	02/21/1992
From:	Cunningham R NRC/NMSS/IMNS
To:
References
IN-92-014, NUDOCS 9202190037
Download: ML031200616 (11)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555 February 21, 1992 NRC INFORMATION NOTICE 92-14: URANIUM OXIDE FIRES AT. FUEL CYCLE FACILITIES

Addressees

All fuel cycle and uranium fuel research and development licensees.

Purpose

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

notice to alert addressees to the potential for fires involving uranium dioxide

(UO2 ) powder at various stages of transfer and conversion. 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 new NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

In licensed fuel-fabrication facilities, there have been one recent and several

past incidents of fires involving uranium at various stages of oxidation. The

circumstances of two of them are described below in some detail.

Incident 1:

In the most recent incident, a fire was discovered, in a fuel-fabrication

facility, involving a hood, hopper, and feed-screw assembly, which was

being used to transfer calciner drop powder (uranium oxide) to a nitric

acid dissolver tank. (See Figure 1.) According to a report submitted by

the licensee, an operator had started to feed a batch of the powder into

the dissolver tank when the feed-screw of the Model 608 Accu-Rate feeder

stopped. The operator reversed the screw and tapped on the tube-shaped

nylon screw-housing, to free the screw. At this time, he observed smoke

and sparks coming out of the equipment below the hood. A small crack in

the vinyl side of the feeder hopper, apparently the result of contact

with the hot powder inside the hopper, was also noticed. The operator

and other employees then donned full-face respirators and removed

approximately 18 kg of the powder, leaving about 2 kg of powder that

could not be removed, in the screw-housing. Meanwhile, the small crack

on the side of the hopper had developed into a baseball-sized hole, spilling some powder onto a platform below. The employees cleaned up the

spilled powder. Assuming that the incipient fire had been extinguished, the employees then left the area.

92029037

_/o

AA 'VIA ajit eq o32 ra Ads

Dik

111.92-14 February 21, 1992 Approximately one hour later, fire alarm bells sounded throughout the plant, and the source of the fire was determined to be the same hood and feeder

assembly that the employees had been working on. When plant emergency team

members, dressed in protective clothing and using self-contained breathing

apparatuses, entered the room, they found the visibility reduced to about

1 or 2 feet, because of the heavy smoke. Using portable dry chemical and

carbon dioxide fire extinguishers, they extinguished the fire within 15 minutes of the alarm bells sounding.

All components of the hood and the Accu-Rate feeder that were made of

combustible material (e.g., the nylon feed tube, vinyl hopper, rubber parts

of a valve, and "Lexan" faces of the hood) were consumed by the fire. The

primary stage of the high-efficiency particulate air (HEPA) filter for the

room was loaded with soot, and the pre-filter was burnt. The fire alarm

bells stopped ringing after about 3 minutes, as the alarm circuitry in the

room was damaged by the fire. This confused some employees, who could not

tell whether the emergency was over.

The incident exposed a weakness in the emergency communications system

between the licensee and the local city fire department. Shortly before

the incident, the facility had tested a newly installed extension of its

fire alarm system, in conjunction with the fire department. Even though

the facility had notified the fire department that the test was over, the

fire department mistook the alarm, which came in about 18 minutes later, to

be merely a continuation of the test. A 911 call was needed to alert them

of the real emergency. Precious minutes were lost. Fortunately, by the

time the fire department arrived, the plant emergency team had suppressed

the fire.

In other observations, some employees thought that the alarm bells in some

areas were not loud enough. Voice communications over the public address

system were misunderstood by some employees and not heard by others, especially in the office areas.

The cause of the fire is believed to be the oxidation of the calciner drop

powder consisting principally of uranium dioxide (U02), but also including

other unstable oxides of uranium, which could further oxidize at elevated

temperatures. The friction of the feed-screw sliding on the powder or on

the nylon tube, which could have been warped, could conceivably have

contributed to heating the powder.

