JOINDER AGREEMENT
This JOINDER AGREEMENT (as amended, restated, amended and restated, supplemented
or otherwise modified from time to time, this “Agreement”) dated as of May
24, 2019 between BWXT ADVANCED TECHNOLOGIES LLC, a Delaware limited liability
company (the “New Subsidiary”), and WELLS FARGO BANK, N.A., in its capacity as
Administrative Agent (the “Administrative Agent”) under that certain Credit
Agreement, dated as of May 24, 2018 (as amended, restated, amended and restated,
supplemented or otherwise modified from time to time, the “Credit Agreement”),
among BWX TECHNOLOGIES, INC., a Delaware corporation, as a borrower thereunder
(the “Administrative Borrower”), BWXT CANADA LTD., an Ontario corporation (the
“Canadian Borrower”), the Lenders party thereto, the Administrative Agent, the
Swing Line Lender and each L/C Issuer (each as defined therein). All capitalized
terms used and not defined herein shall have the meanings given thereto in the
Credit Agreement or the applicable Loan Document referred to herein.
The Administrative Borrower desires to or is required by Section 6.22 of the
Credit Agreement to cause the New Subsidiary to become a “Domestic Guarantor”.
Accordingly, the New Subsidiary hereby agrees as follows with the Administrative
Agent, for the benefit of the Guaranteed Parties:
1.The New Subsidiary hereby agrees that by execution of this Agreement it is a
Domestic Guarantor (as defined in the Domestic Guaranty) under the Domestic
Guaranty as if a signatory thereof on the Closing Date, and the New Subsidiary
(a) shall comply with, and be subject to, and have the benefit of, all of the
terms, conditions, covenants, agreements and obligations set forth in the
Domestic Guaranty and (b) hereby makes each representation and warranty of a
Domestic Guarantor, as set forth in the Domestic Guaranty. The New Subsidiary
hereby agrees that (i) each reference to a “Domestic Guarantor” or the “Domestic
Guarantors” in the Domestic Guaranty and the other Loan Documents shall include
the New Subsidiary and (ii) each reference to the “Domestic Guaranty” as used
therein shall mean the Domestic Guaranty as supplemented hereby and as otherwise
amended, restated, amended and restated, supplemented or otherwise modified
prior to the date hereof. Without limiting the generality of the foregoing terms
of this paragraph 1, the New Subsidiary hereby, jointly and severally together
with the other Domestic Guarantors, guarantees to the Administrative Agent, for
the benefit of the Guaranteed Parties, as provided in the Domestic Guaranty, the
prompt payment and performance of the Guaranteed Obligations in full when due
(whether at stated maturity, as a mandatory prepayment, by acceleration or
otherwise) strictly in accordance with the terms thereof.
2.The New Subsidiary hereby agrees that by execution of this Agreement it is a
Domestic Grantor (as defined in the Domestic Collateral Agreement) under the
Domestic Collateral Agreement as if a signatory thereof on the Closing Date, and
the New Subsidiary (a) shall comply with, and be subject to, and have the
benefit of, all of the terms, conditions, covenants, agreements and obligations
set forth in the Domestic Collateral Agreement and (b) hereby makes each
representation and warranty of a Domestic Grantor, as set forth in the Domestic
Collateral Agreement. The New Subsidiary hereby agrees that (i) each reference
to a “Domestic Grantor” or the “Domestic Grantors” in the Domestic Collateral
Agreement and the other Loan Documents shall include the New Subsidiary, (ii)
each reference to the “Domestic Collateral Agreement” as used therein shall mean
the Domestic Collateral Agreement as supplemented hereby and as otherwise
amended, restated, amended and restated, supplemented or otherwise modified as
of the date hereof and (iii) each reference to a “Collateral” in the Domestic
Collateral Agreement and the other Loan Documents shall include all Collateral
(as defined in the Domestic Collateral Agreement) of the New Subsidiary (other
than any of New Subsidiary’s Excluded Assets). Without limiting the generality
of the foregoing terms of this paragraph 2, the New Subsidiary hereby grants to
the Administrative Agent, for the benefit of the Secured Parties, a security
interest in, and a right of setoff against, any and all right, title and
interest, whether now or hereafter owned or acquired, of the New Subsidiary in
and to the Collateral of the New Subsidiary.
3.Attached hereto as Annex A are supplements to Schedules 5.03 and 5.17(b) of
the Credit Agreement and each of the Schedules to the Domestic Collateral
Agreement to the extent such Schedules have or will change after the execution
and delivery hereof (which supplements include, as of the date hereof, all
information required to be provided therein with respect to the New Subsidiary).

--------------------------------------------------------------------------------

4.All notices and communications to the New Subsidiary shall be given to the
address of the Administrative Borrower set forth in, and otherwise made in
accordance with, Section 10.02 of the Credit Agreement.
5.The New Subsidiary hereby waives acceptance by the Administrative Agent and
the Guaranteed Parties of the guarantee by the New Subsidiary under the Domestic
Guaranty upon the execution of this Agreement by the New Subsidiary.
6.The New Subsidiary hereby acknowledges that (a) it has been advised by counsel
in the negotiation, execution and delivery of this Agreement and the other Loan
Documents to which it is deemed a party and (b) it has received a copy of the
Credit Agreement and the other Loan Documents and has reviewed and understands
the same.
7.This Agreement may be executed in counterparts (and by different parties
hereto in different counterparts), each of which shall constitute an original,
but all of which when taken together shall constitute a single contract.
Delivery of an executed counterpart of a signature page of this Agreement by
facsimile or other electronic imaging means shall be effective as delivery of a
manually executed counterpart of this Agreement.
8.This Agreement shall be governed by, and construed and interpreted in
accordance with, the laws of the State of New York.

[Signature Pages Follow]

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to be
duly executed as of the date first above written.
BWXT ADVANCED TECHNOLOGIES LLC,
as Domestic Guarantor

By: /s/ Kirt J. Kubbs                
Name:     Kirt J. Kubbs
Title:     Treasurer

--------------------------------------------------------------------------------

Acknowledged and accepted:

WELLS FARGO BANK, N.A.,
as Administrative Agent

By: /s/ Jonathan D. Beck                
Name:     Jonathan D. Beck
Title:     Vice President

--------------------------------------------------------------------------------

ANNEX A
Supplemental Schedules
Schedules to Credit Agreement

--------------------------------------------------------------------------------

Schedules to Domestic Collateral Agreement