SEVERANCE AND RELEASE AGREEMENT

Exhibit 10(kk)

SEVERANCE AND RELEASE AGREEMENT

This Severance and Release Agreement (the “Agreement”) is entered into by and among Luminant Holding Company LLC (the “Company”), Energy Future Holdings Corp. (the parent entity of the Company, “Holdings”), and Michael McCall (“Executive”). Executive and the Company are referred to in this Agreement as the “Parties.”

RECITALS

WHEREAS, the Executive previously notified Company that he has decided to terminate his employment with the Company for Good Reason, as defined in the amended and restated employment agreement between Executive and the Company dated June 6, 2008 (“Employment Agreement”);

WHEREAS, the Company has accepted Executive’s resignation for Good Reason; and

WHEREAS, the Company and Executive desire to enter into this Agreement setting forth the terms of Executive’s separation from the Company.

NOW, THEREFORE, in consideration of the promises and mutual agreements in this Agreement, and for other good and valuable consideration, the receipt and legal sufficiency which are acknowledged, the Company and Executive agree as follows:

ARTICLE 1

RESIGNATION AND TERMINATION OF EMPLOYMENT

Effective 12:01 a.m. on January 31, 2009 (the “Separation Date”), Executive’s employment with the Company shall end and he shall resign from all positions he held as an officer of the Company and any entity that controls, is controlled by, or is under common control with the Company (an “Affiliate”).

On or before the Separation Date, Executive shall return all property of the Company and its Affiliates, including all Confidential Information (as defined below), in his possession. If Executive discovers, or comes into possession of, any such Confidential Information after the Separation Date, he shall promptly return it to the General Counsel for Energy Future Holdings Corp.

ARTICLE 2

SEVERANCE PAYMENT AND BENEFITS

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ARTICLE 3

WAIVER AND RELEASE

Executive represents that he has not filed any complaints of any kind whatsoever with any local, state, federal, or governmental agency or court against the Company based upon, or in any way related to, Executive’s employment with the Company. Executive further represents that he understands that the payments and benefits provided for in Article 2 constitute a full and complete satisfaction of any claims, asserted or unasserted, known or unknown, that Executive has or may have against the Company or an Affiliate except as provided below. In exchange for the payments to be made by the Company and benefits to be received by Executive under this Agreement, Executive individually and on behalf of Executive’s spouse, heirs, successors, and assigns hereby agrees not to sue or instigate any grievance, charge, claim, action, or suit, at law or in equity, and unconditionally releases, dismisses, and forever discharges the Company, including its predecessors, successors, parents, subsidiaries, affiliated corporations, limited liability companies and partnerships, including (but not limited to) Energy Future Holdings Corp., Energy Future Competitive Holdings Company, Luminant Holding Company LLC, Luminant Energy Services Company, Luminant Mining Services Company, Luminant Power Services Company, EFH Corporate Services Company, TXU Retail Services Company, Texas Competitive Electric Holdings Company LLC, TXU Energy Retail Company LLC, Luminant Energy Company LLC, TXU Energy Solutions Company LLC, Oncor Electric Delivery Holdings Company LLC, Oncor Electric Delivery Company LLC, Luminant Generation Company LLC, Generation MT Company LLC, Generation SVC Company, Luminant Mining Company LLC, and all of their employee benefit plans, officers, directors, fiduciaries, employees, assigns, representatives, agents, and counsel (collectively the “Released Parties”) from any and all claims, demands, liabilities, obligations, agreements, damages, debts, and causes of action arising out of, or in any way connected with, Executive’s employment with or separation from the Company or any of the Released Parties. This waiver and release includes, but is not limited to, all claims and causes of action arising under or related to Title VII of the Civil Rights Act of 1964, as amended; the Civil Rights Act of 1991; the Civil Rights Act of 1866; Section 1981 of Title 42 of the United States Code, as amended; the Age Discrimination in Employment Act of 1967, as amended; the Americans with Disabilities Act; the Employee Retirement Income Security Act of 1974, as amended; Section 211 of the Energy Reorganization Act; the Sarbanes-Oxley Act of 2002; the Older Workers Benefit Protection Act of 1990; the Worker Adjustment and Retraining Notification Act; the Occupational Safety and Health Act, as amended; the Family and Medical Leave Act; the Texas Labor Code, including (but not limited to) Chapter 451; the Texas Commission on Human Rights Act; all state and federal statutes and regulations; all oral or written contract rights, including any rights under any Company incentive plan, program, or labor agreement; and all claims arising under common law including breach of contract, tort, or for personal injury of any sort.

