Introduction to Mod Packages


The mod package is the delivery mechanism for presenting your design to upper management, other engineers, work planners, and possibly even the NRC. . . .

The mod package contains the engineering drawings created during the design process. It contains the engineering evaluations that were used to justify the changes depicted on the drawings. It also contains forms of various kinds. Here is an overview of the information compiled within a completed mod package:

  • background, problem and solution description
  • list of affected documents and equipment
  • design input record
  • engineering evaluations
  • formal calculations created to provide a basis for critical engineering decisions
  • software quality documentation and cyber security evaluations
  • work instructions that will be used by work planners to generate the step-by-step implementation procedures the craft will use to install the mod
  • testing requirements that verify that the modification has been correctly installed
  • materials list
  • cable and raceway management database updates
  • 50.59 screenings and licensing basis document updates
  • preventative maintenance database updates
  • equipment database updates
  • operations and maintenance procedure updates


Economic theory informs us that consumers impute value to goods and services. Their value is largely subjective. If they perceive that a particular product or service is valuable, then they will be willing to pay a lot for it. If not, then they’ll be reluctant to pay top, or even medium, dollar.

An audience’s first impression of your design will be shaped by their initial impressions of your mod package’s quality. Think of your mod package as an expensive sports car.

If your dealership delivered your brand new sports car with a giant scratch down its side, you would be unhappy. Even though this scratch has absolutely no effect on the engine’s performance or the premium sound system’s fidelity, it is going to lower your perceived value of the entire product. You tell yourself that the scratch is superficial; it can be easily fixed with a little sanding, a brush of paint, a couple clear coats, and some final polishing. But nevertheless, if your dealer received a brand new sports car for your pick-up, and it had a scratch in its side, you would demand a discount or partial refund if they refused to fix the blemish at their own expense.

Such a thing distracts us from the rest of the value embedded throughout. It makes us focus on the outrageously bad spots and forget all else that’s good. In fact, we may ask ourselves “If the outside was so carelessly taken care of, then what does it look like under the hood? Is my engine going to explode, or my transmission eject while I’m barreling down the highway at 70 miles per hour?”

Submitting a poorly formatted mod package that contains typos, grammatical errors, inconsistent font sizes and font types, and incorrect cross-references destroys the perceived value of the entire product. Not only that, but it calls into question the design’s ability to achieve its purpose without generating a new series of never-ending headaches and maintenance problems for the plant — headaches nobody wants, especially the plant.

Cosmetic errors also create doubt about the skill level of the engineer or group of engineers who prepared it. That’s because, though we may think of them as “just typos,” if that typo is a math error it could propagate throughout the entire design and lead to major safety problems and expensive rework.

Once you’ve gone through the critical process of producing a rigorous and technically correct design, don’t burn out in the final moments of the race. Press on towards the end with as much dedication as you exhibited while working out the design details earlier in the process. Make your final package look good.

To learn a few simple ways to write better mod packages, click here.