Work for Others Agreement No. ERD-99-1731

                                     Between

                   LOCKHEED MARTIN ENERGY RESEARCH CORPORATION

           Operating Under Prime Contract No.DE-ACO5-96OR22464 for the
                           U. S. Department of Energy

                                       And

                             Theragenics Corporation

The  obligations  of the  above-identified  DOE  Contractor  shall  apply to any
successor in interest to said  Contractor  continuing  the  operation of the DOE
facility involved in this Work for Others Agreement.

Article I.  PARTIES TO THE AGREEMENT

The U. S.  Department of Energy  Contractor,  LOCKHEED  MARTIN  ENERGY  RESEARCH
CORPORATION  (hereinafter referred to as the "Contractor") has been requested by
Theragenics  Corporation  (hereinafter  referred to as the "Sponsor") to perform
the work set forth in each Task  Order,  attached  hereto as  Appendix  A. It is
understood by the Parties that, except for the intellectual  property provisions
of this  Agreement,  the  Contractor  is  obligated to comply with the terms and
conditions of its M&O contract with the United  States  Government  (hereinafter
called the  "Government")  represented by the United States Department of Energy
(hereinafter  called the "Department" or "DOE") when providing goods,  services,
products,  processes,  materials,  or  information  to the  Sponsor  under  this
Agreement.

Article II.  TERM OF THE AGREEMENT: MULTIPLE TASK ORDERS: ADMINISTRATION 
             ------------------------------------------------------------
             (DEVIATION)
             -----------

A.     The estimated period of performance will be set forth in each Task Order.
       The term of this  Agreement  shall be  effective as of the latter date of
       (1) the date on which it is signed by the last of the Parties thereto, or
       (2) the date on which it is approved by DOE.

B.     This is a master Work for Others Agreement that contemplates the issuance
       of an indefinite  number of Task Orders  pursuant to Attachment 1,  
       Statement of Work to the Agreement.  The  individual  Task Orders are set
       forth in Appendix A and approved by DOE. The  Contractor has further  
       agreed to enter into  additional  Task Orders  consistent  with the terms
       of the Statement of Work including the estimated  costs  therein,  if and
       when so requested by Sponsor,  provided that Sponsor's  options to enter 
       into these additional  Statement of Work will expire if not  exercised by
       written  notice to  Contractor  on or before  [Confidential  Treatment
       Requested].  It is the intention of the Parties to extend the  Agreement 
       throughout  the operating  life of the High Flux Isotope  Reactor and the
       Contractor  has initiated  the  procedure for obtaining  approval of
       such an extension.  Contractor  acknowledges  that Sponsor is investing 
       in the initial Task Order as well as other  initiatives  based on 
       Contractor's  commitment to perform the additional Task Orders specified 
       above as well, and Contractor  agrees that it shall perform these 
       additional Task Orders,  subject to the terms of this Agreement,  if 
       requested by  Sponsor,[Confidential  Treatment Requested] is incompatible
       with the DOE's mission or [Confidential Treatment Requested].

C.     The  Contractor  shall use its best efforts to provide the services under
       each Task Order as described therein.

D.     The Principal  Investigator(s)  and other key personnel to be assigned to
       each Task Order shall be specified in each Task Order, and shall,  except
       in case of events such as illness, resignation, other employment actions,
       conflicts of interest or if DOE determines that such personnel are needed
       to perform DOE mission or programmatic requirements,  be available to the
       specific  projects  listed in the Task  Order.  If any of such  personnel
       become unavailable as stated above,  Contractor will use its best efforts
       to  replace   them   promptly   with  other   personnel   of   comparable
       qualifications.

E      In addition to the work to be performed under the Task Orders, in 
       accordance  with DOE Order 481.1,  this Agreement  provides  for  access 
       to highly  specialized  or unique  DOE  facilities,  that is, the High 
       Flux Isotope  Reactor  ("HFIR") as follows.  Neither LMER nor DOE is 
       obligated  hereunder to maintain the HFIR in operation  or to keep it  
       operating  any  specified  percentage  of the time, but as long as the 
       HFIR is in operation and Sponsor has a continuing  need for its use,  
       Sponsor shall have the following  access  rights: (1)  [Confidential  
       Treatment  Requested]  (2) Sponsor shall have the exclusive right to  
       [Confidential Treatment  Requested] to irradiate  material, which right 
       will be exercised  through  Contractor under this Agreement,  as 
       contemplated  by  the  Statement  of  Work.  DOE  may,  however,   
       [Confidential  Treatment Requested],  on  terms to be  mutually  agreed, 
       for [Confidential Treatment Requested],  including  production  of
       isotopes for sale as long as the isotope is not  competitive  with the 
       Sponsor's  mission.  (3) Sponsor will be required to pay for irradiation 
       of target  material  [Confidential  Treatment  Requested] in accordance
       with DOE Accounting Policy. (4) Sponsor may [Confidential  Treatment  
       Requested] to irradiate  palladium for research or for medical or 
       commercial use for its own account or for sale to third  parties, subject
       to all applicable  laws and  regulations  governing the  production of 
       isotopes;  and (5)  [Confidential  Treatment Requested].


Article III.  COSTS (DEVIATION)
              -----------------

A.    The estimated cost for the work to be performed  under this Agreement will
      be set forth in each Task Order.

B.    The  Contractor  has no obligation to continue or complete  performance of
      the work on any Task Order issued  pursuant to this agreement at a cost in
      excess of the estimated cost, including any subsequent amendment set forth
      in each Task Order, except as provided in paragraph C below.