Executive understands that this Waiver and Release precludes him from recovering any relief as a result of any lawsuit, grievance, or claim brought on his behalf and arising out of his employment or separation from employment with the Company. However, nothing in this Waiver and Release restricts Executive in any way from truthful communications with, filing a charge or complaint with, or full cooperation in the investigations of, any governmental agency

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on matters within their jurisdictions or from cooperating with the Company in any internal investigation. Furthermore, nothing in this Waiver and Release shall preclude any claim relating to: (i) Executive’s rights under this Agreement, (ii) Executive’s rights under Exhibit IV of the Employment Agreement with respect to the imposition of excise taxes imposed pursuant to Section 4999 of the Code (“Excise Taxes”) arising by reason of or in connection with the October 10, 2007 closing of the transactions contemplated by the agreement and plan of merger among TXU Corp., Texas Energy Future Holdings Limited Partnership and Texas Energy Future Merger Sub Corp ( the “Merger Agreement”), (iii) any rights to indemnification (including any to advancement or payment of defense and/or related legal costs) and rights to coverage under director and officer liability insurance under Section 10(h) of the Employment Agreement or Section 6.11 of the Merger Agreement, and (iv) facts, agreements, or causes of action arising after the date hereof.

The Company, on behalf of itself and its Affiliates, hereby releases, discharges and agrees to indemnify and hold harmless Executive from any and all claims and causes of action that it or they may have against Executive arising out of his employment with, or separation from, the Company or any Affiliate. Such release, discharge, and indemnification does not include claims for violation of any law, including any securities law or willful misconduct (the Company acknowledges that it is not aware of any such conduct as of the execution of this Agreement). Company further acknowledges and agrees that Executive’s sole obligations to Company from and after the Separation Date are set forth in this Agreement and that, except as provided below, all prior and contemporaneous agreements, whether written or oral, are terminated and of no further force and effect as of the Separation Date.

ARTICLE 4

CONSULTATION AND REVOCATION PERIODS

Executive understands that signing this Agreement, including the Waiver and Release described in Article 3, is an important legal act. Executive acknowledges that he has been advised to consult with legal counsel of his own choosing in connection with the matters addressed in this Agreement. Executive further acknowledges that he has twenty-one (21) days from the day he received this offer to consider this Agreement. Executive understands further that, for a period of seven (7) days following his signing of this Agreement (“Revocation Period”), he may revoke his acceptance of the offer represented by this Agreement by either delivering or mailing a written statement revoking his acceptance to the General Counsel, Energy Future Holdings Corp. at 1601 Bryan Street, Dallas, Texas 75201. In the event of such a revocation, the terms of this Agreement will be null and void, and any payments made to Executive pursuant to this Agreement prior to the end of the Revocation Period (other than the Accrued Rights described under Section 2.1.a.(i) and any other payments the Company is otherwise legally obligated to make to Executive) must be promptly repaid to the Company, and Executive expressly acknowledges a debt to the Company for the full amount of such payments plus any interest earned on such payments between the time of payment to Executive and his repayment to the Company. Employee acknowledges a personal debt to the Company of such amount and agrees to promptly pay the Company the full amount of that debt.

