I don’t do highly technical stuff, but you certainly can use this as a leverage to charge a bit more than your standard rates. Nuclear physics is a serious business. If you’re an expert in this subject, they’d have less reason not to hire you. Although in the end, it depends on how much they care about quality. Please bear in mind, that agencies would typically offer lower rates compared to direct clients.
You will need to know (or at least guesstimate) how much progress on average can you make in an hour. Then you’ll need to determine what is the acceptable hourly wage for you. Let's say you can make 4 runtime minutes of progress per hour, give or take. And you consider 35 USD as a liveable hourly wage. That means 35/4 = 8.75 USD per runtime minute. As I said before, you can bump this rate up if the content is highly technical and requires true expertise in order to make a coherent subtitle translation.
Regarding the time estimate to finish up a subtitling assignment, I’ll just quote a couple sources.
From Subtitling: Concepts and Practices (Jorge Díaz-Cintas, Aline Remael) – Chapter 2: Professional ecosystem.
It is rather challenging to ascertain exactly how long it takes, on average, to subtitle a standard-length film of some 90 minutes. The time invested will depend on factors such as the density of the dialogue, the editing of the scenes and number of shot changes, the terminology employed, the cultural references mentioned and the overall difficulty of the topic, as well as on the practitioner’s experience and expertise. Under normal circumstances, dealing with a film containing some 1,000 to 1,200 subs, the spotting can take around two days, and the translator is given between four and seven days to produce the TL subtitles, with an extra couple of days to conduct the QC.
From Audiovisual Translators Europe (avteurope.eu) – Wannabe section.
Subtitling
Documentary or hour-long episode of a TV series (52 min): 1 week
Feature-length film (100 min): 2-3 weeks
…
In reality the actual work can be done significantly faster than this (and clients will be quick to point this out!), but keep in mind that as a freelancer you always have a lot more work to do than just the translating that you actually get paid for. The work load is sometimes difficult to predict. Most of us do our own bookkeeping, we have to deal with tax authorities, communicate with clients, apply for new jobs, plan our work, do proof reading, manage our software and so on. Some jobs are more difficult than others and may require many hours of extensive research. What this adds up to is that nobody can translate effectively 8 hours a day, 5 days a week, so you shouldn’t expect to be doing that.
HTH
[Edited at 2022-10-20 17:53 GMT]