Iodine filters in nuclear installations

Directorate-General For Employment Social Affairs And Inclusion

Description

Energy research

Sujets

• Air pollution
• Iodine
• Nuclear power
• Nuclear safety
• Radioactive waste
• Sciences et techniques

Informations

• Publié par: DIRECTORATE-GENERAL-FOR-EMPLOYMENT_SOCIAL-AFFAIRS-AND-INCLUSION
• Nombre de lectures: 54
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

COMMISSION OF
THE EUROPEAN COMMUNITIES
IODINE FILTERS IN
NUCLEAR INSTALLATIONS
J. G. WILHELM
OCTOBER 1982 COMMISSION OF
THE EUROPEAN COMMUNITIES
IODINE FILTERS IN
NUCLEAR INSTALLATIONS
J. G. WILHELM
Contract No. 1175-80-12 L/V
Directorate General
Employment, Social Affairs and Education
Health and Safety Directorate
Jean Monnet Building
LUXEMBOURG (Grand-Duchy)
V/2110/83 EN LEGAL NOTICE
Neither the Commission of the European Communities nor any person
acting on behalf of the Commission is responsible for the use which
might be made of the following information. CONTENT
Page
Summary 1
1. Iodine isotopes relevant to safety 2
2. Relative importance of radioiodine releases in
environmental exposure due to nuclear installations 2
2.1 Nuclear power stations
2.2 Reprocessing plants 9
3. Airborne radioiodine species and their significance for the
environmental impact of nuclear power stations 13
3.1 Iodine compounds and iodine aerosols3
3.2 Significance of airborne radioiodine species with
respect to environmental exposure 17
4. Iodine release in nuclear power stations 23
4.1 Release into the reactor coolant3
4.2e pathways in PWR nuclear power stations 23
4.3 Release pathways in BWR nuclear power stations 26
4.4e pathways in the TMI-2 accident 29
4.5 Authorized operational discharge limits and recorded
discharges of 1-131 with the gaseous effluent from
nuclear power stations 31
5. Iodine release in reprocessing plants4
5.1 Dissolver of f ga s4
5.2 Other offgases 36
5.3 Authorized operational discharge limits 36 Page
6. Solid sorbents for radioiodine removal 37
6.1 Units of measurement used to indicate the removal
efficiency of radioiodine sorbents
6.2 Activated charcoal 39
6.2.1 Removal of elemental iodine by activated charcoal 40
6.2.2l of organic radioiodine compounds by acti­
vated charcoal 44
6.2.3 Removal of hypoiodous acid by activated charcoal 47
6.2.4l of aromatic iodine compounds 48
6.2.5 Iodine removal by activated charcoal as a function
of concentration
6.3 Inorganic sorbents for iodine 52
7. Status of fission product iodine removal by activated charcoal 56
7.1 Normal operation of nuclear power plants 56
7.2 Design basis accidents 58
7.2.1 Removal of fission product iodine by activated
charcoal at high temperatures9
7.2.2 Removal of fission product iodine by activated
charcoal at high radiation dose rates 61
7.2.3 Removal of fission product iodine at high relative
humidities of the air 62
8. Removal of fission product iodine from saturated and super­
heated steam 68
9. Requirements for iodine filter systems in nuclear power plants 70
9.1 Ventilation concepts and filters for normal operation 70
9.2 Containment concepts and standby emergency filter
systems for cleanup of the annul us exhaust air 73
9.3t venting via filter systems in
accidents involving core meltdown 77
II Page
9.4 Requirements for iodine filter systems in normal
and design basis accident operation 81
10. Design of iodine filter systems 85
10.1 Individual components and their arrangement 8
10.2 Redundancy requirements7
10.3 Design and construction of iodine filters 89
11. Surveillance tests of iodine filter systems 100
11.1 Testing the iodine sorbent
11.1.1 Scope of the tests 10
11.1.2 Test agents and equipment2
11.1.3 Test conditions3
11.1.4 Collecting representative samples of activated
charcoal from iodine filters6
