Information Notice 1996-54, Vulnerability of Stainless Steel to Corrosion When Sensitized

Vulnerability of Stainless Steel to Corrosion When Sensitized

ML031050603
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:	10/17/1996
From:	Cool D NRC/NMSS/IMNS
To:
References
IN-96-054, NUDOCS 9610100212
Download: ML031050603 (6)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, DC 20555 October 17, 1996 NRC INFORMATION NOTICE 96-54: VULNERABILITY OF STAINLESS STEEL TO

CORROSION WHEN SENSITIZED

Addressees

All materials licensees.

Purpose

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

licensees aware of the vulnerability of stainless steel to corrosion when sensitized. This issue

is of particular concern to the NRC when it involves sources or devices constructed of stainless

steels. Although the corrosion in the incident described below involved only 316L stainless

steel, the inherent concerns extend to other types of stainless steel that may be subjected to

temperatures that sensitize the material. It is expected that recipients will review the

information for applicability to their programs. However, suggestions contained in this

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

is required.

Description of Circumstances

Recently, the NRC was informed of the discovery of corrosion found on a particular

manufacturer's 316L stainless steel irradiator source used in Category IV irradiator facilities.

These sources were similar in design and construction to other manufacturers' sources;

however, their sources showed signs of intergranular corrosion, whereas other manufacturer's

sources located in the same irradiator pool did not.

Analysis of test data and reports provided by the manufacturer revealed that the 316L stainless

steel sources were heat sensitized as a result of improper loading of the sources in the shipping

container. The heat generated by these high activity sources resulted in higher than normal

temperatures inside the container. The sensitized stainless steel was then vulnerable to

intergranular corrosion. The intergranular corrosion was initiated due to the sensitized material

being in an environment favorable for corrosion (i.e., poor pool water quality).

Discussion

Although stainless steels are considered as having excellent corrosion resistance, they can be

susceptible to corrosion when exposed to certain conditions. Stainless steels are protected

against corrosion by alloying them with protective elements such as chromium. For

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IN 96-54 October 17, 1996 example, 316L stainless steel, which is considered to have high corrosion

resistance, contains 17 percent chromium. However, if the level of these protective

elements is reduced

below the minimum percentage necessary, the protective properties

are reduced and the

material becomes vulnerable to corrosion.

One of the ways that these protective properties can be compromised

occurs when the

stainless steel is subjected to temperatures within a certain critical

temperature range. The

critical temperature range for this to occur varies for different stainless

steels, and is typically

higher than the normal operating temperatures that the material would

be subjected to.

Stainless steels subjected to temperatures within this critical range

for a sufficient length of time

will become heat sensitized. Heat sensitization refers to a condition

where the protective

elements in the material structure of the stainless steel are reduced

to levels below the

minimum necessary for corrosion protection. The amount of time

before heat sensitization

occurs is temperature and time dependent, and is typically longer

for temperatures at the lower

end of the temperature range. For example, a material may need

to be exposed to

temperatures at the low end of the range for a year or longer before

heat

occur, while at the upper end of the scale, heat sensitization may occur sensitization would

within seconds. These

higher than normal temperatures may occur in a number of ways, including, but not limited to, loading too many sources in a shipping or storage container, loading

the sources in an improper

configuration within the shipping or storage container, and use or

accident

result in the material experiencing high temperatures. If these sensitized conditions which

materials are placed

in an environment favorable to corrosion, such as an electrolyte or

conducting liquid medium, then intergranular corrosion, which is a type of corrosion that occurs

along the

between the grains of the stainless steel; can occur. The rate of intergranular boundaries

to predict and is based on a complex relationship involving time, corrosion is hard

temperature, and environment.

All licensees should be aware of the potential for sensitization and

resulting corrosion in

stainless steel, and should consider their own circumstances and

take action appropriately.

Licensees should be particularly sensitive to past and potential situations

involving

transportation, and to situations involving accident conditions and

incident response. Licensees

should avoid subjecting their sources and devices to conditions that

could cause sensitization.

Licensees who suspect that a source or device may have been

subjected to conditions that

could cause sensitization, should monitor the source or device for

signs of corrosion. Sources

or devices showing signs of corrosion should be isolated and placed

in an environment not

favorable to corrosion. They should be evaluated before continued

use. Licensees may

contact the manufacturer or a knowledgeable consultant to obtain

assistance in evaluating

whether sensitization and corrosion is a concern for their particular

circumstances.

K-i

IN 96-54 October 17, 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 contacts listed below

or the appropriate regional office.

DFuion of Industrial and'

Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Technical contacts: Michele Burgess, IMAB

(301) 415-5868 Email: mlb5@nrc.gov

Thomas Rich, IMAB

(301) 415-7893 Email: twr@nrc.gov

Attachments:

1. List of Recently Issued NMSS Information Notices

2. List of Recently Issued NRC Information Notices

Afit-, Le t J-4,6

I

Attachment 1 IN 96-54 October 17, 1996 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-53 Retrofit to Amersham 660 10/15/96 All industrial radiography

Posilock Radiography licensees

Camera to Correct Incon- sistency in 10 CFR Part 34 Compatibility

96-52 Cracked Insertion Rods 09/26/96 All U.S. Nuclear Regulatory

on Troxier Model 3400 Commission portable gauge

Series Portable Moisture licensees and vendors

Density Gauges

96-51 Residual Contamination 09/11/96 All material licensees

Remaining in Krypton-85 Handling System After

Venting

96-47 Recordkeeping, Decommis- 08/19196 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

96-33 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

I

Attachment 2 IN 96-54 October 14, 1996 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-53 Retrofit to Amersham 660 10115/96 All industrial radio- Posilock Radiography graphy licensees

Camera to Correct Incon- sistency in 10 CFR Part 34 Compatibility

95-04, Excessive Cooldown 10/11/96 All holders of OLs or CPs

Supp. I and Depressurization and vendors for nuclear

of the Reactor Coolant power reactors

System Following Loss

li

of Offsite Power

96-40, Deficiencies in 10/07/96 All holders of OLs or CPs

Supp. 1 Material Dedication for nuclear power reactors

and Procurement

Practices and in

Audits of Vendors

96-52 Cracked Insertion 09126/96 All U.S. Nuclear Regulatory

Rods on Troxler Commission portable gauge

Model 3400 Series licensees and vendors

Portable Moisture

Density Gauges

92-68, Potentially Sub- 09/16/96 All holders of OLs or CPs

Supp. 1 standard Slip-On, for nuclear power reactors

Welding Neck, and

Blind Flanges

96-51 Residual Contamina- 09111/96 All material licensees

tion Remaining in

Krypton-85 Handling

System After Venting

OL = Operating License

CP = Construction Permit

UNITED STATES

hUCLEAR REGULATORY COMMISSION FIRST CLASS MAIL

WASHINGTON, D.C. 20555-0001 POSTAGE AND FEES PAID

USNRC

PERMIT NO. G-67 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE, S300

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