United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 94-02: Corrosion Problems in Certain Stainless Steel Packagings Used to Transport Uranium Hexafluoride

                                                                  NRCB 94-02
                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
               OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
                            WASHINGTON, D.C. 20555

                               November 14, 1994


NRC BULLETIN 94-02:  CORROSION PROBLEMS IN CERTAIN STAINLESS STEEL PACKAGINGS
                     USED TO TRANSPORT URANIUM HEXAFLUORIDE

Addressees

      For Action      - Registered users of Model Nos. NCI-21PF-1 and
                        GE-21PF-1 uranium hexafluoride transportation packages

      For Information - None

Purpose

The U.S. Nuclear Regulatory Commission is issuing this bulletin to:  
(1) notify addressees that some uranium hexafluoride transportation packagings
manufactured with a phenolic foam high in chlorides have exhibited pitting and
corrosion problems; (2) advise addressees that uranium hexafluoride packagings
with the high-chloride foam do not conform to the applicable NRC Certificate
of Compliance; (3) remind addressees that packagings that are not in
accordance with the NRC Certificate of Compliance, or that are in an impaired
physical condition, are not authorized for transport under the general license
provisions of 10 CFR 71.12; and (4) require addressees to reply in writing
regarding whether or not they intend to discontinue use of the packagings with
the high-chloride foam that are not in accordance with the NRC Certificate of
Compliance.

Description of Circumstances

Some packagings used for transport of uranium hexafluoride have experienced
varying degrees of pitting and corrosion of the stainless steel shells caused
by a high concentration of chlorides present in the foam used to construct the
packagings.  These packagings were manufactured using a high-chloride phenolic
foam that does not conform to the phenolic foam specifically authorized by the
applicable NRC Certificate of Compliance.

The packagings fabricated with the high-chloride foam were manufactured during
the period June 1, 1986, through November 30, 1991, by Nuclear Containers,
Inc., (NCI) of Elizabethton, Tennessee.  The affected packagings are:  (1)
Model No. GE-21PF-1 (NRC Certificate of Compliance No. 4909), all units
fabricated after June 1, 1986; and (2) Model No. NCI-21PF-1 (NRC Certificate
of Compliance No. 9234), all units fabricated during the period June 1, 1986,
to November 30, 1991, that have NCI serial Nos. 1 through 486, and 487A and
488A.  These packagings do not conform to the NRC Certificate of Compliance

9411090300.                                                      NRCB 94-02
                                                      November 14, 1994
                                                      Page 2 of 3


and are not authorized for transport under the general license provisions of
10 CFR 71.12.

Packagings manufactured after November 30, 1991, by Nuclear Containers, Inc.,
use a foam that has a lower concentration of chlorides.  Although the low-
chloride foam is not in accordance with the NRC Certificate of Compliance,
there are no known safety problems with packagings manufactured with low-
chloride foam, and there have been no instances of pitting or corrosion.  The
mechanical and thermal properties of the low-chloride foam are believed to be
similar to those of foam that conforms to the NRC Certificate of Compliance. 
NRC Certificate of Compliance No. 9234 has been amended to authorize continued
use, for one year, of packagings made with low-chloride foam.  The one-year
period is to allow time for an applicant to submit, for NRC review and
approval, an application that shows that packagings fabricated with low-
chloride foam meet the requirements of 10 CFR Part 71.

Discussion

Defects observed in the stainless steel shells of packagings manufactured with
high-chloride foam range from a few pinholes to hundreds of holes.  Stress
corrosion cracking has been reported in at least one of these packagings. 
Since the pitting is initiated on the foam side of the stainless steel shells,
the presence and severity of the corrosion is not readily determined by visual
inspection.  The pitting of the foam side of the shell has been reported to be
50 to 100 times more severe than the pitting of the outer surface.  There
appear to be no known, effective means of repairing these packagings nor of
stopping the corrosion process.  Defects in the stainless steel shell caused
by corrosion could reduce the effectiveness of the packaging under accident
conditions.  

Since the packagings with the high-chloride foam are not in conformance with
the NRC Certificate of Compliance, and since the corrosion could reduce the
effectiveness of the packaging under accident conditions, use of packagings
fabricated with high-chloride foam is not authorized under the general license
provisions of 10 CFR 71.12.

Required Response

Within 30 days of the date of this bulletin, each action addressee is required
to submit a response indicating whether or not the addressee intends to
discontinue use of the following packagings:  (1) Model No. GE-21PF-1
packagings that were fabricated by Nuclear Containers, Inc., after June 1,
1986; and (2) Model No. NCI-21PF-1 packagings that were fabricated by Nuclear
Containers, Inc., during the period June 1, 1986, to November 30, 1991, that
have NCI serial Nos. 1 through 486, and 487A and 488A.  
.                                                      NRCB 94-02
                                                      November 14, 1994
                                                      Page 3 of 3


Address the required written responses to the U.S. Nuclear Regulatory
Commission, ATTN: Document Control Desk, Washington, D.C. 20555, under oath or
affirmation under the provisions of Section 182a, Atomic Energy Act of 1954,
as amended.  In addition, submit a copy to the appropriate Regional
Administrator.

Paperwork Reduction Act Statement

The response requirements contained in this bulletin affect fewer than ten
respondents.  Therefore, Office of Management and Budget approval is not
required pursuant to the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et
seq.)

If you have any questions about this matter, please contact one of the
technical contacts listed below or the appropriate regional office.

                                    ORIG /S/'D BY E WILLIAM BRACH


                                    Carl J. Paperiello, Director
                                    Division of Industrial
                                      and Medical Nuclear Safety
                                    Office of Nuclear Material Safety
                                      and Safeguards

Contacts:   Ross Chappell, NMSS
            (301) 415-7276

            Nancy Osgood, NMSS
            (301) 415-7879

 

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