Exhibit 10.1 February 4, 1999 Thermo Power Corporation 45 First Avenue Waltham, MA 02454 RE: $160,000,000 Promissory Note due November 1999 Thermo Electron hereby confirms its commitment to refinance the above referenced note upon its maturity on November 16, 1999, under the following terms and conditions: Amount: Up to but not exceeding $160,000,000.00 USD Maturity: October 30, 2008 Interest Rate: 7.625% per annum payable semi-annually in arrears each April 30th and October 30th, assuming a 360-day year consisting of twelve 30-day months. Prepayment: Note can be prepaid in full or in part at any time without penalty You must notify Thermo Electron Corporation (attn: Treasurer) no later than October 15, 1999 if you intend to accept this refinancing option, and the amount required. This refinancing will only be available once all amounts due and owing to Thermo Electron Corporation under the existing promissory note have been satisfied. Thermo Electron Corporation /s/ Kenneth J. Apicerno By: Kenneth J. Apicerno Title: Treasurer