TECHNICAL REPORTS SERIES No.

Control of Semivolatile in Gaseous Effluents at Nuclear Facilities

INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1982

CONTROL OF SEMIVOLATILE RADIONUCLIDES IN GASEOUS EFFLUENTS AT NUCLEAR FACILITIES The following States are Members of the International Atomic Energy Agency:

AFGHANISTAN HOLY SEE PHILIPPINES ALBANIA HUNGARY POLAND ALGERIA ICELAND PORTUGAL ARGENTINA INDIA QATAR AUSTRALIA INDONESIA ROMANIA AUSTRIA IRAN ISLAMIC REPUBLIC SAUDI ARABIA BANGLADESH IRAQ SENEGAL BELGIUM IRELAND SIERRA LEONE BOLIVIA ISRAEL SINGAPORE BRAZIL ITALY SOUTH AFRICA BULGARIA IVORY COAST SPAIN BURMA JAMAICA SRI LANKA BYELORUSSIAN SOVIET JAPAN SUDAN SOCIALIST REPUBLIC JORDAN SWEDEN CANADA KENYA SWITZERLAND CHILE KOREA, REPUBLIC OF SYRIAN ARAB REPUBLIC COLOMBIA KUWAIT THAILAND COSTA RICA LEBANON TUNISIA CUBA LIBERIA TURKEY CYPRUS LIBYAN ARAB JAMAHIRIYA UGANDA CZECHOSLOVAKIA LIECHTENSTEIN UKRAINIAN SOVIET SOCIALIST DEMOCRATIC KAMPUCHEA LUXEMBOURG REPUBLIC DEMOCRATIC PEOPLE'S MADAGASCAR UNION OF SOVIET SOCIALIST REPUBLIC OF KOREA MALAYSIA REPUBLICS DENMARK MALI UNITED ARAB EMIRATES DOMINICAN REPUBLIC MAURITIUS UNITED KINGDOM OF GREAT ECUADOR MEXICO BRITAIN AND NORTHERN EGYPT MONACO IRELAND EL SALVADOR MONGOLIA UNITED REPUBLIC OF ETHIOPIA MOROCCO CAMEROON FINLAND NETHERLANDS UNITED REPUBLIC OF FRANCE NEW ZEALAND TANZANIA GABON NICARAGUA UNITED STATES OF AMERICA GERMAN DEMOCRATIC REPUBLIC NIGER URUGUAY GERMANY, FEDERAL REPUBLIC OF NIGERIA VENEZUELA GHANA NORWAY VIET NAM GREECE PAKISTAN YUGOSLAVIA GUATEMALA PANAMA ZAIRE HAITI PARAGUAY ZAMBIA PERU

The Agency's Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is "to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world".

© IAEA, 1982

Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Wagramerstrasse 5, P.O. Box 100, A-1400 Vienna, Austria.

Printed by the IAEA in Austria December 1982 TECHNICAL REPORTS SERIES No. 220

CONTROL OF SEMIVOLATILE RADIONUCLIDES IN GASEOUS EFFLUENTS AT NUCLEAR FACILITIES

INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1982 CONTROL OF SEMIVOLATILE RADIONUCLIDES IN GASEOUS EFFLUENTS AT NUCLEAR FACILITIES IAEA, VIENNA, 1982 STI/DOC/10/220 ISBN 92-0-125482-2 FOREWORD

In the context of an expanding nuclear fuel cycle, where more and more electrical power is generated by nuclear fission, increased attention is being paid to control of releases of radioactive effluents to the environment. To assist £ national authorities responsible for restricting the discharge of effluents in order to limit population exposure, the International Atomic Energy Agency has undertaken a programme to collect, review and disseminate information on technologies for handling and treatment of gaseous and particulate radioactive wastes from nuclear facilities. The IAEA's programme of work covers different aspects of radioactive airborne effluents and wastes. The results of IAEA meetings on handling -85, radioiodine and tritium have been published in the Agency's Technical Reports Series, as follows:

Separation, Storage and Disposal of Krypton-85, Technical Reports Series No. 199, IAEA, Vienna (1980).

Radioiodine Removal in Nuclear Facilities: Methods and Techniques for Normal and Emergency Situations, Technical Reports Series No. 201, IAEA, Vienna (1980).

Further documents are in preparation on the retention of gaseous radionuclides from nuclear power plants under normal and accident conditions and on testing and in-plant monitoring of offgas cleaning systems. A Symposium on Management of Gaseous Wastes from Nuclear Facilities, jointly organized by IAEA and OECD-NEA in Vienna in 1980, and published by the IAEA in 1980, dealt with current practice and the latest developments in the field. The contents of this Technical Report are based on the results of a Techni- cal Committee Meeting on Retention of Semivolatile Radionuclides at Nuclear Facilities, held in Vienna from 27 to 31 October 1980. Additional information was collected subsequently from the USA, the USSR and India and has been incorporated. The information contained in this report represents an up-to-date review of the subject, combining the results of laboratory studies on control of the most important semivolatile radionuclides in gaseous effluents at nuclear facilities and the results of operating experience in that area. The Agency wishes to express its thanks to all participants of the meeting, particularly to M. Klein, Belgium, who served as Chairman. The Agency is also grateful to those who contributed information after the meeting, particularly to H. Deuber, Federal Republic of Germany, who as a consultant to the Agency collected most of this information and compiled the present report. The officer of the IAEA responsible for this work was V. Tsyplenkov of the Waste Manage- ment Section. CONTENTS

1. INTRODUCTION 1

2. SIGNIFICANCE OF THE CONTROL OF SEMIVOLATILES 1 2.1. Solidification of high-level liquid waste (HLLW) 3 2.2. Reprocessing of nuclear fuel 3

3. PROPERTIES OF 5 3.1. Volatilization of ruthenium 5 3.1.1. Volatilization of ruthenium at low temperatures 5 3.1.2. Volatilization of ruthenium at high temperatures 8 3.2. Deposition of ruthenium 10 3.3. Retention of ruthenium 14 3.3.1. Retention of ruthenium by solids 14 — General - Silica gel — Ferric-oxide-based materials - Catalytic decomposition 3.3.2. Retention of ruthenium by liquids 18

