<PAGE>
                                                                  Exhibit 10(gg)

                        September 22, 1997


Mr. Roger M. Marino
c/o David M. Duchesneau, Esq.
The Duchesneau Group, Inc.
Riverside Office Park
13 Riverside Road
Weston, MA  02193

    Re:  Sale of Nuclear Metals, Inc. Debenture and Warrant

Dear Roger:

    The purpose of this letter is to set forth the following terms and 
conditions which shall apply to the sale of a $500,000 Nuclear Metals, Inc. 
10% Subordinated Debenture (the "Debenture") and accompanying Warrant to 
purchase 60,000 shares of Nuclear Metals, Inc. Common Stock (the "Warrant") 
by the Company to you.

    The purchase price for the Debenture and Warrant shall be Five Hundred 
Thousand ($500,000) Dollars.   

    You acknowledge and understand that the Debenture and Warrant, and the 
underlying stock (the "Securities") are being offered and sold without 
registration under the Securities Act of 1933, as amended (the "Act") and in 
reliance upon an exemption from the registration requirements contained in 
the Act and the rules and regulations promulgated thereunder.

    You hereby make the following representations and warranties to the 
Company: 

    (1)  You are an "accredited investor" within the meaning of Rule 501(a)
         under the Act.

    (2)  You have sufficient knowledge and experience in financial and business
         matters which enable you to evaluate the merits and risks of making an
         investment in the Company.  We have provided you with any and all
         public information concerning the Company which you deem relevant. 
         You have had the opportunity to ask and have received answers to any
         questions you have with respect to the business and prospects of the
         Company.  You recognize and agree that non-public information provided
         to you may be used only for purposes of evaluating the investment
         described above, and for no other purpose.

    (3)  You are acquiring the Securities with your own funds, for your own
         benefit, for investment, and not with a view to the resale or
         distribution thereof or any interest therein.


<PAGE>

Mr. Roger M. Marino
September 22, 1997
Page 2


    (4)  You agree with the Company that, as the Securities are unregistered
         under the Act, they must be held indefinitely unless they are
         subsequently registered under the Act or an exemption from such
         registration is available.  In addition, you agree not to transfer or
         dispose of any of the Securities, or any interest therein, except in
         accordance with all applicable Federal and state laws.  You agree that
         there may be affixed to any certificate representing the Securities
         and to all certificates issued thereafter representing such Securities
         (until in the opinion of counsel, which opinion must be satisfactory
         to counsel to the Company, it is no longer necessary or required) an
         appropriate legend evidencing the applicable restrictions under the
         Act.

    Please acknowledge the foregoing by signing the acknowledgement below and 
returning it to me.  If you have any questions or comments, feel free to give 
me a call.  I look forward to having you aboard.

                                  Very truly yours,

                                  Nuclear Metals, Inc.


                                  By: /s/ James M. Spiezio
                                     -------------------------------



Acknowledgement of :


/s/ Roger M. Marino
---------------------------
Roger M. Marino