When the insiders can sell — from the filing, in their words

LLC and Jefferies LLC for a period of 180 days after the date of this prospectus (the "restricted period"). The restrictions on our actions, as described above, do not apply to certain customary transactions, including (A) the offer, issuance, sale and disposition of the shares of Class A common stock in this offering; (B) the issuance of our stock pursuant to employee stock option plans existing on, or upon the conversion or exchange of convertible or exchangeable securities outstanding as of, the date of this prospectus; (C) grants of stock options, stock awards, restricted stock, RSUs, st…

Upon completion of this offering, we will have 63,653,980 shares of Class A common stock outstanding (or 69,728,980 shares of Class A common stock if the underwriters exercise their option to purchase additional shares in full), 340,676,786 shares of Class B common stock outstanding, no shares of Class C common stock outstanding and one share of convertible common stock outstanding. All shares sold in this offering will be freely transferable without restriction or registration under the Securities Act, except for any shares purchased by one of our "affiliates," as that term is defined in Rule 144 under the Securities Act.

Our directors and executive officers, and substantially all of our shareholders (such persons, the "lock-up parties") have entered into lock-up agreements with the underwriters prior to the commencement of this offering pursuant to which each lock-up party, with limited exceptions, for a period of 180 days after the date of this prospectus (such period, the "restricted period"), may not (and may not cause any of their direct or indirect affiliates to), without the prior written consent of J.P. Morgan Securities LLC and BofA Securities, Inc., (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any shares of our common stock or any securities convertible into or exe…

Total common stock to be outstanding immediately after this offering 66,521,425 shares (or 68,208,925 shares if the underwriters exercise their option to purchase additional shares in full). Use of proceeds We estimate that the net proceeds from this offering will be approximately $171.5 million (or approximately $198.2 million if the underwriters exercise their option to purchase additional shares in full), based on the initial public offering price of $17.00 per share, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

…enter into any swap, hedge or other agreement or transaction that transfers, in whole or in part, the economic consequence of ownership of common stock, or securities exchangeable or exercisable for or convertible into shares of common stock, or publicly announce an intention to do any of the foregoing for a period of 180 days after the date of this prospectus without the prior written consent of the Representative. In addition, we and each such person agrees that, without the prior written consent of the Representative, we or such other person will not, during the restricted period, make any demand for, or exercise any right with respect to, the registration of any shares of our common stock or any security convertible into or exercisable or exchangeable for common stock. The restrictions on transfer do not apply in certain circumstances, including: (a) transfers in…

Common Stock to be Outstanding After this Offering 28,847,649 shares (or 30,133,363 shares if the underwriters over -allotment option is exercised in full). Over-Allotment Option We have granted the representative of the underwriters a 30 -day option to purchase up to an additional 1,285,714 shares of our common stock at the initial public offering price to cover over -allotments , if any. Use of Proceeds We estimate that the net proceeds to us from this offering, after deducting underwriting discounts and commissions and estimated offering expenses payable by us, are approximately $109.0 million, based on the initial public offering price of $14.00 per share.

…g shares of Class A common stock and securities convertible into or exercisable or exchangeable for shares of our Class A common stock are subject to restrictions on their ability to sell or transfer their equity either prior to the pricing of this offering or from the pricing of this offering through the date that is 180 days after the date of this prospectus. We refer to such period as the "lock-up period". Pursuant to the lock-up agreements with the underwriters, if (1) at least 120 days have elapsed since the date of this prospectus and (2) such lock-up period is scheduled to end during or within five trading days prior to a broadly applicable period during which trading in our securities would not be permitted under our insider trading policy, or a blackout period, such lock-up period will end ten trading days prior to the commencement of such blackout period. J.P.

Class A common stock to be outstanding after this offering 273,442,494 shares, or 280,080,692 shares if the underwriters exercise their option to purchase additional shares of Class A common stock in full. Class B common stock to be outstanding after this offering 118,907,374 shares, representing approximately 30.3% of the combined voting power of all of X-Energy Inc.'s common stock, or approximately 29.8% of the combined voting power of all of X-Energy, Inc.'s common stock if the underwriters exercise in full their option to purchase additional shares of Class A common stock.

