Information Notice 1994-15, Radiation Exposures During an Event Involving a Fixed Nuclear Gauge

Radiation Exposures During an Event Involving a Fixed Nuclear Gauge

ML031060618
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:	03/02/1994
From:	Paperiello C NRC/NMSS/IMNS
To:
References
IN-94-015, NUDOCS 9402240194
Download: ML031060618 (8)

K>

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555 March 2, 1994 NRC INFORMATION NOTICE NO. 94-15: RADIATION EXPOSURES DURING AN EVENT

INVOLVING A FIXED NUCLEAR GAUGE

Addressees

All U.S. Nuclear Regulatory Commission licensees authorized to possess, use, manufacture, or distribute industrial nuclear gauges.

PurDose

NRC is issuing this information notice to alert addressees to events, involving industrial gauges, that resulted, or may have resulted, in

unnecessary radiation exposure to members of the public and licensee

personnel. It is expected that recipients will review the information for

applicability to their operation and consider action, as appropriate, to avoid

similar problems. However, suggestions contained in this information notice

are not new NRC requirements; therefore, no specific action nor written

response is required.

DescriDtion of Circumstances

A recent incident occurred at a glass factory where a level gauge with

approximately 185 gigabecquerels (5 curies) of cesium-137 was subjected to a

severe heat environment that resulted in the loss of lead shielding, producing

a high radiation dose rate near the source housing. Licensees were alerted to

similar incidents in Information Notice No. 81-37 (see Attachment 1).

The glass manufacturing company (an NRC licensee) informed NRC on August 23,

1993, that lead shielding melted from one of the level gauges that was mounted

on the exterior surface of a glass furnace. The licensee believed that the

damage occurred when it lost electrical power for approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> on

Saturday, August 21, 1993, and the glass furnaces were operated using natural

gas, which caused higher than normal temperatures. During the outage, an

employee noticed that some lead had melted and accumulated on a mounting

bracket adjacent to a level-measuring nuclear gauge; however, the employee did

not notify the facility Radiation Safety Officer (RSO) at that time. The -

following Monday, the same employee noticed more lead on the mounting bracket

and other adjacent areas. The RSO was then notified, who restricted access to

the area.

The lead melt was apparently caused by intense heat emanating through

refractory board covering an opening in the furnace wall adjacent to the

source housing. It was later determined that this opening had been in the

furnace wall for some time, to be used for another type of measuring device.

However, on this occasion when the device was not in use, the opening was

9402240194 PW C t E- o je ll-,

--IN 94-15 March 2, 1994 covered with refractory board instead of being closed with the original

refractory brick. Radiation surveys performed by the licensee and a

manufacturer's representative revealed an exposure rate of 1.29 X 10 s C/(kg- hr) at 2.44 meters (50 mR/hr at 8 feet) and 5.16 X 10 C/(kg-hr) at 1.22 meters (200 mR/hr at 4 feet) from the source housing. The representative

estimated the highest exposure rate at the surface of the source housing to be

7.74 X 10' C/(kg-hr) (3000 mR/hr). He indicated that the shutter block of

this device might be melted, and that half of the lead might no longer be

contained in the source housing. This particular device contained a nominal

185 gigabecquerels (5 curies) of cesium-137, and between 86 and 91 kilograms

(190 and 200 pounds) of lead shielding. Although there was no facility or

personnel contamination, since the cesium-137 source did not leak, dose

equivalent calculations indicated that one Individual may have received

approximately 2 mSv (200 mrem) to the whole body. Other individuals working

in the vicinity (about 34 people) received lower doses.

The major causes of the incident were: 1) the licensee did not take into

consideration the effect of extreme heat on the source housing before removing

the refractory brick; and 2) the licensee failed to follow its emergency

procedures by not immediately notifying the RSO when the leaking lead was

first discovered. This contributed to delays in establishing appropriate

radiological controls to minimize radiation exposure to personnel.

Discussion

Under normal working conditions, these gauges are designed and can be operated

without problems related to radiological safety. Operational history has

shown that many devices will also survive severe conditions such as fires and

explosions, but there are limitations on the source housing. A common factor

in incidents described in this information notice and within IN 81-37 is the

impact that modification of a gauge's environment has on its safety and

integrity. It is important that licensees consider the effects on nuclear

gauges when changes are made to the gauge's environment. Individuals working

near a nuclear gauge should be aware of the potential hazard. Any changes in

gauge surroundings, or the gauge itself, need to be reviewed by radiation

safety personnel, and compared with the manufacturer's design criteria, so

that inadvertent exposure can be avoided.