4. PROPERTIES OF OTHER SEMIVOLATILES 18 4.1. Properties of 19 4.2. Properties of , , and 19

5. PRINCIPLES OF HIGH-LEVEL WASTE SOLIDIFICATION PROCESSES 20 5.1. Solidification methods 20 5.2. Offgas treatment systems 21 5.2.1. Individual components 23 5.2.2. Integrated systems 23

6. EXPERIENCE WITH CONTROL OF SEMIVOLATILES IN HIGH-LEVEL LIQUID WASTE SOLIDIFICATION PROCESSES 24 6.1. Fluidized-bed calcination 24 6.2. Spray calcination 30 6.3. Rotary-kiln calcination 33 6.4. Pot calcination 35 6.5. Liquid-fed ceramic melter 46 6.6. Summary 48 7. SAMPLING AND MONITORING 49

8. CONCLUSIONS 50

REFERENCES 51

LIST OF PARTICIPANTS 55 1. INTRODUCTION

The contaminants in gaseous effluents of nuclear facilities are usually con- sidered to consist of particulates and gases. There are, however, also contaminants which are generally present in the condensed form and which volatilize significantly owing to rise in temperature or chemical reactions. These semivolatile contaminants may not be trapped sufficiently by the devices commonly used for decontaminating the gaseous effluents of nuclear facilities and may therefore have to be dealt with separately. The semivolatile contaminants include of selenium, technetium, ruthenium, antimony, tellurium and caesium. This report reviews the present knowledge of control of these semivolatiles in the gaseous effluents of nuclear facilities under normal conditions. The main topics of this report have been reviewed up to 1976, and up to 1977 in Refs [1—3]. The literature contained in these reviews is taken into account in this report, although it is not usually cited unless tables or figures are reproduced. The emphasis is, rather, on quoting literature published later.

2. SIGNIFICANCE OF THE CONTROL OF SEMIVOLATILES

The significance of control of radionuclides in gaseous effluents may be related both to the environmental impact and to the influence within the facilities. The environmental impact may be characterized by the efforts necessary to comply with the retention requirements which are determined by the activity inventories or processing rates and the maximum permissible releases of the radionuclides. Thus, apart from the retention requirement, the environmental impact depends on the release potential and the behaviour of the radionuclides in the offgas treatment system. The significance in terms of the impact within the plants is associated with the creation of high radiation fields in unshielded areas, plugging of pipes due to deposition, and contamination of secondary-effluent streams. Apart from activity, mass is an important factor in this context. As will be shown later, semivolatiles may volatilize to a large extent with high temperatures and/or oxidizing conditions. Therefore, in normal operation it is only in solidification of high-level liquid waste (HLLW) and in reprocessing nuclear fuel that appreciable volatilization of semivolatiles has to be reckoned with. Only these processes will be considered further.

1 TABLE I. CONTENT OF RADIONUCLIDES IN LWR HIGH-LEVEL LIQUID WASTE3 [2]

Isotope Half-life Activity Mass 1 (Ci-r1 U) (g-r u)

Volatile

H-3 12.33 a 33 3.5 X 10"J Kr-85 10.73 a 8X10"3 2.0 X 10"s 1-129 1.59 X 107 a 3 X 10"s 0.2

Potentially volatile

Se-79. 6.5 X 104 a 0.34 4.9 Tc-99 2.13 X 105 a 13 7.4 X 102 Ru-103 0.1084 a 72 2.2 X 10~3 Ru-106 1.01 a 1.8 X 10s 54

b Rh-103m 56 min 72 -

b s Rh-106 29.9 s 1.8 X 10 - Te-123m 0.3275 a 1.5 X 10"2 1.8 X 10"6 Te-127m 0.298 a 4.2 X 102 4.5 X 10~2 Sb-124 0.1648 a 0.68 3.9 X 10"5 Sb-125 2.73 a 5.7 X 103 5.5 Sb-126mb 19.0 min 0.54 . 6.8 X 10"' Sb-126b 12.4 d 0.53 6.4 X 10"6 Cs-134 . 2.06 a 1.2 X 10s 91 Cs-135 2.3 X 106 a 0.31 2.7 X 102 Cs-137 30.1 a 9.3 X 104 1.1 X 103

Potential solids (major activities only)0

s Ce-144 0.7787 a 2.4 X 10 -

b s Pr-144 17.28 min 2.4 X 10 -

4 Sr-90 29 a 6.0 X 10 -

b 4 Y-90 64.0 h 6.0 X 10 - Cm-244 • 17.9a 7.0 X 103 _

Note: 1 curie (Ci)= 3.70 X 1010 Bq. a Fuel burnup is 28 700 MW-d-t-1 U. Waste age is lj years after discharge from reactor. b These isotopes are supported by longer-lived parents. c In addition to those listed as potentially volatile (Ru, Rh-106 and Cs-137).

2 2.1. SOLIDIFICATION OF HIGH-LEVEL LIQUID WASTE (HLLW)

The major operations generally to be found in solidification of HLLW are evaporation, calcination and preparation of glass (see Section 5). These operations generally involve high temperatures and oxidizing conditions to such an extent that complete volatilization of individual semivolatiles may occur (see Sections 3 and 4). The content of the most important radionuclides of HLLW from light-water reactor (LWR) fuel one and a half years after discharge from the reactor is presented in Table I. Of the semivolatiles, 106Ru, 134Cs and 137Cs contribute by far the highest activities. The corresponding maximum permissible release rates at the stack and the minimum required feed-to-stack decontamination factors for a large HLLW solidification plant (6§ t U-d-1) are given in Table II (a safety factor of 10 has been incorporated). Although the values given apply to specific conditions only (USA), the relative importance of the semivolatiles is clearly illustrated: for 106Ru, 134Cs and 137Cs the minimum required decontamination factors (not taking into account a safety factor of 10 as in Table II) are 103 to 104; for the Te and Sb isotopes they are much smaller and Se and Tc may be completely volatilized and released. Because of the as-low-as-reasonably-achievable (ALARA) principle, the maximum permissible release rates for 106Ru and the critical Cs isotopes may be lower by a factor of 10s. This would translate to required decontamination factors for 106Ru and the critical Cs isotopes of 108 to 109.

