Analysis of the revaporisation behaviour of radioactive deposits of fission products in non-stationary thermal conditions and constant atmosphere

K Knebel, P D W Bottomley, V V Rondinella, Ari Auvinen, Jora Jokiniemi

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

In case of a severe accident in a nuclear reactor, the revaporisation of fission products can have a major effect on the late phase release source term. An experimental revaporisation facility was built in the Institute for Transuranium Elements to study this phenomenon with sample of fission product deposits originating from the upper vertical line of the Phébus FP experimental reactor. The PHEBUS reactor core was equipped with a test loop which allowed investigating fuel rod bundle degradation and melting behaviour. Such tests promoted the release of fission products, particularly 137Cs, and their transport/deposition through the primary circuit of the loop. The revaporisation facility consists of a compact high temperature furnace in which the deposit samples can be heated up to 1273 K under controlled atmosphere conditions simulating the late phase of a severe accident. The revaporisation behaviour of the 137Cs deposited on the sample is scrutinized by means of an on-line gamma spectroscopy system. In the current experimental campaign, three samples from the Phébus FPT3 experiment were investigated and first heated up by 10 K/min to 573 K in a nitrogen atmosphere. In a second step, each sample was analysed with a specific carrier gas (i.e. hydrogen, steam or air) and heated further by 2 K/min to 1273 K. For the last experiment in air, measures were also adopted to collect samples of the FPs after revaporisation and their subsequent recondensation as aerosols for further analysis via Transmission Electron Microscopy. Revaporisation results deduced from the on-line measurement showed very similar behaviour in terms of starting temperature and kinetics for either steam or air. This indicates that the variation in oxygen potential between steam and air does not affect so much the reaction kinetics (and the active Cs species is not changed). The experiment with hydrogen showed a far higher starting temperature and slower kinetics. This suggests that in a nuclear accident fission products under reducing conditions would form deposits up to rather high temperatures; the deposits may be remobilized at lower temperatures under oxidising conditions
Original languageEnglish
Pages (from-to)139-154
JournalHigh Temperatures - High Pressures
Volume43
Issue number2-3
Publication statusPublished - 2014
MoE publication typeA1 Journal article-refereed
Event10th International Workshop On Subsecond Thermophysics - Karlsruhe, Sweden
Duration: 26 Jun 201328 Jun 2013

Fingerprint

fission products
Fission products
Deposits
deposits
Steam
atmospheres
accidents
Accidents
steam
Air
air
Hydrogen
Transuranium elements
Temperature
transuranium elements
Experimental reactors
Kinetics
Reactor cores
Experiments
controlled atmospheres

Keywords

  • Caesium
  • fission product
  • gamma-ray spectroscopy
  • nuclear aerosols
  • Phébus FP
  • release source term
  • revaporisation
  • severe accident

Cite this

Knebel, K ; Bottomley, P D W ; Rondinella, V V ; Auvinen, Ari ; Jokiniemi, Jora. / Analysis of the revaporisation behaviour of radioactive deposits of fission products in non-stationary thermal conditions and constant atmosphere. In: High Temperatures - High Pressures. 2014 ; Vol. 43, No. 2-3. pp. 139-154.
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Analysis of the revaporisation behaviour of radioactive deposits of fission products in non-stationary thermal conditions and constant atmosphere. / Knebel, K; Bottomley, P D W; Rondinella, V V; Auvinen, Ari; Jokiniemi, Jora.

In: High Temperatures - High Pressures, Vol. 43, No. 2-3, 2014, p. 139-154.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Analysis of the revaporisation behaviour of radioactive deposits of fission products in non-stationary thermal conditions and constant atmosphere

AU - Knebel, K

AU - Bottomley, P D W

AU - Rondinella, V V

AU - Auvinen, Ari

AU - Jokiniemi, Jora

PY - 2014

Y1 - 2014

N2 - In case of a severe accident in a nuclear reactor, the revaporisation of fission products can have a major effect on the late phase release source term. An experimental revaporisation facility was built in the Institute for Transuranium Elements to study this phenomenon with sample of fission product deposits originating from the upper vertical line of the Phébus FP experimental reactor. The PHEBUS reactor core was equipped with a test loop which allowed investigating fuel rod bundle degradation and melting behaviour. Such tests promoted the release of fission products, particularly 137Cs, and their transport/deposition through the primary circuit of the loop. The revaporisation facility consists of a compact high temperature furnace in which the deposit samples can be heated up to 1273 K under controlled atmosphere conditions simulating the late phase of a severe accident. The revaporisation behaviour of the 137Cs deposited on the sample is scrutinized by means of an on-line gamma spectroscopy system. In the current experimental campaign, three samples from the Phébus FPT3 experiment were investigated and first heated up by 10 K/min to 573 K in a nitrogen atmosphere. In a second step, each sample was analysed with a specific carrier gas (i.e. hydrogen, steam or air) and heated further by 2 K/min to 1273 K. For the last experiment in air, measures were also adopted to collect samples of the FPs after revaporisation and their subsequent recondensation as aerosols for further analysis via Transmission Electron Microscopy. Revaporisation results deduced from the on-line measurement showed very similar behaviour in terms of starting temperature and kinetics for either steam or air. This indicates that the variation in oxygen potential between steam and air does not affect so much the reaction kinetics (and the active Cs species is not changed). The experiment with hydrogen showed a far higher starting temperature and slower kinetics. This suggests that in a nuclear accident fission products under reducing conditions would form deposits up to rather high temperatures; the deposits may be remobilized at lower temperatures under oxidising conditions

AB - In case of a severe accident in a nuclear reactor, the revaporisation of fission products can have a major effect on the late phase release source term. An experimental revaporisation facility was built in the Institute for Transuranium Elements to study this phenomenon with sample of fission product deposits originating from the upper vertical line of the Phébus FP experimental reactor. The PHEBUS reactor core was equipped with a test loop which allowed investigating fuel rod bundle degradation and melting behaviour. Such tests promoted the release of fission products, particularly 137Cs, and their transport/deposition through the primary circuit of the loop. The revaporisation facility consists of a compact high temperature furnace in which the deposit samples can be heated up to 1273 K under controlled atmosphere conditions simulating the late phase of a severe accident. The revaporisation behaviour of the 137Cs deposited on the sample is scrutinized by means of an on-line gamma spectroscopy system. In the current experimental campaign, three samples from the Phébus FPT3 experiment were investigated and first heated up by 10 K/min to 573 K in a nitrogen atmosphere. In a second step, each sample was analysed with a specific carrier gas (i.e. hydrogen, steam or air) and heated further by 2 K/min to 1273 K. For the last experiment in air, measures were also adopted to collect samples of the FPs after revaporisation and their subsequent recondensation as aerosols for further analysis via Transmission Electron Microscopy. Revaporisation results deduced from the on-line measurement showed very similar behaviour in terms of starting temperature and kinetics for either steam or air. This indicates that the variation in oxygen potential between steam and air does not affect so much the reaction kinetics (and the active Cs species is not changed). The experiment with hydrogen showed a far higher starting temperature and slower kinetics. This suggests that in a nuclear accident fission products under reducing conditions would form deposits up to rather high temperatures; the deposits may be remobilized at lower temperatures under oxidising conditions

KW - Caesium

KW - fission product

KW - gamma-ray spectroscopy

KW - nuclear aerosols

KW - Phébus FP

KW - release source term

KW - revaporisation

KW - severe accident

M3 - Article

VL - 43

SP - 139

EP - 154

JO - High Temperatures - High Pressures

JF - High Temperatures - High Pressures

SN - 0018-1544

IS - 2-3

ER -