• I-

"-' IN 94-15 March 2, 1994 This Information notice requires no specific action nor written response. If

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

one of the technical contacts below, or the appropriate regional office.

Carl J. Pape e o, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Judith A. Joustra, RI

215) 337-5257 Joseph E. DeCicco, NMSS

(301) 504-2067 Attachments:

1. Excerpts from Information Notice No. 81-37

2. List of Recently Issued NMSS Information Notices

3. List of Recently Issued NRC Information Notices

v Attachment 1 IN 94-15 March 2, 1994 Excerpts from Information Notice 81-37: UNNECESSARY RADIATION EXPOSURES TO

THE PUBLIC AND WORKERS DURING EVENTS INVOLVING THICKNESS AND LEVEL MEASURING

DEVICES, dated December 15, 1981.

Case 1: An NRC licensee was closing a facility in Oklahoma City, Oklahoma, and had sold a trailer containing a mounted measuring device (Tube Wall

caliper) for determining pipe wall thickness. Since the device contained a

55.5-gigabecquerel (1.5-curie) cesium-137 source and the new owner had not yet

obtained a license to possess the radioactive source, the licensee removed the

device from the trailer before the new owner took possession. During removal

of the device (which was performed by an unauthorized user), the radioactive

source was inadvertently released from its shielded position in the device and

fell to the trailer floor. The dismounting of the device was performed

without benefit of a survey meter or personnel monitoring equipment. The

radiation dose to the individual may have been as high as 6 mSv (600 mrem).

Subsequently, the new owner had the trailer towed to Houston, Texas, with an

interim stop for tow truck engine repair in Norman, Oklahoma. The driver, who

was not aware of the presence of the radioactive source, waited near the

trailer for approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. He may have received a radiation dose as

high as 0.014 Sv (1.4 rem). The next day, the licensee found that the source

was missing from the measuring device. Local health authorities performed a

search using radiation detection equipment along the highway route between

Oklahoma City and Houston. The source was found lodged on a bridge support

structure near Lewisville, Texas.

The major causes of the event were: (1)the licensee failed to employ an

authorized user to remove the device; and (2)the unauthorized user failed

to make a radiation survey.

Case 2: A cooler in an iron ore pellet plant was shut down for repairs on

March 30, 1981. On that day, the shutter mechanism of a level control device, which contained a nominal 370-gigabecquerel (10-curie) cesium-137 sealed

source, was locked in the closed position. Radiation surveys performed at

that time indicated that the source appeared to be properly shielded. After a

cooldown period, workmen entered the cooler on April 3, 1981, to replace

refractory material on the cooler walls. On April 7, licensee personnel

discovered that there were radiation levels in excess of 100 millirem per hour

within the cooler (later determined to be as high as 0.022 Sv (2.2 rem) per

hour, where the radiation beam entered the cooler). It was determined that

several individuals had been exposed to a radiation beam from the source

during the working days between April 3 and 7, 1981. The device source holder

was removed from its mounting, and licensee personnel found that the lead

shielding in the shutter had melted and drained from the shielded location.

This rendered the shielding integrity of the shutter useless.

V Attachment 1 IN 94-15 March 2, 1994 Investigation showed that 17 licensee personnel and 14 contractor personnel

had entered the cooler between April 3 and 7, 1981. The calculated radiation

exposures received ranged from 1.4 to 30 mSv (140 to 3000 mrem). During the

repairs, the pellet cooler area was considered an unrestricted area. It is

estimated that 14 of the 31 individuals exposed may have received whole-body

dose equivalent in excess of 5 mSv (500 mrem). No health effects were

observed or would be expected from these exposures.