2.2. REPROCESSING OF NUCLEAR FUEL

At present, the Purex process is the only method used for reprocessing nuclear fuel on a technical scale. The major operations are dissolution of the fuel in nitric acid, extraction of and with tributylphosphate (TBP) and concentration of the fission-product solution for subsequent high-level waste storage. Because of the low temperatures involved, the potential for volatilization of semivolatiles is small (see Sections 3 and 4). No quantitative data from plants seem to exist. For a reference reprocessing facility (2000 t U.a-1) a ruthenium volatilization of 0.01% has been estimated for the dissolution step [4, 5]. Because of the low ruthenium volatility, practically no ruthenium adsorbers are being used at present in the dissolver offgas of reprocessing plants. However, for the large reference reprocessing facility mentioned, ruthenium adsorbers have been provided at an early stage of the dissolver offgas cleanup system [4, 5], The ruthenium radioisotopes might require more attention in future reprocessing of fast-breeder reactor (LMFBR) and high-temperature reactor (HTGR) fuel. In LMFBR fuel reprocessing, voloxidation, carried out at high

3 TABLE II. RELEASE DATA FOR RADIONUCLIDES IN LWR HIGH-LEVEL LIQUID WASTE3 [2]

Isotope Limiting 1/10 maximum 10 X minimum 1/10 maximum MPCb permissible required allowed (/nCimL"1) release rate feed-to-stack volatility at stack DF for complete (Cid-')c release (%)

Volatile

H-3 2 X 107 2 X 104 1 X 10"2 8 X 103 Kr-85 3 X 10"7 3 X 104 2 X 10"' 5 X 107 1-129 2 X 10'11 2 IX 10"4 8X 10s

Potentially volatile

Se-79 2 X 10"'° 9 3 X 10"' 4 X 102 Tc-99 2 X 10"® 2 X 102 3 X 10"' 4 X 102 Ru-103 3 X 10"9 3 X 101 2 6 X 101 Ru-106 2 X 10~10 2 X 10' 7 X 104 1 X 10"3 Rh-103mb 2 X 10-6 2 X 10s 3 X 10"3 4 X 104 Rh-106b 1 X 10"'° 9 1 X 10s 7 X 10"4 Te-123m 1 X 10"'° 9 1 X 10~2 8 X 103 Te-127m 1 X 10"' 9 X 10" 3 X 10' 3 Sb-124 7 X 10"'° 8 X 10' 8 X 10~' 1 X 102 Sb-125 9 X 10~'° 8 X 10' SX 102 2 X 10"' Sb-126mb 1 X 10"'° 9 4 X 10"' 2 X 10* Sb-126b 1 X 10"10 9 4 X 10"' 2 X 102 Cs-134 4 X 10"10 3 X 10' 2 X 104 4 X 10"3 Cs-135 3 X 10"' 3 X 10* 8X 103 1 X 104 Cs-137 5 X 10"'° 4 X 10' 1 X 104 7 X 10-3

Potential solids (major activities on!y)d

4 Ce-144 2 X 10-'° 2 X 10' 9 X 10 - s Pr-144 1 X 10>° 9 2 X 10 - s Sr-90 3 X 10" 3 2 X 10 - 2 3 Y-90 3 X 10-' 3 X 10 2 X 10 - 3 2 Cm-244 3 X 10-' 3 X lO- 2 X 10* -

Note: 1 curie (Ci) = 3.70 X 10'° Bq. a High-level liquid waste from 6§ t Ud~' of fuel irradiated to 28 700 MW d t"1 U and cooled years. b Limiting MPC = smallest of maximum permissible limits for soluble, insoluble and gaseous species. c Assumes X/Q from stack to ground at site boundary = 1 X 10"7 snT3. d In addition to those listed as potentially volatile (Ru, Rh-106 and Cs-137). temperatures, might be included as a head-end process [6], possibly causing some ruthenium volatilization [7]. Moreover, owing to a short cooling time, the 103Ru release could be relatively high. In HTGR fuel reprocessing, burning of the graphite matrix could to higher ruthenium volatilization [8], In a proposed offgas treatment system for a LMFBR fuel-reprocessing pilot plant, ruthenium adsorbers are provided in the combined offgases of the voloxidation and dis- solution steps [9], Because of its relative unimportance and the lack of data, control of semi- volatiles in the effluents from reprocessing nuclear fuel is not considered further in this report.

3. PROPERTIES OF RUTHENIUM

This section covers basic aspects of volatilization, deposition and retention of ruthenium relating specifically to conditions relevant to concentration and solidification of high-level liquid waste; knowledge that has frequently been obtained in laboratory studies. Experience with some solidification processes is presented in Section 6.

3.1. VOLATILIZATION OF RUTHENIUM

Surveys of investigations on volatilization of ruthenium have been published [10, 1] and, in addition, research on the properties of the ruthenium oxides which are important in this context have been reviewed [11]. Recent work covering certain aspects of ruthenium volatilization is described in the literature [12—14], In this section a distinction is made between volatilization at low tempera- tures as found during evaporation and at high temperatures during calcination and vitrification of HLLW.

3.1.1. Volatilization of ruthenium at low temperatures

In solutions containing nitric acid, ruthenium exists largely in a complex form. Depending on the conditions, nitro and nitrato complexes of nitrosyl ruthenium (RuNO) usually prevail. On boiling or with the influence of oxidants, the ruthenium complexes may be destroyed and Ru4 + ions may be formed. These

in turn may be oxidized to Ru04 which may volatilize [10]:

4+ + Ru + 02 + 2H20 - Ru04 + 4H (1)

4+ + Ru + 2N02 + 2H20 - Ru04 + 2NO + 4H (2)

The volatilization potential of Ru04 under these conditions is on the order of 1%.

5 FIG.l. Ru volatility during evaporation as a function of the initial nitric acid concentration (no nitrates present) [10\

There is no full agreement between the results of different investigators concerning the influence of various parameters on ruthenium volatilization. However, as regards the influence of the main parameters, temperature and composition of the solution, the following results have frequently been obtained:

(a) Influence of temperature

With rising temperature, ruthenium volatility increases slightly. At the end of evaporation, however, a strong increase in ruthenium vaporization is observed owing to a calcination phenomenon.