Pursuant to the lock-up agreements with the underwriters, if (1) at least 120 days have elapsed since the date of this prospectus and (2) such lock-up period is scheduled to end during or within five trading days prior to a broadly applicable period during which trading in our securities would not be permitted under our insider trading policy, or a blackout period, such lock-up period will end ten trading days prior to the commencement of such blackout period. J.P. Morgan Securities LLC, on behalf of the underwriters, may release certain stockholders from the market standoff agreements or lock-up agreements prior to the end of the lock-up period and, in such event, certain other stockholders may have pro rata release rights. Record holders of our securities are typically the parties to the lock-up agreements with the underwriters and to th…

Of these, the shares sold in this offering will be freely tradable immediately after this offering and substantially all of 67 Table of Contents the additional shares of common stock will be available for sale in the public market beginning 180 days after the date of this prospectus following the expiration of lock-up agreements between our directors, officers, substantially all of our stockholders and the underwriters. The foregoing agreements are subject to certain limited exceptions, and Morgan Stanley & Co. LLC, Jefferies LLC and Evercore Group L.L.C. may release these stockholders from their lock-up agreements with the underwriters at any time and without notice, which would allow for earlier sales of shares in the public market. See Underwriting . In addition, we intend to file one or…

Common stock to be outstanding immediately after this offering 41,812,047 shares (or 44,312,047 shares if the underwriters exercise their option to purchase additional shares of common stock in full) We will have two series of common stock authorized immediately following this offering: voting common stock and non-voting common stock. We are offering shares of voting common stock in this offering and unless otherwise noted or context otherwise requires, all references in this prospectus to our common stock refer to our voting common stock.

…will agree with the underwriters, subject to certain exceptions, not to dispose of or hedge any of our or their common stock or securities convertible into or exchangeable for shares of common stock, or collectively, the Lock-Up Securities, during the period from the date of this prospectus continuing through the date 180 days after the date of this prospectus, except with the 229 Table of Contents prior written consent of Goldman Sachs & Co. LLC and J.P. Morgan Securities LLC and the Company. This agreement does not apply to any existing employee benefit plans. See the section titled "Shares Available for Future Sale" for a discussion of certain transfer restrictions. The restrictions described in the immediately preceding paragraph do not apply to our officers, directors and holders of substantially all of our capital stock and securities convertible into or exchang…

Common stock to be outstanding immediately after this offering 53,027,817 shares (or 55,151,817 shares if the underwriters exercise their option to purchase additional shares of common stock in full) We will have two series of common stock authorized immediately following this offering: voting common stock and non-voting common stock. We are offering voting stock in this offering and unless otherwise noted, all references in this prospectus to our "common stock" refer to our voting common stock. The non-voting common stock will not be listed for trading on any securities exchange.

…on behalf of the underwriters, we and they will not, and will not publicly disclose an intention to, dispose of or hedge any shares of our Class A common stock or securities convertible into or exchangeable for shares of our Class A common stock during the period ending 180 days after the date of this prospectus, subject to certain exceptions. See "Underwriting" for a description of these lock-up agreements. Upon the expiration of the contractual lock-up agreements pertaining to this offering, up to an additional 205,005,185 shares of our Class A common stock will be eligible for sale in the public market, of which 89,126,623 are held by directors, executive officers and other affiliates and will be subject to volume, manner of sale and other limitations under Rule 144. Following completion of this offering, shares cove…

Upon the expiration of the contractual lock-up agreements pertaining to this offering, up to an additional 205,005,185 shares of our Class A common stock will be eligible for sale in the public market, of which 89,126,623 are held by directors, executive officers and other affiliates and will be subject to volume, manner of sale and other limitations under Rule 144. Following completion of this offering, shares covered by registration rights would represent approximately 71% of our outstanding Class A common stock (or approximately 69%, if the underwriters exercise in full their option to purchase additional shares). Registration of any of these outstanding shares of Class A common stock would result in such shares becoming freely tradable without compliance with Rule 144 upon effectiveness of the registration statement.

