INCREMENTAL TERM LOAN ASSUMPTION AGREEMENT

Exhibit 10.81

EXECUTION COPY

     INCREMENTAL TERM LOAN ASSUMPTION AGREEMENT dated as of January 4, 2007 (this “Assumption Agreement ”), related to the CREDIT AGREEMENT dated as of August 2, 2004, as amended pursuant to that certain Incremental Term Loan Assumption Agreement and Amendment No. 1 dated as of April 1, 2005, that certain Incremental Term Loan Assumption Agreement and Amendment No. 2 dated as of March 24, 2006, as amended as of April 21, 2006, and that certain Incremental Term Loan Assumption Agreement and Amendment No. 3 dated as of June 30, 2006 (as amended, the “Credit Agreement”), among ALION SCIENCE AND TECHNOLOGY CORPORATION (the “Borrower”), the Subsidiary Guarantors listed on the signature pages hereto (solely with respect to Sections 6, 7, 9 and 10 hereof), the lenders from time to time party to the Credit Agreement (the “Lenders”) and CREDIT SUISSE (formerly known as Credit Suisse First Boston), as administrative agent (in such capacity, the “Administrative Agent”) and as collateral agent for the Lenders.

     A. The Borrower has requested that the person set forth on Schedule I hereto (the “Incremental Term Lender”) make Incremental Term Loans to the Borrower pursuant to Section 2.24 of the Credit Agreement, in the aggregate principal amount of $15,000,000.

     B. The Incremental Term Lender is willing to make Incremental Term Loans to the Borrower on the Effective Date (as defined below), on the terms and subject to the conditions set forth herein and in the Credit Agreement.

     Accordingly, in consideration of the mutual agreements herein contained and other good and valuable consideration, the sufficiency and receipt of which are hereby acknowledged, the parties hereto agree as follows:

     SECTION 1. Defined Terms; Interpretation; Etc. Capitalized terms used and not defined herein shall have the meanings assigned to such terms in the Credit Agreement. The rules of construction set forth in Section 1.02 of the Credit Agreement shall apply equally to this Assumption Agreement. This Assumption Agreement shall be a “Loan Document” and an “Incremental Term Loan Assumption Agreement” for all purposes of the Credit Agreement and the other Loan Documents.

     SECTION 2. Incremental Term Loans. (a) The Incremental Term Lender hereby agrees, severally and not jointly, to make an Incremental Term Loan to the Borrower on the Effective Date in a principal amount equal to the Incremental Term Loan amount set forth next to such Incremental Term Lender’s name on Schedule I hereto.

     (b) All such Incremental Term Loans shall constitute “Term Loans” for all purposes of the Credit Agreement and the other Loan Documents.

     (c) The proceeds of the Incremental Term Loans are to be used by the Borrower solely for general corporate and other working capital purposes of the Borrower and the Subsidiaries.

     SECTION 3. Conditions Precedent to Incremental Term Loans. The obligation of the Incremental Term Lender to make Incremental Term Loans on the Effective Date shall be subject to the satisfaction of the following conditions precedent:

     (a) On the Effective Date, each of the conditions set forth in paragraphs (b) and (c) of Section 4.01 of the Credit Agreement shall be satisfied and the Administrative Agent shall have received a certificate to that effect dated as of the Effective Date and executed by a Financial Officer of the Borrower.

     (b) The Administrative Agent shall have received (with sufficient copies for each Incremental Term Lender) such legal opinions, board resolutions and other closing certificates and documentation as shall be reasonably required by the Incremental Term Lender, in each case consistent with those delivered on the Closing Date under clauses (a), (c) and (d) of Section 4.02 of the Credit Agreement.

     (c) The Administrative Agent shall have received a certificate, dated the Effective Date and executed by a Financial Officer of the Borrower, confirming that the Borrower will be in Pro Forma Compliance after giving effect to the making of the Incremental Term Loans on the Effective Date and the application of the proceeds therefrom.

