Technical and regulatory analysis of the fuel transfer system valves in nuclear power plants

Abstract

This project presents a technical and regulatory analysis of the motor‑operated valves of the Fuel Transfer System (FTS) in a PWR‑type nuclear power plant. The main objective of the work is to define the thrust and torque adjustment windows required to ensure that the system’s gate valves can fulfil their safety function under the most demanding operating scenario: an empty reactor cavity, a full spent fuel pool, and an isolated transfer channel. To achieve this objective, the system scenario was characterized, available plant, valve, and actuator data were collected, and internal methodologies were applied together with industry reference guidelines, such as EPRI recommendations and manufacturer documentation. Based on this information, minimum and maximum closing thrust values, the maximum opening thrust , and the allowable closing torque limits were calculated, integrating uncertainties and safety margins. The results obtained allow for the definition of clear and justified adjustment windows for the actuator, confirming that the mechanical capabilities of the equipment are sufficient and that the proposed values comply with regulatory requirements and defense‑in‑depth principles. The analysis also confirms that the valves can operate reliably under the most unfavorable system conditions, maintaining leak‑tightness and avoiding mechanical overstress. The conclusions of the work indicate that the objectives initially established have been satisfactorily achieved. The analysis provides a solid technical basis for adjusting the valves of the fuel transfer system and contributes to improving the understanding of their behavior under demanding conditions. Finally, recommendations are proposed for future field validation activities, performance monitoring of the valves, and the extension of the study to other operating scenarios or related equipment.