(b) Influence of nitric acid concentration

Results obtained on the influence of the HN03 concentration are presented in Fig.l. With increase of HN03 concentration, ruthenium volatilization initially

6 NC>3 CONCENTRATION (M)

FIG.2. Ru volatility during evaporation as a function of the initial nitrate concentration for an initial nitric acid concentration of approximately 8M [10\

rises too, but at higher HN03 concentrations of the order of 10M a decline of ruthenium volatilization is found. This is probably due to the formation of the nitronium ions NOj which reduces Ru(VIII) to Ru(VI).

(c) Influence of nitrate concentration

With increase of nitrate concentration, the percentage of ruthenium volatilized may diminish as shown in Fig.2.

(d) Influence of reductants

Ruthenium volatility is lowered in the presence of various reductants, such as phosphite, hypophosphite, nitrite, formaldehyde, formic acid and sugar. These reductants also include those that may be formed in the solution by radiolysis, such as nitric oxide (NO).

7 (e) Influence of ruthenium species

In solutions of low HN03 concentrations (8M) the chemical form of the ruthenium introduced may exert an influence; not, however, in solutions of high

HN03 concentrations (>8M).

3.1.2. Volatilization of ruthenium at high temperatures

In high-temperature processes such as calcination and vitrification, ruthenium may volatilize in the form of Ru04 and (above 800°C) Ru03. Because ruthenium volatilization at less than about 600°C may be found to be higher than predicted by the reactions involving these species only, the existence of another unidentified gaseous ruthenium species of higher volatility has been suggested. The reactions involved in ruthenium volatilization at high temperatures may be similar to reactions (1) and (2), (s denoting solid; g denoting gaseous) [15, 16]:

Ru02(s) + 02 - Ru04 (g) (3)

Ru02(s) + 2N02 Ru04(g) + 2NO (4)

Ru02(s) + £02 ^ Ru03(g) (5)

100

>o

0 100 200 300 400 500 600 700 800 900 1000 1100 1200

TEMPERATURE (°C)

FIG.3. Ru volatility during calcination as a function of temperature [10\

8 CALCINING TEMPERATURE (°C)

FIG.4. Ru volatility during fluidized-bed calcination as a function of calcining temperature [i 7],

Formation of volatile ruthenium species according to these reactions is favoured by high temperature. Virtually all of the ruthenium may be volatilized. The main parameters influencing ruthenium volatility at high temperatures are: temperature, method of solidification, method of supplying heat, composition of the solid phase, and composition of the gaseous phase. Numerous investigators have obtained the following results:

(a) Influence of temperature and solidification method

High temperature is generally favourable to ruthenium vaporization. Results obtained during heating of an evaporated simulated waste solution are shown in Fig.3. Ruthenium volatilizes strongly at the beginning of calcination (130-140°C); thereafter there is little increase in volatility. However, when spraying a simulated waste solution on a fluidized bed of solidified waste granules, a decrease of volatility with increase in temperature is observed in the range investigated. This is shown in Fig.4.

9 (b) Influence of method of supplying heat

In fluidized-bed calcination (see Section 6) different ruthenium volatilization is found with different methods of heating (indirect heating or in-bed combustion). Examples are given in Section 6.

(c) Influence of reductants

As with low temperatures, ruthenium volatility may be abated at high temperatures by the addition of reductants. However, the efficiency of reductants at high temperatures may differ from that at low temperatures. For example, formic acid and sugar have been found to abate ruthenium volatility efficiently during rotary-kiln calcination (see Section 5). This is not the case, however, with formaldehyde. sulphide has been successfully employed in India with pot calcination (see Section 5).

(d) Influence of other substances

Substances such as the alkaline earth metals may be effective in reducing ruthenium volatility by forming compounds like SrRu03. For the calcination step, however, poor efficiency has been reported. High ruthenium volatility in the presence of phosphates has been reported [18].

(e) Influence of inert gases

In the presence of inert gases (e.g. N2) and of gases such as NO and CO, ruthenium volatility is reduced.

3.2. DEPOSITION OF RUTHENIUM

Deposition of volatilized ruthenium on surfaces such as pipes is important in offgas cleanup since plugging of pipes and creation of high radiation fields in unshielded areas (gas pipes, filters, ventilators) may occur. (Reviews of investigations on deposition of ruthenium have been published [19, 1 ].) Important mechanisms in deposition of volatilized ruthenium include physical adsorption of the gaseous species and chemical processes like reactions (3) and (4), which lead to the formation of solid Ru02. Formation of metallic ruthenium and interaction with the solid phase, e.g. steel, may also be involved.

Metallic ruthenium or Ru02 may also interact with volatilized ruthenium, leading to further deposition.

10 TABLE III. RUTHENIUM DEPOSITION ON STAINLESS STEEL MESH [20] AND TUBE [19]

Atmosphere Flow Temp. Temp. Ru deposited (v/v) velocity at peak max. range of peak in peak region (cm-s"1)8 (°C) (°C) (%)

Mesh, volatile Ru from heated Ru02

02 2.3 425 400-475 16.8

02 2.3 560 480-585 18.2

50% 02, 50% N2 2.3 780 695-810 21.1

10% 02, 90% N2 2.3 810 760-880 37.2

10% 02, 90% N2 2.3 810 745-880 29.7

10% 02, 90% N2 2.3 820 730-860 41.0

10% 02) 90% N2 3.5 690 635-810 17.4

02" 2.3 620 515-690 18.6

Tube, volatile Ru from calcined Ru/HN03 solution

c N2 75 470 300-510 c,d N2 75 610 400-900 c n2 280 490 400-600 140 470 220-580 70 490 250-600 c e N2 ' 85 620 320-760 a e Calculated flow velocity at 500°C. 0.5 g Fe203 on tube. b f Pre-oxidized surface. 0.8 g Fe203 on tube. c 8 Also HN03 decomposition gases. 0.3 g Ru02 on tube. d Tube contaminated with RuO,.

