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Iodine behaviour in severe accidents

Abstract

A description is given of analyses which identify which aspects of the modelling and data are most important in evaluating the release of radioactive iodine to the environment following a potential severe accident at a PWR and which identify the major uncertainties which affect that release. Three iodine codes are used namely INSPECT, IODE and IMPAIR, and their predictions are compared with those of the PSA code MAAP. INSPECT is a mechanistic code which models iodine behaviour in the aqueous aerosol, spray water and sump water, and the partitioning of volatile species between the aqueous phases and containment gas space. Organic iodine is not modelled. IODE and IMPAIR are semi-empirical codes which do not model iodine behaviour in the aqueous aerosol, but model organic iodine. The fault sequences addressed are based on analyses for the Sizewell `B` design. Two types of sequence have been analysed.: (a) those in which a major release of fission products from the primary circuit to the containment occur, e.g. a large LOCAS, (b) those where the release by-passes the containment, e.g. a leak into the auxiliary building. In the analysis of the LOCA sequences where the pH of the sump is controlled to be a  More>>
Authors:
Dutton, L M.C.; Grindon, E; Handy, B J; Sutherland, L; [1]  Bruns, W G; Sims, H E; [2]  Dickinson, S; [3]  Hueber, C; Jacquemain, D [4] 
  1. NNC Ltd., Knutsford (United Kingdom)
  2. AEA Technology, Harwell (United Kingdom)
  3. AEA Technology, Winfrith (United Kingdom)
  4. IPSN/CEA, Cadarache, Saint Paul-Lez-Durance (France)
Publication Date:
Dec 01, 1996
Product Type:
Technical Report
Report Number:
PSI-97-02; CONF-9606320-; NEA/CSNI/R(96)-6.
Reference Number:
SCA: 210200; PA: AIX-28:037570; EDB-97:078516; SN: 97001796026
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:
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS; FISSION PRODUCT RELEASE; COMPUTERIZED SIMULATION; IODINE; SIZEWELL-B REACTOR; REACTOR ACCIDENTS; I CODES; LOSS OF COOLANT; M CODES; PH VALUE; THEORETICAL DATA
OSTI ID:
484106
Research Organizations:
Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Country of Origin:
Switzerland
Language:
English
Other Identifying Numbers:
Other: ON: DE97624048; TRN: CH9700224037570
Availability:
INIS; OSTI as DE97624048
Submitting Site:
CHN
Size:
pp. 615-633
Announcement Date:

Citation Formats

Dutton, L M.C., Grindon, E, Handy, B J, Sutherland, L, Bruns, W G, Sims, H E, Dickinson, S, Hueber, C, and Jacquemain, D. Iodine behaviour in severe accidents. Switzerland: N. p., 1996. Web.
Dutton, L M.C., Grindon, E, Handy, B J, Sutherland, L, Bruns, W G, Sims, H E, Dickinson, S, Hueber, C, & Jacquemain, D. Iodine behaviour in severe accidents. Switzerland.
Dutton, L M.C., Grindon, E, Handy, B J, Sutherland, L, Bruns, W G, Sims, H E, Dickinson, S, Hueber, C, and Jacquemain, D. 1996. "Iodine behaviour in severe accidents." Switzerland.
@misc{etde_484106,
title = {Iodine behaviour in severe accidents}
author = {Dutton, L M.C., Grindon, E, Handy, B J, Sutherland, L, Bruns, W G, Sims, H E, Dickinson, S, Hueber, C, and Jacquemain, D}
abstractNote = {A description is given of analyses which identify which aspects of the modelling and data are most important in evaluating the release of radioactive iodine to the environment following a potential severe accident at a PWR and which identify the major uncertainties which affect that release. Three iodine codes are used namely INSPECT, IODE and IMPAIR, and their predictions are compared with those of the PSA code MAAP. INSPECT is a mechanistic code which models iodine behaviour in the aqueous aerosol, spray water and sump water, and the partitioning of volatile species between the aqueous phases and containment gas space. Organic iodine is not modelled. IODE and IMPAIR are semi-empirical codes which do not model iodine behaviour in the aqueous aerosol, but model organic iodine. The fault sequences addressed are based on analyses for the Sizewell `B` design. Two types of sequence have been analysed.: (a) those in which a major release of fission products from the primary circuit to the containment occur, e.g. a large LOCAS, (b) those where the release by-passes the containment, e.g. a leak into the auxiliary building. In the analysis of the LOCA sequences where the pH of the sump is controlled to be a value of 8 or greater, all three codes predict that the oxidation of iodine to produce gas phase species does not make a significant contribution to the source term due to leakage from the reactor building and that the latter is dominated by iodide in the aerosol. In the case where the pH of the sump is not controlled, it is found that the proportion of gas phase iodine increases significantly, although the cumulative leakage predicted by all three codes is not significantly different from that predicted by MAAP. The radiolytic production of nitric acid could be a major factor in determining the pH, and if the pH were reduced, the codes predict an increase in gas phase iodine species leaked from the containment. (author) 4 figs., 7 tabs., 13 refs.}
place = {Switzerland}
year = {1996}
month = {Dec}
}