NPP and reactor design

Sometimes it can help you to internalize what you know to try and write it down on one page. A  colleague asked me how you design a reactor, and how does this fit into the design of an Nuclear Power Plant. I guess I went a bit off topic but I thought that if I had to distill 10 years of doing this at PBMR and what I thought were the most important lessons. Especially if we do it over again at Bufo.

Design of a NPP happens at three levels, Plant design, System Design and Component Design.  You can add more levels but avoid unnecessary hierarchy.

Design of an NPP happens concurrently.  You need to find a balance between all-at-once and first-things-first. In reality things must happen in parallel. If you get key activities out of sequence, you are dead. (dead = rework, strong iterations and rework kills projects).  Working in the three levels helps you sequence better.  Plant ahead of system ahead of component.

You need to break the cycle of “Everybody waiting for inputs”.  The equation is:

Assumptions + margin = progress

How do you manage the project?  I think the best is a Stage-gate approach. All work in parallel.  Gat only reached when the last activity finished.

How to be most effective? Break the design work into suitable Life Cycle Phases.  This is consistent with a Front end loaded view of project management.  Normal split Pre-feasibility, feasibility / concept, Engineering, Construction, Commissioning and test.

Where is the boundary between these phases? There is no right answer, it is flexible and project specific.  Defining the boundary between phases must match the specific project goals/objectives. A yellow flag is when the boundary keeps being moved (typically in scope to stick to a date). 

When can you launch a DCD?  You can choose.  Remember though:  after the DCD you need to exercise change control, so not too early.  What detail do you need for a DCD?  You can choose.  Some are written as requirements documents, some written based on a full design.  Personally I would recommend a near complete Plant level design, supported by design of key systems.  Component design is probably unnecessary.

Change control?  How does it work in design.  The three levels are key.  Simplest rule we could find.  Specify higher level to lower.  A change at the lower level only needs to be controlled if it affects the document above it.  After DCD submission, its effect on the DCD needs to be considered as well.

What is design? It consists of 3 activities: (This is about the only thing that applies at all levels P/S/C)

1. Define the Inputs
2. Generate the Outputs (Lower level specs etc.) by: Defining the architecture, separating this (of the functionally) then specifying.
3. Document the Justification – link the inputs to the outputs.

What order is best to attack them in. 1.2.3.  Why?  Forwards development (1)-(2), backwards check. (2)-(3)-(1).

What are the main issues - Nuclear design (Mechanical).  Codes and Standards, which to use? Selecting loads and load classification.  This is sorted out at system design largely.

What are the key Red flags[1]:

• Strictly Hierarchical template. Same activities at P/S/C – you do different things at each level. One size fits all.
• Extreme idealization/abstraction
• Rigid rules
• Plans that are too Generic
• Fixation on: breakdowns (Product / system / facility / document …), processes, Baselines.  In fact any focus on process not product is counterproductive.  Especially at early stages

What makes a good designer?

• Ownership.  Own what you do.
• Invest yourself.  Then walk away.  You don’t always have the best idea, but if you don’t act like it you won’t prosper.

Specifically, is the design process broken into stages? 

•  Yes, in two dimensions P/S/C and life cycle.
• What inputs are required for each one of these stages with respect to design loads (vibration, seismic, transients, etc.) and how are they developed? 
•  For design loads: Plant – where to site, how it will be operated. System, what the system level loads are, how does the system response to plant operation, pressures etc. Component how does system response load the component.

How does the licensing and construction process fit in with these stages?

• Licensing:  As soon as you have the information you need.  What you license if fixed so no too early, licensing is risky and takes time so not too late.
• Construction,  you can only start when activity (2) lower level specs is complete a component level.  That is why you do justification after as well – to speed up the programme.

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[1] Note that this document raises all of them.