**1. Introduction**

The VVR-S (water cooled and moderated) type, nuclear research reactor) from "Horia Hulubei" National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), Romania was operated between 1957 and 1997 without any radiological major incident. The reactor main purposes were the radioisotopes production for medical and industrial applications and the research in physics, biophysics, and biochemistry.

Due to the reactor' components and systems aging the specialists and the Romanian Government decided to decommission the facility. Thus, the reactor decommissioning was performed between 2010 and 2020.

During the operation period, the radioisotopes production was performed using four Hot Cells located in the Reactor Building basement (see **Figure 1**). A detailed description of the Hot Cells design, purpose and usage is presented in paper [2].

#### **Figure 1.** *Reactor overview [1].*

The reactor decommissioning process was split in 3 main phases. The Hot Cells were decommissioned in the 3-rd one. The main tasks performed during Hot Cells decommissioning consisted of waste evacuation, internal surfaces decontamination and internal components dismantling (equipment's and stainless-steel lining). The wastes from the Hot Cells no. 3, 2 and 1 were remotely controlled evacuated using the mechanical arms and a trolley [2].

The wastes from the Hot Cell no. 4 were manually evacuated due to the mechanical arms malfunction. Also, the internal surfaces decontamination was performed manually. After the waste's evacuation the Hot Cell internal surfaces were scanned to identify the contamination level [2].

The measurements revealed that the main contamination is located on the Hot Cell floor because of the irradiated substances spilling from vials or capsules during the operation period [2].

Prior the Hot Cells decontamination the dose rate equivalent was assessed by two different methods to prevent over exposure for the workers involved in this process.
