Document:

<PAGE>

                                                                   EXHIBIT 10.45

             FIRST AMENDMENT TO CREDIT AND REIMBURSEMENT AGREEMENT

          THIS FIRST AMENDMENT TO CREDIT AND REIMBURSEMENT AGREEMENT (the
"Amendment") is made and dated as of the 27th day of March, 2000, by and among
SANWA BANK CALIFORNIA ("Sanwa"), as agent (the "Agent") for the Lenders
referenced below, KEYBANK NATIONAL ASSOCIATION, as Bond L/C Issuing Bank for the
Bond Letter of Credit referred to below (in such capacity, the "Bond L/C Issuing
Bank") and as co-agent (the "Co-Agent"), Sanwa Bank California, as issuing bank
for the Standard Letters of Credit referred to below (the "Standard L/C Issuing
Bank"), the Lenders from time to time party hereto, and ATG INC., a California
corporation (the "Company").

                                   RECITALS

          A.   The Company, the Agent, the Lenders, the Bond L/C Issuing
Bank and the Standard L/C Issuing Bank entered into a Credit and Reimbursement
Agreement dated as of November 1, 1999 (as amended, modified, or waived, the
"Agreement") pursuant to which the Lenders agreed to extend credit to the
Company on the terms and conditions set forth therein.

          B.   The Company has requested the Agent, the Lenders, the Bond L/C
Issuing Bank and the Standard L/C Issuing Bank to:

               (1)  Waive the Events of Default that have occurred as of
December 31, 1999 under the Agreement by reason of (1) the failure of the
Company to have a Current Ratio (as such term and all other capitalized terms
used herein and not otherwise defined are defined in the Agreement) of at least
1.10:1.00 and (2) the failure of the Company to have a Net Funded Debt/EBITDA
Ratio of not more than 3.50:1.00.

               (2)  Consent to the sale of its headquarters building in Fremont,
California in a sale-leaseback transaction prohibited by Paragraph 12(h) of the
                                                         ---------------
Agreement and to the incurrence by the Company of up to $15,000,000 of
Subordinated Debt not otherwise permitted by Paragraph 12(b) of the Agreement.
                                             ---------------

               (3)  Temporarily increase the Revolving Credit Limit by
$6,000,000.

               (4)  Amend the Agreement in certain other respects.

          C.   The Agent,  the Lenders,  the Bond L/C Issuing Bank and the
Standard L/C Issuing Bank have agreed to provide such waivers,  consents,  loans
and amendments on the terms and conditions contained in this Amendment.

          NOW, THEREFORE, in consideration of the above Recitals and for
other good and  valuable  consideration,  the receipt and  adequacy of which are
hereby acknowledged, the parties hereto hereby agree as follows:
<PAGE>

                                    AGREEMENT

          1.   Inducement Representations by the Company and Waivers and
               ---------------------------------------------------------
Consents.
--------

                    1(a) Inducement Representations.  In addition to the other
                         --------------------------
representations and warranties contained in this Amendment and the other terms
and provision hereof, to induce the other parties hereto to grant the waivers
and consents requested by the Company and to enter into this Amendment, the
Company hereby represents and warrants as of the Amendment Effective Date (as
such term is defined in Paragraph 3 below):
                        -----------
                         (1)  As of December 31, 1999, its Current Ratio was
0.71:1.00.

                         (2)  As of December 31, 1999, its Net Funded
Debt/EBITDA Ratio was 4.00:1.00.

                         (3)  Except for the breach of the covenants contained
in Paragraph 12(m) of the Agreement as described in the foregoing clauses (1)
   ---------------
and (2) (the "Existing Defaults"), no Events of Default or Potential Defaults
have occurred under the Agreement.

                         (4)  The Company (i) has fully and accurately disclosed
to the Agent, the Bond L/C Issuing Bank, the Standard L/C Issuing Bank, and the
Lenders the terms and conditions on which the Company intends to sell its
headquarters building in Fremont, CA and (ii) upon sale of such building, will
cause to be repaid in full all Indebtedness secured, in whole or in part, by a
Lien thereon and all such Liens will be terminated.

                         (5)  The Company (i) has fully and accurately disclosed
to the Agent, the Bond L/C Issuing Bank, the Standard L/C Issuing Bank, and the
Lenders the terms on which the Company intends to incur Subordinated Debt and
(ii) will not incur Subordinated Debt on terms materially less advantageous to
the Lenders than the terms contained in the draft commitment letter to the
Company dated as of February 24, 2000 from Key Mezzanine, a copy of which has
been delivered to each of the Lenders.

                    1(b) Waiver.  As of the Amendment Effective Date and subject
                         ------
to the terms and conditions of this Amendment, the Agent, the Lenders, the Bond
L/C Issuing Bank and the Standard L/C Issuing Bank waive the Existing Defaults.

                    1(c) Consents.  The Agent, the Lenders, the Bond L/C Issuing
                         --------
Bank and the Standard L/C Issuing Bank (1) consent to the sale of the Company's
headquarters building in Fremont, CA substantially on the terms and conditions
described in Paragraph 1(a)(4) above and (2) consent to the incurrence of
             -----------------
Subordinated Debt by the Company in an amount not less than $12,500,000 and not
greater than $15,000,000
<PAGE>

substantially on the terms and conditions  described in Paragraph 1(a)(5) above
                                                        -----------------
and otherwise on terms and conditions satisfactory to the Agent.

