EXHIBIT 10.1

27 November 2025
| To: | ASP Isotopes Inc. |
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| 601 Pennsylvania Avenue NW, South Building, Suite 900 Washington, DC; and |
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| ASP Isotopes South Africa Proprietary Limited |
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| Unit 19, 2nd Floor |
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| 1 Melrose Boulevard Johannesburg 2196 |
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| From: | Renergen Limited Sandton Gate, Second Floor, 25 Minerva Avenue, Glenadrienne, Sandton, Gauteng, 2196 |
Attn: Robert Ainscow/Paul E. Mann
LETTER TO THE TERM LOAN FACILITY AGREEMENT: EXTENSION OF FINAL REPAYMENT DATE TO 30 JANUARY 2026
| 1. | INTRODUCTION | |
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| 1.1. | The Parties entered into a Term Loan Facility Agreement dated 19 May 2025 (the Facility Agreement). |
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| 1.2. | Pursuant to the Facility Agreement, the Lender made available to the Borrower a term loan facility in an aggregate principal amount of USD 30,000,000 (the Facility) to support the Borrower's operational funding requirements, including those arising from delays in the implementation of the Borrower's Phase 1 Virginia Gas Project. |
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| 1.3. | The intention of this letter is to clarify and, where necessary, supplement the Facility Agreement solely with regard to the extension of the Final Repayment Date (as defined in the Facility Agreement) (the Letter). Except as expressly set out herein, this Letter does not amend, vary or waive any provision of the Facility Agreement, all of which remain in full force and effect. |
| SANDTON GATE 25 MINERVA AVE, GLENADRIENNE SANDTON, 2196 SECOND FLOOR T: +27 10 045 6000 E: INFO@RENERGEN.CO.ZA | DIRECTORS: D KING (CHAIRMAN), S MARANI (CEO), N MITCHELL (COO), B HARVEY (CFO), M SWANA, D HLATSHWAYO REG. NUMBER: 2014/195093/06 VAT REG NUMBER: 4620273716 |
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| 2. | EXTENSION OF FINAL REPAYMENT DATE | |
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| 2.1. | The Parties acknowledge that, under the Facility Agreement, the Final Repayment Date was 30 September 2025. |
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| 2.2. | The Parties hereby agree that the Final Repayment Date is extended to 30 January 2026 (the Extended Repayment Date). |
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| 2.3. | All interest, fees and other amounts shall continue to accrue and be payable in accordance with the Facility Agreement until the outstanding principal amount is repaid in full on or before the Extended Repayment Date. |
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| 3. | CONFIRMATION OF EXISTING TERMS | |
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| 3.1. | Save as expressly provided in this Letter, the Facility Agreement remains unamended and in full force and effect. |
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| 3.2. | This Letter does not constitute a waiver of, or consent to, any default or Event of Default (as defined in the Facility Agreement) or any other provision thereunder. |
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| 3.3. | All defined terms used but not otherwise defined in this Letter shall have the meanings ascribed to them in the Facility Agreement. |
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| 4. | GENERAL | |
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| No varying, adding to, deleting from, or cancelling this Letter, and no waiver of any right under this Letter, shall be effective unless reduced to writing and signed by or on behalf of the Parties. | |
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| 5. | GOVERNING LAW | |
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| This Letter shall be governed by, and construed in accordance with, the laws of the Republic of South Africa. | |
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| 6. | COUNTERPARTS | |
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| This Letter may be signed in any number of counterparts by the different Parties to this Letter, each of which shall be deemed an original, and all of which together shall constitute one and the same letter as at the date of signature of the last counterpart. | |
[SINGATURE PAGE FOLLOWS]
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Signed
At UK on 27 November 2025
For and on behalf of
ASP Isotopes Inc.
| /s/ Robert Ainscow |
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| Name: Robert Ainscow Capacity: Interim CEO and COO
Who warrants authority |
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Signed
At Sandton on 27 November 2025
For and on behalf of
Renergen Limited
| /s/ Nick Mitchell |
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| Name: Nick Mitchell Capacity: COO |
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Who warrants authority
Signed
At Preotria on 27 November 2025
For and on behalf of
ASP Isotopes South Africa Proprietary Limited
| /s/ Mangaliso Mithi |
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| Name: Mangaliso Mithi Capacity: Finance Director
Who warrants authority |
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