Incident 2:

In another incident, at another nuclear fuel-fabrication facility, a fire

was reported to have occurred in a slugger press containment housing. In

this configuration, uranium oxide powder, following a blending process, was gravity-fed from a second floor hammermill baghouse through a 4-inch

diameter x 6-foot long "Viton" hose to a first floor slugger press. The

Viton hose was connected to the slugger press shuttle by a "Neoprene"

boot. The slugger press shuttle area, including the Viton hose and the

IN 92- 14 February 21, 1992 Neoprene boot, was enclosed by the containment housing, which had two

Lexan panels for access to the shuttle area. Containment ventilation was

provided through primary and secondary HEPA filters and a water scrubber

before exhausting to the environment.

In this incident, the operator noticed that the granulator downstream of

the slugger was not discharging powder. Apparently, this was not an

unusual occurrence, and he started to arrange for replacement of the

granulator screen, as was the normal practice. He then noticed a fire in

the slugger housing. The ventilation system smoke detector had by that

time sensed the fire and alarm bells were sounding. Employees extinguished

the fire within minutes using portable carbon dioxide fire extinguishers.

All of the combustible elements in the containment between the hammermill

and the slugger press (e.g., the Viton hose and the Neoprene boot, as well

as the Lexan parts of the containment housing) were consumed by the fire.

The primary HEPA filters were extensively damaged. The secondary filters, however, were intact. In this case, also, heat generated by oxidation of

the powder, which ignited the Neoprene boot, was judged to be the cause of

the fire.

In other incidents, dating back to 1977, several fires involving calciner

discharge lines and at least one involving a hammermill hood have been reported.

In all cases, the oxidizing uranium powder was believed to be the source of

ignition, and combustible materials, such as transfer hoses and boots, provided

the fuel. All the fires were promptly extinguished.

Discussion

It has been common experience that unstable uranium oxide feed material

(comprised mostly of U02, with a few other oxide forms present) in granulated

form and in contact with oxygen undergoes exothermic oxidation-reactions. In

some cases, the heat generated by the reactions ignites combustible elements

of the transfer passages or other powder-handling equipment (e.g., hoses, boots, etc.), which then contribute fuel to the fire. The fires described above have

this commonality of cause and effect. -

The fuel fabrication process generates several oxides of uranium. The final

and most stable oxide is U02. The literature on uranium chemistry describes

oxidation reactions that are complex, with their rates, heat evolution, and

final products depending on several parameters, but most importantly on the

fineness of the powder and the temperature. Indeed, according to one author*,

normally stable U02 may-be pyrophoric or oxidize rapidly even at room

temperatures when in very fine powder form (specific surface area >10 m2 /g).

Coarser powders, as is more commonly the case, .may require elevated temperatures

(>300 0 C) to oxidize. The account of the most recent fire suggests that elevated

temperatures may have been generated by the Accu-Rate feed-screw binding on its

nylon housing. -Friction of the granulated material in motion may also have

generated heat that raised the temperature.

• Cordfunke, E.H.P., The Chemistry of Uranium, Elsevier Publishing Company, 1969.

IN 92-14 February 21, 1992 Since, by the very nature of the manufacturing process, unstable uranium powder

must be handled, certain preventive measures should be taken in order to reduce

the potential for fires; and many of these have been adopted at licensed

facilities. They are:

1. Limit the type of feed to stable powder whenever possible.

2. Store unstable powder in closed metal containers.

3. Replace the combustible components of powder-transfer lines and of

equipment, such as the Accu-Rate feeder, with components made of

noncombustible materials, as far as practicable.

4. Require an operator to be present when a process is under way, and improve

visibility around vulnerable equipment.

5. Incorporate fire safety of vulnerable equipment in the operator training

program, including use of portable fire extinguishers.

6. Implement a preventive maintenance program for vulnerable equipment.

Periodic inspection may alert the operator to telltale signs of

overheating.

Additionally, the following measures for upgrading the fire detection, alarm, and suppression systems may be considered:

1. Install fire detectors in hoods and equipment exhaust ducts. These

detectors should be connected to a central panel, which is continuously

supervised.

2. Check alarm system wiring for vulnerability to fire and reroute, if

necessary and feasible. Implement a manual restart procedure, if alarm

circuitry is partially disabled and the alarm stops.

