Information Notice 1996-52, Cracked Insertion Rods on Troxler Model 3400 Series Portable Moisture Density Gauges

Cracked Insertion Rods on Troxler Model 3400 Series Portable Moisture Density Gauges

ML031060065
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:	09/26/1996
From:	Cool D NRC/NMSS/IMNS
To:
References
IN-96-052, NUDOCS 9609200181
Download: ML031060065 (14)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555 September 26, 1996 NRC INFORMATION NOTICE 96-52: CRACKED INSERTION RODS ON TROXLER

MODEL 3400 SERIES PORTABLE MOISTURE

DENSITY GAUGES

Addressees

All U.S. Nuclear Regulatory Commission portable gauge licensees and vendors.

Purpose

NRC is issuing this information notice to alert addressees to the potential for cracks to develop

in the insertion rod of Troxler model 3400 portable moisture density gauges. If not detected

early, the cracks may propagate, eventually leading to complete failure of the insertion rod and

release of the contained radioactive material. This notice provides information that users of

these gauges may consider to avoid crack initiation and to detect existing cracks. It is expected

that recipients will review the information for applicability to their licensed activities and consider

actions, as appropriate, to avoid similar problems. However, suggestions contained in this

information notice are not NRC requirements; therefore, no specific action nor written response

is required.

Description of Circumstances

NRC was notified of several incidents where the source cup of a Troxler model 3401 portable

moisture density gauge separated from its insertion rod, releasing the contained, nominal 333 MBq (9.0 mCi), cesium-137, sealed source. One of the users of a failed gauge contacted the

manufacturer and requested an.examination of its failed gauge and all other Troxler gauges it

possessed. The examination determined that the failure occurred in the vicinity of the weld

joining the stainless steel insertion rod and source cup and that several other gauges in the

user's possession were suspected of containing cracked rods/cups, as well. The manufacturer

recommended that the user discontinue use of all gauges suspected of being damaged until

further inspection.

Following examination of the users gauges, the manufacturer initiated an inspection and testing

program on model 3400 series gauges returned to it for disposal or repair that contained

unthreaded" (not joined with a threaded connection) source cups and insertion rods. This

included only gauges with serial numbers less than 13301. The manufacturer only examined

gauges with unthreaded" rods/cups because all gauges that were reported as having cracks

were this configuration. The manufacturer provided the following information and results from

its investigation:

235 gauges that had been returned for repair and 75 gauges that had been returned for

disposal were inspected.

9609200181 .LUb(t LiIL/

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IN 96-52 September 26, 1996 * Drop and bending tests were performed on the 75 gauges that had been returned

for

disposal to determine the force necessary to cause failure of the weld joint.

Fatigue was

not considered during the testing.

• Two of the 75 gauges returned for disposal were determined to contain a transverse

crack on the insertion rod in the weld region.

• A number of the rod/cup welds of the 235 gauges returned for repair were determined

be 'unusual, but none were determined to contain cracks. to

• The manufacturer received a report of another gauge, not included in the investigation, whose rod/cup joint had also failed completely in the field, releasing the contained

sealed source. The manufacturer suspected that the gauge had been abused

during

use, but the gauge was not available for the manufacturer to perform a full

examination.

Based on the results of its investigation, the manufacturer concluded that weld

failure is an -

unlikely event when the gauge is subjected to nornal conditions of use and

accident conditions. It also concluded that fatigue and thermal stresses would typical drop)

not be expected

to have an adverse effect on the weld joint under normal conditions. However, fatigue nor thermal testing during its investigation. there was no

Concurrent with the manufacturer's investigation, NRC contracted an independent

testing facility to examine, in detail, the failed gauge, previously examined by third-party

the manufacturer, and four other of the users model 3400 series gauges (three of which were

suspected of also

being damaged), and determine the root cause of the failure, if possible.

resulted in a number of conclusions and observations, including: This examination

• The failure resulted from an initial crack in the weld region of the insertion rod

that

progressively until it failed completely in a brittle manner, releasing the contained grew

sealed

source.

• The initial transverse crack likely resulted from the insertion rod being subjected

to a

severe bending load (possibly an impact) not sufficient to cause catastrophic

brittle

failure.

• The initial crack propagated slowly due to repeated loads during use. The

crack

extended approximately 2900 before the final brittle fracture.

