Radiološke implikacije povećanja kapaciteta bazena za istrošeno gorivo

scientific master's theses

• Author: Josip Lebegner
• Mentor: Dubravko Pevec (mentor)
• Committee member: Nikola Čavlina (član povjerenstva)
• Committee member: Dubravko Pevec (član povjerenstva)
• Committee member: Stjepan Lulić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Applied Physics); Zagreb
• Defense date and country: 2000, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

Nedovoljni kapaciteti postojećih bazena za istrošeno gorivo kod jednog dijela nuklearnih elektrana inicirali su nalaženje novih tehnologija u cilju proširenja postojećih bazena. U stručnoj literaturi spominju se tri načina povećanja kapaciteta bazena za istrošeno gorivo: gušći smještaj gorivnih elemenata, konsolidacija i dvorazinsko punjenje bazena. Svaki od spomenutih postupaka ima određeni utjecaj na porast brzine doze u blizini bazena za istrošeno gorivo. Na konkretnom primjeru bazena za istrošeno gorivo NE Krško računate su brzine doza na površini bazena za sva tri navedena slučaja. Brzine doza dobivene su SAS4 sekvencom računalskog programa SCALE koja služi za analizu štitova, a ulazni podaci o intenzitetu zračenja u bazenu dobiveni su ORIGEN2-PC računarskim programom. Brzine doza od gama i neutronskog zračenja računate su za pet različitih položaja na površini bazena na kraju životnog vijeka elektrane. U proračunima su korišteni podaci o stvarnom odgoru postojećeg inventara istrošenog goriva, a za preostale cikluse do kraja životnog vijeka elektrane napravljena je ocjena prema odgoru i broju istrošenih gorivnih elemenata tekućeg radnog ciklusa. Izračunate brzine doza za gušći smještaj i konsolidaciju istrošenog goriva bitno su ispod vrijednosti propisanih američkom zakonskom regulativom za prostore s ograničenim pristupom (10CFR20, 25 μSv/h). Brzina doze na površini bazena NE Krško za slučaj dvorazinskog punjenja na razini je preporučenih 25 μSv/h. Glavni razlog za tako visoku dozu leži u krajnje konzervativnim pretpostavkama korištenim u izračunu. Može se zaključiti da proširenje kapaciteta bazena za istrošeno gorivo gušćim smještajem ili konsolidacijom istrošenih gorivnih elemenata neće bitno promijeniti brzine doza zračenja na površini bazena.

Abstract (english)

In order to solve the problem of insufficient spent fuel pool capacities in some nuclear power plants, three advanced techniques have been analysed: reracking, spent fuel consolidation and double tiering of existing spent fuel pool. All approaches have particular impact on the boosting of the radiation dose rates in the vicinity of spent fuel pool. The radiation dose rates on the surface of the NPP Krško spent fuel pool have been calculated for all of three techniques. The radiation dose rates were calculated via SAS4 sequence, which is a standard part of SCALE code system used for shielding analysis. ORIGEN2-PC computational tools provided isotop inventory of the spent fuel. The gamma dose rates and neutron dose rates have been calculated on the five different locations close to the NPP Krško pool surface at the end of the NPP Krško projected lifetime. In the calculations, the actual burnup of the spent fuel from already finished cycles have been taken into account. For the rest of the spent fuel, the burnup structure similar to discharge burnup of the current cycle has been assumed. The results show that dose rates calculated for reracking and consolidation are notable under dose rates level for unrestricted areas limited by the American Code of Federal Regulations (10CFR25, 25 μSv/h). By contrast, the double tiering radioactive dose rates are comparable with this level. The main reason for such a high doses are very conservative assumptions used in the double tiering dose rates calculations. As a conclusion, in order to expanding the NPP Krško spent fuel pool, rerackig and consolidation techniques might be used without significant changes of radiation dose rates on the spent fuel pool surface.

• Keywords: Bazen za istrošeno gorivo; gušći smještaj gorivnih elemenata; konsolidacija; dvorazinsko punjenje
• Keywords (english): Spent fuel pool; reracking; consolidation of spent nuclear fuel; double tiering
• Language: croatian
• URN:NBN: urn:nbn:hr:168:820448
• Study programme: Title: Postgraduate master programme in electrical engineering; Study programme type: university; Study level: postgraduate; Academic / professional title: Magistar znanosti elektrotehnike (Magistar znanosti elektrotehnike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-04-03 13:25:22