C.    The  Contractor agrees to provide at least 30 days' notice to the Sponsor 
      if the actual cost to complete performance will exceed the estimated cost 
      set forth in each Task Order.  If so requested by the Sponsor, the 
      Contractor  will  provide  its  best  estimate  of the  additional  cost, 
      and of the time  needed,  for completion,  or for  completion to the next 
      milestone in the Task Order,  if  applicable.  If upon receipt of
      this  information  Sponsor  elects to  continue  funding  the  effort, 
      the Task  Order  shall be  amended to appropriately  increase the budget 
      for the project and, if  applicable,  to extend the milestone  dates,  and
      the  Contractor  shall  continue  the work so long as Sponsor provides the
      needed  additional  funding in accordance  with the  principles of Article
      IV. Nothing  shall,  however,  require the Contractor to continue
      work if the  Contractor  concludes  in good  faith  that the  objective  
      of the work  will not be  reasonably attainable.

Article IV.  FUNDING AND PAYMENT (DEVIATION)
             --------------------------------

A.     The Sponsor shall provide  sufficient  funds in advance to reimburse the 
       Contractor for costs to be incurred in  performance of the work described
       in this  Agreement,  and the  Contractor  shall have no obligation to
       perform in the absence of adequate  advance funds.  If the estimated  
       period of performance for a given Task Order  exceeds  90  days  or  the
       estimated  cost  exceeds   $25,000,   the  Sponsor  may,   advance  funds
       incrementally.  In such a case, the Contractor  will initially  invoice 
       the Sponsor in an amount  sufficient to permit the work to proceed for 
       ninety  (90) days and  thereafter invoice the Sponsor  monthly so as to
       maintain  approximately  a 90-day  period that is funded in advance.  
       Payment  shall be made directly to the Contractor as specified in 
       Appendix A. Upon  termination or  completion,  any excess funds shall be 
       refunded by the Contractor to the Sponsor.

B.     The Contractor shall maintain such records as are normally maintained for
       DOE-supported work. The records of the Contractor shall not be subject to
       audit by the Sponsor;  however,  the Contractor shall make available upon
       request of the Sponsor,  where  reasonably  necessary  for the Sponsor to
       evaluate its expenditures or where otherwise considered appropriate, cost
       data and other  documents  concerning the services  performed  under this
       Agreement,   together  with  any  related  findings  and  all  reasonably
       necessary explanations or discussions.

Article V.  SOURCE OF FUNDS
            ---------------

The Sponsor  hereby  warrants and  represents  that, if the funding it brings to
this Agreement has been secured through other agreements,  such other agreements
do not have any terms and conditions  (including  intellectual  property)  which
conflict with the terms of this Agreement.

Article VI.  PROPERTY (DEVIATION)
             --------------------

Unless the  Parties  otherwise  agree in  writing,  all  equipment  produced  or
acquired with funds  provided by the Sponsor,  shall be delivered to the Sponsor
or otherwise disposed of as instructed by the Sponsor at the Sponsor's expense.

Article VII.  PUBLICATION MATTERS (DEVIATION)
              -------------------------------

The publishing  Party shall provide the other Party a sixty  (60)-day  period in
which to review and submit  comments  upon proposed  publications,  which either
disclose technical developments and/or research findings generated in the course
of this agreement, or identify or contain Proprietary Information (as defined in
paragraph  A.2 of  Article  XV).  The  publishing  Party  shall not  publish  or
otherwise disclose Proprietary Information identified by the other Party, except
as required by law or agreed to by both Parties.

Article VIII.  LEGAL NOTICE (DEVIATION)
               -------------------------

The  Parties  agree that the  following  legal  notice  shall be affixed to each
report  furnished to the Sponsor under this Agreement and to any report prepared
by Contractor under this Agreement which may be distributed by the Sponsor:

                               "DISCLAIMER NOTICE
                               ------------------

         This report was prepared by LOCKHEED MARTIN ENERGY RESEARCH CORPORATION
         (LMER) on behalf of the U. S. Department of Energy (DOE), as an account
         of work sponsored by  Theragenics  Corporation. Neither LMER,  DOE, the
         U. S.  Government,  or any person  acting on their behalf: (a) makes 
         any warranty or representation, express or implied, with respect to the
         information  contained in this report;  or (b) assumes any  liabilities
         with respect to the use of, or damages resulting from the use of any 
         information contained in the report"

Article IX.  DISCLAIMER; BEST EFFORTS (DEVIATION)
            -------------------------------------

THE GOVERNMENT AND THE CONTRACTOR MAKE NO EXPRESS OR IMPLIED  WARRANTY AS TO THE
CONDITIONS OF THE RESEARCH OR ANY INTELLECTUAL PROPERTY,  GENERATED INFORMATION,
OR  PRODUCT  MADE OR  DEVELOPED  UNDER THIS WORK FOR  OTHERS  AGREEMENT,  OR THE
OWNERSHIP,  MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE OF THE RESEARCH
OR RESULTING PRODUCT, THAT THE GOODS, SERVICES, MATERIALS,  PRODUCTS, PROCESSES,
INFORMATION,  OR DATA TO BE FURNISHED HEREUNDER WILL ACCOMPLISH INTENDED RESULTS
OR ARE SAFE FOR ANY PURPOSE INCLUDING THE INTENDED  PURPOSE,  OR THAT ANY OF THE
ABOVE WILL NOT  INTERFERE  WITH  PRIVATELY  OWNED RIGHTS OF OTHERS.  NEITHER THE
GOVERNMENT NOR THE  CONTRACTOR  SHALL BE LIABLE FOR SPECIAL,  CONSEQUENTIAL,  OR
INCIDENTAL   DAMAGES   ATTRIBUTED  TO  SUCH   RESEARCH  OR  RESULTING   PRODUCT,
INTELLECTUAL PROPERTY, GENERATED INFORMATION, OR PRODUCT MADE OR DELIVERED UNDER
THIS WORK FOR OTHERS AGREEMENT.