                    2.   Amendments.  As of the Amendment Effective Date, the
                         ----------
Agreement is amended as follows:

                    2(a) Principal Repayment of Revolving Loans from Proceeds of
                         -------------------------------------------------------
Subordinated Debt. To require the Company to repay outstanding Revolving Loans
-----------------
from the proceeds of Subordinated Debt, Paragraph 2(b) is amended to read as
                                        --------------
follows :

                         "2(b) Principal Repayment of Revolving Loans. The
                               ---------------------------------------
                    Company shall (i) finally repay the principal amount of each
                    Revolving Loan on the Revolving Loan Maturity Date and (ii)
                    subject to reborrowing in accordance with the other terms
                    and conditions of this Agreement, upon receipt of Net
                    Proceeds of Subordinated Debt, repay outstanding Revolving
                    Loans in an amount equal to such Net Proceeds."

                    2(b) Conditions to Disbursement of Richland Advances. To add
                         ------------------------------------------------
certain conditions precedent to the disbursement of the Richland Facility
Reserved Amount, the introductory paragraph to Paragraph 9(c) is amended to read
                                               --------------
as follows:

                         "9(c) Conditions to disbursements of funds from
                               -----------------------------------------
                    Disbursement Account. As conditions precedent to
                    --------------------
                    disbursement (i) from the Disbursement Account established
                    in Section 11(m) hereof and (ii) of Richland Facility
                    Advances to or for the account of the Company, unless waived
                    by the Lenders, each of the following conditions shall have
                    been fulfilled to the Agent's satisfaction:"

                    2(c) Accounts  Receivable  Aging. To require the Company to
                         ---------------------------
deliver accounts aging reports, Paragraph 11(a) of the Agreement is amended to
                                ---------------
replace the period (.) at the end of Paragraph 11(a)(5) with a semicolon (;) and
                                     ------------------
to insert thereafter a new Paragraph 11(a)(6) to read as follows:
                           ------------------

                         "(6) Within twenty (20) days after the end of each
                    fiscal quarter, an accounts receivable aging report (in form
                    and substance satisfactory to the Agent) for the accounts
                    receivable of the Company and its Subsidiaries as of the end
                    of such fiscal quarter."

                    2(d) Capital Expenditures.   To increase the Capital
                         --------------------
Expenditures that the Company may make in fiscal year 2000, to provide for
yearly adjustments thereafter and to require delivery of periodic budgets
therefor, Paragraph 12(i) of the Agreement is amended to read as follows:
          ---------------

                         "12(i) Capital Expenditures. Make or commit to make
                                --------------------
                    Capital Expenditures in any year in excess of the amount
                    budgeted therefor as set forth in a budget (which shall be
                    in form and substance satisfactory to the Agent) which the
                    Company shall deliver to the Agent at least ninety (90)
<PAGE>

                    days prior to the beginning of such fiscal year but, in any
                    event, not in excess of, (i) in fiscal year 2000, (a)
                    $7,000,000 plus (b) the aggregate amount of Richland
                    Facility Advances made under this Agreement plus (c) the
                    principal amount of the proceeds of the Bonds disbursed to
                    the Company pursuant to the Indenture during such year or
                    (ii) in any fiscal year thereafter, an amount acceptable to
                    the Required Lenders."

                    2(e) Financial Covenants.  To modify the financial
                         -------------------
covenants relating to the Net Funded Debt/EBITDA Ratio, Debt Service Ratio, and
Current Ratio consistent with the waivers contained in this Amendment,
Paragraphs 12 of the Agreement are amended to read as follows:
-------------

                         "12(m) Financial Covenants. On a consolidated basis,
                                -------------------
                    permit (or incur or agree to incur Indebtedness or become
                    liable in respect of any Contractual Obligation that is
                    reasonably likely to result in the Company, on a
                    consolidated basis, permitting):

                                        "(1) As at the end of any fiscal
                         quarter, the Net Funded Debt/ EBITDA Ratio to exceed
                         (i) as of March 31, 2000, 4.50: 1.00; (ii) as of June
                         30, 2000, 4.00:1.00; (iii) as of September 30, 2000,
                         3.50:1.00; (iv) as of December 31, 2000. March 31,
                         2001, June 30, 2001, and September 30, 2001, 3.00:1.00;
                         and (v) as of December 31, 2001 and thereafter,
                         2.50:1.00.

                                        "(2) As of the end of any fiscal
                         quarter, the Debt Service Ratio to be less than 1.25:
                         1.00.

                                        "(3) As of the end of any fiscal
                         quarter, the Current Ratio to be less than (i) as of
                         March 31, 2000, 0.70:1.00; (ii) as of June 30, 2000 and
                         September 30, 2000, 1.10:1.00; and (iii) thereafter,
                         1.20:1.00.

