<PAGE>
                                                              Exhibit 10(kk)

                         SECOND AMENDMENT TO CREDIT AGREEMENT


    Agreement is made as of this 29th day of December, 1997 among STARMET
CORPORATION, a Massachusetts corporation (f/k/a Nuclear Metals, Inc.)
("StarMet"), STARMET POWDERS, LLC, a Delaware limited liability corporation
("Powders"), STARMET AEROCAST, LLC, a Delaware limited liability corporation
("AeroCast"), STARMET COMCAST, LLC, a Delaware limited liability corporation
("ComCast"), STARMET NMI CORPORATION, a Massachusetts corporation ("NMI"),
STARMET CMI CORPORATION, a Delaware corporation (f/k/a Carolina Metals, Inc.)
("CMI"), STARMET HOLDINGS CORPORATION, a Massachusetts corporation ("Holdings"),
NMI FOREIGN SALES CORPORATION, a U.S. Virgin Islands corporation ("FSC", and
together with StarMet, Powders, AeroCast, ComCast, NMI, CMI and Holdings, the
"Borrowers") and STATE STREET BANK AND TRUST COMPANY, a Massachusetts chartered
trust company ("Bank").

    WHEREAS, the Borrowers and the Bank are parties to an Amended and Restated
Credit Agreement dated as of October 1, 1997 (the "Credit Agreement"); and

    WHEREAS, the parties have agreed to certain modifications;

    NOW THEREFORE, the parties agree as follows:

    1.   Section 1.01.  The Credit.  Section 1.01 of the Credit Agreement is
hereby amended by deleting the reference to "$8,050,000" in the third line and
"$8,050,000" in the last line and replacing both references with "$9,550,000".  

    2.   Section 1.02(a).  Amount.  Section 1.02(a) of the Credit Agreement is
hereby amended by deleting the proviso at the end of Section 1.02(a) and
substituting therefor the following:

    "provided that the aggregate of all Advances outstanding at any time less
    the maximum aggregate liability of the Borrowers under any outstanding
    letters of credit issued prior to the date hereof or pursuant to this
    Credit Agreement shall not exceed (i) $9,550,000 through June 30, 1998,
    (ii) $8,050,000 from July 1, 1998 through September 30, 1998, and (iii)
    $6,550,000 on October 1, 1998 and thereafter (such amount as in effect from
    time to time may be referred to as the "Maximum Credit")."

    3.   Section 1.02(b).  Revolving Credit Agreement.  Section 1.02(b) of the
Credit Agreement is hereby amended by adding the following at the end: 

<PAGE>


    "As provided in Section 1.02(a), the Maximum Credit shall reduce from
    $9,550,000 to $8,050,000 on July 1, 1998 and from $8,050,000 to $6,550,000
    on October 1, 1998, and any amount in excess of the Maximum Credit as so
    reduced shall be paid on or before such dates".

    4.   Section 1.02(c).  The Revolving Credit Note.  Section 1.02(c) of the
Credit Agreement is hereby amended by  deleting the first sentence in Section
1.02(c) its entirety and substituting therefor the following:

    "Amounts owed to Bank with respect to Advances made by Bank shall be
    evidenced by Bank's books and records and may, at the request of the Bank,
    be further evidenced by one or more revolving credit notes (collectively,
    the "Revolving Credit Note").  As of the date of this Second Amendment, the
    Advances are evidenced by an Amended and Restated Revolving Credit Note
    dated as of March 31, 1995 (as amended and restated October 1, 1997) in the
    principal amount of $6,550,000 (the "Original Note") and a Second
    Additional Revolving Credit Note dated as of the date of this Second
    Amendment in the principal amount of $3,000,000 (the "Additional Note"). 
    All Advances shall be deemed made pursuant to the Original Note up to the
    maximum principal amount thereof and thereafter pursuant to the Additional
    Note.  Any repayments of principal shall be applied first to the Additional
    Note, then to the Original Note".


    5.   Section 4.20.  Debt-Tangible Capital Base.  The first sentence is
amended in its entirety to read as follows:

    "The ratio of Debt to Tangible Capital Base of the Borrowers on a
    consolidated basis shall not exceed 0.60 to 1.00."

    6.   Section 4.21.  Tangible Capital Base shall be amended in its entirety
to read as follows:

    "The Tangible Capital Base of the Borrowers on a consolidated basis shall
    be not less than $26,750,000 as of January 10, 1998, and $26,750,000 plus
    an increase equal to the aggregate of 75% of the Borrowers' Net Income for
    each fiscal quarter after December 31, 1997 in which the Borrowers have
    positive net income (with no reduction for fiscal quarters in which the
    Borrowers incur a loss) determined as of the end of each fiscal quarter
    commencing March 31, 1998."