Subject to the foregoing,  Contractor  represents that Contractor shall,  within
sixty days after execution of this agreement,  use its best efforts to determine
whether  the  Contractor's  Office  of  Technology  Transfer  or  the  principal
investigators  named in the initial Task Orders have any actual  knowledge  that
any of the work to be done under this agreement,  or any of the goods, services,
materials,  products, processes,  information, or data to be furnished hereunder
as indicated in Attachment 1, the Statement of Work, will infringe or is claimed
to infringe,  any proprietary or intellectual  property rights of third parties.
As additional Task Orders are entered into  hereunder,  the Contractor will make
similar  inquiries of the  principal  investigators  named  therein as to actual
knowledge of infringement or claims of  infringement,  and will, if appropriate,
make additional  investigation  as to infringement  matters within the Office of
Technology  Transfer in light of the specific scopes of work agreed to for those
new Task  Orders.  If,  prior  to or  during  the  performance  of a task  order
Contractor  learns of any such  infringement  or claim thereof  relating to that
Task Order,  Contractor will promptly notify sponsor.  If during the term hereof
Sponsor raises specific  questions  related to possible claims of  infringement,
Contractor  will,  upon request,  use its best efforts to determine  what actual
knowledge  Contractor's  Office of Technology  Transfer or applicable  principal
investigators  have  that is  pertinent  to the  matter  in  question,  and will
disclose that pertinent information to Sponsor.

The  Contractor  shall use its best  reasonable  efforts to provide the services
under  each Task  Order as  described  therein.  Neither  the  Government,  DOE,
Contractor, nor persons acting on their behalf will be responsible, irrespective
of causes, for failure:

         (1) to perform the work,

         (2) provide the services, or

         (3) furnish the materials or information hereunder

at any  particular  time  or in any  specific  manner.  If at any  time  Sponsor
believes  that  Contractor  is not  using  its best  reasonable  efforts  in the
performance the work hereunder or is performing  contrary to this agreement or a
Task Order,  or if the Sponsor has any other problem with the performance of the
Contractor  hereunder,  Sponsor  shall be  entitled  to bring the problem to the
attention  of the  Assistant  Manager  for  Laboratories  of the DOE  Oak  Ridge
Operations  Office (the "Assistant  Manager").  The Assistant Manager shall hear
the matter  within a reasonable  time,  in a manner  deemed  appropriate  by the
Assistant  Manager,  and the Contractor  agrees to comply with any decision that
the Assistant Manager may, in his sole discretion,  issue to the Contractor with
respect to the matter. This right of Sponsor to present a matter for decision to
the Assistant  Manager is in addition to, and not in lieu of, Sponsor's right to
seek  alternate  dispute  resolution  under  Article XX, and any other rights of
Sponsor  under  this  agreement,   but  nothing  in  this  Article  creates  any
enforceable right against DOE.

Article X.  GENERAL INDEMNITY (DEVIATION)
           ------------------------------

The  Sponsor  agrees  to  indemnify  and  hold  harmless  the  Government,   the
Department,  the  Contractor  and  persons  acting  on  their  behalf  from  all
liability,  including costs and expenses incurred, to any person,  including the
Sponsor,  for injury to or death of persons or other living  things or injury to
or  destruction of property  arising out of the  performance of the Agreement by
the  Government,  the  Department,  the  Contractor,  or persons acting on their
behalf, or arising out of the use of the services performed, materials supplied,
or  information  given  hereunder  by any  person  including  the  Sponsor.  The
foregoing  indemnity shall not, however,  apply to liability  directly resulting
from the fault or negligence of the Government,  the Department, the Contractor,
or persons acting on their behalf.

Article XI.  PRODUCT LIABILITY INDEMNITY (DEVIATION)
             ---------------------------------------

Except for any liability resulting from any willful misconduct or negligent acts
or  omissions  of the  Government  or the  Contractor,  the  Sponsor  agrees  to
indemnify the Government and defend  Contractor  against any claim or proceeding
and pay all damages,  costs, and expenses,  including  attorney's fees,  arising
from  personal  injury or property  damage  occurring as a result of the making,
using,  or  selling  of a  product,  process,  or service by or on behalf of the
Sponsor, its assignees, or licensees,  which was derived from the work performed
under this Work for Others  Agreement.  In respect to this Article,  neither the
Government nor the Contractor shall be considered  assignees or licensees of the
Sponsor, as a result of reserved Government and Contractor rights. The indemnity
set forth in this  paragraph  shall  apply only if the  Sponsor  shall have been
informed as soon and as  completely  as practical by the  Contractor  and/or the
Government  of the  action  alleging  such  claim and shall  have been  given an
opportunity,  to the maximum  extent  afforded by  applicable  laws,  rules,  or
regulations,  to  participate  in and control its  defense,  and the  Contractor
and/or Government shall have provided all reasonably  available  information and
reasonable  assistance  requested by the  Sponsor.  No  settlement  of an action
against  the  Contractor  and/or  Government  for  which  the  Sponsor  would be
responsible  shall  be  made  without  the  consent  of the  Sponsor  and of the
Contractor and the Government (whenever either or both of the latter two parties
are  involved),  unless  required  by  final  decree  of a  court  of  competent
jurisdiction.