                                        "(4) At any time, the Tangible Net Worth
                         to be less than the Company's Tangible Net Worth as at
                         December 31, 1999 plus, as of the end of each fiscal
                         year thereafter, Net Profit after Tax plus an amount
                         equal to Net Proceeds of Equity Securities Issuances."

                    2(f) Definitions.   To (1) temporarily reduce Obligations
                         -----------
incurred under the Revolving Credit Limit that are included in the definition of
"Current Liabilities," (2) exclude Subordinated Debt from the definition of "Net
Funded Debt," (3) temporarily increase the amount defined as the "Revolving
Credit Limit," and (5) add definitions of "Richland Facility Advance," "Richland
Facility Reserved Amount, " such definitions are amended or added, as
appropriate, to Paragraph 16 of the Agreement to read as follows:
                ------------

                    "Current Liabilities shall mean, as of any date of
                     -------------------
                    determination, the total liabilities of the Company and its
                    Subsidiaries, determined on a
<PAGE>

                    consolidated basis, which would be shown as current
                    liabilities on a balance sheet prepared in accordance with
                    GAAP, plus the principal amount of outstanding Revolving
                    Loans less (a) until and including September 30, 2000,
                    $6,000,000; (b) from October 1, 2000 through and including
                    March 31, 2001, $4,000,000; (c) from April 1, 2001 through
                    and including September 30, 2001, $2,000,000; and (d)
                    thereafter, $0.00."

                    "Net Funded Debt' shall mean, as of any date, (i) the sum of
                     ---------------
                    Funded Debt and the face amount of Standard Letters of
                    Credit Outstanding minus (ii) Subordinated Debt minus (iii)
                    the amount then on deposit in the Disbursement Account, the
                    Sinking Fund Account, and the Excess Cash Account."

                    "'Revolving Credit Limit' shall mean:
                      ----------------------

                              "(i) until but not including June 30, 2000,
                              $24,000,000 and, thereafter, $18,000.000; minus

                              "(ii) on receipt, an amount equal to 100% of the
                              Net Proceeds of Subordinated Debt received by the
                              Company and its Subsidiaries; provided, however,
                              in no event shall the Revolving Credit Limit be
                              reduced below $18,000,000 by reason of such Net
                              Proceeds.

                              "(iii) any amount by which the Revolving Credit
                              Limit may be reduced in accordance with the
                              written request of the Company delivered to the
                              Agent not less than five (5) Business Days prior
                              to the proposed effectiveness of such reduction;
                              provided, that any such reduction shall be in a
                              minimum amount of $500,000 and in increments of
                              $500,000 in excess thereof."

                    "'Richland Facility Advance' shall mean a Revolving Loan
                      -------------------------
                    requested by the Company to complete the Project. Revolving
                    Loans requested by the Company shall be deemed Richland
                    Facility Advances (and be subject to the additional
                    conditions precedent to the disbursement thereof provided in
                    this Agreement) if, after making such Revolving Loans, the
                    aggregate outstanding Revolving Loans plus Standard Letters
                    of Credit otherwise would exceed the Revolving Credit Limit
                    minus the Richland Facility Reserved Amount."

                    "'Richland Facility Reserved Amount' shall mean One and One
                      ---------------------------------
                    Half Millions Dollars ($1,500,000) minus the aggregate
                    amount of Richland Facility Advances made under this
                    Agreement."

                    2(g) Interest, Fee and Percentage Share Schedules. To modify
                         --------------------------------------------
the interest and fees payable by the Company under the Agreement and to modify
the Percentage Shares of the Lenders, Appendix I and Schedule 2 to the Agreement
                                      ----------     ----------
are amended to read as set forth on Appendix I and Schedule 2 to this Amendment.
                                    ----------     ----------
Such amendment to Appendix I and Schedule 2 shall be effective April 3, 2000.
                  ----------     ----------
<PAGE>

          3.   Conditions.  This Amendment shall not be effective until the date
               ----------
(the "Amendment Effective Date") that each of the following conditions shall
have been satisfied or waived:

                   3(a)  The Company shall have delivered or shall have had
delivered to the Agent, in form and substance satisfactory to the Agent and its
counsel, each of the following (with sufficient copies for each of the Lenders):

                    (1)  A duly executed copy of this Amendment

                    (2)  A duly executed acknowledgment of this Amendment from
     each of the Guarantors;

                    (3)  Such credit applications, financial statements,
     authorizations and such information concerning the Company, the Guarantors
     and their respective business, operations and condition (financial and
     otherwise) as any Lender may reasonably request;

                    (4)  Certified copies of resolutions of the Board of
     Directors of the Company approving the execution and delivery of this
     Amendment; and

                    (5)  A certificate of the Secretary or Assistant Secretary
     of the Company certifying the names and true signatures of the officers of
     the Company authorized to sign this Amendment.

                    (6)  An opinion of counsel to the Company and the
     Guarantors, in form and substance satisfactory to the Agent, with respect
     to the due execution, delivery and enforceability of this Amendment and the
     enforceability of the Agreement as amended hereby

                    3(b) All acts and conditions (including, without limitation,
     the obtaining of any necessary regulatory approvals and the making of any
     required filings, recordings or registrations) required to be done and
     performed and to have happened precedent to the execution, delivery and
     performance of this Amendment and to constitute the same legal, valid and
     binding obligations, enforceable in accordance with their respective terms,
     shall have been done and performed and shall have happened in due and
     strict compliance with all applicable laws.