The parameters which influence the deposition of volatilized ruthenium include temperature, flowrate of the gas, composition Of the gas, nature of the surface, and conditions of calcination. Results are presented in Table III and Figs 5 and 6 which were obtained by passing a gas stream containing volatilized ruthenium through different materials (mesh, wool) or through a tube of stainless steel with decreasing temperature in the direction of flow. The influence of the various parameters can be summarized generally as follows:

1360 o o 5 10 -

NO: "RICH" ATMOSPHERE

NO: "POOR" ATMOSPHERE o-

o< 5 -

UJ cc

n 300 200 100 68

TEMPERATURE OF STAINLESS-STEEL WOOL (°C)

FIG.5. Deposition ofRu-103 on stainless-steel wool as a function of NO concentration in offgas (HNOi feed calcined at 500°C) [21].

(a) Influence of temperature: Deposition of ruthenium is generally enhanced by decreasing temperature. In the systems described, there is a maximum in de- position at specific temperatures. However, a secondary peak at a different temperature may also occur.

(b) Influence of gas flowrate: With decreasing flowrate, ruthenium deposition may be enhanced, i.e. the maximum of the ruthenium deposition is found at higher temperatures.

(c) Influence of gas composition: With increasing partial pressure of inert gas (N2) or reducing gas (NO), the maximum ruthenium deposition occurs at higher temperatures.

12 1—: r

I | HN03 feed calcined at 400°C

HN03 feed calcined at 500°C 60 - ^^ HNO3 feed calcined at 600°C

HH HF feed calcined at 500°C

30 -

20 -

10 -

Jill Jill 300 200 100 68

TEMPERATURE OF STAINLESS-STEEL WOOL (°C)

FIG. 6. Deposition ofRu-103 on stainless-steel wool as a function of calcination temperature and calciner feed (NO: poor atmosphere) [21],

(d) Influence of the nature of the surface: Deposits of Ru02 favour deposition of ruthenium. This is not found with other deposits such as Fe203. It has also been observed that ruthenium deposition on steel is generally much higher than on glass.

(e) Influence of calcination conditions: A high calcination temperature has been found to favour ruthenium deposition.

13 3.3. RETENTION OF RUTHENIUM Reviews of work on retention of ruthenium by various adsorbents are to be found in the literature [11,1,2]. In this section, retention by solids as used in ruthenium filters and retention by liquids as formed in condensers or employed in scrubbers are distinguished.

3.3.1. Retention of ruthenium by solids

3.3.1.1. General With retention of volatilized ruthenium by solids, the aspects to be considered include resistance against oxides, pressure drop, decontamination factor (DF), capacity, and treatment after loading (regeneration or incorporation in glass). Many materials have been examined for retention of volatilized ruthenium. These materials include silica gel, alumina, molecular sieves, metals, metal oxides, metal carbonates [22, 23] and polyethylene. The method of ruthenium auto- catalytic removal from a gaseous phase has recently been developed by using catalysts containing Ru02 (as well as NiO, Mn203, ZnO) [24, 25], Silica gel and metal-oxide-based materials seem to be most suitable. However, some of the results obtained with silica gel and ferric-oxide-based materials have been contradictory (for example, so far as the acceptable ranges of temperature are concerned). This might be one of the reasons why investigations with these materials are continuing [26—28], The retention of volatilized ruthenium by silica gel is largely due to physical adsorption. In the case of ferric oxide, processes like reactions (3) and (4), which involve decomposition of the gaseous ruthenium species, seem to play an important role. In the case of Ru02 the autocatalytic mode of the reaction (3) plays a decisive part in the process of trapping radioruthenium, since the catalyst is coated with solid reaction products and can operate for a prolonged of time only when solid reaction products catalyse the process. The parameters affecting retention of volatilized ruthenium include tempera- ture, residence time or flowrate, operating time, composition of the gas, and the nature of the solid, including particle size. The influence of these parameters with silica gel, ferric-oxide-based and ruthenium-oxide-based materials is described below.

3.3.1.2. Silica gel

(a) Influence of temperature: To obtain high decontamination factors of 102 to 103, the temperature may rise to relatively low values only. Several

14 TABLE IV. RUTHENIUM RETENTION BY SILICA GEL AND FERRIC OXIDE ADSORBENTS3

Adsorbent Silica gel Silica gel Ferric oxide Ferric oxide

Grain size (mesh) 18-25 12-40 18-25 6-20 Bed temperature (°C) 150 80 150-250 300-550

Dew point temperature (°C) - «80 - =»80 Bed depth (cm) 5 66 5 66 Superficial velocity (cm -s"1) 9 12 9 12-21 Residence time (s) 0.6 5.5 0.6 3.1-5.5 Decontamination factor >102 102-103 102-103 Capacity (gRu-L"1 adsorbent) >20 >5 >40 >5

Reference [29] [30] [29] [30]

a Volatile Ru from calcined Ru/HN03 solutions.

TABLE V. RUTHENIUM RETENTION BY VARIOUS ADSORBENTS [31 ]

Adsorbent Decontamination Capacity factor (gRu-L-1 absorbent)

Siliceous insulation brick (SIB) <«10' -

Phosphoric-acid-treated kieselguhr (PAT) <10' - Iron-oxide-coated SIB >60a -oxide-coated PAT 102-103 >40

Grain size: 6—10 mesh Bed temperature: «=300°C Bed depth: 13 cm Superficial velocity: 4 cm s-1 Residence time: ^3 —12 s a Higher values found after pretreatment of iron-oxide-coated SIB with perchloric acid.

15 investigators have found an upper acceptable value of about 80°C. Others have obtained high DFs even at 100°C. (b) Influence of residence time: High DFs can be achieved if the residence time (volume of sorbent divided by gas volume flow) is at least five seconds. (c) Influence of operating time: It has been found that the DF may rise with increasing operating time because of an autocatalytic reaction. Owing to desorption or capacity limit the DF may, however, also decline with increasing operating time. (d) Influence of gas composition: High DFs have been found in the presence of nitrogen oxides. However, there are also results which show a detrimental influence of nitrogen oxides. (e) Capacity: Several investigators have found that silica gel may absorb about five grams of ruthenium per litre and more with no significant effect on the DF. (f) Regenerability: Loaded silica gel may be regenerated several times by treatment with liquids (e.g. water). However, if this treatment is not performed immediately after loading, it may hardly be effective. Some results of investigations on ruthenium retention by silica gel are contained in Table IV (see also Table V).