Article XII.  INTELLECTUAL PROPERTY INDEMNITY - LIMITED (DEVIATION)
              -----------------------------------------------------

The  Sponsor  shall  indemnify  the  Government  and the  Contractor  and  their
officers,  agents,  and  employees  against  liability,   including  costs,  for
infringement  of any United  States  patent,  copyright,  or other  intellectual
property  arising  out of any acts  required  or  directed  by the Sponsor to be
performed under this Agreement to the extent such acts are not already performed
at the facility.  Such indemnity shall not apply to a claimed infringement which
is settled  without  the consent of the  Sponsor  unless  required by a court of
competent jurisdiction.  Sponsor shall be entitled to notice, the opportunity to
defend and control the defense,  and  cooperation  from the  Contractor  and the
Government as more fully described in Article XI.

Article XIII.  NOTICE AND ASSISTANCE REGARDING PATENT AND COPYRIGHT INFRINGEMENT
               -----------------------------------------------------------------

The Sponsor shall report to the Department and the  Contractor,  promptly and in
reasonable written detail, each claim of patent or copyright  infringement based
on the  performance of this  Agreement of which the Sponsor has  knowledge.  The
Sponsor shall furnish to the  Department and the  Contractor,  when requested by
the Department or the Contractor, all evidence and information in the possession
of the Sponsor pertaining to such claim.

Article XIV.   PATENT RIGHTS - USE OF FACILITIES (CLASS WAIVER) (DEVIATION)
               ------------------------------------------------------------


1.       Definitions
         -----------  

         A.     "Subject  Invention"  means any  invention  or  discovery of the
                Contractor, or, to the extent the Sponsor is performing any work
                under this Agreement, of the Sponsor, conceived in the course of
                or  under  this  Agreement,  or,  in the  case  of an  invention
                previously  conceived by the Sponsor,  first actually reduced to
                practice  in the  course of or under  this  Agreement.  "Subject
                Invention"   includes  any  art,   method,   process,   machine,
                manufacture,  design or  composition  of matter,  or any new and
                useful  improvement  thereof,  or any variety of plant,  whether
                patented  or  unpatented  under the  Patent  Laws of the  United
                States of America or any foreign country.

         B.     "Patent  Counsel"  means the DOE Patent  Counsel  assisting  the
                procuring activity which has the  administrative  responsibility
                for the  facility  where the work under this  Agreement is to be
                performed.

2.       Rights of the Sponsor
         ---------------------

                  Election to retain rights

                  Subject to the  provisions  of paragraph  3.B. with respect to
                  any Subject Invention  reported and elected in accordance with
                  paragraph 4. of this  clause,  the Sponsor may elect to obtain
                  the entire right,  title, and interest throughout the world to
                  each Subject Invention and any patent application filed in any
                  country on a Subject  Invention  and in any  resulting  patent
                  secured  by the  Sponsor.  Where  appropriate,  the  filing of
                  patent applications by the Sponsor is subject to DOE and other
                  Government security regulations and requirements.

                  Minimum License

                  The Sponsor  reserves an  irrevocable,  nonexclusive,  paid-up
                  license in each patent  application  filed in any country on a
                  subject  invention  and any  resulting  patent  in  which  the
                  Sponsor  does  not  elect  to  take  title  or  in  which  the
                  Government  acquires  title.  The license  shall extend to the
                  Sponsor's  domestic  subsidiaries,  and  affiliates,  if  any,
                  within the corporate  structure of which the Sponsor is a part
                  and shall include the right to grant  sublicenses  of the same
                  scope as the  Sponsor was  legally  obligated  to do so at the
                  time this  agreement  was entered  into.  The license shall be
                  transferable  only  with  the  approval  of  DOE  except  when
                  transferred  to the  successor  of that part of the  Sponsor's
                  business to which the invention pertains.

3.       Rights of Contractor and Government
         -----------------------------------

                  A.       Assignment to either the Contractor or the Government
                  --------------------------------------------------------------

                           The Sponsor agrees to assign to either the Contractor
                           or the  Government,  as requested by the  Contractor,
                           the entire right,  title, and interest in any country
                           to each Subject  Invention of the Sponsor and to each
                           Subject  Invention  of  the  Contractor,   where  the
                           Sponsor:

                           (1)   does not elect pursuant to this clause to 
                                 retain such rights; or

                           (2)   elects to obtain  title to a Subject  Invention
                                 pursuant  to  paragraph  2. but fails to have a
                                 patent application filed in that country on the
                                 Subject  Invention  or decides  not to continue
                                 prosecution or not to pay any maintenance  fees
                                 covering the invention.

                  B.       Terms and Conditions of Waived Rights

                            (1)  To   preserve   the    Contractor's   and   the
                                 Government's   residual   rights   to   Subject
                                 Inventions,  and  in  patent  applications  and
                                 patents  on  Subject  Inventions,  the  Sponsor
                                 shall take all actions in reporting,  electing,
                                 filing   on,   prosecuting,   and   maintaining
                                 invention rights promptly, but in any event, in
                                 sufficient time to satisfy domestic and foreign
                                 statutory and regulatory time requirements, or,
                                 if the Sponsor decides not to take  appropriate
                                 steps to protect the invention rights, it shall
                                 notify the  Contractor  in  sufficient  time to
                                 permit either the  Contractor or the Government
                                 to  file,   prosecute,   and  maintain   patent
                                 applications and any resulting patents prior to
                                 the end of such  domestic or foreign  statutory
                                 or regulatory time requirements.

