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Prevention of organic iodide formation in BWR`s

Abstract

During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR`s as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to  More>>
Authors:
Karjunen, T; [1]  Laitinen, T; Piippo, J; Sirkiae, P [2] 
  1. Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland)
  2. VTT Manufacturing Technology (Finland)
Publication Date:
Dec 01, 1996
Product Type:
Technical Report
Report Number:
PSI-97-02; CONF-9606320-; NEA/CSNI/R(96)-6.
Reference Number:
SCA: 400702; 400201; 210100; PA: AIX-28:035772; EDB-97:080946; SN: 97001795099
Resource Relation:
Conference: 4. CSNI workshop on the chemistry of iodine in reactor safety, Wuerenlingen (Switzerland), 10-12 Jun 1996; Other Information: PBD: Dec 1996; Related Information: Is Part Of Proceedings of the 4. CSNI workshop on the chemistry of iodine in reactor safety; Guentay, S. [ed.] [Paul Scherrer Inst. (PSI), Villigen (Switzerland)]; PB: 716 p.
Subject:
40 CHEMISTRY; 21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS; BORON CARBIDES; OXIDATION; BWR TYPE REACTORS; REACTOR ACCIDENTS; ELECTRIC CABLES; ELECTRICAL INSULATION; IODIDES; ORGANIC COMPOUNDS; SYNTHESIS; CORROSION; EVAPORATION; EXPERIMENTAL DATA; PH VALUE; WATER CHEMISTRY
OSTI ID:
481453
Research Organizations:
Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Country of Origin:
Switzerland
Language:
English
Other Identifying Numbers:
Other: ON: DE97624048; TRN: CH9700213035772
Availability:
INIS; OSTI as DE97624048
Submitting Site:
CHN
Size:
pp. 385-398
Announcement Date:

Citation Formats

Karjunen, T, Laitinen, T, Piippo, J, and Sirkiae, P. Prevention of organic iodide formation in BWR`s. Switzerland: N. p., 1996. Web.
Karjunen, T, Laitinen, T, Piippo, J, & Sirkiae, P. Prevention of organic iodide formation in BWR`s. Switzerland.
Karjunen, T, Laitinen, T, Piippo, J, and Sirkiae, P. 1996. "Prevention of organic iodide formation in BWR`s." Switzerland.
@misc{etde_481453,
title = {Prevention of organic iodide formation in BWR`s}
author = {Karjunen, T, Laitinen, T, Piippo, J, and Sirkiae, P}
abstractNote = {During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR`s as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs.}
place = {Switzerland}
year = {1996}
month = {Dec}
}