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ARTICLE 5

NON-DISCLOSURE, NON-COMPETITION, NON-SOLICITATION

AND NON-DISPARAGEMENT

Confidential Information shall mean information: (i) disclosed to or known by Executive as a consequence of or through his employment with Holdings, the Company or any of their respective Affiliates; (ii) not publicly available or not generally known outside Holdings, the Company or any of their respective Affiliates; and (iii) that relates to the business and development of Holdings, the Company or any of their respective Affiliates. Any information that does not meet each of the criteria listed above (in subsections (i) – (iii)) shall not constitute Confidential Information. By way of example, Confidential Information shall include but not be limited to the following: all non-public information or trade secrets of Holdings, the Company or any of their respective Affiliates that gives Holdings, the Company or any of their respective Affiliates a competitive business advantage or the opportunity of obtaining such advantage, or disclosure of which might be detrimental to the interests of Holdings, the Company or any of their respective Affiliates; information regarding Holdings’, the Company’s or any of their respective Affiliates’ business operations, such as financial and sales data (including budgets, forecasts, and historical financial data), operational information, plans, and strategies; business and marketing strategies and plans for various products and services; rate and regulatory strategy and plans; information regarding suppliers, consultants, employees, and contractors; technical information concerning products, equipment, services, and processes; procurement procedures; pricing and pricing techniques; information concerning past, current and prospective customers, investors, and business affiliates; plans or strategies for expansion or acquisitions; budgets; research; trading methodologies and terms; communications information; evaluations, opinions, and interpretations of information and data; marketing and merchandising techniques; electronic databases; models; specifications; computer programs; contracts; bids or proposals; technologies and methods; training methods and processes; organizational structure; personnel information; payments or rates paid to consultants or other service providers; and Holdings’, Company’s or any of their respective Affiliates’ files, physical or electronic documents, equipment, and proprietary data or material in whatever form including all copies of all such materials. By way of clarification (but not limitation), information that Executive conceived or developed during his employment with Holdings or its subsidiaries or learned from other employees or contractors of Holdings or its subsidiaries that meets the definition of Confidential Information shall be treated as such.

Executive understands and confirms that, as a result of his employment with the Company and its Affiliates, he has obtained Confidential Information. Executive hereby reconfirms his prior commitments in Section 9.a.(i) of the Employment Agreement and Section II of the Code of Conduct, and hereby agrees to maintain all Confidential Information in strictest confidence. Accordingly, Executive will not: (a) use Confidential Information in any way (including, without limitation, to the detriment of the Released Parties or in any future business relationship of Executive); (b) publish or disclose any Confidential Information; or (c) authorize anyone else to use, publish, or disclose any Confidential Information. Executive also agrees and acknowledges that all terms and conditions contained in this Agreement are to remain strictly

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confidential, and he agrees not to communicate or otherwise disclose the existence, terms, conditions, contents, or negotiations relating to this Agreement to any person or entity other than his spouse, financial advisor, tax advisor, or attorney in any manner, whether directly or indirectly, without prior written consent from the Company authorizing the particular disclosure requested. Any authorized disclosure to Executive’s spouse, financial advisor, tax advisor, or attorney shall be accompanied by an instruction that the Agreement and related information remain confidential.

Executive agrees to promptly notify Company of any attempts to compel disclosure of Confidential Information or information regarding this Agreement and to provide Company an opportunity to challenge such disclosure by promptly sending written notice to the General Counsel of Holdings.

The Parties shall not make, repeat, or publish to any third party any false, disparaging, defamatory, accusatory, or derogatory remarks or references about one another, whether oral or in writing, concerning the other Party or any of the Released Parties, or otherwise take any such action that might reasonably be expected to cause damage or harm to the other Party or any of the Released Parties, provided however that this Section 5.2 shall not apply to statements made by or about any affiliates (other than the Company, Holdings, and its subsidiaries) of Kohlberg Kravis Roberts & Co. LP, TPG Capital LP, Goldman Sachs & Co. or any future owner of the Company. The Company’s obligations under this Paragraph are limited to only those individuals who are Executive Officers (as defined in Rule 16a-1(f) of the Securities Exchange Act of 1934, as amended) of the Company or Holdings at the time of the Separation Date and who are acting in their capacity as Executive Officers of the Company or Holdings at the time they make a remark or reference that allegedly violates this Section 5.2. This Section 5.2 does not prohibit either Party from making truthful statements regarding the other Party or any of the Released Parties while cooperating with a governmental investigation or testifying under oath. Executive acknowledges that he is making, after the opportunity to confer with counsel, a knowing, voluntary, and intelligent waiver of rights Executive may have to make disparaging comments regarding the Company, including rights under the First Amendment to the United States Constitution and any other applicable federal and state constitutional rights.