                           (2)   The   Sponsor   shall   convey  or  ensure  the
                                 conveyance   of   any   executed    instruments
                                 necessary to vest in either the  Contractor  or
                                 the  Government  the  rights  set forth in this
                                 clause.

                           (3)   With  respect to any Subject Invention in which
                                 the Sponsor obtains title, the Sponsor hereby 
                                 grants to the Government a  non-exclusive,  
                                 nontransferable, irrevocable,  paid-up  license
                                 to  practice  or have practiced  by or on 
                                 behalf of the  United  States the Subject 
                                 Invention throughout the world.

                           (4)   The Sponsor shall provide the Government a copy
                                 of any  patent  application  filed on a Subject
                                 Invention    within   6   months   after   such
                                 application  is  filed,  including  its  serial
                                 number and filing date.

                           (5)   Preference for U.S.  Industry.  Notwithstanding
                                 any other provision of this clause, the Sponsor
                                 agrees that  neither it nor any  assignee  will
                                 grant to any person the exclusive  right to use
                                 or sell any  Subject  Invention  in the  United
                                 States  unless  such  person  agrees  that  any
                                 products  embodying  the Subject  Invention  or
                                 produced   through   the  use  of  the  Subject
                                 Invention will be manufactured substantially in
                                 the  United  States.   However,  in  individual
                                 cases,  the  requirement  for such an agreement
                                 may be  waived  by DOE  upon a  showing  by the
                                 Sponsor or its  assignee  that  reasonable  but
                                 unsuccessful  efforts  have  been made to grant
                                 licenses   on   similar   terms  to   potential
                                 licensees  that would be likely to  manufacture
                                 substantially  in the  United  States  or  that
                                 under the circumstances domestic manufacture is
                                 not commercially feasible.

                           (6)   March-In  Rights.  The Sponsor agrees that with
                                 respect  to  any  Subject   Invention   of  the
                                 Contractor in which it has acquired title,  the
                                 DOE  shall  retain  the  right to  require  the
                                 Sponsor  to  grant a  responsible  applicant  a
                                 nonexclusive, partially exclusive, or exclusive
                                 license  to use the  Subject  Invention  in any
                                 field  of use,  on terms  that  are  reasonable
                                 under  the  circumstances,  or if  the  Sponsor
                                 fails to grant  such a  license,  to grant  the
                                 license  itself.  DOE may  exercise  this right
                                 only in exceptional  circumstances  and only if
                                 DOE determines that:

                                 (a)  the action is  necessary to meet health or
                                      safety  needs  that  are  not   reasonably
                                      satisfied by the Sponsor; or

                                 (b)  the  action  is   necessary  to  meet  the
                                      requirements  for public use  specified by
                                      Federal  regulations and such requirements
                                      are  not   reasonably   satisfied  by  the
                                      Sponsor; or

                                 (c)  such   action  is   necessary   because  a
                                      licensee of the exclusive  right to use or
                                      sell any Subject  Invention  in the United
                                      States  is  in  breach  of  the  agreement
                                      required by paragraph 3.B.(5).


                           (7)   The  Sponsor   agrees  to  refund  any  amounts
                                 received  as  royalty  charges  on any  Subject
                                 Invention in procurement by or on behalf of the
                                 Government  and to provide  for that  refund in
                                 any instrument transferring rights to any party
                                 in the invention.

                           (8)  The  Sponsor  agrees  to  include,   within  the
                                specification  of  any  United   States  patent
                                applications  and any patent issuing thereon 
                                covering a Subject Invention, the following 
                                statement.  "The Government has rights in this  
                                invention  pursuant to
                                (specify this underlying Agreement)."

4.       Invention Identification, Disclosures, and Reports
         ---------------------------------------------------

         A.     The  Sponsor  shall  furnish  the Patent  Counsel a written  
                report  containing  full and  complete technical  information  
                concerning each Subject Invention it makes within 6 months 
                after conception or first actual  reduction  to practice,  
                whichever  occurs  first,  in the course of or under this
                Agreement,  but in any  event  prior to any on sale,  public  
                use,  or  public  disclosure  of such invention  known to the 
                Sponsor.  The report shall  identify the contract and inventor 
                and shall be sufficiently  complete in technical  detail and  
                appropriately  illustrated by sketch or diagram to convey to one
                skilled  in the art to which the  invention  pertains a clear  
                understanding  to the extent  known at the time of  disclosure, 
                of the  nature,  purpose,  operation,  and to the extent
                known, the physical,  chemical,  biological,  or electrical  
                characteristics of the invention.  The report  should also 
                include any election of invention  rights under this clause.  
                When an invention is  reported  under  this  paragraph  
                4.A,  it shall be  presumed  to have been made in the  manner
                specified in Section (a)(1) and (2) of 42 USC 5908.

         B.     The  Contractor  shall report  Subject  Inventions it makes in 
                accordance  with the  procedures set forth in contract  
                DE-AC05-96OR22464.  In addition,  the  Contractor shall disclose
                to the Sponsor at the same time as disclosure to the  Department
                any Subject  Inventions  made by the  Contractor under this  
                Agreement  and the Sponsor  shall notify the  Department within 
                6 months of receipt of such  disclosure  by the Sponsor of any 
                election of patent  rights under this clause.  With respect
                to Subject  Inventions of which  Contractor  personnel are 
                inventors,  Contractor shall execute and deliver, or as 
                appropriate,  cause  the  inventors  to  execute  and  deliver, 
                to  Sponsor  any assignments  or other  instruments  reasonably 
                necessary to the filing of patent  applications  by
                Sponsor, or to the perfection and confirmation of Sponsor's 
                title in the Subject Invention.

