NTEC N13 Criticality Safety Management assignment 2023-24

Questions

Each question is worth 5% of the overall unit mark. Write as much as you need to for each answer, but no more. As a guide, if you’ve written a sentence the answer is too short, if you’ve written more than a page for a single question it’s too long.

1.   Write down the point kinetics equations. Explain the meaning of each symbol used

(excluding +, -, = and taking dt/d as one symbol).  Based on your explanations of the symbols, describe the physical processes that are represented in the equations and explain how they contribute to the time behaviour of the system.

2.   The double contingency principle is described as reinforcing the key engineering

principles EKP.1 to EKP.5 laid out by the Office for Nuclear Regulation (ONR) in the Safety Assessment Principles for Nuclear Facilities (SAPs). Look up the key

engineering principles and explain how each of them is implemented in criticality  safety, giving examples where possible. Make sure you are clear on the difference between safety functions and safety measures.

3.   Explain how the criticality safety index (CSI) is determined and how it is used to control the transport of fissile material.

4.   Select one of the criticality accidents described in LA-13638, excluding those that  were reviewed in the lectures. Summarise the events of the accident. Identify the parameter(s) that were being used to control criticality and explain how control based on the given parameter(s) broke down.

Scenario

Mixed-oxide fuels are one way that surplus plutonium can be recycled to produce useful power. These fuels are made of PuO2  and UO2 together in a single fuel pellet. Producing sufficient fuel pellets to fuel a reactor would require the handling and storage of significant quantities of this material. A hypothetical facility is proposed to manage these fuel pellets,  and a criticality safety assessment is required to ensure appropriate safety measures are included in the design of the facility.

You should propose a design for the criticality safety measures to be used in the storage and transport of material within the facility, including consideration of credible accident conditions. You may propose any reasonable solution to address part or all of the problem, and you should provide analysis to demonstrate that it ensures criticality safety. You may make use of the subcritical limits given inTable 1.

Table 1: Subcritical limits for scenario problem

The values in Table 1 are provided for the purposes of the scenario only. They must not be used for any real-world application.

Submission

Word count: The scenario exercise has a limit of 4000 words (± 25%) excluding appendices. Reports that are below 3,000 words will not be penalised, but are unlikely to develop sufficient depth to succeed. Reports over 5,000 words will be marked as though they end at the 5,000th word.

Your report must be word processed. All working must be shown but, if cited in the text, can be presented in an appendix (which will be exempt from the word count). To prevent gaming the word court, the work in the report must make sense and cover the key points without the information in the appendices. Assignment marking is anonymous, please do  not include your name on the report, or e.g. embed links to spreadsheets on Google docs.

It is expected that you will apply at least two numerical criticality safety assessment methods (e.g. hand calculations, computer modelling). Demonstrated use of more than one  method is required or marks will be lost. Due to its simplicity, fraction critical does not count as a method in its own right, but it can be used to support the use of other methods. It is not a requirement that criticality modelling software is used, but the use of such software will count as one of these methods. Repeating calculations in e.g. two different Monte Carlo codes will only count as one method. If computer modelling is used, the input file or a representative example input file should be included as an appendix.

If you obtain values by reading from a graph (e.g. a subcritical limit curve), you should include in your report an annotated, referenced copy of the graph showing how the value used was found and where the graph came from.

You are not required to carry out detailed safety analyses such as design basis assessment (DBA) or probabilistic safety analysis (PSA), as these were not covered on the course. You should however show that you have considered reasonably foreseeable accident conditions and give a clear demonstration of how your proposals comply with the double contingency  approach.

You should submit your completed assignments in the manner requested by the NTEC office.

Deadline 5th  February 2024: Submissions are due by 23:59 on the submission deadline. Any work submitted at any time within the first 24 hours following the published submission deadline will receive a penalty of 10% of the maximum amount of marks available. Any work submitted at any time between 24 hours and up to 48 hours late will receive a deduction of   20% of the marks available, and so on, at the rate of an additional 10% of available marks deducted per 24 hours, until the assignment is submitted or no marks remain. You can view the University Policy on Submission of Work for Summative Assessment on Taught

Programmes athttps://documents.manchester.ac.uk/DocuInfo.aspx?DocID=24561.

Scenario assessment strategy

The scenario report will be marked out of 100%, but remember that the scenario constitutes 60% of the mark for the unit. You will be marked against the following criteria:

Achievement (80%): This measures how well the report addresses the problem and provides

appropriate solutions. Particular emphasis is placed on demonstrable understanding of the problem, the overall conclusions/suggestions and the extent to which these are supported  by detailed investigation and quantitative work. Evidence of originality and/or the depth of the analysis (e.g. sensitivity analysis) will be rewarded.

The achievement mark is sub-divided into four categories:

•           Demonstration of understanding (20%)

•           Results - supported by investigation/calculation (20%)

•           Conclusions/suggestions (20%)

•           Originality/depth of study (20%)

Report writing (20%): This assesses the quality of the written report. The work should be clear, coherent, and succinct. The report should have a logical structure with appropriate use of sentences, paragraphs, and sections. The report should use correct units, meaningful  captions for figures and tables, and appropriate labelling of axes. Padding with unnecessary, irrelevant or repetitive material should be avoided. The report writing mark is sub-divided into:

•           Quality of writing (10%)

•           Use of figures, tables and references (10%)