• The region of crack initiation (the heat-affected zone around the weld) was very

hard, but

the weld was very soft. This differential in hardness was caused by material

selection, joint configuration, and the welding procedure, and provided a stress concentration

the region around the weld. The stress concentration made the weld area in

more

susceptible to crack initiation in a high-bending load condition.

• One of the other gauges received from the licensee was confirmed to contain

transverse crack in the region of the weld. Hardness testing indicated that a

this gauge

also contained a soft weld and a high-hardness region surrounding the weld.

In

addition, the rod/cup was constructed using the same materials and processes

as the

failed gauge.

IN 96-52 September 26, 1996 * The remaining three other gauges were undamaged, but had similar hardness

characteristics as the failed gauge.

• All gauges received for testing contained "unthreaded" rods/cups and were constructed

using the same materials and processes. The source cups on newer model 3400 series

gauges (serial numbers above 13300) are threaded to the insertion rod before joining by

welding.

• The weld configuration of the rod/cup connection Is not optimum for its intended

application, and provides a high stress concentration in the weld area. An alternate

selection of materials and joint configuration, and a post-heat treatment may have

reduced the high-hardness region, resulting in a lower stress concentration in the weld

area.

Based on the above observations and testing performed, the third-party contractor concluded

that all gauges manufactured in the same manner as the failed gauges would be susceptible to

crack initiation when subjected to a severe bending load. In addition, the contractor concluded

that a crack on this type of gauge would be expected to propagate slowly over time and could

be easily detected visually, either by using a dye penetrant evaluation technique or by observing

the weld area under magnification. The contractors visual examination without dye penetrant or

magnification indicated a potential crack in an insertion rod,' that was subsequently determined

to only be a surface feature. Therefore, visual examination should not be considered a reliable

way to identify cracks.

The figure below shows the typical configuration of a Troxler model 3400 series gauge and the

locations of the insertion rod, source cup, and weld:

Weld Source Cup

Typical Model 3400 Series Gauge

IN 96-52 September 26, 1996 In June 1996, Troxler issued a bulletin (attached) discussing the above

incidents and the results

of its investigation. The bulletin provided gauge users with three recommendations

reduce the likelihood of future'source cup detachment incidents. These on how to

included:

1. Gauges should be used in accordance with the manufacturer's instructions

operator's manual. Under no circumstances should the insertion rod found in the

ever be driven or

forced into the test material. A drill rod accessory is provided with

the gauge to prepare

a hole in the test material Into which the rod is inserted. If the user

purchases

gauge that does not include the drill rod accessory, the user should contact a used

manufacturer to obtain a replacement drill rod. the

2. Users should have the gauge and insertion rod inspected at least once

every 5 years for

unusual wear and tear.

3. Companies purchasing used gauges should require an inspection

before purchase.

Gauges involved in accidents should be inspected before further use.

Discussion

The aforementioned observations and investigations indicate that a

gauge manufactured using

the same materials, welding process, and rod/cup configuration as

those identified as'

containing cracks would be expected to be susceptible to crack initiation

when placed in a high-bending load. Cracks in the weld region of the in the weld region

insertion rods would be

expected to propagate over time, possibly leading to complete failure

contained sealed source. However, before complete failure, a crack and release of the

of

identifiable by macroscopic visual examination or dye-penetrant testing. this type should be

crack initiation could occur under other conditions not discussed here It is unknown whether

nor considered during the

testing performed by the manufacturer or the third-party contractor.

When used according to the manufacturer's instructions and recommended

crack initiation would not be expected. Users of Troxler model 3400 conditions of use, series gauges, and other

similar gauges, should always operate their devices in accordance with

the manufacturers

instructions and under the recommended conditions of use, and should

insertion rod in a bending-load condition. The bending-load force necessary never place the

was not determined during either the manufacturer's or the third-party to initiate a crack

investigations. Therefore, bending-loads on the insertion rod, other contractor's

than those encountered

during normal use, should be avoided.