         C.     Requests for extension of time for election under  subparagraphs
                A and B may be granted by Patent Counsel for good cause shown in
                writing.

5.       Limitation of Rights
         ----------------------

         Nothing  contained in this patent rights clause shall be deemed to give
         the  Government  any rights with respect to any invention  other than a
         Subject  Invention  except as set forth in the  Facilities  License  of
         paragraph 6.

6.       Facilities License
         ------------------

         In addition to the rights of the Parties with respect to  inventions or
         discoveries  conceived  or first  actually  reduced to  practice in the
         course  of or under  this  Agreement,  the  Sponsor  agrees to and does
         hereby grant to the Government an irrevocable,  non-exclusive,  paid-up
         license in and to any  inventions  or  discoveries  regardless  of when
         conceived  or first  actually  reduced to  practice  or acquired by the
         Sponsor,  which at any time, through completion of this Agreement,  are
         owned or controlled by the Sponsor and are incorporated in the facility
         as a result of this  Agreement  to such an extent that the  facility is
         not restored to the  condition  existing  prior to the Agreement (1) to
         practice or to have practiced by or for the Government at the facility,
         and (2) to transfer such license with the transfer of the facility. The
         acceptance or exercise by the  Government  of the aforesaid  rights and
         license shall not prevent the  Government  at any time from  contesting
         the enforceability,  validity,  or scope of, or title to, any rights or
         patents herein licensed.

7.       Early Termination of Agreement
         ------------------------------

         The terms and conditions of this clause shall survive the Agreement, in
         the event that the  Agreement is  terminated  before  completion of the
         Statement of Work.


Article XV.  RIGHTS IN TECHNICAL DATA - USE OF FACILITY     
                  (DEVIATION) 

A.       Definitions

         1.   "Generated Information" means information produced in the 
              performance of this Agreement.


         2.   Proprietary  Information" means information which is developed  at
              private  expense and (1) trade secrets or (2)  commercial or 
              financial information which is privileged or confidential under 
              the Freedom of Information  Act (5 USC 552 (b)(4)).  The term 
              includes  information  communicated  orally or by other means,  
              if the  information  is  designated at the time of disclosure or 
              thirty (30) days thereafter  as  Proprietary  Information,  or if 
              it  is  identical  to  of  documentary  information designated as 
              Proprietary  Information,  or if the  recipient  knows that it  
              embodies  Proprietary Information  previously  submitted  in  
              documentary  form  and  appropriately   designated  as  such.
              Proprietary  Information includes Generated  Information  which  
              is  categorized  and  marked  as Proprietary  Information by 
              Sponsor or by Contractor at Sponsor's direction. Generated 
              Information which has not yet been categorized by Sponsor as to 
              whether it is Proprietary  Information  will be treated as 
              Proprietary  Information of the Sponsor  pending such  
              categorization.  Information  shall be  deemed  appropriately  
              marked  as  Proprietary  Information  if  it  is  marked  as  
              "Proprietary Information"  or marked with words of manifestly  
              similar meaning such as  "Confidential",  "Secret",
              "Trade Secret" or "Proprietary".

         3.   "Unlimited  Rights" means the right to use,  disclose,  reproduce,
              prepare  derivative works,  distribute  copies to the public,  and
              perform publicly and display  publicly,  in any manner and for any
              purpose, and to have or permit others to do so.

B.       The Sponsor agrees to furnish to the Contractor or leave at the 
         facility that  information,  if any, which is (1) essential to the 
         performance of work by the Contractor personnel or (2) necessary for 
         the health and  safety  of  such  personnel  in the  performance  of  
         the  work.  Any  information  furnished  to the Contractor  shall be 
         presumed to have been delivered with Unlimited Rights unless marked as 
         described in paragraph A.2 above;  provided,  that if Sponsor  
         inadvertently  delivers Proprietary  Information without such markings,
         then (1) Sponsor shall have the right at any time to place such 
         markings  thereon,  and Contractor  shall  cooperate fully with such 
         effort;  and (ii)  Contractor  shall not be liable to Sponsor
         for any use or disclosure of that  information,  in good faith,  
         between the time of initial  delivery and the time Sponsor informs  
         Contractor that the information is Proprietary  Information and should 
         be marked as such.  Once the items are so marked, they shall from that
         point forward be treated as Proprietary Information.

C.      The Sponsor may  designate as  Proprietary  Information  any Generated  
        Information, where such data would embody trade secrets or would 
        comprise commercial or financial information that is privileged  or
        confidential if it were obtained from the Sponsor.  Such Proprietary  
        Information  will,  to the extent permitted by law, be maintained  in 
        confidence  and  disclosed or used by the  Contractor  (under  suitable
        protective  conditions) only for the purpose of carrying out the 
        Contractor's  responsibilities  under this Agreement.  If so authorized 
        by Sponsor, Contractor shall, on Sponsor's behalf, use its best efforts 
        to locate and  appropriately  mark all  copies of  Generated Information
        which Sponsor has designated as Proprietary Information (such 
        designation to be either by specific reference to particular 
        information, or categorical descriptions of types of Generated 
        Information constituting  Proprietary  Information.).  If
        information  is not marked by the  Contractor  when  delivered  to the 
        Sponsor and the Sponsor  believes it should be marked,  the Sponsor will
        mark the  information  itself and notify the Contractor of the omission
        that the Sponsor  believes to have occurred and the fact that the 
        Sponsor has affixed such  marking.  Until such  time as any  particular 
        Generated  Information  has  been  categorized and marked as Proprietary
        Information , Contractor will treat it as Proprietary  Information.  
        Contractor  may, at any time,  request guidance from Sponsor as to 
        whether particular information should be designated and marked as 
        Proprietary Information.  Upon completion of activities under this 
        Agreement (or, if appropriate,  upon completion of a given Task Order), 
        such  Proprietary  Information  and all copies thereof will be disposed 
        of as requested by the Sponsor,  at the  Sponsor's  expense.  Before the
        Contractor  releases  data  associated  with this Agreement  to anyone, 
        the  Sponsor  will be afforded  the  opportunity  to review  that data 
        to  ascertain whether it is Proprietary Information and to mark it as 
        such.