                    3(c) All documentation, including, without limitation,
     documentation for corporate and legal proceedings in connection with the
     transactions contemplated by this Amendment shall be satisfactory in form
     and substance to the Agent, the Bond L/C Issuing Bank, the Standard L/C
     Issuing Bank, the Lenders and their counsel.

                    3(d) The Company shall have paid to the Agent for the pro
rata account of each of the Lenders a fee equal to $120,000, and all reasonable
out-of pocket
<PAGE>

expenses (including fees and disbursements of counsel) of the Agent incurred in
connection with the preparation and negotiation of this Amendment shall have
been paid.

          4.   Representations and Warranties of the Company. In addition to the
               ---------------------------------------------
other representations and warranties of the Company contained in this Amendment,
as an inducement to the Agent, the Bond L/C Issuing Bank, the Standard L/C
Issuing Bank and each Lender to enter into this Amendment, the Company
represents and warrants to the Agent, the Bond L/C Issuing Bank, the Standard
L/C Issuing Bank and each Lender that:

                    4(a) Financial Condition.  The financial statements, dated
                         -------------------
December 31, 1999, copies of which have heretofore been furnished to each Lender
by the Agent, are complete and correct and present fairly in accordance with
GAAP the financial condition of the Company and its consolidated Subsidiaries at
such dates and the consolidated and consolidating results of their operations
and changes in financial position for the fiscal periods then ended .

                    4(b) No Change.  Since December 31, 1999, there has been no
                         ---------
material adverse change in the business, operations, assets or financial or
other condition of the Company or the Company and its Subsidiaries taken as a
whole.

                    4(c) Corporate Power; Authorization; Enforceable
                         -------------------------------------------
Obligations. The Company and each of its Subsidiaries has the corporate power
-----------
and authority and the legal right to execute and deliver this Amendment and to
perform the Agreement as amended hereby and has taken all necessary corporate
action to authorize the execution, delivery and performance of such Loan
Documents. This Amendment duly executed and delivered on behalf of the Company
and each of its Subsidiaries and constitutes the legal, valid and binding
obligation of such Person enforceable against such Person in accordance with its
terms, subject to the effect of applicable bankruptcy and other similar laws
affecting the rights of creditors generally and the effect of equitable
principles whether applied in an action at law or a suit in equity.

                    4(d) No Legal Bar.  The execution, delivery and performance
                         ------------
of this Amendment and the Agreement as amended hereby will not violate any
Requirement of Law or any Contractual Obligation of the Company or any of its
Subsidiaries the violation of which could have a Material Adverse Effect or
result in the creation of any Lien on any assets of the Company or any of its
Subsidiaries.

                    4(e) Accuracy of Representations in Agreement.  As of the
                         ----------------------------------------
Amendment Effective Date, all of the representations and warranties contained in
the Agreement and each of the other Loan Documents are true and correct in all
material respects except to the extent relating solely to an earlier date.

                    4(f) No Events of Default or Potential Defaults.  Except for
                         ------------------------------------------
the Existing Defaults, no Events of Default or Potential Defaults have occurred
under the Agreement.

          5.        Miscellaneous Provisions.
                    ------------------------
<PAGE>

                    5(a) Cumulative Rights; Waivers Limited.  The rights, powers
                         ----------------------------------
and remedies of the Agent, the Bond L/C Issuing Bank, the Standard L/C Issuing
Bank and the Lenders hereunder are cumulative and in addition to all rights,
power and remedies provided under any and all agreements between the Company and
any of such Persons relating hereto, at law, in equity or otherwise. The waivers
and consents granted by this Amendment are specific and limited to their terms.
Neither such waivers or consents or any delay or failure by the Agent, the Bond
L/C Issuing Bank, the Standard L/C Issuing Bank or the Lenders to exercise any
right, power or remedy shall constitute a waiver of any right, power or
privilege by such Persons (other than as specifically provided in this
Amendment), and no single or partial exercise by any of such Persons of any
right, power or remedy shall preclude other or further exercise thereof or any
exercise of any other rights, powers or remedies.

                    5(b) Entire Agreement.  This Amendment embodies the entire
                         ----------------
agreement and understanding between the parties hereto and supersede all prior
agreements and understandings relating to the subject matter hereof and thereof.

                    5(c) Survival.  All representations, warranties, covenants
                         --------
and agreements herein contained on the part of the Company shall survive the
termination of this Amendment and shall be effective until the Obligations are
paid and performed in full or longer as expressly provided herein.

                    5(d) Governing Law.  This Amendment shall be governed by and
                         -------------
construed in accordance with the internal laws of the State of California
without giving effect to its choice of law rules.

                    5(e) Counterparts.  This Amendment may be executed in any
                         ------------
number of counterparts, all of which together shall constitute one agreement.