3.3.1.3. Ferric-oxide-based materials (a) Influence of temperature: To achieve high decontamination factors of 102 to 103, the temperature should be at least 200°C. A minimum acceptable temperature of 300°C has also been found. (b) Influence of residence time: The minimum required residence time is about one second. (c) Influence of operating time: An increase in DF with rise in operating time has been found. (d) Influence of gas composition: Both negligible and detrimental influence of nitrogen oxides have been observed.

16 100 200 300 400 500 TEMPERATURE (°CI

1 0.5 0.25

RESIDENCE TIME (s)

0 1 2 3 4 5 6 7 OPERATING TIME (d|

FIG. 7. Ru retention by ferric-oxide granules as a function of various parameters [32],

(e) Capacity: A loading of much more than five grams of ruthenium per litre may be reached without a fall of DF. (f) Regenerability: The loaded sorbent cannot be regenerated. Some retention results for ferric oxide are presented in Table IV and in Fig.7 (see also Table V). 3.3.1.4. Ca taly tic decomposition

(a) Influence of temperature: The decomposition of Ru04 takes place at higher temperatures. The decontamination factor was 1.1, 7.25, 150, 1.8 X 103 and 1.1 X 104 at 250°C, 300°C, 350°C, 400°C and 500°C, respectively. (b) Influence of residence time: The highest DF has been achieved with residence time of 0.15 seconds. (c) Influence of operating time: The catalysts operate only at the initial stage of the column operation. Following some period of time the surface of catalysts becomes coated with ruthenium dioxide, and the column then operates under the conditions of the autocatalytic reaction. (d) Influence of gas composition: High DF has been found in the presence of nitrogen oxide with 5% concentration. (e) Capacity: A loading of catalyst has been more than 500 grams of ruthenium per litre.

3.3.2. Retention of ruthenium by liquids Although considerable retention of volatilized ruthenium by liquids used in scrubbers and formed in condensers of offgas cleanup systems has been observed (see Section 6), little work has been directed to the assessment of the influence of process parameters. The retention mechanisms involved include solution of the gaseous species in the liquid as well as formation and capture of particulate species [33], Temperature and composition of the liquid are important parameters. From investigations on the retention of vaporized ruthenium by a nitric acid scrubber it was concluded that a DF of about 100 might be achieved with a temperature of less than 80°C and a nitric acid concentration of less than 10M [34].

4. PROPERTIES OF OTHER SEMIVOLATILES

Because of their relative insignificance (see Section 2), little work has been performed on volatilization and retention of the semivolatiles other than ruthenium. This section contains some results, mainly from laboratory work. Experience with various solidification processes is to be found in Section 6.

18 TABLE VI. LOSS OF SEMIVOLATILES DURING CALCINATION AND VITRIFICATION OF SIMULATED WASTE [40]

Loss to the offgas (%)

Element Calcination Vitrification

Se 1.8 18.1 Tc 0.005 2.9 Sb 4.2 11.3 Te 0.004 0.2

Calcination: 1 hour at 500°C; vitrification: 6 hours at 1050°C.

4.1. PROPERTIES OF CAESIUM Caesium may volatilize in the form of elemental caesium, but also in the form of compounds such as Cs20 and CsOH [35, 36]. During calcination the volatility of caesium is much lower than during vitrification. With simulated waste, a loss to the offgas of less than 1% was found during calcination, but of about 10% during vitrification [37/38], There are, however, indications that during melting at full-scale facilities the volatilization of caesium may be less than 1% [32, 35, 39, 40]. The volatility of caesium may be abated by addition of certain oxides (e.g. oxide), which form thermally stable compounds [31, 35]. The use of cover materials such as silicate has also been found effective [31 ]. In retention of caesium, apart from plate-out, the formation and capture of particulates are mainly involved. Condensers, scrubbers and HEPA filters have been found effective for removing caesium [27, 35, 37, 40].

4.2. PROPERTIES OF SELENIUM, TECHNETIUM, ANTIMONY AND TELLURIUM In volatilization of these semivolatiles the oxides are of primary importance [15, 16, 33, 41]. Some data on volatilization during calcination and vitrification of simulated waste are presented in Table VI. As in the case of caesium, volatilization is much lower during calcination than during vitrification. Moreover, volatilization of selenium and antimony exceeds by far that of technetium and tellurium under the conditions of the experiment. In other investigations much higher losses to the offgas were found [37, 41]. The volatility may be reduced by formation of thermally stable compounds [31].

19 As in the case of caesium, formation and capture of particulates are involved in retention of these semivolatiles. Condensers, scrubbers and HEPA filters are therefore effective removal devices [37, 40, 41].

5. PRINCIPLES OF HIGH-LEVEL WASTE SOLIDIFICATION PROCESSES Basic aspects of solidification methods and offgas treatment systems are presented in this section. Reviews on high-level liquid waste (HLLW) solidification technology [42, 43] and offgas treatment technology for HLLW solidification processes [2] have been published.

5.1. SOLIDIFICATION METHODS The possible steps of major HLLW solidification processes include evaporation, denization, calcination, addition of glass frits and preparation of glass. Generally, calcination is performed at 300°C to 800°C and preparation of glass at 1000°C to 1300°C. The process steps mentioned may be performed separately or be combined. The processes which feature separation of the glass-melting from the other steps may be classified according to the calcination method, e.g. fluidized bed, spray, rotary-kiln, and pot calcination (see Table XVIII). (a) Fluidized-bed calcination The waste is sprayed at a fluidized bed of solidified waste granules main- tained at high temperatures. With indirect heating, the calcining temperature may be 400°C; with in-bed combustion (of hydrocarbon fuel), the calcining temperature may be 500°C. Vitrification is performed in another unit. (b) Spray calcination The waste is sprayed in a vessel held at the temperature range from 600°C to 800°C. Vitrification occurs in another vessel. (c) Rotary-kiln calcination The waste is fed into the upper end of a slightly inclined rotating tube held at high temperatures. The resulting calcine is discharged from the lower end to the vitrification unit.