D.       The Government and Contractor agree to not disclose Proprietary 
         Information that is properly marked,  or Generated  Information  that 
         has not yet been  categorized  by the Sponsor as to whether it is 
         Proprietary Information  to  anyone  other  than the  Sponsor  without 
         written  approval  of the  Sponsor,  except to Government  employees  
         who are subject to the statutory provisions against disclosure of  
         confidential information  set forth in the Trade Secrets Act 
         (18 USC 1905).  The Government  and Contractor  shall have the right, 
         at reasonable  times up to 3 years after the  termination or completion
         of the  Agreement,  to inspect  any  information  designated  as  
         Proprietary  Information  by the  Sponsor,  for the  purpose of
         verifying that such information has been properly identified as 
         Proprietary Information.

E.       By, or within ninety (90) days after,  the date of  termination or 
         expiration of this  Agreement,  Sponsor shall  request the removal of 
         all of its Proprietary Information from the facility, at the  Sponsor's
         expense,  and when such request is made Contractor  shall assemble and
         deliver to the Sponsor the original and all copies of such information 
         and the Sponsor shall accept it and shall then be responsible for its
         removal from the facility.  The Government and Contractor  shall have 
         Unlimited  Rights in any information which is not removed from the 
         facility by Sponsor  after  delivery by  Contractor  to Sponsor as 
         described above,  or which is not  requested  by Sponsor to be  
         assembled  and  delivered  to Sponsor by  Contractor within the time 
         limit described  above.  Notwithstanding  the foregoing,  by mutual  
         consent,  Sponsor may allow Contractor or the Government to retain 
         copies of Proprietary  Information  without  compromising its
         status as such; for example,  the  information  might be needed for 
         follow-on tasks hereunder or for other projects to be undertaken by the
         Contractor or the Government with Sponsor's  consent. The Government 
         and Contractor  shall have Unlimited  Rights in any Proprietary  
         Information  which is  incorporated  into the facility or  equipment  
         under this  Agreement at  Sponsor's  request,  to such extent that the 
         facility or equipment is not restored to the condition existing prior 
         to such incorporation.

F.       The Sponsor agrees that the Contractor will provide to the Department a
         nonproprietary description of the work performed under this Agreement.

G.       The Government shall have Unlimited Rights in all Generated Information
         produced or information  provided by the Parties under this  Agreement,
         except  for  information  which is  disclosed  in a  Subject  Invention
         disclosure  being  considered  for  patent  protection,   or  which  is
         Proprietary Information.

H.       Copyrights
         ----------

         The Sponsor may assert  copyright in any of its Generated  Information,
         and may also  require the  Contractor,  at the  Sponsor's  expense,  to
         register  copyright  and/or  to  assign  to  Sponsor  copyright  in any
         Generated  Information produced by the Contractor and designated by the
         Sponsor.  Subject to the other  provisions  of this  clause,  including
         particularly  those  relating to  Proprietary  Information,  and to the
         extent that copyright is asserted, the Government reserves for itself a
         royalty-free,   world-wide,  irrevocable,   non-exclusive  license  for
         Governmental  purposes to publish,  distribute,  translate,  duplicate,
         exhibit,  prepare  derivative works, and perform any such data assigned
         to the Sponsor.

I.       The terms and conditions of this clause shall survive the Agreement.

Article XVI.  ASSIGNMENT (DEVIATION)
              ----------------------

Neither this  Agreement nor any interest  therein or claim  thereunder  shall be
assigned or transferred by either Party,  except as authorized in writing by the
other Party to this  Agreement,  which  authorization  shall not be unreasonably
withheld or delayed, provided, the Contractor may transfer it to the Department,
or its designee, with notice of such transfer to the Sponsor, and the Contractor
shall have no further  responsibilities  except  for the  confidentiality,  use,
and/or  non-disclosure  obligations of this Agreement.  In the event  Contractor
proposes to disapprove any assignment or transfer by Sponsor, Sponsor shall have
the right to appeal that decision to the Director of the DOE Oak Ridge Office of
Partnerships  and  Program  Development,  and  Contractor  shall  comply  with a
decision,  if any, by such  Director  that this  Agreement  shall be assigned or
transferred as requested by Sponsor. Further provided,  however, that nothing in
this Article creates any enforceable right against DOE.

Article XVII.  SIMILAR OR IDENTICAL SERVICES
               -----------------------------

The  Government  and/or  Contractor  shall have the right to perform  similar or
identical  services in the Statement of Work (SOW) for other Sponsors as long as
the Sponsor's Proprietary Information is not utilized.

Article XVIII.  EXPORT CONTROL
                --------------

Each  Party is  responsible  for its own  compliance  with laws and  regulations
governing export control.