    7.   Section 4.22.  Net Income shall be amended in its entirety as follows:

    "The Net Income of the Borrowers for the periods set forth below shall be
    not less than the amounts set forth opposite such periods:


                                         -2-
<PAGE>


    Period                             Net Income
    ------                             ----------
    Quarter ending December 31, 1997   ($1,100,000)

    Quarter ending March 31, 1998      $1

    Quarter ending June 30, 1998       $300,000

    Quarter ending September 30, 1997       
    and thereafter                     $750,000"

    "Net Income" shall mean the consolidated net income of the Borrowers before
interest and taxes, plus (a) to the extent deducted in calculating Net Income
prior to March 31, 1998, any reserves established as a result of the litigation
commenced by Brush Wellman, and (b) costs associated with the execution of the
Second Amendment including the fees set forth in paragraph 11 of the Second
Amendment."
    
    8.   Section 4.23.  Capital Expenditures.  The amount "$1,000,000" is
amended to read "$2,000,000".  The Bank waives compliance with this covenant for
the year ending September 30, 1997.

    9.   Subordinated Debt.  The Bank acknowledges that the following
constitutes Subordinated Debt: $900,000 principal amount of 10% Convertible
Subordinated Debentures Due December 31, 1999 substantially in the form
delivered to the Bank on December 26, 1997.

    10.  IRB Waiver.  The Bank waives defaults under the CMI Industrial
Development Bond through September 30, 1998.

    11.  Fees.  The Borrowers shall (a) pay a closing fee of $15,000 upon
execution of this Second Amendment, (b) issue prior to January 31, 1998 a
seven-year warrant to purchase 25,000 shares of the common stock of StarMet at a
price equal to the average closing price on the ten consecutive trading days
ending December 29, 1997 and otherwise on the terms of warrants previously
issued to the Bank.  If the Advances (exclusive of letters of credit) exceed the
amounts set forth below on or after the indicated date, the Borrowers shall pay
an additional fee of $50,000 as of each such date:

              amounts                  date
              -------                  ----
              $4,750,000               March 15, 1997
              $3,000,000               July 15, 1997


                                         -3-
<PAGE>

    If the Borrowers Net Income for the three month period ended 3/31/98 is 
less then $300,000 or less then $750,000 for the three month period ended 
6/30/98, the Borrowers shall pay a further fee of $10,000 as of each such 
date.

    12.  Effectiveness.  This Second Amendment to Credit Agreement shall become
effective upon (a) execution of this Second Amendment by the Borrowers and the
Bank, (b) execution by the Borrowers of the Additional Note substantially in the
form of Exhibit A attached hereto, (c) receipt by the Bank of evidence
satisfactory to the Bank that the Borrowers are authorized to execute this First
Amendment.

    13.  Miscellaneous. 

         (a)  The Borrowers hereby confirm to the Bank that the representations
    and warranties of the Borrowers set forth in Article II of the Credit
    Agreement are true and correct as of the date hereof, as if set forth
    herein in full.

         (b)       There is no Event of Default, and no condition which, with
    the passage of time or giving of notice or both, would constitute an Event
    of Default under the Credit Agreement except as amended or waived in this
    Second Amendment.

         (c)       Except as set forth above and in the First Amendment dated
    as of December 19, 1997, the Credit Agreement remains in full force and
    effect.

    14.  Section 1.02(a). Amount. Section 1.02(a) of the Credit Agreement is 
hereby amended by deleting in the fourth line reference to February 28, 1998 
(the ""Maturity Date'') and substituting therefor February 28, 1999 (the 
""Maturity Date'').
                                         -4-
<PAGE>

    IN WITNESS WHEREOF, the parties have executed this First Amendment to
Credit Agreement under seal as of the date first above written.
    

