Use of a Fork-like detector for the safeguards verification of Lead-cooled Fast Reactor spent fuel

Introduction

More than 80 Small Modular Reactor (SMR) designs are being investigated globally for their potential to decarbonise various sectors of society. Among the proposed SMR concepts, lead-cooled fast reactors (LFRs) are envisaged for their passive safety systems, high-temperature operation, and potential high fuel utilisation. To ensure that nuclear material is not diverted from peaceful use and that reactors are not misused for military purposes, SMRs will require nuclear safeguards verification. Measurement of spent fuel is an important aspect of safeguards verifications at reactor sites. The Fork detector is one of the non-destructive assays (NDA) approved by the International Atomic Energy Agency (IAEA) and the Euratom inspectorate for the verification of spent fuel from current nuclear power plants. The Fork detector combines small neutron and gamma-ray detectors that measure the total neutron and gamma-ray emission from spent fuel.

Objectives

The objective of this thesis is to investigate the feasibility of using a Fork-like detector for the measurement of spent fuel from a SMR-LFR. In the first part of the thesis, a model of a Fork-like detector will be developed in a Monte-Carlo simulation code based on information in open-source literature. The developed model will provide the expected neutron and gamma-ray detector response. A dataset of spent fuel compositions from SMR-LFR is available and will be used to generate multiple scenarios where some of the spent fuel pins are replaced by dummy pins. In the second part of the thesis, Monte Carlo simulations will be carried out to create a large dataset of diversion scenarios, considering different replacement patterns and fuel compositions. The third part of the thesis will conduct the data analysis to estimate the count rate expected from measurement of SMR-LFR spent fuel. In addition, the data analysis will evaluate the detectable level of fuel diversion achievable by such Fork-like NDA equipment. 

Research questions

• What is the expected count rate range from measurement of spent fuel from SMR-LFR using a Fork-like detector?

• What is the sensitivity of a Fork-like detector to the replacement of SMR-LFR spent fuel pins?