The manufacturer has changed the design, materials, and manufacturing

3400 series gauges several times since their introduction. The manufacturer's process for model

contractor's investigations were limited to model 3400 series gauges and third-party

with serial numbers less

than 13301 (gauges with Nunthreaded* rods/cups and the same materials

construction). Therefore, the susceptibility to crack initiation of gauges and methods of

with "threadedn

rods/cups or with other materials of construction and welding processes

(models with serial

numbers greater than 13300) is not known. However, all failed gauges

to

numbers less than 13301. A threaded rod/cup connection may provide date have had serial

of safety even if a crack began and led to complete failure, as the an additional measure.

source cup would likely still

need to be unthreaded from the rod to release the contained sealed

source.

K>

IN 96-52 September 26, 1996 Based on the results of the manufacturers and the third-party contractor's Investigations, and

the recommendations made in Troxier's bulletin, users of Troxler model 3400 series gauges

with serial numbers less than 13301 are encouraged to have their gauges inspected for cracks

in the weld area of the insertion rod. In addition, it is recommended that these gauges be

rechecked for cracks on at least a 5 year basis (more or less frequently depending on use level

and conditions). It is further recommended that users of model 3400 series gauges with serial

numbers 13301 and above also have their insertion rods checked for cracks in the weld area

and consider periodic re-inspection, as well.

Inspections of insertion rod weld areas should only be performed by persons qualified to

conduct an appropriate nondestructive examination (NDE) for macroscopic cracks (e.g., visual

examination with magnification or dye penetrant) and licensed to handle the contained

radioactive material. Visual examinations without magnification and examinations by

unqualified persons are not recommended, as these could lead to inaccurate results and

unnecessary doses to persons performing the examination. Persons who possess Troxler

model 3400 series gauges who wish to have their insertion rods inspected should contact either

the manufacturer or an NDE inspector qualified to perform the inspection. For guidance on

finding qualified NDE inspectors, licensees may contact the Technical Services Division of the

American Society for Nondestructive Testing, Inc., at (800) 222-2768 or the Non-Destructive

Testing Management Association at (800) 317-0822.

Users who determine that their gauge's insertion rod contains a crack should immediately stop

using the gauge and notify the manufacturer. Repair or replacement of cracked insertion rods

should only be performed by qualified persons, authorized by license to perform these activities.

The manufacturer or other licensee authorized to performed the repair or replacement will

indicate the manner in which the gauge should be returned for service.

The incidents and investigations discussed in this notice also demonstrate the need to

determine the appropriate weld material, configuration, and processes for a particular use

application when designing gauges of this type. The choice of weld specifications should be

based on the requirements of the gauge during normal and accident conditions of use that it Is

likely to encounter during its working life. It is imperative that manufacturers identify these likely

conditions as best as possible and design their gauges accordingly. Although the choice of

weld material, configuration, and processes for model 3400 series gauges with serial numbers

below 13301 appears to be sufficient under normal conditions of use, it appears to provide a

means by which a crack could begin in the weld area if subjected to higher than normal bending

loads.

IN 96-52 September 26, 1996 This information notice requires no specific action nor written response.

If you have any

questions about the information in this notice, please contact the technical

contact listed below

or the appropriate regional office.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contact: Douglas Broaddus, NMSS

(301) 415-5847 E-mail: dab@nrc.gov

Attachments:

1. Troxder Bulletin Issued June 1996

2. Ust of Recently Issued NMSS Information Notices

3. Ust of Recently Issued NRC Information Notices

Attachment 1 IN 96-52 September 26, 1996 Page 1ofI

As a result of several recent incidents that have occurred in which the source cup has

become detached from the extendable source rod of Troxler 3400 series gauges, Troxler is issuing this bulletin to assist users of surface/moisture gauges in using the

gauges safely in compliance'with the manufacturer's instructions. Troxler anticipates

that this bulletin will help prevent additional source cup detachment incidents.

In order to simpli* the manufacturing process, and not due to any incident,

3400 series gauges with serial numbers 13,300 and greater (i.e., manufactured since

mid-1986) rely on a combination of a weld and a threaded design to secure the source

cup to the source rod. With the addition of threads, the source cups will not dislodge

unless the cups are physically unscrewed from the rod. The cases involving detached

cups occurred with serial numbers below 13,300 which did not incorporate the

threaded design and rely on the weld.

