UNITED STATES 

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555

March 24, 2003

NRC INFORMATION NOTICE 2002-31, SUPPLEMENT 1 POTENTIALLY DEFECTIVE

 UF6 CYLINDER VALVES

(1-INCH)

Addressees

All U.S. Nuclear Regulatory Commission (NRC) licensees authorized to possess and use

source material and/or special nuclear material for heating, emptying, filling, or shipping 30- and

48-inch cylinders of uranium hexafluoride (UF6).

Purpose

The NRC previously issued Information Notice 2002-31 to inform addressees about two safety

concerns related to 1-inch UF6 cylinder valves manufactured by the Hunt Valve Company, Inc.,

of Salem, Ohio. The safety concerns were: (1) cracked packing nuts and; (2) the loss of

material traceability and failure to conduct hardness testing of the valve stems. Since then, the

United States Enrichment Corporation (USEC) has conducted a series of tests to verify that the

valves would perform their intended safety function. 

The NRC is issuing this supplement to inform addressees that, as a result of those tests, a

number of valves failed to meet the seat leakage performance requirements. It is expected that

recipients will review the information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. Suggestions contained in this information notice do not

constitute new NRC requirements; therefore, no specific action or written response is required. 

Description of Circumstances

USEC conducted a series of tests to determine whether the 1-inch UF6 cylinder valves

manufactured by the Hunt Valve Company meet the critical characteristics specified in ANSI 

N 14.1, “American National Standard for Nuclear Materials - Uranium Hexafluoride - Packaging

for Transport.” One of the more important critical characteristics tested was seat leakage. 

ANSI N 14.1 requires a 400 psig leak test with no leakage permitted. USEC initially tested a

sample size of 56 valves in its stores. Of those tested, one valve failed, and another possible

failure has been referred to the ANSI N14.1 Committee for interpretation. The two valves in

question came from one specific vendor lot of 100 valves. 

USEC then proceeded to conduct additional seat leakage tests on all of the remaining valves in

the parent lot. As a result of the testing conducted to date, USEC has identified 13 valve

failures out of 210 valves tested. Preliminary indications are that the failures are caused by

bronze debris on the valve seats. The jagged debris was apparently cut from the valve body

bronze threads by the harder monel valve stem threads that were not adequately de-burred or

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polished. An optical inspection of valves manufactured by other vendors and previously

manufactured Hunt valves found significantly less debris present and a polished finish. USEC

polished the valve stems of several of the leaking valves and successfully retested them to the

ANSI N14.1 test acceptance criteria.

Discussion

Although the nonconforming valves identified thus far belong to one valve lot, the potential

nonconformance may extend to other lots. During an inspection at Hunt Valve in 2001, the

NRC identified an ineffective quality assurance program. It could not be determined how long

the quality assurance problems had existed. Consequently, the potential nonconforming

problems have not been limited to any single Hunt valve lot at this time.

As indicated in the original Information Notice, the 1-inch UF6 valves form part of the pressure

boundary for Model No. 30B (30-inch diameter) cylinders that contain low-enriched uranium (up

to 5 percent U235) and various 48-inch diameter cylinders containing enriched, natural and

depleted (tails) uranium. As such, the valves perform several safety functions as described in

IN 2002-31 dated October 31, 2002. In addition, packages shipped under an NRC Certificate

of Compliance must conform to ANSI N14.1. Conformance to ANSI N14.1 is also required by

Department of Transportation regulations (see 49 CFR 173.420).

Related Generic Communications

• Information Notice No. 89-78: “Failure of Packing Nuts on One-Inch Uranium

Hexafluoride Cylinder Valves”

• Information Notice No. 97-24: “Failure of Packing Nuts on One-Inch Uranium

Hexafluoride Cylinder Valves”

• Information Notice No. 02-31: “Potentially Defective UF6 Cylinder Valves (1-inch)”

This notice does not require any specific action or written response. If you have any questions

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

appropriate project manager in the NRC’s Office of Nuclear Material Safety and Safeguards.

/RA/

Robert C. Pierson, Director

Division of Fuel Cycle, Safety and Safeguards

Office of Nuclear Material Safety and Safeguards

Technical Contact: William Troskoski, NMSS

(301) 415-8076

E-mail: wmt@nrc.gov

Attachments:

1. List of Recently Issued NRC Information Notices

2. List of Recently Issued NMSS Information Notices