Regarding Personnel Access to the Location Area of the Shelter Object Unstable Structures to be Dismantled

O. V. Balan, L. I. Pavlovsky, S. S. Pidbereznyi, V. M. Rudko

Institute for Safety Problems of Nuclear Power Plants, NAS of Ukraine, Kirova st., 36a, Chornobyl, 07270, Ukraine

DOI: doi.org/10.31717/2311-8253.24.2.5

Abstract

The need to dismantle the unstable structures of the Shelter object is due to several reasons, including the rather high probability of the collapse of these structures even in the conditions of operation inside the New Safe Confinement (NSC). Thus, all metal structures, which, respectively, make up the Shelter object, will be subject to dismantling. It is claimed that the activity of dismantling the unstable structures of the Shelter object is rather difficult engineering task. First of all, this circumstance is caused by the need to perform work in very difficult radiation conditions, where the values of the dose rate (DR) in many zones reach more than 10 mSv/h. The highest values of DR were recorded in the work area zone (WAZ) on the runup from the pipes, in the area of the “Dog’s House” block (over 48 mSv/h) and on the rubble above the deaerator stack (DS) overlap (over 35 mSv/h). It is emphasized that the involvement of personnel in physical work in such conditions should be excluded or minimized. The paper presents the main results of the study of personnel access routes to the work area (WA) for the dismantling of unstable structures of the Shelter object and radiation conditions in the areas where they are located. Possible individual doses of personnel on the access routes to the WAZ and back are given. With the help of existing data on the radiation situation and the angular distribution of gamma radiation along the routes, by means of the program ChNPP VRdose Planner Pro v. 2.2.2 modeling of the shielding parameters of the protective cabin in the area of the “Octopus” beam was carried out. On the example of dismantling works of the connecting truss structure of the southern part of the Shelter object roof, the calculations of the time spent on the access of personnel to the emergency room and back by their own pace and with the use of a protective cabin for personnel movement, which in turn is transported by a crane of the NSC, were made. The amount of averted dose to personnel due to the use of a protective cabin was estimated. The work emphasizes that the protection of personnel from the effects of radiation on the access routes can be solved by using a shielded protective cabin, which will be transported by one of the NSC cranes from the parking place at the temporary storage site to the WAZ for dismantling the unstable structures of the Shelter object. The protective cabin should be universal and allow its use for any Shelter object zone due to the ability to adjust the orientation of the cabin in relation to the existing radiation sources, as well as the ability to adjust the thickness of the shielding layer on all six sides. Possibilities for transporting the cabin by the NSC crane, changing the orientation due to the turning mechanism and adjusting the thickness of the shielding layer should be included in the design of the protective cabin.

Keywords: Shelter object, LC-1 (LC-2) launch complex, access routes, work area, unstable structures, protective cabin, deflected dose.

References

1. Krasnov V. O., Nosovskyi A. V., Paskevych S. A., Rudko V. M.; A. V. Nosovskyi (ed.) (2021). Obiekt “Ukryttia”v umovakh novoho bezpechnoho konfainmenta [The Shelter Object in Conditions of the New Safe Confinement]. Chornobyl: ISP NPP, NAS of Ukraine, 344 p. (in Ukr.)

2. Balan O. V., Brylka S. H., Pidbereznyi S. S., Rudko V. M. (2023). Peculiarities of the Shelter object individual unstable structures dismantling. Nuclear Power and Environment, vol. 27, no. 2, pp. 56–66.

3. New Safe Confinement (NSC). Launch complex 2 (LC-2). Dismantling of unstable structures of the Shelter object of the ChNPP as part of the “early” dismantling. Stage 2. Radiation survey on the access roads and in the work areas. (in Ukr.)

4. Launch complex 2 (LC-2). Dismantling of unstable structures of the Shelter object of the ChNPP as part of the “early” dismantling. Stage 3. Inspection of sites for temporary storage of dismantled structures and routes of their transportation from work areas. (in Ukr.)

5. Pavlovskyi L. I., Khomenko D. O., Yehorov V. V. [Determination of the radiation situation in the areas of unstable structures dismantling of the Shelter object]. Nuclear Power and Environment, vol. 25, no. 3, pp. 16–23. (in Ukr.)

6. Design, manufacture, construction and commissioning of the NSC to the second launch complex of the NSC (LC-2). Infrastructure for performing dismantling of unstable structures of the Shelter object. Working project “Reconstruction of the Shelter object of the ChNPP chipboard in part of dismantling the metal truss of the southern roof reinforcement”. (in Ukr.)

7. РО-ШД-03. Act on the performance of pre-project radiation studies on the access route to the NSC-SO structures, which are subject to “early” dismantling in the WAZ from the south side of the Shelter object, dated 21.10.2021. (in Ukr.)

8. Technological solutions. Internal transport system. SIPN-KP-22-E06__TEN-061-01/99-925.100.011.OT06.01. (in Rus.)

Full Text (PDF)