Search - Issue 31 - BRIEF ANALYSIS OF RESULTS OF MEASURED NEUTRON FLUX DENSITY AND GAMMA DOSE RATE IN BOREHOLE Ю.12.78 OF "UKRYTTYA" OBJECT

BRIEF ANALYSIS OF RESULTS OF MEASURED NEUTRON FLUX DENSITY AND GAMMA DOSE RATE IN BOREHOLE Ю.12.78 OF "UKRYTTYA" OBJECT
DOI: https://doi.org/10.31717/1813-3584.18.31.11
Cover not present BRIEF ANALYSIS OF RESULTS OF MEASURED NEUTRON FLUX DENSITY AND GAMMA DOSE RATE IN BOREHOLE Ю.12.78 OF
Category: Issue 31
Publication: 31
Summary

After New Safe Confiment (NSC) was installed in its designed position above the "Ukryttya" (UO) object, microclimatic conditions in "NSC-UO" complex has changed. It, foremost, relates to the changes in temperature and humidity mode due to the fact that precipitation ingress through a roof inside UO was ceased. It can influence the existing nuclear and radiation hazard for UO conditions, for example, humidity drop in fuel–containing materials (FCM) would bring to a growth in neutron flux density (NFD) and in exposure dose rate (EDR). A brief analysis of NFD and EDR parameter dynamics is presented. The parameters were measured in the borehole Ю. 12.78 of UO object after the NSC was installed in its designed position. The NSC was set in its designed position in November 2016, and a slight growth in NFD and EDR parameters began at the beginning of 2017 year. Correlation of NFD and EDR parameters in borehole was studied and their correlation factor was identified. Its value made 0,79, which corresponds to a strong relation between the values (parameters). A method to build NFD and GDR graphs (for illustrative proposes) is offered, in which the next principle of vertical scale choice is used: 1 mm = m1, where m1 is a standard deviation of values . It was stated that the increase in NFD and EDR values is provided by FCM humidity reduction, and it was determined that the controllable FCM cluster is now considered as a nucler safe one; and basic critical parameters of FCM clusters require the further researches, which would enable entering more precise information in the programs for modeling of self-sustained chain reaction occurrence in FCM clusters of "Ukryttya" object.

Keywords: neutron flux density, nuclearly hazardous clusters, nuclear safety monitoring system, correlation factor, fuel-containing materials.

REFERENCE

1. Borovoy А. А. Under-reactor room of the Unit 4 of Chernnobyl NPP: Its state, Fuel Quantity Evaluetion / A. A.

Borovoy, A. S. Lagunenko, E. M. Pazukhin. - Chernobyl, 1997. - 12 p. - (Prepr. NAS of Ukraine. Interdiscplionary Scientific and Technical Center "Shelter; 97-7). (Rus)

2. NSMS System description. SIP05 - 3-008-01. Identification Number NSMS - GS - 3101 - R. 2005.

3. Results of measuring of neutron flux density and of gamma dose rate in mining hole of Number Ю. 12.78 by channels № 001 (NFD), № 001(GDR) by the system of NSMS. (Ukr)

4. Bolshev L. N. Tables of mathematical statistics / L. N. Bolshev, N. V. Smirnov. – Мoskva : Science, 1983. (Rus)

5. Gmurman V. E. Theory of chances and mathematical statistics : Publ. 4th, complemented. Studies. manual for the institutes of higher / V. E. Gmurmanю. – Мoskva : Higher school, 1972. - 308 p. (Rus)

6. Instruction on magnetic survey (surface magnetic survey, airborne magnetics, hydromagnetic survey) / Dep-t of geology of the USSR. – Leningrad : Nedra, 1981. - 263 p. (Rus)

7. Critical parameters of the systems with the fissile materials and of nuclear safety: reference Book / B. G. Dubovskiy, A. V. Kamaev, F. M. Kuzneszov et al. - Мoskva : Atomizdat, 1966. - 226 p. (Rus)

8. Estimation of changes in evaporation-condensation dynamics of moisture in the SO under the NSC, behavior of FCM under changed conditions, and assessment of the change in dust generation : (Report, final, agreement No. 374/17) / Institute for Safety Problems of Nuclear Power Plants, National Academy of Sciences of Ukraine. SR No. 0117U002963. - Chernobyl, 2017. – P. 183. (Rus)

9. Scientific and technical support during the stages of NSC-SO commissioning and operation (aspects of nuclear and radiation safety) : (Report, interim, stage 1, agreement No. 377/18) / Institute for Safety Problems of Nuclear Power Plants, National Academy of Sciences of Ukraine. SR No. 0118U001405. - Chernobyl, 2018. – P.139. (Rus)