     (d) The Administrative Agent shall have received all fees and other amounts due and payable on or prior to the Effective Date, including, to the extent invoiced, reimbursement or payment of all out-of-pocket expenses required to be reimbursed or paid by the Borrower hereunder or under any other Loan Document.

     SECTION 4. Eurodollar Borrowings. To facilitate the inclusion of the Incremental Term Loans, when made, in each outstanding Term Borrowing, the Borrower and the Incremental Term Lender hereby agree pursuant to Section 2.24(d) of the Credit Agreement that the Incremental Term Loans made hereunder will be allocated ratably to each outstanding Eurodollar Term Borrowing for purposes of determining the initial interest rate thereon, in each case notwithstanding any contrary provision of the Credit Agreement. After giving effect to the last sentence in Section 2.24(d), to give effect to the making of the Incremental Term Loans hereunder and the treatment thereof as “Term Loans” for all purposes of the Credit Agreement, the table in Section 2.11(a) of the Credit Agreement shall be as set forth below:

     SECTION 5. Representations and Warranties. To induce the other party hereto to enter into this Assumption Agreement, the Borrower represents and warrants to the Administrative Agent and each of the Lenders that, as of the Effective Date:

     (a) This Assumption Agreement has been duly authorized, executed and delivered by each Loan Party party hereto, and constitutes a legal, valid and binding obligation of such Loan Party in accordance with its terms. The Credit Agreement constitutes a legal, valid and binding obligation of the Borrower in accordance with its terms.

     (b) The representations and warranties set forth in Article III of the Credit Agreement are true and correct in all material respects on and as of the Effective Date with the same effect as though made on and as of the Effective Date, except to the extent such representations and warranties expressly relate to an earlier date (in which case such representations and warranties were true and correct in all material respects as of such earlier date).

     (c) No Default or Event of Default has occurred and is continuing.

     SECTION 6. Effectiveness. This Assumption Agreement shall become effective as of the date (the “Effective Date”) occurring on or prior to January 31, 2007 that (a) the Administrative Agent shall have received counterparts of this Assumption Agreement that, when taken together, bear the signatures of (i) the Borrower, (ii) each Subsidiary Guarantor, (iii) the Administrative Agent and (iv) the Incremental Term Lender and (b) each of the conditions precedent set forth in Section 3 hereof shall have been satisfied (or waived in writing by the Incremental Term Lenders).

     SECTION 7. Consent and Reaffirmation. Each Subsidiary Guarantor hereby consents to this Assumption Agreement and the transactions contemplated hereby, and each Loan Party hereby (a) agrees that, notwithstanding the effectiveness of this Assumption Agreement, the Guarantee and Collateral Agreement and each of the other Security Documents continue to be in full force and effect, (b) confirms its guarantee of the Obligations (with respect to each Subsidiary Guarantor) and its grant of a security interest in its assets as Collateral therefor, all as provided in the Loan Documents as originally executed and (c) acknowledges that such guarantee and/or grant continue in full force and effect in respect of, and to secure, the Obligations under the Credit Agreement and the other Loan Documents, including the Incremental Term Loans.

     SECTION 8. Expenses. The Borrower agrees to reimburse the Administrative Agent for all reasonable out-of-pocket expenses incurred in connection with this Assumption Agreement in accordance with the Credit Agreement, including the reasonable fees, charges and disbursements of counsel for the Administrative Agent.

     SECTION 9. Counterparts. This Assumption Agreement may be executed in any number of counterparts and by different parties hereto in separate counterparts, each of which when so executed and delivered shall be deemed an original, but all such counterparts together shall constitute but one and the same contract. Delivery of an executed counterpart of a signature page of this Assumption Agreement by facsimile or electronic transmission shall be as effective as delivery of a manually executed counterpart hereof.

     SECTION 10. Applicable Law. THIS ASSUMPTION AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

     SECTION 11. Headings. The headings of this Assumption Agreement are for purposes of reference only and shall not limit or otherwise affect the meaning hereof.

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     IN WITNESS WHEREOF, the parties hereto have caused this Assumption Agreement to be duly executed by their respective authorized officers as of the day and year first above written.