OSI Tabletop Exercise strengthens collaboration to prepare for CTBT’s entry into force

On 14 December 2023, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) held a daylong tabletop exercise for senior managers to explore executive decision making in the context of an on-site inspection (OSI). This was the second such exercise held by the OSI Division to prepare senior managers for scenarios they may encounter once the Comprehensive Nuclear-Test-Ban Treaty (CTBT) enters into force and in the event an on-site inspection is requested to verify compliance with the Treaty. 

What are on-site inspections?

On-site inspections are the final component of the CTBT’s verification regime, enabling Member States to request the CTBTO to gather evidence on the ground if the Treaty’s global monitoring system detects a possible nuclear test. However, an OSI can only be launched once the Treaty enters into force.

Until then, CTBTO is charged with building up OSI capability, including training potential inspectors, preparing equipment, and testing procedures in exercises both in Vienna and in the field.

Exploring challenging scenarios in the build-up to an OSI

Many potentially challenging issues might arise during an OSI to assess whether a nuclear test explosion has taken place. Such issues might not only occur in the field, but also at CTBTO headquarters in Vienna, Austria.

During the December 2023 tabletop exercise, CTBTO’s senior leadership was asked to consider several scenarios with which they might be confronted should an OSI be requested. The simulations ranged from responding to media inquiries to dealing with sensitive information, as well as dealing with confidentiality of information and safeguarding the health and safety of an inspection team in the field.

The exercise was conducted as a directed role-play, with all exercise participants discussing the merits and drawbacks of their potential actions to arrive at recommendations for CTBTO’ s Executive Secretary, Robert Floyd.

The exercise took place exactly one and a half years after the first such OSI tabletop exercise for senior managers.

It’s hard to script how executive decisions are made. What I appreciated about today’s exercise was the great level of realism. Today, we were actually playing with the difficulty, the ambiguity of real decision-making.

Executive Secretary Robert Floyd in discussion during TTE scenario

Oleg Rozhkov, Director of On-Site Inspection (OSI) Division

The importance of cross-divisional coordination in the event of an OSI

The main objective of the tabletop exercise was to prepare PTS senior management and staff for their involvement in upcoming OSI field exercises: a build-up exercise in 2024 (BUE24) and the Integrated Field Exercise in 2025 (IFE25).

In addition to engaging senior management in the work of the OSI Division, the exercise also reinforced the cross-divisional considerations that would go into making decisions during an OSI. It also highlighted the importance of organization-wide efforts for future response preparedness relating to OSI and events of potential or actual CTBT relevance.

Oleg Rozhkov, Director of the OSI Division, noted the importance of continuous preparations to meet the requirements outlined in the CTBT.

Upholding the integrity of the global norm against nuclear testing requires a robust verification regime, and CTBTO’s OSI is the ultimate verification measure that ensures no nuclear explosion can go undetected. Exercises such as the recent TTE and upcoming BUE24 and IFE25 offer opportunities to further develop OSI operational capabilities, to ensure their immediate availability upon the Treaty’s entry into force.

Ambassador Darío Chirú of Panama and Executive Secretary Robert Floyd in role-play scenario during TTE

Deepti Choubey, Director of Knowledge Management and Human Resources Services

The 2023 tabletop exercise was both a continuation of the 2022 exercise and an expansion in both the realism and scope of the situations that were presented.

During one scenario related to the confidentiality of inspection-related information, Ambassador Darío Ernesto Chirú Ochoa of Panama participated in the exercise by playing the role of ambassador of the Inspected State Party and meeting with Dr. Floyd and his team to negotiate some of the complex and sensitive issues inherent in an on-site inspection.

It was a great opportunity to participate in the exercise. Seeing first-hand CTBTO’s work to test and validate the OSI capabilities strengthens our support for the development of this complex verification measure of the Treaty. As current co-chair of the Article XIV process 2023-2025, Panama looks forward to strengthening the engagement with all States Parties, Signatories and Observers to achieve the objectives of the Article XIV Conference, and ensure we are ready for the Treaty’s entry into force.

CTBTO’s continuous work to build OSI capabilities

The tabletop exercise represents just one aspect of the OSI Division’s ongoing efforts to prepare for the Treaty’s entry into force. The division also conducts training for on-site inspectors, both in person and virtually, as well as large-scale field exercises that simulate an on-site inspection from beginning to end.

For example, a series of parallel Directed Exercises to test OSI procedures, assess equipment, and provide training and practice for participants was conducted in September 2023. The next OSI field exercises are BUE24 that will take place in Hungary from 16 June to 6 July 2024, and IFE25 that will take place in Sri Lanka the following year. These activities are all part of a comprehensive exercise programme that will conclude in 2025, leading to a thorough process of evaluation and validation to further strengthen the OSI element of the verification regime.


Elran Sason Ben Or, Chief, Policy Planning & Operations Section

Junan Zhang, Director of Legal and External Relations Division

Xyoli Pérez Campos, Director of International Monitoring System (IMS) Division

(Left to right) Cinthia Echavarria, Chief of General Services Section; Uday Dayal, Director of Division of Administration; and Melissa Buerbaumer, Chief of Budget and Finance Section

(From left to right) Andrew Bramnik, Policy Planning Officer and Ryan Gonzalez, Training Officer

(From left to right) Verity Robson, Chief, Legal Services; and Joseph Ballard, Legal and External Relations Coordinator

Andrew Collinson, Health and Safety Officer

CTBTO senior management and staff participating in the 2023 Tabletop Exercise