Experimental and analytical studies of boric acid concentrations in a VVER-440 reactor during the long-term cooling period of loss-of-coolant accidents

Jari Tuunanen, Heikki Tuomisto, Pekka Raussi

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17 Citations (Scopus)

Abstract

Concentrating and mixing of boric acid (H3BO3) during the long-term cooling period of loss-of-coolant accidents (LOCAs) in the Loviisa VVER-440 reactors has been studied with the REWET-II and VEERA facilities. To get more detailed information on boric acid mass transfer, a specific facility was built to simulate boron mixing in the lower plenum of the reactor. The experiments with the VEERA facility showed that in the VVER-440 reactor fuel bundles the mixing is complete due to boiling and U-tube oscillations and, hence, concentration distribution of boric acid in the bundles is uniform. The U-tube oscillations proved to be an important mechanism in transferring concentrated boric acid from the core to the lower plenum. The experiments demonstrated that crystallization of boric acid in the reactor core simulator is possible, if a stable long-term cooling situation with water boiling in the core continues long enough. In the experiments the crystallization of boric acid in the core simulator led to a flow blockage of the fuel rod bundle and overheating of the rod simulators when the flow through the core ceased.

Experimental results were used to develop a computational model for calculations of boric acid concentrations in the reactor during LOCAs. The development work was supported with a series of RELAP5/MOD3 small-break LOCA analyses. The results of the RELAP5/MOD3 calculations were used to determine the boundary conditions under which concentrating of boric acid might occur. Reactor analysis showed that the crystallization of boric acid in the reactor is not possible during the long-term cooling period of LOCAs. This is mainly due to the fact that the ice-condenser in the Loviisa plant contains sodium tetraborate Na2B4O710H2O (borax), which enters the reactor when emergency core cooling water is taken from the sump. Borax increases greatly the solubility of boric acid in water and, hence, decreases the risk of crystallization.
Original languageEnglish
Pages (from-to)217-231
Number of pages15
JournalNuclear Engineering and Design
Volume148
Issue number2-3
DOIs
Publication statusPublished - 1994
MoE publication typeA1 Journal article-refereed

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loss of coolant
boric acids
Boric acid
Loss of coolant accidents
accidents
accident
reactors
Cooling
cooling
acid
Crystallization
Sodium borate
crystallization
simulators
bundles
simulator
manometers
Simulators
concentrating
boiling

Cite this

@article{e4ed0e1e12304dc0af321aaf3a0a6d72,
title = "Experimental and analytical studies of boric acid concentrations in a VVER-440 reactor during the long-term cooling period of loss-of-coolant accidents",
abstract = "Concentrating and mixing of boric acid (H3BO3) during the long-term cooling period of loss-of-coolant accidents (LOCAs) in the Loviisa VVER-440 reactors has been studied with the REWET-II and VEERA facilities. To get more detailed information on boric acid mass transfer, a specific facility was built to simulate boron mixing in the lower plenum of the reactor. The experiments with the VEERA facility showed that in the VVER-440 reactor fuel bundles the mixing is complete due to boiling and U-tube oscillations and, hence, concentration distribution of boric acid in the bundles is uniform. The U-tube oscillations proved to be an important mechanism in transferring concentrated boric acid from the core to the lower plenum. The experiments demonstrated that crystallization of boric acid in the reactor core simulator is possible, if a stable long-term cooling situation with water boiling in the core continues long enough. In the experiments the crystallization of boric acid in the core simulator led to a flow blockage of the fuel rod bundle and overheating of the rod simulators when the flow through the core ceased.Experimental results were used to develop a computational model for calculations of boric acid concentrations in the reactor during LOCAs. The development work was supported with a series of RELAP5/MOD3 small-break LOCA analyses. The results of the RELAP5/MOD3 calculations were used to determine the boundary conditions under which concentrating of boric acid might occur. Reactor analysis showed that the crystallization of boric acid in the reactor is not possible during the long-term cooling period of LOCAs. This is mainly due to the fact that the ice-condenser in the Loviisa plant contains sodium tetraborate Na2B4O710H2O (borax), which enters the reactor when emergency core cooling water is taken from the sump. Borax increases greatly the solubility of boric acid in water and, hence, decreases the risk of crystallization.",
author = "Jari Tuunanen and Heikki Tuomisto and Pekka Raussi",
year = "1994",
doi = "10.1016/0029-5493(94)90111-2",
language = "English",
volume = "148",
pages = "217--231",
journal = "Nuclear Engineering and Design",
issn = "0029-5493",
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number = "2-3",

}

Experimental and analytical studies of boric acid concentrations in a VVER-440 reactor during the long-term cooling period of loss-of-coolant accidents. / Tuunanen, Jari; Tuomisto, Heikki; Raussi, Pekka.