3. Upgrade the alarm system and public address system for audibility, if

necessary.

4. Add visible alarm signals in noisy areas.

5. Install carbon dioxide total flooding or local application system in

equipment enclosure. For use and limitations of such systems, see

NFPA-12, "Standard on Carbon Dioxide Extinguishing Systems," published by

the National Fire Protection Association. This should not preclude the

availability of portable fire extinguishers of both carbon dioxide and dry

chemical types.

Some lessons on emergency communications may be learned from Incident 1 above.

Some protocol should be established between the facility and the offsite fire

department so that emergency calls are not misunderstood. Licensees should

consider reviewing this information notice with their local fire department.

The public address system announcement of an emergency and related directives

IN 92-14 February 21, 1992 should follow standard wording that is familiar to all employees and minimizes

misunderstandings.

Fuel cycle licensees should review the Branch Technical Position (BTP) on Fire

Protection for Fuel Cycle Facilities, published in the Federal Register

(54 FR 11590-98) dated March 21, 1989. Licensees should examine their

facilities, procedures, and records to assure that the stipulations of the BTP

are met or exceeded.

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 regional office.

Richard E. Cunningham, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Amar Datta, NMSS

(301) 504-2536 Charles H. Robinson, NMSS

(301) 504-2576 - . I

.

Attachments: 'k" /

1. Figure 1

2. List of Recently Issued NRC Information Notices

3. List of Recently Issued NMSS Information Notices

IN 92-14 February 21, 1992 should follow standard wording that is familiar to all employees and minimizes

misunderstandings.

Fuel cycle licensees should review the Branch Technical Position (BTP) on Fire

Protection for Fuel Cycle Facilities, published in the Federal Register

(54 FR 11590-98) dated March 21, 1989. Licensees should examine their

facilities, procedures, and records to assure that the stipulations of the BTP

are met or exceeded.

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 regional office.

Richard E. Cunningham, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Amar Datta, NMSS

(301) 504-2536 Charles H. Robinson, NMSS

(301) 504-2576 Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

3. List of Recently Issued NMSS Information Notices

Editor/NMSS

EKraus

1/24/92

• - See previous concurrence

OFC :IMUF :IMUF :IMUF :IMUF :IMSB :IMOB :IMNS

___________________________________________

NAME:ADatta/mh :CRobinson :VTharpe :GHBidinger:JHickey :KRamsey :JGreeves :

___________________________________________

DATE:1/13/92* :1/13/92* :1/14/92* :1/16/92* :2/06/92*:2/06/92* :2/11/92*

OFC :IMNS -e

NAME:nEunnfngham:

DATE:2/11/92*

OFFICIAL RECORD COPY

DOCUMENT NAME: IN 92-14

IN 92- February , 1992 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 regional office.

Richard E. Cunningham, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Amar Datta, NMSS

(301) 504-2536 Charles H. Robinson, NMSS

(301) 504-2576 Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

3. List of Recently Issued NMSS Information Notices

DISTRIBUTION:

See attached checklist

IMUF r/f

IMSB r/f

IMOB r/f

IMNS r/f

Editor/NMSS

EKraus

1/24/92

• - See previous concurrence

OFC :IMUF :IMUF :IMUF :IMUF :I B :IMOS: MNSS t Lb

NAME:ADatta/mh :CRobinson :VTharpe :GHBidinger:Jlkey :KRamsey :JG eves

_ - - - - - - - - - - - -_ __ __ _ _ _ _ _ __ _ - - -_ _ _ _ _ _ - - - - - _ _ _ __ _ _ _ ---------------

_ _- --- -----

DATE:1/13/92* :1/13/92* :1/14/92* :1/16/92* :21(192 :2/1i/92 :2/ 2 N: Cunnngham:

DATE:2//1/92 OFFICIAL RECORD COPY

AD/INFORMATION NOTICE

IN 92 (inso .Januaty 1~992

-, 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 regional office.