Article XIX.  TERMINATION (DEVIATION)
              -----------------------

Performance of work under this Agreement may be terminated at any time by either
Party,  without  liability,  except as provided above, upon giving a thirty (30)
day  written  notice to the other  Party.  [Confidential  Treatment  Requested],
provided  however,  that the Contractor shall have the right to terminate if the
Sponsor shall have failed to advance the funds required by Article IV and failed
to cure the same within thirty (30) days after written  notice to Sponsor of the
default.  In the event of termination,  the Sponsor shall be responsible for the
Contractor's  costs through the effective date of  termination  which are either
(a)  incurred in the  performance  of tasks  which the Sponsor has  specifically
requested  Contractor to perform after the notice of termination is given,  such
as completing  experiments  in process,  providing the Sponsor with the research
data generated through the date of termination,  to finalize required reporting,
etc, or (b) are necessary closeout costs,  including but not limited to costs to
shut down any  experiment in process  which  Sponsor does not wish  completed or
which  cannot  be  completed  prior to  termination,  to pack  and ship  surplus
material and equipment, to finish categorizing Generated Information as provided
for in  Article  XV,  and to  assemble  Generated  Information  and  Proprietary
Information for transmittal to Sponsor; but in no event shall the Sponsor's cost
responsibility exceed the total cost to the Sponsor as described in Article III,
above. Closeout costs do not include costs for transitioning personnel.

It  is  agreed  that  any  obligations  of  the  Parties  regarding  Proprietary
Information or other intellectual property will remain in effect,  despite early
termination of the Agreement.

Article XX.  ALTERNATE DISPUTE RESOLUTION (DEVIATION)
             ----------------------------------------

Step 1.  NEGOTIATION

The Parties shall attempt in good faith to resolve any dispute arising out of or
relating to this Agreement by negotiating  between  executives  and/or officials
who have  authority to settle the  controversy  and who are at a higher level of
management than the persons with direct  responsibility  for  administration  of
this  contract.  Either  Party may give the other  Party  written  notice of any
dispute not  resolved  in the normal  course of  business.  Within 15 days after
delivery of the notice,  the receiving Party shall submit to the other a written
response.  The notice and the  response  shall  include (a) a statement  of each
Party's  position and a summary of arguments  supporting that position,  and (b)
the name and title of the  executive or official who will  represent  that Party
and of any other person(s) who will accompany the executive or official.  Within
30 days after delivery of the disputing  Party's notice,  the executives of both
Parties shall meet at a mutually  acceptable  time and place,  and thereafter as
often as they reasonably deem necessary,  to attempt to resolve the dispute. All
reasonable  requests  for  information  made by one party to the  other  will be
honored.

If the  matter has not been  resolved  within 60 days of the  disputing  Party's
notice,  or if the Parties fail to meet within 30 days,  either  party  initiate
mediation of the controversy or claim as provided hereafter.

All  negotiations  pursuant  to this  Agreement  are  confidential  and shall be
treated as compromise  and settlement  negotiations  for purposes of the Federal
Rules of Evidence and state rules of evidence.

Step 2.  MEDIATION

In the event the  dispute  has not been  resolved  by  negotiation  as  provided
herein,  the  Parties  agree  to  participate  in a one day  mediation,  using a
mutually agreed upon mediator. The mediator will not render a decision, but will
assist the Parties in reaching a mutually satisfactory agreement.

The  Parties  agree to  equally  split  the  costs of the  mediation.  The first
mediation  session shall commence within 30 days from agreement on the selection
of mediator.  The Parties may contact the DOE Office of Dispute  Resolution with
questions or for assistance  with selection of neutrals or samples of Agreements
to Mediate.

All  meditations  are  confidential  and  shall be  treated  as  compromise  and
settlement  negotiations for purposes of the Federal Rules of Evidence and state
rules of evidence.

Step 3.  ARBITRATION

Any dispute not otherwise  satisfactorily  resolved may, by mutual agreement, be
submitted to arbitration,  provided that both parties shall bear their own costs
of arbitration and further provided that such arbitration  shall be binding only
if the  Parties  have  previously  agreed upon the limits of the awards that may
result from arbitration,  pursuant to the Administrative  Dispute Resolution Act
through the American Arbitration  Association,  Jams/Endispute Center for Public
Resources,  United States  Arbitration  and  Mediation,  or other  reputable ADR
provider.


Article XXI.      CERTIFICATION

Sponsor  certifies  that to the best of its knowledge and belief the analysis or
other work or services to be provided hereunder cannot reasonably or practicably
be  conducted  in  private  facilities  or  with  private  equipment  reasonably
available.


IN WITNESS WHEREOF, THE PARTIES HERETO HAVE EXECUTED THIS 
AGREEMENT NO. ERD-99-1731


FOR LOCKHEED MARTIN ENERGY RESEARCH CORPORATION


Name:     /s/ Frank V. Damiano                                                  
         -----------------------------------
Title:   Sr. Contracts Admin                                                    
         -----------------------------------
Date:    March 25, 1999                                                     
         -----------------------------------


FOR THERAGENICS CORPORATION

Name:     /s/ Bruce W. Smith                                                   
         ------------------------------------
Title:   Executive V/P & CFO                                                    
         ------------------------------------
Date:    March 25, 1999                                                     
         ------------------------------------


ON BEHALF OF THE DEPARTMENT OF ENERGY

Name:    /s/ James A. Reafsnyder                                              
         ------------------------------------
         James A. Reafsnyder, Director       

Title:   Office of Partnerships and Program Development
         ----------------------------------------------

Date:    March 25, 1999                                                    
         -------------------------------------