Upon notification of the above incidents, the Troxler Research and

Development Department initiated an inspection program for gauges received for

service and disposal. This inspection program looked at 310 gauges, 235 received for

service and 75 received for disposal. No cracked rods were found in the gauges

received for service. In the group of disposal gauges, two rods were identified as

having a crack approximately 40% around the circumference. Further evaluation of

these two rods demonstrated that they would not fail in normal use or typical accident

conditions in the environment in which they are used. Several thousand gauges have

been inspected over the last two years. Based on this inspection program Troxler has

seen no signs of manufacturing defects. Inspections have revealed some cases of abuse

of the equipment.

In an effort to reduce the likelihood of future source cup detachment incidents, Troxier, in cooperation with the North Carolina Division of Radiation-Protection, has

drafted several recommendations for gauge users as follows:

1. Gauges should be used in-accordance with manufacturer's instructions found

in the accompanying operator's manual. Under no circumstances should the source

rod ever be driven or forced into the test material. A drill rod accessory is provided

with the gauge to prepare a hole in the test material into which the source rod is

inserted. If the user purchased a used gauge from someone other than Troxler which

does not include the accessory, the user should contact Troxler to obtain a drill rod.

2. Troxler recommends that the user return the gauge to the manufacturer at

least once every five years to allow the manufacturer to inspect the gauge and source

rod for unusual wear and tear.

3. Troxler recommends that companies purchasing used gauges require an

inspection by the manufacturer prior to purchase. Troxler takes no position regarding

gauge inspections and source rod evaluations performed by anyone other than

authorized Troxier Service Centers. Troxler recommends that any gauge involved in

an accident be returned to the manufacturer for inspection prior to further use.

For further information, contact Michael Dishman, the Troxler Corporate Radiation

Safety Officer, at (919) 549-8661.

Issued June 1996

GIoAQ

Attachment 2 IN 96-52 September 26, 1996 Page 1 of I

UST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

-51 Residual Contamination 09111/96 All material licensees

Remaining in Krypton-85 Handling System After

Venting

98-47 Recordkeeping, Decommis- 08/19/96 All U.S. Nuclear Regulatory

sioning Notifications for Commission licensees

Disposals of Radioactive

Waste by Land Burial

Authorized Under Former

10 CFR 20.304,20.302, and Current 20.2002

96-35 Failure of Safety Systems 06/11/96 All U.S. Nuclear Regulatory

on Self-Shielded Irradia- Commission Irradiator

tors Because of Inadequate licensees and vendors

Maintenance and Training

633 Erroneous Data from Defec- 05/224/96 All material and fuel cycle

tive Thermocouple Results licensees that monitor tem- in a Fire perature with thermocouples

96-28 Suggested Guidance Relat- 05/01/96 All material and fuel cycle

ing to Development and licensees

Implementation of Correc- tive Action

96-21 Safety Concerns Related 04110/96 All NRC Medical Ucensees

to the Design of the Door authorized to use brachy- Interlock Circuit on therapy sources in high- Nucletron High-Dose Rate and pulsed-dose-rate remote

and Pulsed Dose Rate

Remote Afterloading Brachy- therapy Devices

96-20 Demonstration of Associ- 04/04/96 All industrial radiography

ated Equipment Compliance licensees and radiography

with 10 CFR 34.20 equipment manufacturers

96-18 Compliance With 10 CFR 03/25X96 All material licensees

Part 20 for Airborne authorized to possess and

Thorium use thorium in unsealed form

Attachment 3 IN 96-52 September 26, 1996 Page 1 of I

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

92-68, Potentially Sub-standard 09/16196 All holders of OLs or CPs

Supp. 1 Slip-On, Welding Neck, for nuclear power reactors

and Blind Flanges

96-51 Residual Contamination 09/111/96 All material licensees

Remaining in Krypton-85 Handling System After

Venting

96-50 Problems with 09104/96 All holders of OLs and CPs

Levering-In Devices for nuclear power plants

in Westinghouse

Circuit Breakers

96-49 Thermally Induced 08/20/96 All holders of OLs or CPs

pressurization of Nuclear for nuclear power reactors

Power facility Piping

96-48 Motor-Operated Valve 08121196 All holders of OLs or CPs

Performance Issues for nuclear power reactors

96-47 Recordkeeping, Decommis- 08/19/96 All U.S. Nuclear Regulatory

sioning Notifications for Commission licensees

Disposals of Radioactive

Waste by Land Burial

Authorized Under Former

10 CFR 20.304, 20.302, and Current 20.2002

96-46 Zinc Plating of Hardened 08/12/96 All holders of OLs or CPs

Metal Parts and Removal for nuclear power reactors

of Protective Coatings in

Refurbished Circuit Breakers

96-45 Potential Common-Mode 8/12196 All holders of OLs or CPs

Post-Accident Failure of for nuclear power reactors

Containment Coolers

OL = Operating License

CP = Construction Permit

Vendor List for Portable Moisture Density Gauges

Boart Longyear Company

CPN Products

2830 Howe Rd.

Martinez, CA 94533 Campbell Security Equipment Co. (CESCO)

