Terrestrial Energy (IMSR) director Kathryn McCarthy submits initial Form 3

Rhea-AI Filing Summary

Terrestrial Energy Inc. has a new Form 3 on file for director Kathryn Ann McCarthy. The Form 3 identifies her as a director, not an officer and not a ten percent owner. It does not report any insider transactions or any securities currently held as beneficially owned.

Key Figures

Insider buy transactions: 0 shares Insider sell transactions: 0 shares Reported holding entries: 0

3 metrics

Insider buy transactions 0 shares Buy shares reported for Kathryn Ann McCarthy on Form 3

Insider sell transactions 0 shares Sell shares reported for Kathryn Ann McCarthy on Form 3

Reported holding entries 0 Number of separate security holdings reported as beneficially owned

Key Terms

Power of Attorny, reporting person, ten percent owner

3 terms

Power of Attorny regulatory

"Remarks reference "Exhibit 24 - Power of Attorny" for authority."

reporting person regulatory

"Reporting person listed as McCarthy Kathryn Ann, a director."

ten percent owner regulatory

"is_ten_percent_owner field indicates ten percent owner status."

AI-generated analysis. How Rhea-AI works. Not financial advice.

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FAQ

What does Terrestrial Energy (IMSR) disclose about Kathryn Ann McCarthy in this Form 3?

Terrestrial Energy’s Form 3 lists Kathryn Ann McCarthy as a director and reporting person. She is not identified as an officer or ten percent owner, and no securities or insider transactions are reported as beneficially owned at this time.

Is Kathryn Ann McCarthy a ten percent owner of Terrestrial Energy (IMSR)?

No. The Form 3 for Terrestrial Energy marks Kathryn Ann McCarthy’s ten percent owner status as negative. She is reported solely in her capacity as a director, with no indication she holds a ten percent equity position.

Does the IMSR Form 3 report any insider trades for Kathryn Ann McCarthy?

No insider trades are reported. The transaction summary shows 0 buy shares and 0 sell shares, with no transactions listed, indicating no purchases, sales, or derivative exercises are disclosed in this initial ownership report.

Does the Terrestrial Energy (IMSR) Form 3 show any current share holdings?

No current holdings are shown. The structured data indicates 0 holding entries, so no specific number of Terrestrial Energy securities is reported as beneficially owned by Kathryn Ann McCarthy on this Form 3.

What is the role of the Exhibit 24 Power of Attorny mentioned for IMSR?

The remarks reference an Exhibit 24 - Power of Attorny, indicating authority has been granted for signing or handling aspects of the Form 3 on the reporting person’s behalf, a common administrative arrangement in insider reporting.

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0104
Estimated average burden
hours per response:			0.5

1. Name and Address of Reporting Person^*

McCarthy Kathryn Ann

(Last) (First) (Middle)

C/O TERRESTRIAL ENERGY INC

2730 W. TYVOLA ROAD, SUITE 100

(Street)

CHARLOTTE NORTH CAROLINA 28217

(City) (State) (Zip)

UNITED STATES

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
07/23/2026

3. Issuer Name and Ticker or Trading Symbol
Terrestrial Energy Inc. /DE/ [ IMSR ]

3a. Foreign Trading Symbol

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

Remarks:

Exhibit 24 - Power of Attorny

No securities are beneficially owned.

	/s/ Brian Thrasher, Attorney-in-Fact	07/27/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 3: SEC 1473 (03-26)