                                 STARMET CORPORATION


                                        By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:   James M. Spiezio
                                        Title:  VP Finance


                                 STARMET POWDERS, LLC


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                                STARMET AEROCAST, LLC


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                                 STARMET COMCAST, LLC


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                               STARMET NMI CORPORATION


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer

                                         -5-
<PAGE>

                               STARMET CMI CORPORATION


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                             STARMET HOLDINGS CORPORATION


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                            NMI FOREIGN SALES CORPORATION


                                         By: /s/ James M. Spiezio
                                            -------------------------
                                        Name:    James M. Spiezio
                                        Title:   Treasurer


                             STATE STREET BANK AND TRUST
                                       COMPANY

                                         By: /s/ William R. Dewey, IV
                                            -------------------------
                                        Name:    William R. Dewey, IV
                                        Title:   Vice President



                                         -6-
<PAGE>

                                      EXHIBIT A

                       SECOND ADDITIONAL REVOLVING CREDIT NOTE


$3,000,000                                                 December 29, 1997

    FOR VALUE RECEIVED, the undersigned, STARMET CORPORATION, STARMET POWDERS,
LLC, STARMET AEROCAST, LLC, STARMET COMCAST, LLC, STARMET NMI CORPORATION,
STARMET CMI CORPORATION, STARMET HOLDINGS CORPORATION, NMI FOREIGN SALES
CORPORATION (the "Borrowers"), hereby jointly and severally, promise to pay to
the order of STATE STREET BANK AND TRUST COMPANY, a Massachusetts trust company
("Bank"), in lawful money of the United States of America in immediately
available funds at its office at 225 Franklin Street, Boston, Massachusetts
02110 the principal sum of THREE MILLION DOLLARS ($3,000,000) or such lesser sum
as may from time to time be outstanding under the terms of the Credit Agreement
between the Borrowers and Bank of even date herewith, as amended, modified,
supplemented and/or restated from time to time (the "Credit Agreement").

    The Borrowers promise to pay interest on the unpaid principal balance at
the rates and at the times provided in the Credit Agreement.  This Note may be
prepaid only in accordance with the terms of the Credit Agreement.

    The principal balance of this Note shall be reduced as provided in the
Credit Agreement and the remaining balance shall become due and payable on July
15, 1998 and earlier upon the occurrence of an Event of Default (as defined in
the Credit Agreement).  This Note replaces an Additional Revolving Credit Note
dated December 19, 1997 in the principal amount of $1,500,000.  The Borrowers
agree to pay all reasonable legal fees and other costs of collection of this
Note.

    No delay or omission on the part of the holder in exercising any right
hereunder shall operate as a waiver of such right, nor shall any waiver on one
occasion be deemed to be an amendment or waiver of any such right with respect
to any future occasion.  The Borrowers hereby waive presentment, demand, protest
and notice of every kind and assents to any one or more indulgences, to any
substitution, exchange or release of collateral (if at any time there be
available collateral to the holder of this Note) and to the addition or release
of any other party or persons primarily or secondarily liable.


                                         -7-
<PAGE>


    This Note shall be governed and construed under the laws of the
Commonwealth of Massachusetts and shall be deemed to be under seal.
              
                                 STARMET CORPORATION

WITNESS: /s/ Rebecca Perry
                                 By: /s/ James M. Spiezio
                                    --------------------------
                                 Name:   James M. Spiezio
                                 Title:  VP Finance


                                 STARMET POWDERS, LLC

WITNESS: /s/ Rebecca Perry
                                 By: /s/ James M. Spiezio        
                                    --------------------------
                                 Name:   James M. Spiezio
                                 Title:  Treasurer


                                 STARMET AEROCAST, LLC

WITNESS: /s/ Rebecca Perry
                                 By: /s/ James M. Spiezio
                                    --------------------------
                                 Name:   James M. Spiezio
                                 Title:  Treasurer

                                 STARMET COMCAST, LLC

WITNESS: /s/ Rebecca Perry
                                 By: /s/ James M. Spiezio
                                    -------------------------- 
                                 Name:   James M. Spiezio
                                 Title:  Treasurer


                                 STARMET NMI CORPORATION

WITNESS: /s/ Rebecca Perry
                                 By: /s/ James M. Spiezio                   
                                    --------------------------  
                                 Name:   James M. Spiezio
                                 Title:  Treasurer

                                         -8-
<PAGE>



                                STARMET CMI CORPORATION

WITNESS: /s/ Rebecca Perry
                                By: /s/ James M. Spiezio
                                    --------------------------  
                                Name:   James M. Spiezio
                                Title:  Treasurer


                                STARMET HOLDINGS CORPORATION

WITNESS: /s/ Rebecca Perry
                                By:  /s/ James M. Spiezio  
                                    --------------------------  
                                Name:    James M. Spiezio
                                Title:   Treasurer


                                NMI FOREIGN SALES CORPORATION

WITNESS: /s/ Rebecca Perry
                                By:  /s/ James M. Spiezio
                                    --------------------------  
                                Name:    James M. Spiezio
                                Title:   Treasurer