Kenneth Griffin group discloses 2.2% Terrestrial Energy (IMSR) stake

Rhea-AI Filing Summary

Citadel affiliates and Kenneth Griffin report beneficial ownership in Terrestrial Energy Inc. They may be deemed to beneficially own a total of 2,303,796 common shares, representing 2.2% of the outstanding Shares as of December 15, 2025.

Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC each may be deemed to own 2,029,208 Shares, or 1.9% of the class. Citadel Securities LLC, Citadel Securities Group LP and Citadel Securities GP LLC each may be deemed to own 274,588 Shares, or 0.3% of the class.

The Reporting Persons state they share voting and dispositive power over these Shares and certify that the securities were not acquired and are not held for the purpose of changing or influencing control of Terrestrial Energy Inc.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

TERRESTRIAL ENERGY INC.

(Name of Issuer)

Common stock, par value $0.0001 per share (the "Shares")

(Title of Class of Securities)

881454102

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel Advisors LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,029,208.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,029,208.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,029,208.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

1.9 %

12

Type of Reporting Person (See Instructions)

IA, HC, OO

Comment for Type of Reporting Person: The percentages reported in this Schedule 13G are based upon 105,782,452 Shares outstanding as of December 15, 2025, comprised of (i) 81,771,423 Shares of the issuer outstanding as of December 15, 2025, and (ii) 24,011,029 Shares issuable upon the conversion of common shares and preferred shares of Terrestrial Energy Canada (Exchange) Inc. (in each case as according to the issuer's prospectus as filed with the Securities and Exchange Commission on December 30, 2025).

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel Advisors Holdings LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,029,208.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,029,208.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,029,208.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

1.9 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel GP LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,029,208.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,029,208.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,029,208.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

1.9 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel Securities LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 274,588.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 274,588.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

274,588.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.3 %

12

Type of Reporting Person (See Instructions)

BD, OO

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel Securities Group LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 274,588.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 274,588.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

274,588.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.3 %

12

Type of Reporting Person (See Instructions)

HC, PN

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Citadel Securities GP LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 274,588.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 274,588.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

274,588.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.3 %

12

Type of Reporting Person (See Instructions)

HC, OO

SCHEDULE 13G

CUSIP No. 881454102

1

Names of Reporting Persons

Kenneth Griffin

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,303,796.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,303,796.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,303,796.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.2 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: TERRESTRIAL ENERGY INC.
(b)	Address of issuer's principal executive offices: 2730 W. Tyvola Road, Suite 100, Charlotte, NC, 28217
Item 2.
(a)	Name of person filing: This Schedule 13G is being jointly filed by Citadel Advisors LLC ("Citadel Advisors"), Citadel Advisors Holdings LP ("CAH"), Citadel GP LLC ("CGP"), Citadel Securities LLC ("Citadel Securities"), Citadel Securities Group LP ("CALC4"), Citadel Securities GP LLC ("CSGP") and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH, CGP, Citadel Securities, CALC4 and CSGP, the "Reporting Persons") with respect to the Shares of the above-named issuer owned by Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands company ("CM"), Citadel Multi-Asset Master Fund Ltd., a Cayman Islands company ("CMAM"), and Citadel Securities. Such owned Shares may include other instruments exercisable for or convertible into Shares. Citadel Advisors is the portfolio manager for CM and CMAM. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities. CSGP is the general partner of CALC4. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP and CSGP. The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any).
(b)	Address or principal business office or, if none, residence: The address of each of the Reporting Persons is 830 Brickell Plaza, Miami, Florida 33131.
(c)	Citizenship: Each of Citadel Advisors, CGP, Citadel Securities and CSGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen.
(d)	Title of class of securities: Common stock, par value $0.0001 per share (the "Shares")
(e)	CUSIP No.: 881454102
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 2,029,208 Shares. 2. Citadel Securities LLC may be deemed to beneficially own 274,588 Shares. 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 274,588 Shares. 4. Mr. Griffin may be deemed to beneficially own 2,303,796 Shares.
(b)	Percent of class: 1. The number of Shares that each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes 1.9% of the Shares outstanding. 2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 0.3% of the Shares outstanding. 3. The number of Shares that each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes 0.3% of the Shares outstanding. 4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 2.2% of the Shares outstanding.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0 2. Citadel Securities LLC: 0 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0 4. Mr. Griffin: 0
	(ii) Shared power to vote or to direct the vote: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 2,029,208 2. Citadel Securities LLC: 274,588 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 274,588 4. Mr. Griffin: 2,303,796
	(iii) Sole power to dispose or to direct the disposition of: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0 2. Citadel Securities LLC: 0 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0 4. Mr. Griffin: 0
	(iv) Shared power to dispose or to direct the disposition of: 1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 2,029,208 2. Citadel Securities LLC: 274,588 3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 274,588 4. Mr. Griffin: 2,303,796
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Citadel Advisors LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Citadel Advisors Holdings LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Citadel GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Citadel Securities LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Citadel Securities Group LP

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Citadel Securities GP LLC

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, Authorized Signatory
Date:	02/17/2026

Kenneth Griffin

Signature:	/s/ Seth Levy
Name/Title:	Seth Levy, attorney-in-fact*
Date:	02/17/2026

Comments accompanying signature: * Seth Levy is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Allakos Inc. on October 13, 2023.

FAQ

What stake in Terrestrial Energy Inc. (IMSR) does Kenneth Griffin report?

Kenneth Griffin may be deemed to beneficially own 2,303,796 common Shares of Terrestrial Energy Inc., representing 2.2% of the outstanding class as of December 15, 2025, according to the Schedule 13G/A ownership disclosure.

How many Terrestrial Energy (IMSR) shares are attributed to Citadel Advisors entities?

Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may each be deemed to beneficially own 2,029,208 Terrestrial Energy common Shares, representing 1.9% of the outstanding class, based on 105,782,452 Shares outstanding as of December 15, 2025.

What ownership does Citadel Securities report in Terrestrial Energy Inc. (IMSR)?

Citadel Securities LLC may be deemed to beneficially own 274,588 Terrestrial Energy common Shares. This holding represents 0.3% of the Shares outstanding, with shared voting and dispositive power reported in the Schedule 13G/A filing.

What total shares outstanding are used in this Terrestrial Energy (IMSR) 13G/A?

The ownership percentages are calculated using 105,782,452 Terrestrial Energy Shares outstanding as of December 15, 2025, including 81,771,423 Shares outstanding and 24,011,029 Shares issuable upon conversion of Terrestrial Energy Canada (Exchange) Inc. securities.

Are Citadel and Kenneth Griffin seeking control of Terrestrial Energy Inc. (IMSR)?

The Reporting Persons certify that the securities were not acquired and are not held to change or influence control of Terrestrial Energy Inc., and are not held in connection with any transaction having that purpose, other than activities tied to a nomination under Rule 14a-11.

Who signed the Terrestrial Energy (IMSR) Schedule 13G/A for Citadel and Kenneth Griffin?

Seth Levy signed as an authorized signatory for the Citadel entities and as attorney-in-fact for Kenneth Griffin, pursuant to a previously filed power of attorney incorporated by reference in the Schedule 13G/A ownership statement.