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Effects of Heat from High-Level Waste on Performance of Deep Geological Repository Components Iaea, Vienna, 1984 Iaea-Tecdoc-319

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Effects of Heat from High-Level Waste on Performance of Deep Geological Repository Components Iaea, Vienna, 1984 Iaea-Tecdoc-319 IAEA-TECDOC-319 EFFECTS OF HEAT FROM HIGH-LEVEL WASTE ON PERFORMANC DEEF EO P GEOLOGICAL REPOSITORY COMPONENTS REPORT OF A TECHNICAL COMMITTEE MEETING ON EFFECTS OF HEAT FROM RADIOACTIVE WASTE IN DEEP GEOLOGICAL REPOSITORIES ORGANIZEE TH Y DB INTERNATIONAL ATOMIC ENERGY AGENCY AND HELD IN STOCKHOLM, 28 AUGUST - 2 SEPTEMBER 1983 A TECHNICAL DOCUMENT ISSUEE TH Y DB INTERNATIONAL ATOMIC ENERGY AGENCY. VIENNA, 1984 EFFECTS OF HEAT FROM HIGH-LEVEL WASTE ON PERFORMANCE OF DEEP GEOLOGICAL REPOSITORY COMPONENTS IAEA, VIENNA, 1984 IAEA-TECDOC-319 Printed by the IAEA in Austria November 1984 PLEASE BE AWARE THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK The IAEA doe t maintaisno n stock f reportso thin si s series. However, microfiche copies of these reports can be obtained from IN IS Clearinghouse International Atomic Energy Agency Wagramerstrasse5 P.O.Bo0 x10 A-1400 Vienna, Austria Orders shoul accompaniee db prepaymeny db f Austriao t n Schillings 80.00 in the form of a cheque or in the form of IAEA microfiche service coupons orderee whicb y hdma separatel ClearinghouseS I y N froI e mth . FOREWORD This report discusse effecte th sdeee th f heapso n geologicato l repository systems and its different components. It reviews the experimental dat d theoreticaaan l effectmodele th f f heaso o s t botn o h the behaviou engineeref o r d naturadan l barriers. This document aimt a s supporting another IAEA publicatio relatea n i n d subject, viz. "Deep Underground Disposal of Radioactive Waste - Near Field Effects", Technical Reports Serie n preparation)s(i lattee Th . r deals witl hal those effects occurring in the near field which affect the mobilization of radionuclide d theisan r subsequent r fieldmigratiofa e Th e .th o t n document deals mainly with high-level wast d spenean t fuel considert bu , s other types of waste as well, whenever appropriate. The present report, however, is focussed specifically on effects due to thermal energy release solely from high-level waste or spent fuel. This outcome repor IAEn th a s Af i te o Technica l Committee Meetinn go "Effects of Heat from Radioactive Waste in Deep Geological Repositories", held in Stockholm from 28 August to 2 September 1983. The initial draft repore o th fmads Mssrst wa y Bourk eb . J . .P e Werm. L (UK d e)an (Sweden). After the Technical Committee Meeting, Mr. Werme revised the draft of the report. e responsiblTh e office e IAEr thith Afo s t ra repor s twa Tsyplenko. S . V . Mr v froWaste th m e Management SectioDivisioe th f no f no Nuclear Fuel Heinone. CycleU e wore . completes th J Th . kwa f . no Mr y b d same Division. CONTENTS 1. INTRODUCTION .................................................... 2. DECAY HEAT PRODUCTION ....»••*•«•»*«««•»••••*••»••••••.»••••••••••. • 2.1. Heat release characteristics of waste form .............. 11 2.2. Mean heaf so t transfer ...........•........*............4 1 . 2.3. Thermophysical properties .......»..........«.*........... 16 2.4. Repository design variables ..............................J 1 . 2.5. Representative temperature field ........................8 1 . 3. THERMAL EFFECTS ON THE ENGINEERED BARRIER COMPONENTS 3.1. Effect wastn so e form prio dissolutioo t r n .............9 1 . 3.1.1. Borosilicate glass .............................9 1 . 3.1.1.1. Liquid-liquid phase separation ...... 19 3.1.1.2. Crystallization ...................... 20 3.1.1.3. Crackin glasf go s ...................0 2 . 3.1.2. Spent fuel ....................................1 2 . 3.2. Dissolutio waste th ef no for m ...........................2 2 . 3.3. Corrosion of containers ................................. 23 3.3.1. Consideration choicr containea sfo f eo r .......4 2 . 3.3.2. Thermodynamically stable containers ............ 25 3.3.3. Kinetically stable container .................... 27 3.3.4. Sacrificial containers ......*.................9 2 . 3.4. Backfill, buffer materials ••••••••*••••••••••••••••••••• 30 3.4.1. Swelling clays •••••••••••••••••••••••••••••••••• 30 3.4.2. Zeolites ........................................ 31 3.4.3. Crushed salt ................................... 32 3.4.4. Granular material...............................2 3 . 3.4.5. Cementatious materials........................... 32 4. THERMAL EFFECTS ON THE SURROUNDING ROCK 4.1. Thermomechanical effects ................................. 33 4.2. Change waten si r flow pattern ...........................7 3 . 4.3. Thermally induced geochemical effects .................... 40 5. NUMERICAL EVALUATION OF THE EFFECTS OF HEAT 5.1. Introduction .............................................. 