Executive hereby reconfirms his agreement in Section 9.a.(ii) of the Employment Agreement that he shall not, for a period of eighteen (18) months after the Separation Date, directly or indirectly, act as a proprietor, investor, director, officer, employee, substantial stockholder, consultant, or partner in any Competing Business in Texas or any other geographic area in which Texas Energy Future Holdings Limited Partnership, Holdings, the Company or any of their respective subsidiaries operates or conducts business. For purposes of this Agreement, Competing Business shall mean any business that directly or indirectly competes, at the relevant determination date, with one or more of the businesses of Holdings, the Company, or any of their respective Affiliates in any geographic area where Texas Energy Future Holdings Limited Partnership, Holdings, the Company, or any of their respective subsidiaries operates.

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Notwithstanding the foregoing, the restrictions set forth in this Section 5.3 shall not apply with respect to Kohlberg Kravis Roberts & Co. L.P., TPG Capital L.P., and Goldman, Sachs & Co. or any of their Affiliates that are not engaged in any business that competes, directly or indirectly, with Holdings or any of its subsidiaries in any geographic area where they operate. Moreover, for the purposes of Article 5, Executive may, directly or indirectly own, solely as an investment, securities of any Person (as such term is used for purposes of Section 13(a) or 14(d) of the Securities and Exchange Act of 1934, as amended) engaged in the business of Holdings, the Company or any of their respective Affiliates which are publicly traded on a national or regional stock exchange or quotation system or on the over-the-counter market if Executive (I) is not a controlling person of, or a member of a group which controls, such person and (II) does not, directly or indirectly, own 5% or more of any class of securities of such Person.

Executive hereby reconfirms his agreement in Section 9.a.(iii) of the Employment Agreement that he shall not, for a period of eighteen (18) months following the Separation Date, directly or indirectly (A) solicit customers or clients of Holdings, the Company, or any of their respective Affiliates to terminate their relationship with Holdings, the Company, or any of their respective Affiliates or otherwise solicit such customers or clients to compete with any business of Holdings, the Company or any of their respective Affiliates, or (B) solicit or offer employment to any person who is, or has been at any time during the twelve (12) months immediately preceding the termination of Executive’s employment, employed by Holdings, the Company or any of their respective Affiliates. Notwithstanding the foregoing, the restrictions set forth in this Section 5.4 shall not apply with respect to Kohlberg Kravis Roberts & Co. L.P., TPG Capital L.P., and Goldman, Sachs & Co. or any of their Affiliates that are not engaged in any business that competes, directly or indirectly, with Holdings or any of its subsidiaries in any geographic area where they operate.

Notwithstanding Sections 5.1 through 5.4, above, if at any time a court holds that the restrictions stated in those sections are unreasonable or otherwise unenforceable under circumstances then existing, the parties hereto agree that the maximum period, scope or geographic area determined to be reasonable under such circumstances by such court will be substituted for the stated period, scope or area.

Because Executive’s services are unique and because Executive has had access to Confidential Information, the parties hereto agree that breach of this Agreement would cause immediate and irreparable harm, damage, and injury and that money damages will be an inadequate remedy for any breach of this Agreement. In the event of a breach or threatened breach of this Agreement, Holdings, the Company or any of their respective Affiliates, successors or assigns may, in addition to other rights and remedies existing in their favor, apply to any court of competent jurisdiction for specific performance and/or injunctive relief in order to enforce, or prevent any violations of, the provisions hereof (without the posting of a bond or other security). Executive acknowledges and agrees that such specific performance and/or injunctive relief would be appropriate relief for such breach and to prevent further breaches. Notwithstanding the foregoing, in the event Executive breaches the covenants set forth in Article

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5, the Company’s rights and remedies with respect Executive’s Options, Option Stock, and Stock and payments related thereto, as those terms are defined in the Management Stockholder’s Agreement between Executive and Holdings (the “MSA”), shall be limited to those set forth in Section 22(c) of the MSA.

