I was told that if someone is on probation that no NPP would give UA/UAA. Is that true? And if it is where is that written? I was arrested last Aug for a DUI, Last Tuesday it was dropped to reckless driving and probation. I have had treatment and want to further my career in nuclear power. I have been held accountable for my stupid decision and cannot and will not let this be what defines myself. Looking for answers!!!! 
Each utility handles it their own way. The utilities I have worked for typically will not allow someone on probation in. Of course there are always the exceptions that happen. Sometimes it comes down to who is over access for the utility you are trying to gain access or their own internal policies. There is no NRC regulation that says if someone is on probation they aren't allowed in. I will say though that usually exceptions to someone being on probation are things that aren't drug/alcohol related, such as domestic violence. (Then again we all know a lot of DV cases are influenced by alcohol so that may not be the best example but I think you get my gist)
You have a few options really..
First option is to try to gain access. If you do try to gain access and get denied you will typically be denied for a year, according to how they classify your reason for denial, and up to 3 years. In some cases you can be kind of in a pending status until more information is provided to complete the process... in other words when the probation is complete you can give them your paperwork and they will complete the background process. However, the job may be over at that point but it does help as far as trying to gain access again or at another plant.
Forewarned you will have to go back to your 18th birthday as far as criminal history is concerned. You will also be required to give a 5 year work history. Initial access typically only requires a 3 year background. If there are any drug/alcohol related charges in the past 5 years then you have to go back the extended 2 years in the work history. You will also have to provide 3-4 references in most cases. Those references are ONLY used as a resource to develop 2 more references that you did not list.
Second option is basically what I wrote up above about waiting until your probation is complete. I'm not sure how long you are on probation for but you would have to see a psychologist regarding the drug/alcohol related charge (even though it was dropped to reckless driving). The psychs I work with typically are skeptical of recommending access to anyone who has had a drug/alcohol related charge unless it was completely dropped. They are well aware of the judicial process and that a lot of times people can get charges reduced even though they know they were guilty. (Not saying that is the case) But point is these psychs don't have the "FINAL" say... but their recommendation is taken.
The MAIN reason people on probation aren't very favorable is because the requirements of probation are tough for a lot of people. It is very easy for people to get their probation revoked. A lot of times if your probation is revoked the original charge can come back on you. So instead of reckless driving you'd be back with a DUI...gotta remember lots of people need jobs.. and with the way the nuke industry is under the scope for safety why would the utility REALLY want to risk that? Also, being denied in the system is never good to have in PADS cause it will follow you forever..but also because it costs companies a lot of money to bring people in as an Initial. When you get done with training, drug screening, background you are talking up to 1,000 bucks per applicant that is being spent.
My honest opinion is that you wait until your probation is finished. If you are really struggling for work and this is all you got then you can gamble but I don't like your chances too much simply because it was so recent and the fact you are still on probation.
Either way goodluck and let me know if you have anymore questions.