Is Zero Risk Possible? Beyond Piping Calculations in the Nuclear and Renewable Industries
The Risk of Nuclear Facilities
While the target of “zero risk” will always remain unattainable, in modern society reducing risk wherever possible has become a top priority. As this mentality spreads and evolves, the presence of new kinds of risk (such as terrorist risk) prompt safety rules in the power industry to become stricter.
For organizations to address this risk, designs must integrate new loads (airplane crashes, for example) and adopt innovative approaches to the aftermath of incidents. If the old perspective was to segregate the accidents, reminding us of the statistic “impossibility” of risk, the new perspective is opposing and considers that different accidents can be correlated and mitigated.
Analysis solutions have become a more and more powerful tool in this context and can help to limit the additional costs of extra layers of security for organizations. While it’s possible to try to obtain zero risk in a facility, we can never perfectly simulate how a new system will act in reality, especially once integrated within an already complex facility. However, better technology can help engineers create models and simulations, and, at the very least, engineers can be equipped with a solution that has checks and balances to ensure assets are created in accordance with industry codes. With these factors addressed, engineers can be confident in their results when it comes to anticipated friction, corrosion or even weather events.
The Holy Grail of Safety
The pursuit of safety within nuclear power facilities holds an almost sacred level of importance, akin to the revered “Holy Grail.” It is universally agreed that safety must be maximized to the absolute in the nuclear domain.
The way a nuclear facility works is by separating different loops, particularly the first and second cycles. The first cycle features radioactive water directly connected to the reactor's core. This cycle requires a special set of rules called “Class 1 piping codes” for analysis.
There are two key things organizations need to get right for Class 1 piping systems: temperature changes (thermal gradients) and wear and tear over time (fatigue).
Temperature changes can cause significant stresses because of shifts in the fluid. Simply put, a nuclear facility doesn't always work at the same power level throughout its lifespan, which could be 30, 40, 50 years or more. The power changes based on needs, like seasonal demands or other facilities' statuses, altering the piping systems' operating conditions (temperature and pressure). These changing conditions are connected to thermal gradients.
Fatigue is the next important factor. Repeated use (loads and cycles) can weaken the piping system over time. The goal is to predict the number of load cycles (like five earthquakes, 10 water hammers, 100 shutdowns, etc.) and then estimate the maximum damage these cycles could cause. We can't predict the exact life of the system over 50 years, so analysis allows us to prepare for the most demanding conditions the system might face over its lifetime to prevent damage.
The Solution
Class 1 calculations are specific and complex and require a trusted, all-in-one nuclear piping analysis solution. Hexagon’s PIPESTRESS has been used by the nuclear industry for more than 50 years and is continuously improved to keep up to date with the latest industry standards and codes, in addition to new approaches to calculations. Users call it the “reference” solution in nuclear pipe stress analysis.
When it comes to thermal gradients (temperature changes) and fatigue, PIPESTRESS allows organizations to easily design with these considerations in mind, alongside analyzing existing systems for possible faults due to these conditions.
Additionally, PIPESTRESS can complete full Class 1 nuclear analysis on its own, without the use of any third-party tools, integrations or data transfer, enabling accurate and efficient Class 1 nuclear piping system projects. It includes:
- A heat transfer solver to calculate the temperature across the pipe thickness over time, from which the thermal gradients can be estimated at each time step.
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A fatigue solver that generates and orders all the pairs of load sets (variation between different states of stress).
These two solvers have been recently improved according to the requirements of our main clients, to increase the precision of the calculations. The Class 1 Heat Transfer solver can now include temperature-dependent properties for pipe material (conductivity and diffusivity), while also enabling engineers to alter steel thermal conductivity and diffusivity with time, during the analysis. The fatigue solver has had its accuracy and Cumulative Usage Factor (CUF) calculation enhanced.
Read the latest PIPESTRESS Case Study
Aiming for Perfection
Piping calculations are an important part of having a safe and efficient facility, but not the only part. The design of a full system requires expertise in various domains and processes. Hexagon enables each department to be more efficient and productive with design and analysis solutions through increased collaboration and communication.
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PV Elite® for the design and analysis of pressure vessels and heat exchangers
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TANK for the design and analysis of storage tanks
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GT STRUDL® for the design and analysis of structures
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Intergraph Smart® 3D and CADWorx® for the design of facilities
Hexagon also offers another piping analysis software: CAESAR II®, the word leader in piping analysis, which in tandem with PIPESTRESS creates the most efficient and complete pipe stress analysis package on the market for projects in any industry.
These solutions are also interoperable, meaning that organizations can address facility design from the ground up while eliminating re-work, and increasing collaboration across departments and processes. Users have seen great success in building oil refineries, power plants and more using multiple Hexagon solutions together in an integrated ecosystem, such as Intergraph Smart 3D and CAESAR II together for piping layout, piping support design and piping analysis. CAESAR II can also be integrated with CADWorx Plant to provide further pipe flexibility and stress analysis tests.
Want to learn more about how you can harness interoperability between Hexagon’s design and analysis solutions to enhance your nuclear projects and more?
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