2500 Annalisa Dr.

Concord, CA 94520

Humboldt Scientific, INC

553E Pylon Dr.

Raleigh, NC 27607

Ohmart Corp.

4241 Allendorf Dr.

Cincinnati, OH 45209

Seaman Nuclear Corp.

3846 West Wisconsin Av.

Milwaukee, WI 53208

Texas Nuclear Products

TN Technologies, INC

2555 North IH-35, P.O. Box 800

Round Rock, TX 78680-0800

Troxler Electronic Labs, INC

3008 Comwallis Rd.

P.O. Box 12057

Research Triangle Park, NC 27709

J1 IN 96-52 September 26, 1996 This information notice requires no specific action nor written response. If you have any

questions about the information in this notice, please contact the technical contact listed below

or the appropriate regional office.

Donald A. Cool, Director

Division of Industrial and

, Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contact: Douglas Broaddus, NMSS

(301) 415-5847 E-mail: dab@nrc.gov

Attachments:

1. Troxler Bulletin Issued June 1996

2. List of Recently Issued NMSS Information Notices

3. List of Recently Issued NRC Information Notices

At&AYcfs ;ePs

a. z7cktr

DOCUMENT NAME: 96-52.IN

• Concurrence via fax

See previous concurrence

To receive acopy of this document. Indicate hIthe box: *v a Copy fthoud aftchmentenckoure T a Copy vlh ettacumentonclosur vW v No cowy

NAME DBroaddus I-Camper EKraus JPiccone DCool

DATE 8/26196 8/29/96 8/26/96 9/10/96 9/16/96 OFFICIAL RECORD COPY

IN 96-XX

September , 1996 This information notice requires no specific action nor written response. If

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

the technical contact listed below or the appropriate regional office.

Donald A. Cool, Director

- Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Contact: Douglas Broaddus, NMSS

(301) 415-5847 E-mail DAB@NRC.GOV

Attachments:

1. Troxler Bulletin issued June 1996

2. List of Recently issued NMSS Information Notices

3. List of Recently issued NRC Information Notices

DOCUMENT NAME: C:\WPDOCS\GENERIC.COM\TROXLER.IN2

• Concurrence via fax

• • See previous concurrence

Toreceive a copy of tWie document. Indicate In the box: C'- Copy without attachment/enclosure 'E Copy with attachmontjenloesur ND No copy

OFFICE IMAB EIMAB Tech Editor L-i7 LI

NAME DBroaddus** LCamper** EKraus*- iPccone D--

DATE 8/26/96 8/29/96 8/26/96 * ///96C/96 OFFICIAL RECORD COPY

IN 96-XX

September , 1996 This information notice requires no specific action nor written response. If

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

the technical contact listed below or the appropriate regional office.

Donald A. Cool, Director

Division of Industrial and

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Contact: Douglas Broaddus, NMSS

(301) 415-5847 E-mail DAB@NRC.GOV

Attachments:

1. Troxler Bulletin issued June 1996

2. List of Recently issued NMSS Information Notices

3. List of Recently issued NRC Information Notices

DOCUMENT NAME: C:\WPDOCS\GENERIC.COM\TROXLER.IN2

• Concurrence via fax

• • See previous concurrence

To Dscelve a copy of thi document, Indcate In the box: 'C

• Copy without attchrnent/enoloure 'E' - Copy with gttachmrent/enclasure N - No copy

OFFICE- IMAB E IMAB Tech Editor N E I

INAME DBroaddus** LCamper** EKraus* Liccone ID H

DATE 8/26/96 8/29/96 8/26/96 __ /_ I96/It /96M

OFFICIAL RECORD COPY

UNITED STATES

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