                    5(f) Severability.  The illegality or unenforceability of
                         ------------
any provision of this Amendment or any instrument or agreement required
hereunder or thereunder shall not in any way affect or impair the legality or
enforceability of the remaining provisions hereof or thereof.
<PAGE>

          IN WITNESS  WHEREOF,  the  parties  hereto  have  caused  this
Amendment to be executed as of the day and year first above written.

                                   ATG INC., a California corporation

                                   By:__________________________________________
                                   Name: Frank Chiu_____________________________
                                   Title: Executive Vice President______________

                                   SANWA BANK CALIFORNIA, as Agent

                                   By___________________________________________
                                   Name: Rochelle F. Dineen_____________________
                                   Title: Vice President________________________

                                   SANWA BANK CALIFORNIA, as
                                   Standard L/C Issuing Bank and a Lender

                                   By___________________________________________
                                   Name: Rochelle F. Dineen_____________________
                                   Title: Vice President________________________

                                   KEYBANK NATIONAL ASSOCIATION,
                                   as Bond L/C Issuing Bank,Co-Agent and a
                                   Lender

                                   By:__________________________________________
                                   Name: Jill Scheuermann_______________________
                                   Title: Vice President________________________
<PAGE>

                                   FIRST BANK OF CALIFORNIA, as a
                                   Lender

                                   By:__________________________________________
                                   Name: Michael G. Barker______________________
                                   Title: Vice President________________________

                                   IMPERIAL BANK, as a Lender

                                   By:__________________________________________
                                   Name: Stephanie Arnold_______________________
                                   Title: Vice President________________________

                                   GENERAL BANK, as a Lender

                                   By:__________________________________________
                                   Name:________________________________________
                                   Title: Vice President________________________
<PAGE>

                             CONSENT OF GUARANTORS
                             ---------------------

Each of the undersigned  Guarantors  hereby consents to the execution,  delivery
and performance of the foregoing  Amendment and the Agreement as amended thereby
and reaffirms its Guaranty of the Obligations as of the Amendment Effective Date
as though such Guaranty were executed and delivered as of such date.

                                   ATG RICHLAND CORPORATION,
                                   a Washington corporation

                                   By:__________________________________________
                                   Name: Frank Chiu_____________________________
                                   Title: Executive Vice President______________

                                   ATG NUCLEAR SERVICES LLC,
                                   a Delaware limited liability company

                                   By:__________________________________________
                                   Name: Frank Chiu_____________________________
                                   Title: Executive Vice President______________

                                   ATG CATALYTICS LLC,
                                   a Delaware limited liability company

                                   By:__________________________________________
                                   Name: Frank Chiu_____________________________
                                   Title: Executive Vice President______________
<PAGE>

                                                                      APPENDIX I

                               PRICING SCHEDULE

     The LIBOR Spread, Base Rate Spread, Bond Letter of Credit Fee Percentage
and Standard Letter of Credit Fee Percentage shall be calculated according to
the following schedule, beginning on the 181st day after the date of this
Agreement, based on the Net Funded Debt/EBITDA Ratio as set forth in the
Compliance Certificate most recently delivered to the Lenders pursuant to
Paragraph 11(a) of this Agreement.
---------------

     If a Compliance Certificate is not delivered in accordance with Paragraph
                                                                     ---------
11(a) of this Agreement, the LIBOR Spread, Base Rate Spread, Bond Letter of
-----
Credit Fee Percentage and Standard Letter of Credit Fee Percentage shall be
calculated according to the following schedule based on the assumption that the
Net Funded Debt/EBITDA Ratio is 4.00 to 1.00 or greater.

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------
If the Net Funded Debt/EBITDA Ratio    The LIBOR Spread     The Base Rate        The Bond Letter of     The Standard Letter
-----------------------------------    ----------------     -------------        ------------------     -------------------
is:                                    is:                  Spread is:           Credit Fee             of Credit Fee
--                                     --                   ---------            -----------            -------------
                                                                                 Percentage is:         Percentage is:
                                                                                 ------------          --------------
---------------------------------------------------------------------------------------------------------------------------
<S>                                    <C>                  <C>                  <C>                    <C>
Equal to or greater than 4.00 to 1.00  3.25%                1.25%                3.25%                  2.75%
---------------------------------------------------------------------------------------------------------------------------
Equal to or greater than 3.50 to       3.00%                1.00%                3.00%                  2.50%
1.00 but less than 4.00 to 1.00
---------------------------------------------------------------------------------------------------------------------------
Equal to or greater than 3.00 to       2.75%                .75%                 2.75%                  2.25%
1.00 but less than 3.50 to 1.00
---------------------------------------------------------------------------------------------------------------------------
Equal to or greater than 2.50 to       2.50%                0.50%                2.50%                  1.50%
1.00 but less than 3.00 to 1.00
---------------------------------------------------------------------------------------------------------------------------
Equal to or greater than 2.00 to       2.25%                0.25%                2.25%                  1.75%
1.00 but less than 2.50 to 1.00
---------------------------------------------------------------------------------------------------------------------------
Equal to or greater than 1.50 to       2.00%                0.00%                2,00%                  1.50%
1.00 but less than 2.00 to 1.00
---------------------------------------------------------------------------------------------------------------------------
Less than 1.50 to 1.00                 1.75%                0.00%                1.75%                  1.25%
---------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