20 TABLE VII. TYPICAL DECONTAMINATION FACTORS ACROSS OFFGAS TREATMENT COMPONENTS [2]

Decontamination factor COMPONENT

Particulates Volatilized Ru NO2 NO

Cyclone 10 1 1 1 Venturi scrubber 100-600 10 2 1 Tube and shell condenser 102-103 2 X 102 2 1

NOx absorber 10 10 5 1 Brink fibre mist eliminator 102 1 1 1 Packed spray tower 103 102 4 1

2 2 2 NOx converter 2 • 4 X 10 10 10 Ruthenium sorber: Silica gel 8 103 1 1 2 Fe203 on glass 2 (1 to 5) X 10 1 1 Sintered metal filter 103 1 1 1 HEPA filter 103 1 1 1

(d) Pot calcination The waste (with additives) is fed to a vessel heated by a multizone furnace for successive evaporation, calcining and melting. The vessel containing the glass may be removed for final storage or the melt may be poured into another vessel. (e) Liquid-fed ceramic melter The waste (with additives) is fed on the top of molten glass where all the necessary steps take place.

5.2. OFFGAS TREATMENT SYSTEMS The offgas of solidification processes contains (by volume) mainly air, water vapour, nitrogen oxides and, in the case of fluidized-bed calcination with in-bed combustion, oxides [44], The radioactive constituents may be present as particulates and gases.

21 N>

HEATER

FTG.8. General flowsheet of a high-level liquid waste solidification process [44]. The offgas treatment systems of solidification processes normally contain devices for removing water vapour, nitrogen oxides, particulates and gaseous ruthenium. The other semivolatiles may also be removed by these devices. Both individual components and integrated systems are dealt with below.

5.2.1. Individual components Water vapour is removed by condensers, and nitrogen oxides by scrubbers (with the possibility of nitric acid recovery) or catalysts (where reduction to ammonia occurs). Particulates are trapped by cyclones, scrubbers, filters (sintered metal or fibre) and demisters. Gaseous ruthenium is retained by adsorbers. The devices enumerated may be effective for partial removal of different constituents. In particular, gaseous ruthenium and the other semivolatiles may be efficiently removed by condensers and scrubbers (see Sections 3 and 4). Estimated decontamination factors for volatilized ruthenium and other constituents across various offgas cleanup devices are given in Table VII. Design principles of various devices for removal of particulates and gases have been indicated [45, 46], For ruthenium filters, both silica gel and ferric-oxide-based materials are used. Filters containing silica gel may be operated at a temperature of 80°C and a residence time of ten seconds. For ferric-oxide-based materials the corresponding values may be 500°C and one second. Silica gel may be re- generated; ferric-oxide-based materials cannot (see Section 3).

5.2.2. Integrated systems Because the offgases from solidification processes may vary from process to process, both qualitatively and quantitatively, with respect to radioactive and non-radioactive constituents, different offgas cleanup systems may be used for different processes. The removal sequence may be as follows: particulates, water vapour, nitrogen oxides, gaseous ruthenium and again particulates. This is depicted in Fig.8, which shows an offgas treatment system suitable for any solidification process. This offgas treatment system also serves for removal. Iodine removal in offgases from solidification processes may also be provided in reference facilities [5], but is not at present carried out. The location of the ruthenium adsorbers may vary considerably. Ruthenium removal may be performed before removal of nitrogen oxides and water vapour. In one instance, ruthenium filters were even placed in the calcination/vitrification pot (see Section 6). Depending on the temperature of the offgas (and other factors), either silica gel or ferric-oxide-based materials may be the preferred adsorbent, as already mentioned. If a ruthenium filter is used for final ruthenium cleanup, regenerability will not be important.

23 6. EXPERIENCE WITH CONTROL OF SEMIVOLATILES IN HIGH-LEVEL LIQUID WASTE SOLIDIFICATION PROCESSES

In this section, experience of the volatilization and retention of semivolatiles in HLLW solidification processes is reviewed. For comparison, other particulate radionuclides are also included to a certain extent. Many solidification processes have been developed to various stages. The processes covered here are those for which many relevant data have been published or which are being developed with high priority. Reviews of pertinent data have been published [1,2]. In the following sections, individual solidification processes are covered and a summary is presented.

6.1. FLUIDIZED-BED CALCINATION Fluidized-bed calcination has been implemented in the Waste Calcining Facility (WCF), USA, from 1963 to 1981 for calcination of non-commercial HLLW [47], Investigations have been carried out on the calcination of simulated HLLW by identical equipment [48, 49, 17]. The WCF offgas treatment system is shown in Fig.9. It consists essentially of a cyclone, two scrubbers, a condenser, a ruthenium filter (silica gel) and HEPA filters. The scrubbing solution is recycled to the calciner. Ruthenium loss (particulate and gaseous) through the cyclone to the offgas was some 50% in campaigns 1 to 3, when indirect heating was performed, and a factor of about 10 lower in campaigns 4 and 5, when in-bed combustion was employed [48, 50], Caesium loss corresponded to the loss of particulates. The ruthenium and caesium decontamination factors across various components of the WCF offgas treatment system are summarized in Table VIII. For ruthenium, when indirect heating was employed the decontamination factors across the silica gel adsorber ranged from about 2 X 10J to 2 X 103 and were 1 for the HEPA filters. With in-bed combustion, little retention of ruthenium was achieved with the silica gel adsorber. In this case the HEPA filters exhibited high DFs of the order of 103. It is therefore assumed that ruthenium is largely in gaseous form with indirect heating but that a particulate form is readily produced with in-bed combustion. The overall ruthenium DFs (feed to stack) ranged from about 103 to 106. With indirect heating, the best caesium removal was obtained with the scrubbers and the HEPA filters; with in-bed combustion it was efficiently retained by the HEPA filters only. The overall DFs were 106 to 107.