45 5.2. Numerical model describo t s processee th e s ...............7 .4 5.2.1. Temperature distribution ..,..,..,.,...........,7 .4 5.2.2. Thermal stress distribution ...................... 48 5.2.3. Thermally induced groundwater convection •••••••5 5 • 5.2.4. Thermally accelerated chemical reactions •••••••6 5 • 5.2.4.1. Waste form dissolution .*............6 .5 5.2.4.2. Container corrosion ••••••••••••••••••• 57 5.2.4.3. Alterations in backfill ...•*...•...... 57 5.2.4.4. Water-rock system •••••••••»•••*••••*•8 5 • 5.3. Experiments to provide data for the models«•••..».....»•»•• 58 5.3.1. Parameters to be determined ••••••••••••••••••••• 53 5.3.2. Laboratory tests »...••»»«,»,»»•»,,»,,,•.....,.,9 5 » 5.3.3. Field tests ....................................9 .5 5.4. Verificatio validatiod nan n ..............................0 .6 5.4.1. Temperature distribution ••••••••••«....».......• 61 5.4.2. Thermal stress distribution ...................4 .6 5.4.3. Thermally induced groundwater convection .......6 .6 5.4.4. Thermally accelerated chemical reactions .......6 .6 . 6 DISCUSSIO RECOMMENDATIOD NAN N 6.1« Introduction «..««..«.....«..«...«.«.«»....««..«........... 67 6.2. Thermal limitations ...................................... 67 6.3. Mitigation strategies ..................................... 68 6.4. Recommendations for further research ..................... 68 REFERENCES •••••••*«••••«••«*«••«••««•«•»•••«•••••»••••«••••••••• Y1 LIST OF PARTICIPANTS ............................................ 79 1. INTRODUCTION High-level radioactive wastes produce nucleae th y b dr power industrie sy whic muswa disposee a htb n assurei f o d s that radionuclides will not reach the human environment in concentrations and quantities that could resuln unacceptabla n i t e detrimen publio t c healtt a h present or in the future. Disposa high-levef lo l waste conditionen i s d carefulla for n i m y designed underground repository constructed a selectedee n i p d geologic environmen present a s mose i t th tt widely accepted approach. e safTh e disposa radioactive th f lo e waste depende th n o s performance of the overall waste disposal system. This system may include both engineered and natural barriers. The isolation effectivenes f eaco s h componen disposae th f o t l system dependa n o s number of natural and emplacement-induced effects. Near—field effects associated wite emplacementh h f highlo t y radioactive waste deea n psi geological repositor e discussear ye th n i d IAEA-TECDOC on "Underground Disposal in Deep Rock Formations, Near-Field Effects". A major consideration in both near and far fields is the heat generated by the waste due primarily to the presence of large amounts of concentrated beta and gamma emitting fission products. Many of the technical uncertainties in the design of a high-level waste disposal system are related to this thermal energy release, the resulting temperature field, and the impact this temperature field has on the waste disposal system. The heat generated by the nuclear wastes will eventually flow from the waste form, through any container and buffer roune surroundin waste th th do t e g rock d the ,an e transferre b n d through this rock and will be ultimately dissipated to the atmosphere. e rat d duratioTh ean heae th t f releasno n affececa t some physical and chemical propertie barriere th a repositorf o sn i s y system. Transport by groundwater is by far the most likely mechanism by which any eventual release of nuclides to the environment may occur. Thermally induced changes in the waste form, containers or buffer materials could affect their integrit r effectivenesso y r exampleFo . , waste glass may undergo devitrification which can eventually increase dissolution containee ratesth s A . r surface temperature increaseo s doesusceptibilits it s corrosiono t y . earlien Thi a lean o sca t d r contact with groundwater, if present, than if the container were not generating heat. e stabilitTh openingf o yheatee th n dsi formatio importann a s ni t consideration. If the structure of the rock is affected, it will change groundwatea r movement transpore patterth d nan t pathwar yfo radionuclide environmente th o st . systematiA c assessmen thermae th f to l loadinrepositore th f go s i y require assuro t d e thaenerge th t y generate emplacee th y b d d wastes will hav econtrollabla e effect. This includes studieeffecte th f sheaf o s o t on the structural stability of the host rock and radionuclide release and migration from the conditioned waste forms to the environment. That should lea establishino t d g maximum acceptable thermal load maximud san m temperature for underground repository components that will not violate safety, engineering, and operational requirements. Well defined thermal limits of the various disposal system components do not yet generally necessarilt no y existma d basee yb ,an d exclusivel absolutn yo e physical criteria attempn
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