I would like to ask if there are organisms or plants that could help in reducing any one of types radioactive contamination?
Your magic search word is 'phyto-remediation'
There a bunch of plants used for this.
None of them remove radioactive material as such. With the possible exception of deuterium, the chemistry of isotopes aren't distinguishable by biological organisms.
So to remove strontium 90, you need something that picks up strontium. It will pick up both the radioactive and non-radioactive forms.
In some cases the metal will combine forming compounds. This may make the radio-isotope inaccessible to a given plant. If, for example, strontium was in the form of SrO and SrSO4 you might need two different plants, or add a reagent to the soil to convert it to an accessible form.
Once the plant tissue has picked up the radio isotope, the usual process is to drive off the plant tissue by burning or destructive distillation, then processing the material to either make it insoluble for disposal, or convert it for use. For material with a fairly short half life and low solubility, it may be sufficient just to bury it.
I recall reading that sunflowers were planted after the Chernobyl nuclear disaster, and I just now read that fields of sunflowers were also used in and around Fukushima.
Apparently sunflowers have an affinity to absorbing toxic heavy metals from the soil. The radioactive isotopes are stored in their stems and leaves. The plants have to be cut down and disposed of as radioactive waste. However, that cost is considerably less than digging up and disposal of topsoil.
Doing a brief google search, I learned other plants such as certain mustard plant species and other herbs can be used for lead and mercury environmental damage. To learn more, I encourage you to spend a little time using your favorite search engine. Undoubtedly you'll learn more than what little I have shared now.