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Source Term

Objective

The source term of a severe accident is defined by the magnitude, chemical species, physical form and timing of the radioactive emission to the environment. A series of assessments, sensitivity studies and state-of-the-art reviews, in connection both with the primary circuit and the containment, are needed to identify uncertainties in the database of the source term.

The objective of the programme is to establish a consensus on the state of knowledge of the radiological source term. Priority is given to research, both through appropriate experiments and modelling activities, on source term phenomena and radionuclides which are most important in the context of PSAs for nuclear power plants.
Overall Strategy

A strategy for source term work within the European Union has been formulated based on the optimum use of facilities and resources.

Plant Assessment

Probabilistic safety assessments have been conducted for commercial plant to highlight the radionuclides and phenomena of greatest importance.

Primary Circuit Studies

Detailed sensitivity studies have been undertaken to highlight the phenomena that contribute most to uncertainties in the source term.

A series of state-of-the-art reviews have also been conducted to support the sensitivity studies, involving reviews of the following topics

(i) fission product release
(ii) aerosol deposition,
(iii) vapour reactions with surfaces and aerosols,
(iv) physical resuspension,
(v) revaporization.

Containment Studies

The main activity undertaken on containment-related issues involves an assessment of the models within iodine codes.

State-of-the-art reviews have also been conducted on two containment-related topics, namely:

(i) coupling of aerosol physics with thermal-hydraulics,
(ii) pool scrubbing.
Work programme

A report outlining a European Source Term strategy has been produced to review source term activities both within the European Union (EU) and in a wider international context.

AEA/Winfrith, in particular, is conducting experiments to quantify the release of FPs in an oxidizing atmosphere (data to be validated against the FPREM code). They are also investigating the behaviour of non-fission product materials like boron, Ag-In-Cd and vapours or aerosols from stainless steels and Inconel, using some results of the Falcon and Harrier experimental facilities. Research is also conducted about FP transport both in the reactor cooling system and in the containment, including revaporization and resuspension (VICTORIA code), iodine chemistry, and iodine behaviour in the sump and under H2 detonation conditions. The above developments of FPREM and VICTORIA are going to be implemented into the KESS code by IKE/Stuttgart, who is also examining the behaviour of the multicomponent aerosol systems using a PSA approach (MAAP code). Aerosol/FP transport and resuspension problems are also investigated by ENEL-VDN/Milano in the frame of the STORM Project to be conducted at JRC Ispra, together with primary circuit thermohydraulics aspects of the radionuclide behaviour. CEA-IPSN/Cadarache is conducting experiments both at their PITEAS facility to validate a model for the hygroscopic effects on particle behaviour and in their TUBA facility to investigate the diffusiophoresis of CsI. Measurements of heat and mass transfer coefficients are also undertaken to understand better the volatilization process. Moreover some PHEBUS-FP-T0 data are provided for a common benchmark calculation exercise conducted with JRC Ispra. The contribution of ENEA-ERG/Bologna and Universities of Bologna and Pisa consists of interpreting thermohydraulics aspects of containment behaviour, like natural circulation and bulk condensation of sprays. The pool scrubbing analysis is performed by CIEMAT/Madrid with emphasis on the aerosol retaining capacity of the churn-turbulent region. Long term release effects, like the low volatile gas release from deep pools, are investigated both by Bochum University and by SIEMENS-KWU/Erlangen. Rossendorf's Forschungszentrum (FZR) is preparing a review of chemical vapour reactions with surfaces and aerosols. Other containment phenomena of thermohydraulics/aerosols behaviour are investigated by NNC/Knutsford in view of MCCI and iodine chemistry calculations, by BATTELLE/Frankfurt using the VANAM-M2 experiments, by VTT using the AHMED and VICTORIA facilities, by Università Politécnica Madrid to improve the ESTER code and by Risø National Laboratory to improve their source term modelling.

Fields of science

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Topic(s)

Call for proposal

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Funding Scheme

CSC - Cost-sharing contracts

Coordinator

United Kingdom Atomic Energy Authority (UKAEA)
EU contribution
No data
Address
Winfrith Technology Centre
DT2 8DH Dorchester
United Kingdom

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Total cost
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Participants (10)

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Last update: 9 January 1996

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Permalink: https://cordis.europa.eu/project/id/FI3S0006

European Union, 2024