In: Nuclear Engineering and Design, Vol. 148, No. 2-3, 1994, p. 217-231.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Experimental and analytical studies of boric acid concentrations in a VVER-440 reactor during the long-term cooling period of loss-of-coolant accidents

AU - Tuunanen, Jari

AU - Tuomisto, Heikki

AU - Raussi, Pekka

PY - 1994

Y1 - 1994

N2 - Concentrating and mixing of boric acid (H3BO3) during the long-term cooling period of loss-of-coolant accidents (LOCAs) in the Loviisa VVER-440 reactors has been studied with the REWET-II and VEERA facilities. To get more detailed information on boric acid mass transfer, a specific facility was built to simulate boron mixing in the lower plenum of the reactor. The experiments with the VEERA facility showed that in the VVER-440 reactor fuel bundles the mixing is complete due to boiling and U-tube oscillations and, hence, concentration distribution of boric acid in the bundles is uniform. The U-tube oscillations proved to be an important mechanism in transferring concentrated boric acid from the core to the lower plenum. The experiments demonstrated that crystallization of boric acid in the reactor core simulator is possible, if a stable long-term cooling situation with water boiling in the core continues long enough. In the experiments the crystallization of boric acid in the core simulator led to a flow blockage of the fuel rod bundle and overheating of the rod simulators when the flow through the core ceased.Experimental results were used to develop a computational model for calculations of boric acid concentrations in the reactor during LOCAs. The development work was supported with a series of RELAP5/MOD3 small-break LOCA analyses. The results of the RELAP5/MOD3 calculations were used to determine the boundary conditions under which concentrating of boric acid might occur. Reactor analysis showed that the crystallization of boric acid in the reactor is not possible during the long-term cooling period of LOCAs. This is mainly due to the fact that the ice-condenser in the Loviisa plant contains sodium tetraborate Na2B4O710H2O (borax), which enters the reactor when emergency core cooling water is taken from the sump. Borax increases greatly the solubility of boric acid in water and, hence, decreases the risk of crystallization.

AB - Concentrating and mixing of boric acid (H3BO3) during the long-term cooling period of loss-of-coolant accidents (LOCAs) in the Loviisa VVER-440 reactors has been studied with the REWET-II and VEERA facilities. To get more detailed information on boric acid mass transfer, a specific facility was built to simulate boron mixing in the lower plenum of the reactor. The experiments with the VEERA facility showed that in the VVER-440 reactor fuel bundles the mixing is complete due to boiling and U-tube oscillations and, hence, concentration distribution of boric acid in the bundles is uniform. The U-tube oscillations proved to be an important mechanism in transferring concentrated boric acid from the core to the lower plenum. The experiments demonstrated that crystallization of boric acid in the reactor core simulator is possible, if a stable long-term cooling situation with water boiling in the core continues long enough. In the experiments the crystallization of boric acid in the core simulator led to a flow blockage of the fuel rod bundle and overheating of the rod simulators when the flow through the core ceased.Experimental results were used to develop a computational model for calculations of boric acid concentrations in the reactor during LOCAs. The development work was supported with a series of RELAP5/MOD3 small-break LOCA analyses. The results of the RELAP5/MOD3 calculations were used to determine the boundary conditions under which concentrating of boric acid might occur. Reactor analysis showed that the crystallization of boric acid in the reactor is not possible during the long-term cooling period of LOCAs. This is mainly due to the fact that the ice-condenser in the Loviisa plant contains sodium tetraborate Na2B4O710H2O (borax), which enters the reactor when emergency core cooling water is taken from the sump. Borax increases greatly the solubility of boric acid in water and, hence, decreases the risk of crystallization.

U2 - 10.1016/0029-5493(94)90111-2

DO - 10.1016/0029-5493(94)90111-2

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JO - Nuclear Engineering and Design

JF - Nuclear Engineering and Design

SN - 0029-5493

IS - 2-3

ER -