Morgan Securities LLC, for a period of 180 days after the date of this prospectus (the "lockup period"). The restrictions described in the immediately preceding paragraph and contained in the lock-up agreements between the underwriters and the lock-up parties do not apply, subject in certain cases to various conditions, to certain transactions, including (a) transfers of lock-up securities: (i) by gift or by will or intestacy to a family member or certain estate planning vehicles, (ii) by a corporation, partnership, limited liability company, trust or other entity, to (a) transfer lock-up sec…

Following this offering and the Concurrent Transactions, we will have 54,021,728 shares of Class A common stock outstanding and 169,123,306 Company Warrants exercisable for shares of Class A common stock and Class B common stock. The rights of the holders of Class A common stock and Class B common stock will be identical, except with respect to voting and conversion. Each share of Class A common stock will be entitled to one vote per share and shares of Class B common stock will be non-voting, except as may be required by law or otherwise provided by the certificate of incorporation. Each share of Class B common stock will automatically convert into one share of Class A common stock upon the sale or other transfer of such share of Class B common stock by the holder thereof.

Eastern Time on the second trading day following our release of earnings for the quarter ending September 30, 2026 or (ii) 180 days after the date of this prospectus (the "Lock-up Period"), subject to certain customary exceptions and provision s that provide for the early release of certain of our securities during the Lock-up Period. In connection with such early- release provisions, we estimate an aggregate of up to approximately 171.1 million shares will be released from lock- up agreements or market standoff provisions during the Lock-up Period, including up to approximately 15.0 million shares held by our directors and officers subject to reporting under Section 16 of the Exchange Act .

Class A common stock to be outstanding immediately after this offering ........................................................... 30,000,000 shares (or 34,500,000 shares if the underwriters exercise their over-allotment option in full). Class B common stock to be outstanding immediately after this offering ........................................................... 185,110,345 shares. Class N common stock to be outstanding immediately after this offering ........................................................... None.

Eastern Time on the second trading day following our release of earnings for the quarter ending September 30, 2026 or (ii) 180 days after the date of this prospectus (the "Lock-up Period"), subject to certain customary exceptions and provision s that provide for the early release of certain of our securities during the Lock-up Period. In connection with such early- release provisions, we estimate an aggregate of up to approximately 171.1 million shares will be released from lock- up agreements or market standoff provisions during the Lock-up Period, including up to approximately 15.0 million shares held by our directors and officers subject to reporting under Section 16 of the Exchange Act .

Eastern Time on the second trading day following our release of earnings for the quarter ended March 31, 2026. If the Second Trading Day Release Trigger was satisfied, an aggregate of up to approximately 27.7 million shares held by Directors and Officers (as defined below) and Non-Employee Holders (as defined below). If the Second Trading Day Release Trigger was not satisfied, an aggregate of up to approximately 30.2 million shares held by Directors and Officers, Non- Executive Employees, and Non-Employee Holders. 6 00 a.m. Eastern Time on the second trading day following our release of earnings for the quarter ending June 30, 2026.

Eastern Time on the second trading day following our release of earnings for the quarter ending June 30, 2026. An aggregate of up to approximately 36.4 million shares held by Directors and Officers, Non-Executive Employees, and Non-Employee Holders. 6 00 a.m. Eastern Time on August 19, 2026. An aggregate of up to approximately 14.6 million shares held by Directors and Officers, Non-Executive Employees, and Non-Employee Holders. 6 00 a.m. Eastern Time on September 2, 2026. An aggregate of up to approximately 14.6 million shares held by Directors and Officers, Non-Executive Employees, and Non-Employee Holders.

Eastern Time on the second trading day following the effectiveness of the registration statement of which this prospectus forms a part, provided that the closing price of our Class A common stock on the Nasdaq Global Select Market on the First Trading Day has exceeded 133% of the initial public offering price per share set forth on the cover page of this prospectus (the "Second Trading Day Release Trigger") . An aggregate of up to 2.5 million shares held by Non- Executive Employees . 190 Table o f Contents Earliest Date Available for Sale in the Public Market Number of Shares of Class A Common Stock 6 00 a.m. Eastern Time on the second trading day following our release of earnings for the quarter ended March 31, 2026.