                                  SCHEDULE 2
                              (Percentage Shares)

Except in respect of the  Revolving  Credit  Limit,  Revolving  Loans,  Standard
Letters of Credit,  Revolving  Credit Limit  facility  fees payable  pursuant to
Paragraph 7(b), and Standard Letter of Credit fees payable pursuant to Paragraph
--------------                                                         ---------
7(c)(1), the Percentage Shares of the Lenders shall be:
-------

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------
              LENDER                                             PERCENTAGE SHARE
              ------                                             ----------------
-------------------------------------------------------------------------------------
<S>                                                        <C>
Sanwa Bank California                                        26.666666667%
-------------------------------------------------------------------------------------
Key Bank                                                     22.222222222%
-------------------------------------------------------------------------------------
General Bank                                                 18.888888889%
-------------------------------------------------------------------------------------
Imperial Bank                                                18.888888889%
-------------------------------------------------------------------------------------
First Bank of California                                     13.333333333%
-------------------------------------------------------------------------------------
</TABLE>

In respect of the Revolving Credit Limit,  Revolving Loans,  Standard Letters of
Credit,  Revolving Credit Limit facility fees payable pursuant to Paragraph 7(b)
and Standard Letter of Credit fees payable  pursuant to Paragraph  7(c)(1),  the
Percentage Shares of the Lenders shall be:

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------
                 LENDER                                         PERCENTAGE SHARE
                 ------                                         ----------------
------------------------------------------------------------------------------------
<S>                                                        <C>
Sanwa Bank California                                        26.6666667%
------------------------------------------------------------------------------------
Key Bank                                                     22.2222222%
------------------------------------------------------------------------------------
Imperial Bank                                                18.8888889%
------------------------------------------------------------------------------------
First Bank of California                                     18.0555555%
------------------------------------------------------------------------------------
General Bank                                                 14.1666667%
------------------------------------------------------------------------------------
</TABLE><PAGE>

                                                                   Exhibit 10.46

                       FORBEARANCE AND CONSENT AGREEMENT

                     TO CREDIT AND REIMBURSEMENT AGREEMENT

          THIS FORBEARANCE AND CONSENT AGREEMENT TO CREDIT AND REIMBURSEMENT
AGREEMENT (the "Forbearance Agreement") is made and dated as of the ___ day of
June, 2000, by and among SANWA BANK CALIFORNIA ("Sanwa"), as agent (the "Agent")
for the Lenders referenced below, KEYBANK NATIONAL ASSOCIATION, as Bond L/C
Issuing Bank for the Bond Letter of Credit (in such capacity, the "Bond L/C
Issuing Bank") and as co-agent (the "Co-Agent"), Sanwa Bank California, as
issuing bank for the Standard Letters of Credit (the "Standard L/C Issuing
Bank"), the Lenders from time to time party hereto, and ATG INC., a California
corporation (the "Company").

                                   RECITALS

          A.   The Company, the Agent, the Lenders, the Bond L/C Issuing Bank
and the Standard L/C Issuing Bank entered into a Credit and Reimbursement
Agreement dated as of November 1, 1999 (as amended by a First Amendment to
Credit and Reimbursement Agreement dated as of March 27, 2000 and as further
amended, modified, or waived, the "Credit Agreement") pursuant to which the
Lenders agreed to extend credit to the Company on the terms and conditions set
forth therein.

          B.   At the request of the Company and subject to the terms and
conditions contained in this Forbearance Agreement, the Lenders have agreed to
forbear until June 30, 2000 in the exercise of their rights under the Credit
Agreement upon the occurrence of Events of Default (as such term and all other
capitalized terms used herein and not otherwise defined are defined in the
Credit Agreement) under Paragraph 13(c) of the Reimbursement Agreement as a
                        ---------------
result of the following events (the "Existing Events of Default"):

                    (1)  In breach of its covenant in Paragraph 12(m)(1) of the
                                                      ------------------
     Reimbursement Agreement, the Company failed to have a Net Funded
     Debt/EBITDA Ratio of not more than 4.50:1.00 as of March 31, 2000; and

                    (2)  In breach of its covenant in Paragraph 12(m)(3) of the
                                                      ------------------
     Reimbursement Agreement, the Company failed to have a Current Ratio of at
     least 0.70:1.00 as of March 31, 2000.

          C.   At the request of the Company and subject to the terms and
conditions contained in this Forbearance Agreement, the Lenders have agreed to
consent to disbursements from the Disbursement Account without satisfaction of
the certain conditions in respect of the Richland Facility Reserved Amount.

          NOW, THEREFORE, in consideration of the above Recitals and for other
good and valuable consideration, the receipt and adequacy of which are hereby
acknowledged, the parties hereto hereby agree as follows:
<PAGE>

                                   AGREEMENT

          1.   Inducement Representations by the Company. In addition to the
               -----------------------------------------
other representations and warranties contained in this Forbearance Agreement and
the other terms and provisions hereof, to induce the other parties hereto to
grant the forbearances and consent requested by the Company and to enter into
this Forbearance Agreement, the Company hereby represents and warrants as of the
Forbearance Effective Date (as such term is defined in Paragraph 4 below):

                    1(a) The Company reasonably anticipates receiving net
     proceeds of not less than $3,000,000 from the issuance of preferred stock
     no later than June 30, 2000.

