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CANDU safety under severe accidents

Abstract

The characteristics of the CANDU reactor relevant to severe accidents are set first by the inherent properties of the design, and second by the Canadian safety/licensing approach. The pressure-tube concept allows the separate, low-pressure, heavy-water moderator to act as a backup heat sink even if there is no water in the fuel channels. Should this also fail, the calandria shell itself can contain the debris, with heat being transferred to the water-filled shield tank around the core. Should the severe core damage sequence progress further, the shield tank and the concrete reactor vault significantly delay the challenge to containment. Furthermore, should core melt lead to containment overpressure, the containment behaviour is such that leaks through the concrete containment wall reduce the possibility of catastrophic structural failure. The Canadian licensing philosophy requires that each accident, together with failure of each safety system in turn, be assessed (and specified dose limits met) as part of the design and licensing basis. In response, designers have provided CANDUs with two independent dedicated shutdown systems, and the likelihood of Anticipated Transients Without Scram is negligible. Probabilistic safety assessment studies have been performed on operating CANDU plants, and on the 4 x 880 MW(e) Darlington station  More>>
Authors:
Snell, V G; Howieson, J Q; [1]  Alikhan, S; [2]  Frescura, G M; King, F; [3]  Rogers, J T; [4]  Tamm, H [5] 
  1. Atomic Energy of Canada Ltd. (Canada)
  2. New Brunswick Electric Power Commission (Canada)
  3. Ontario Hydro (Canada)
  4. Carleton Univ., Ottawa, ON (Canada)
  5. Atomic Energy of Canada Ltd. (Canada). Whiteshell Research Lab.
Publication Date:
Dec 01, 1996
Product Type:
Conference
Report Number:
IAEA-TECDOC-920; CONF-9411339-
Reference Number:
SCA: 210400; PA: AIX-28:021872; EDB-97:039813; SN: 97001747560
Resource Relation:
Conference: Advisory group meeting on technical feasibility and reliability of passive safety systems for nuclear power plants, Juelich (Germany), 21-24 Nov 1994; Other Information: PBD: Dec 1996; Related Information: Is Part Of Technical feasibility and reliability of passive safety systems for nuclear power plants. Proceedings of an advisory group meeting; PB: 357 p.
Subject:
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS; CANDU TYPE REACTORS; REACTOR SAFETY; SAFETY ENGINEERING; CONTAINMENT; DESIGN; LICENSING; PROBABILISTIC ESTIMATION; REACTOR ACCIDENTS; RELIABILITY; RISK ASSESSMENT
OSTI ID:
440067
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 1011-4289; Other: ON: DE97615987; TRN: XA9743178021872
Availability:
INIS; OSTI as DE97615987
Submitting Site:
INIS
Size:
pp. 321-351
Announcement Date:

Citation Formats

Snell, V G, Howieson, J Q, Alikhan, S, Frescura, G M, King, F, Rogers, J T, and Tamm, H. CANDU safety under severe accidents. IAEA: N. p., 1996. Web.
Snell, V G, Howieson, J Q, Alikhan, S, Frescura, G M, King, F, Rogers, J T, & Tamm, H. CANDU safety under severe accidents. IAEA.
Snell, V G, Howieson, J Q, Alikhan, S, Frescura, G M, King, F, Rogers, J T, and Tamm, H. 1996. "CANDU safety under severe accidents." IAEA.
@misc{etde_440067,
title = {CANDU safety under severe accidents}
author = {Snell, V G, Howieson, J Q, Alikhan, S, Frescura, G M, King, F, Rogers, J T, and Tamm, H}
abstractNote = {The characteristics of the CANDU reactor relevant to severe accidents are set first by the inherent properties of the design, and second by the Canadian safety/licensing approach. The pressure-tube concept allows the separate, low-pressure, heavy-water moderator to act as a backup heat sink even if there is no water in the fuel channels. Should this also fail, the calandria shell itself can contain the debris, with heat being transferred to the water-filled shield tank around the core. Should the severe core damage sequence progress further, the shield tank and the concrete reactor vault significantly delay the challenge to containment. Furthermore, should core melt lead to containment overpressure, the containment behaviour is such that leaks through the concrete containment wall reduce the possibility of catastrophic structural failure. The Canadian licensing philosophy requires that each accident, together with failure of each safety system in turn, be assessed (and specified dose limits met) as part of the design and licensing basis. In response, designers have provided CANDUs with two independent dedicated shutdown systems, and the likelihood of Anticipated Transients Without Scram is negligible. Probabilistic safety assessment studies have been performed on operating CANDU plants, and on the 4 x 880 MW(e) Darlington station now under construction; furthermore a scoping risk assessment has been done for a CANDU 600 plant. They indicate that the summed severe core damage frequency is of the order of 5 x 10{sup -6}/year. 95 refs, 3 tabs.}
place = {IAEA}
year = {1996}
month = {Dec}
}