Richard E. Cunningham, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Amar Datta, NMSS

(301) 504-2536 Charles H. Robinson, NMSS

(301) 504-2576 Attachments:

1. Figure 1

2. List of Recently Issued NRC Information Notices

3. List of Recently Issued NMSS Information Notices

AD/INFORMATION NOTICE

set. dAo*

'TrAS1 4$

I0Js r/[

V*0a~ rip

674@w'/1KMS5

.1:f /1z- OFC:I IMUF:. -a IMUF: I

NAME:A*41tataih: CRobinson: VT e6tidinger:

DATE:1/Jf /92: 1/i3/92: 1/\'/92: 1/7(192:

OFC:IMSB: DD/IMNS: D/IMNS:

______________________________________________________________________________

NAME:JHickey: JGreeves: RCunningham:

______________________________________________________________________________

DATE:1/ /92: 1/ /92: 1/ /92:

OFFICIAL RECORD COPY

to C+ C7 l pa I

a01 I-

O CD41 V,

I-

UD

Figure 1. Uranium oxide feeder assembly.

Attachment 2 IN 92-14 February 21, 1992 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

92-11 Soil and Water Contamina- 02/05/92 All uranium fuel fabrica- tion at Fuel Cycle Facil- tion and conversion facil- ities ities.

92-10 Brachytherapy Incidents 01/31/92 All Nuclear Regulatory Com- Involving Iridium-192 Wire mission (NRC) licensees

Used in Endobronchial authorized to use

Treatments iridium-192 for brachy- therapy; manufacturers and

distributors of iridium-192 wire for use in brachy- therapy.

92-08 Revised Protective Action 01/23/92 All fuel cycle and materi- Guidance for Nuclear Inci- als licensees authorized

dents to possess large quanti- ties of radioactive materi- ial.

91-86 New Reporting Requirements 12/27/91 All licensees authorized

for Contamination Events at to use byproduct materials

Medical Facilities for human use.

(10 CFR 30.50)

91-84 Problems with Criticality 12/26/91 All Nuclear Regulatory

Alarm Components/Systems Commission (NRC) fuel

cycle licensees, interim

spent fuel storage licens- ees, and critical mass

licensees.

91-71 Training and Supervision 11/12/91 All NRC medical licensees.

of Individuals Supervised

by an Authorized User

91-66 (1) Erroneous Data in 10/18/91 All fuel cycle licensees,

"Nuclear Safety Guide-, critical mass licensees, TID-7016, Revision 2," interim spent fuel storage

(NUREG/CR-0095, ORNL/ licensees, and all holders

NUREG/CSD-6 (1978)) and of operating licenses or

(2) Thermal Scattering construction permits for

Data Limitation in the test, research, and nuclear

Cross-Section Sets Provided power reactors.

with the KENO and SCALE Codes

Attachment 3 IN 92-14 February 21, 1992 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

92-02, Relap5/Mod3 Computer Code 02/18/92 All holders of OLs or CPs

Supp. 1 Error Associated with the for nuclear power reactors.

Conservation of Energy

Equation

92-13 Inadequate Control Over 02/18/92 All holders of OLs or CPs

Vehicular Traffic at for nuclear power reactors.

Nuclear Power Plant Sites

92-12 Effects of Cable Leakage 02/10/92 All holders of OLs or CPs

Currents on Instrument for nuclear power reactors.

Settings and Indications

92-11 Soil and Water Contamina- 02/05/92 All uranium fuel fabrica- tion at Fuel Cycle Facil- tion and conversion facil- ities ities.

92-10 Brachytherapy Incidents 01/31/92 All Nuclear Regulatory Com- Involving Iridium-192 Wire mission (NRC) licensees

Used in Endobronchial authorized to use

Treatments iridium-192 for brachy- therapy; manufacturers and

distributors of iridium-192 wire for use in brachy- therapy.

92-09 Overloading and Subsequent 01/30/92 All holders of OLs or CPs

Lock Out of Electrical for nuclear power reactors.

Buses During Accident

Conditions

92-08 Revised Protective Action 01/23/92 All fuel cycle and materi- Guidance for Nuclear Inci- als licensees authorized

dents to possess large quanti- ties of radioactive materi- ial.

OL = Operating License

CP = Construction Permit