                    1(b) As of March 31, 2000, its Net Funded Debt/EBITDA Ratio
     was 5.19:1.00.

                    1(c) As of March 31, 2000, its Current Ratio was 0.63:1:00.

                    1(d) Except for the Existing Events of Default, no Events of
     Default or Potential Defaults have occurred under the Reimbursement
     Agreement.

          2.   Forbearance.
               -----------

                    2(a) Agreement to Forbear. For the term described in
                         --------------------
Paragraph 2(b) below, the Lenders hereby agree to forbear in the exercise of any
rights or remedies under the Reimbursement Agreement and any Loan Documents by
reason of the Existing Events of Default.

                    2(b) Terms of Forbearance. The agreement of the Lenders to
                         --------------------
forbear in the exercise of their rights shall terminate on the earlier of (i)
June 30, 2000, (ii) the date that any Potential Default or Event of Default (in
addition to an Existing Event of Default) shall occur under the Reimbursement
Agreement or (iii) the date on which any material adverse change shall occur in
the financial or other condition of the Company. The Company agrees that upon
expiration of the term of the forbearance in accordance with this Paragraph
2(b), the Lenders may, in their sole discretion and without further notice to
the Company, exercise any and all remedies available to them under the
Reimbursement Agreement and the Loan Documents by reason of the occurrence of
any Events of Default thereunder.

          3.   Consent. In accordance with Paragraph 9(c) of the Agreement, the
               -------                     --------------
Lenders agree that the conditions set forth in Paragraph 9(c) shall not be
                                               --------------
conditions to the disbursement of Richland Advances made after the date of this
Forbearance Agreement.

          4.   Conditions. This Forbearance Agreement shall not be effective
               ----------
until the date (the "Forbearance Agreement Effective Date") that each of the
following conditions shall have been satisfied or waived:
<PAGE>

                    4(a) The Company shall have delivered or shall have had
delivered to the Agent, in form and substance satisfactory to the Agent and its
counsel, each of the following (with sufficient copies for each of the Lenders):

                         (1)  A duly executed copy of this Forbearance
          Agreement;

                         (2)  A duly executed acknowledgment of this Forbearance
          Agreement from each of the Guarantors;

                         (3)  Such credit applications, financial statements,
          authorizations and such information concerning the Company, the
          Guarantors and their respective business, operations and condition
          (financial and otherwise) as any Lender may reasonably request;

                    4(b) All acts and conditions (including, without limitation,
     the obtaining of any necessary regulatory approvals and the making of any
     required filings, recordings or registrations) required to be done and
     performed and to have happened precedent to the execution, delivery and
     performance of this Forbearance Agreement and to constitute the same legal,
     valid and binding obligations, enforceable in accordance with their
     respective terms, shall have been done and performed and shall have
     happened in due and strict compliance with all applicable laws.

                    4(c) All documentation, including, without limitation,
documentation for corporate and legal proceedings in connection with the
transactions contemplated by this Forbearance Agreement shall be satisfactory in
form and substance to the Agent, the Bond L/C Issuing Bank, the Standard L/C
Issuing Bank, the Lenders and their counsel.

                    4(d) The Company shall have paid to the Agent for the pro
rata account of each of the Lenders all reasonable out-of pocket expenses
(including fees and disbursements of counsel) of the Agent incurred in
connection with the preparation and negotiation of this Forbearance Agreement.

          5.   Representations and Warranties of the Company. In addition to the
               ---------------------------------------------
other representations and warranties of the Company contained in this
Forbearance Agreement, as an inducement to the Agent, the Bond L/C Issuing Bank,
the Standard L/C Issuing Bank and each Lender to enter into this Forbearance
Agreement, the Company represents and warrants to the Agent, the Bond L/C
Issuing Bank, the Standard L/C Issuing Bank and each Lender that:

                    5(a) Financial Condition. The financial statements, dated
                         -------------------
March 31, 2000, copies of which have heretofore been furnished to each Lender by
the Agent, are complete and correct and present fairly in accordance with GAAP
the financial condition of the Company and its consolidated Subsidiaries at such
dates and the consolidated and consolidating results of their operations and
changes in financial position for the fiscal periods then ended.

                    5(b) No Change. Except as previously disclosed to the
                         ---------
Lenders, since March 31, 2000, there has been no material adverse change in the
business, operations, assets or
<PAGE>

financial or other condition of the Company or the Company and its Subsidiaries
taken as a whole.

               5(c) Corporate Power; Authorization; Enforceable Obligations. The
                    -------------------------------------------------------
Company and each of its Subsidiaries has the corporate power and authority and
the legal right to execute and deliver this Forbearance Agreement and to perform
the Reimbursement Agreement as modified hereby and has taken all necessary
corporate action to authorize the execution, delivery and performance of such
Loan Documents. This Forbearance Agreement duly executed and delivered on behalf
of the Company and each of its Subsidiaries and constitutes the legal, valid and
binding obligation of such Person enforceable against such Person in accordance
with its terms, subject to the effect of applicable bankruptcy and other similar
laws affecting the rights of creditors generally and the effect of equitable
principles whether applied in an action at law or a suit in equity.