The event occurred because a hole had been cut in the side of the cooler to

reduce shielding and allow more effective operation of the cesium-137 source

in the device. During recent efforts to increase production, the pressure of

the air forced into the cooler had been increased as a means of accelerating

the cooling of the pellets. As a result, hot gases may have been forced out

of the aperture in the cooler wall at the location of the source holder. The

temperature of the pellets entering the cooler is about 1300 OC (2400 OF),

considerably higher than the melting point of lead. The heat reaching the

device was sufficient to melt the aluminum alloy dust cover over the device

shutter mechanism and the lead in the shutter, thereby allowing a radiation

beam to escape the device. In addition, the licensee's survey failed to

determine that the radioactive source was not safely shielded.

K> Ativchment 2 IN 94-15 March 2, 1994 Page I of I

LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-09 Release of Patients with 02/03/94 All U.S. Nuclear Regulatory

Residual Radioactivity Commission medical

from Medical Treatment and licensees.

Control of Areas due to

Presence of Patients Con- taining Radioactivity

Following Implementation

of Revised 10 CFR Part 20

94-07 Solubility Criteria for 01/28/94 All byproduct material and

Liquid Effluent Releases fuel cycle licensees with

to Sanitary Sewerage under the exception of licensees

the Revised 10 CFR Part 20 authorized solely for

sealed sources.93-100 Reporting Requirements 12/22/93 All U.S. Nuclear Regulatory

for Bankruptcy Commission licensees.

93-80 Implementation of the 10/08/93 All byproduct, source, and

Revised 10 CFR Part 20 special nuclear material

licensees.

93-77 Human Errors that Result 10/04/93 All nuclear fuel cycle

in Inadvertent Transfers licensees.

of Special Nuclear Material

at Fuel Cycle Facilities

93-69 Radiography Events at 09/02/93 All holders of OLs or CPs

Operating Power Reactors for nuclear power reactors

and all radiography

licensees.

93-60 Reporting Fuel Cycle and 08/04/93 All fuel cycle and materials

Materials Events to the licensees.

NRC Operations Center

93-50 Extended Storage of 07/08/93 All licensees authorized

Sealed Sources to possess sealed sources.

v> Aivchment 3 IN 94-15 March 2, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-14 Failure to Implement 02/24/94 All holders of OLs or CPs

Requirements for Biennial for nuclear power and non- Medical Examinations and power reactors and all

Notification to the NRC licensed reactor operators

of Changes in Licensed and senior reactor

Operator Medical Conditions operators.

92-36, Intersystem LOCA 02/22/94 All holders of OLs or CPs

Supp. 1 Outside Containment for nuclear power reactors.

94-13 Unanticipated and Un- 02/22/94 All holders of OLs or CPs

intended Movement of for nuclear power reactors.

Fuel Assemblies and

Other Components due to

Improper Operation of

Refueling Equipment

94-12 Insights Gained from 02/09/94 All holders of OLs or CPs

Resolving Generic for nuclear power reactors.

Issue 57: Effects of

Fire Protection System

Actuation on Safety- Related Equipment

94-11 Turbine Overspeed and 02/08/94 All holders of OLs or CPs

Reactor Cooldown during for nuclear power reactors.

Shutdown Evolution

94-10 Failure of Motor-Operated 02/04/94 All holders of OLs or CPs

Valve Electric Power for nuclear power reactors.

Train due to Sheared or

Dislodged Motor Pinion

Gear Key

94-09 Release of Patients with 02/03/94 All U.S. Nuclear Regulatory

Residual Radioactivity Commission medical

from Medical Treatment and licensees.

Control of Areas due to

Presence of Patients Con- taining Radioactivity

Following Implementation

of Revised 10 CFR Part 20

OL - Operating License

CP = Construction Permit

IN 94- February , 1994 This information notice requires no specific action nor written response. If

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

one of the technical contacts below, or the appropriate Reglonal office.

Caper rector

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Judith A. Joustra, Region I

(215) 337-5257 Joseph E. DeCicco, NMSS

(301) 504-2067 Attachments:

1. Excerpts from Information Notice No. 81-37

2. List of Recently Issued NMSS Information Notices

3. List of Recently Issued NRC Information Notices

DISTRIBUTION: jvw64-vr7 IMOB r/f IMNS r/f NMSS r/f

OFC IMOPB 6 IMl IS:D

IMND

NAME JDeCi Q C (s E h CPape iello

DATE I0/13 /94 C = COVER

4/ 94 E a COVER

X iE1994 ENCLOSURE N = NO COPY

/94 OFFICIAL RECORD COPY: G:GAUGE IN.JED