ARTICLE 6

MISCELLANEOUS

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If any term, provision, covenant, or restriction of this Agreement is held by a court of competent jurisdiction to be invalid, void, or unenforceable, the remainder of this Agreement and the other terms, provisions, covenants, and restrictions hereof shall remain in full force and effect; they shall in no way be affected, impaired, or invalidated. It is hereby stipulated and declared to be the intention of the Parties that they would have executed this Agreement had the terms, provisions, covenants, and restrictions that may be hereafter declared invalid, void, or unenforceable not been initially included.

The Parties agree that the covenants and agreements set forth in Articles 3, 5, and 6 of this Agreement are of a continuing nature, and they shall survive the expiration, termination, or cancellation of this Agreement, unless such Articles are specifically extinguished, terminated, or cancelled in a writing signed by both Parties and identified as an amendment to this Agreement.

This Agreement is personal between the Company and Executive. Executive may not sell, assign, or transfer any rights or interests created under this Agreement, or delegate any of his duties, without the prior written consent of the Company. The Company may, without Executive’s consent, assign this Agreement and its rights, benefits, and obligations hereunder to any of its Affiliates or a successor entity. In the event of an assignment by the Company to an Affiliate, the Company will act as a guarantor of any obligations to Executive arising from this Agreement.

The Parties agree to perform any further acts and to execute and deliver any further documents which may be necessary or appropriate to carry out the purposes of this Agreement.

Executive hereby reconfirms his agreement in Section 10.n. of the Employment Agreement that, for a period of six (6) years after the Separation Date, Executive shall provide Executive’s reasonable cooperation in connection with any action or proceeding (or any appeal from any action or proceeding) which relates to events occurring during Executive’s employment hereunder, provided that the Company shall use reasonable efforts to avoid material interference with Executive’s business or personal activities. The Company shall pay all of Executive’s reasonable expenses incurred in connection with providing such cooperation.

This Agreement shall be governed by, and construed and enforced in accordance with, the laws of the State of Texas, regardless of choice-of-law principles. Each party submits to the jurisdiction of the courts in Dallas County, Texas, and the Parties agree that the proper venue and jurisdiction for any cause of action relating to this Agreement (whether sounding in tort or contract) shall be in Dallas County, Texas. In the event any issue arising out of this Agreement is litigated by the Parties, the prevailing party shall be entitled to recover from the other party its reasonable attorneys’ fees and costs.

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All notices from one party to the other shall be deemed to have been duly delivered when hand delivered or sent by United States certified mail, return receipt requested, postage prepaid, as follows:

The failure of either Party to enforce or require timely compliance with any term or provision of this Agreement shall not be deemed to be a waiver or relinquishment of rights or obligations arising hereunder, nor shall any such failure preclude the enforcement of any term or provision or avoid the liability for any breach of this Agreement.

This Agreement constitutes the entire agreement between the Parties hereto with respect to the subject matter of this Agreement. Except where specifically referenced otherwise in this Agreement, it supersedes and replaces any and all prior or contemporaneous negotiations, undertakings, understandings, or agreements (whether written or oral) of any kind between Executive and the Company with respect to the terms of Executive’s separation from the Company and its Affiliates except for Executive’s Management Stockholder’s Agreement, Sale Participation Agreement, and Energy Future Holdings Corp. Key Employee Non-Qualified Stock Option Agreement.

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I HAVE READ THIS AGREEMENT AND FULLY UNDERSTAND ALL ITS TERMS AND WHAT THEY MEAN. NO OTHER PROMISE, INDUCEMENT, THREAT, AGREEMENT, OR UNDERSTANDING OF ANY KIND OR DESCRIPTION WHATSOEVER HAS BEEN MADE WITH OR TO ME TO CAUSE ME TO SIGN THIS AGREEMENT. I ENTER INTO AND SIGN THIS AGREEMENT KNOWINGLY AND VOLUNTARILY, WITHOUT DURESS OR COERCION OF ANY KIND WHATSOEVER, AND WITH THE INTENT OF BEING LEGALLY BOUND BY THIS AGREEMENT.

IN WITNESS WHEREOF, the Parties execute this Agreement as follows:

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