11.2 In-place testing of iodine filters 111
11.2.1 Objectives 11
11.2.2 Test agents2
11.2.3 In-place testing with radioactively labeled
methyl iodide6
11.2.4 In-place testing with Freons 117
11.2.5 Validity of in-place tests of iodine filters
with regard to the removal efficiency under
accident conditions9
12. Experience in operating iodine filter systems 120
12.1 Occurrence of mechanical leaks1
12.2 Ageing and poisoning of the iodine sorbent 122
12.3 Experience gained from the TMI-2 accident 13
12.4 Fires in iodine filters 133
III Page
13. Iodine removal requirements in reprocessing plants 134
14. Processes for iodine removal in reprocessing plants5
14.1 Offgas scrubbing 13
14.1.1 Alkalig6
14.1.2 MERCUREX process7
14.1.3 IODOX process8
14.2 Direct removal of iodine by solid sorbents 140
14.2.1 Offgas filtering with AgNO,-impregnated sorbents 142
14.2.2sg with zeolites 145
14.2.3 Leaching tests on sorbents containing silver 147
14.2.4 Filter components for iodine removal on solid
sorbents 148
15. Conclusions and recommendations9
16. Bibliography 152 - 16
Figures 169 - 206
(also see Appendix)
List of Tables V -VII
List of Figures VIII - X
IV APPENDIX
Page
I. Preparation of radioactively labeled methyl iodide and
elemental iodine 19°
II. Laboratory apparatus for testing the removal efficiencies of
solid sorbents for radioiodine3
III. Evaluation of the removal efficiency tests of iodine sorbents 200
IV. In-place testing of iodine filters with radioactively
labeled methyl iodide 201
IV.1 Transport of the radioactive test agent 202
IV.2 Apparatus and method3
IV.3 Calculating the required test agent activity
and the penetration of the iodine filter 207
IV.4 Safety considerations and preliminary testing8
LIST OF TABLES
Tab. I Calculated maximum dose equivalent rates at the site
boundary due to the discharge of noble gases from
1000 MW, \ nuclear power stations 4
Tab. II Calculated maximum dose equivalent rates at the site
boundary due to the discharge of radioiodine from
1000 MW, χ nuclear power stations 5
Tab. Ill Total stack release of long-lived aerosol and gaseous
radionuclides from various LWR nuclear power stations
in 1978 7
Tab. IV Maximum radiation exposure in the vicinity of nuclear
power stations due to the discharge of airborne radio­
nuclides with the exhaust air in 1978 8
Tab. V Radiation exposure due to the reprocessing of fuel for
1 GW(e)a 12 Page
Tab. VI Solvents contained in ventilation exhaust air from
the equipment compartment of a PWR nuclear power station 14
Tab. VII Average normalized release rates for 1-131, Oyster Creek
BWR 21
Tab. VIII Percentages of various 1-131 species in BWR gaseous
effluents2
Tab. IX 1-131 releases via various gaseous effluent streams
from a German pressurized-water reactor 27
Tab. X 1-131 releases via various gaseous effluent streams from
American nuclear power stations 28
Tab. XI Authorized operational discharge limits and recorded
discharges of 1-131 with the gaseous effluents from
German nuclear power plants 32
Tab. XII Desorption of 1-131 in elemental form from activated
charcoal beds with long elution periods at ambient
conditions 43
Tab. XIII Removal efficiencies for 1-131 in the form of CH3I-131
at high and intermediate activity concentrations 51
Tab. XIV Removal efficiencies of an X-Ag silver zeolite
following prolonged exposure to pressurized steam and
high temperature 54
Tab. XV Removal efficiencies of KI-impregnated charcoals for
1-131 in the form of CH, 1-131 at various relative
humidities of the air 6
Tab. XVI Removal efficiencies of various impregnated-charcoal
beds for radioiodine at extremely high humidity of
the air5
Tab. XVII Typical accident conditions for atmosphere cleanup
systems (from USNRC Regulatory Guide 1.52, Rev. 2) 82
VI