               5(d) No Legal Bar. The execution, delivery and performance of
                    ------------
this Forbearance Agreement and the Forbearance Agreement as modified hereby will
not violate any Requirement of Law or any Contractual Obligation of the Company
or any of its Subsidiaries the violation of which could have a Material Adverse
Effect or result in the creation of any Lien on any assets of the Company or any
of its Subsidiaries.

               5(e) Accuracy of Representations in Agreement. As of the
                    ----------------------------------------
Forbearance Agreement Effective Date, all of the representations and warranties
contained in the Reimbursement Agreement and each of the other Loan Documents
are true and correct in all material respects except to the extent relating
solely to an earlier date.

          6.   Miscellaneous Provisions.
               ------------------------

               6(a) Cumulative Rights; Waivers Limited. The rights, powers and
                    ----------------------------------
remedies of the Agent, the Bond L/C Issuing Bank, the Standard L/C Issuing Bank
and the Lenders hereunder are cumulative and in addition to all rights, power
and remedies provided under any and all agreements between the Company and any
of such Persons relating hereto, at law, in equity or otherwise. The consent
granted by this Forbearance Agreement is specific and limited to its terms.
Neither such consent or any delay or failure by the Agent, the Bond L/C Issuing
Bank, the Standard L/C Issuing Bank or the Lenders to exercise any right, power
or remedy shall constitute a waiver of any right, power or privilege by such
Persons (other than as specifically provided in this Forbearance Agreement), and
no single or partial exercise by any of such Persons of any right, power or
remedy shall preclude other or further exercise thereof or any exercise of any
other rights, powers or remedies.

               6(b) Entire Agreement. This Forbearance Agreement embodies the
                    ----------------
entire agreement and understanding between the parties hereto and supersede all
prior agreements and understandings relating to the subject matter hereof and
thereof.

               6(c) Survival. All representations, warranties, covenants and
                    --------
agreements herein contained on the part of the Company shall survive the
termination of this Forbearance Agreement and shall be effective until the
Obligations are paid and performed in full or longer as expressly provided
herein.
<PAGE>

               6(d) Governing Law. This Forbearance Agreement shall be governed
                    -------------
by and construed in accordance with the internal laws of the State of California
without giving effect to its choice of law rules.

               6(e) Counterparts. This Forbearance Agreement may be executed in
                    ------------
any number of counterparts, all of which together shall constitute one
agreement.

               6(f) Severability. The illegality or unenforceability of any
                    ------------
provision of this Forbearance Agreement or any instrument or agreement required
hereunder or thereunder shall not in any way affect or impair the legality or
enforceability of the remaining provisions hereof or thereof.
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Forbearance
Agreement to be executed as of the day and year first above written.

                                    ATG INC., a California corporation

                                    By:_________________________________________
                                    Name: Frank Chiu____________________________
                                    Title: Executive Vice President_____________

                                    SANWA BANK CALIFORNIA, as Agent

                                    By__________________________________________
                                    Name: Rochelle F. Dineen____________________
                                    Title: Vice President_______________________

                                    SANWA BANK CALIFORNIA, as Standard L/C
                                    Issuing Bank and a Lender

                                    By__________________________________________
                                    Name: Rochelle F. Dineen____________________
                                    Title: Vice President_______________________

                                    KEYBANK NATIONAL ASSOCIATION, as Bond L/C
                                    Issuing Bank, Co-Agent and a Lender

                                    By:_________________________________________
                                    Name: Jill Scheuermann______________________
                                    Title: Vice President_______________________
<PAGE>

                                    FIRST BANK OF CALIFORNIA, as a Lender

                                    By:_________________________________________
                                    Name: Michael G. Barker_____________________
                                    Title: Vice President_______________________

                                    IMPERIAL BANK, as a Lender

                                    By:_________________________________________
                                    Name: Stephanie Arnold______________________
                                    Title: Vice President_______________________

                                    GENERAL BANK, as a Lender

                                    By:_________________________________________
                                    Name:_______________________________________
                                    Title:______________________________________
<PAGE>

                             CONSENT OF GUARANTORS
                             ---------------------

Each of the undersigned Guarantors hereby consents to the execution, delivery
and performance of the foregoing Forbearance Agreement and reaffirms its
Guaranty of the Obligations as of the Forbearance Agreement Effective Date as
though such Guaranty were executed and delivered as of such date.

                                    ATG RICHLAND CORPORATION,
                                    a Washington corporation

                                    By:_________________________________________
                                    Name: Frank Chiu____________________________
                                    Title: Executive Vice President_____________

                                    ATG NUCLEAR SERVICES LLC,
                                    a Delaware limited liability company

                                    By:_________________________________________
                                    Name: Frank Chiu____________________________
                                    Title: Executive Vice President_____________

                                    ATG CATALYTICS LLC,
                                    a Delaware limited liability company

                                    By:_________________________________________
                                    Name: Frank Chiu____________________________
                                    Title: Executive Vice President_____________

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