24 to FIGS. Flowsheet of the Waste Calcining Facility (WCF) under typical operating conditions [47]. Ln K) <3\

TABLE VIII. DECONTAMINATION FACTORS ACROSS VARIOUS COMPONENTS OF THE WCF OFFGAS TREATMENT SYSTEM [50]

Campaign Waste type Calciner Nuclide ' Decontamination factor - No. heating system Calciner Scrubber Silica gel Filters Overall and system sorber DFs cyclone (feed to stack)

3 1 A1(N03)3 Indirect Ru-106 -2.5. 11 240 1 3 X 10 heating Cs-137 6.0 690 9 280 107 Sr-90 . .6.5 600 12 160 8 X 106

3 5 2 A1(N03)3 Indirect Ru-106 13 400-2000 1 . 10 -10 heating Sr-90. 1000 10 1000- 2000 107-108

s 3 ZrF4-Al(N03)3 Indirect Ru-106 100 1000 1 10 heating Sr-90 2750 10 3000 108

s 4 ZrF4-Al(N03)3 In-bed Ru-106 80 12 850 8 X 10 combustion Sr-90 2760 8 630 2 X 107

5 5 Mostly ZrF4- In-bed Ru-106 40 3 1030 10 s A1(N03)3 combustion Cs-137 12 25 3 1300 10 AQUEOUS . WASTE .

B-CELL

EVAP. FEED FEED TANK TANK • C MODE BAND C ONLY

' SOLIOIFIER EVAPORATOR FRACTIONATOH — (CONDENSER CONOENSER- CONOENSER

CONDENSER PREHEATER VESSEL riLTER BLOWER VENT JET k CD" l i jf^1, x • LWl FILTER i I |l BUILDING PREHEATER' FILTER BLOWERII VENT IL AT ION VENTILATION FILTERS PROM 01 HER RADIOACTIVE AREAS VENTILATIOvICmtii tTinuronN FROuM * POTENTIALLY RADIOACTIVE AREAS

RECIRCULATION . . PUMP. -

• — —. GAS STREAM

. AQUEOUS OR SOLID STREAM

© GAS SAMPLE POINTS

• ROUTE USED WHEN SOLIDIFIER CONDENSATE - WAS COLLECTED SEPARATELY • *SOLIDIFIER FILTER USED ONLY IN FOUR RUNS

FIG. 10. Flowsheet of the Waste Solidification Engineering Prototypes (WSEPj offgas treatment system [id?]. TABLE IX. DISTRIBUTION OF RADIONUCLIDES IN THE WSEP OFFGAS TREATMENT SYSTEM3 [18]

Radioruthenium Radiocerium Stream Major Ci/Ci in feedb Ci/Ci in feedb constituent PC SS PG PC SS PG

1 1 -2 3 4 3 Solidifier 1 to 6M HN03 2 X 10" 6 X 10" 8 X 10" 6 X 10" 7 X 10" 2 X 10~ condensate (1 X 10"2)c

3 3 -3 6 6 7 Fractionator bottoms 7 to 10M HN03 1 X 10" 4 X 10" 2 X 10" 2 X 10" 5 X 10" 8 X 10"

Accumulated 0.01 to 0.1M 1 X 10"6 1 X 10~s 4 X 10"- 6 1 X 10~8 1 X 10"9 1 X 10"8 4 d fractionator distillate HNO3 (4 X 10" )

Scrubber bottoms 0 to 2M NaOH 1 X 10"5 4 X 10"s 3 X 10" 6 «10"8 «=10"8

Final offgas from scrubber Air «=10~8 «10~8 «10"8 ~10-»d ~10"11

Final offgas to stack Air «10"10 ^lO"10 «10"12 ~10"12 ~1(T12 a Primarily average of typical values for all WSEP runs. b Total curies of accumulated in auxiliary tank during entire run/total curies of radionuclide in feed to solidifier during entire run (1 Ci = 3.70 X 1010 Bq). c In-pot melting runs SS-12 and SS-13. d Average value for last three pot calciner runs.

PC = pot calcination; SS = spray solidification; PG = phosphate glass solidification. MAGNETIC FLOWMETER ATOMIZING AIR CONDENSER FEED STRAINER IT

irsr-txj-jn SINTERED ^hxh-Q-hx^ STAINLESS STEEL FILTERS CALCINE TO MELTER

FEED TANK

VENTURI SCRUB TANK TANK GAS FLOW CONDENSATE — LIQUID FLOW TANK

FIG.11. Flowsheet of the non-radioactive offgas system studied in the High-Level Waste Immobilization Program [55].

to vo TABLE X. DECONTAMINATION FACTORS ACROSS VARIOUS COMPONENTS OF THE HLWIP NON-RADIOACTIVE PROCESS OFFGAS TREATMENT SYSTEM [53]

Decontamination factor Run Feed type3 First scrubber ' Condenser

Ruthenium: DSS-58 PW-7 3.2 2.8 DSS-60 PW-8 2.3 2.9 DSS-62 TW-2 - 15.0 DSS-63 PW^t 36.3 3.8 DSS-44 PW-7 - 1.2 DSS-49 PW-9 - 1.3

Caesium: DSS-60 PW-8 4.8 2.5 DSS-61 TW-2 - " ' 5.0 DSS-62 TW-2 - 4.2 DSS-44 PW-7 - 3.5 DSS-49 PW-9 - 19.5 a PW: LWR waste; TW: Thorex waste (more details in original).

6.2. SPRAY CALCINATION Examples of investigations on spray calcination are those performed within the Waste Solidification Engineering Prototypes (WSEP) programme and within the Nuclear Waste Vitrification Program (NWVP), USA. Within the WSEP programme, performed from 1966 to 1970, various calcination methods were employed in connection with vitrification of simulated commercial HLLW [18, 51], The WSEP offgas treatment system is shown in Fig. 10. The main components were several condensers, an evaporator with a mist eliminator, a fractionator, a scrubber and HEPA filters. With spray calcination there were also sintered-metal filters at the exit of the calcination vessel. The distribution of ruthenium in the WSEP offgas treatment system for the spray calcination (SS) runs is contained in Table IX. On an average the loss of ruthenium (through the sintered-metal filters) to the offgas was some 60%;

30 most of the ruthenium was removed by the first condenser. The overall ruthenium DFs were about 1010 (for the pot calcination runs see below). Within the NWVP, started in 1976 and terminated in 1979, vitrification of actual commercial HLLW was carried out by spray calcination/in-can melting [52], The offgas cleanup system was essentially identical to that used with WSEP. Fission-product distributions in the offgas cleanup system have not yet been published. Within the High-Level Waste Immobilization Program (HLWIP), USA, spray calcination of simulated HLLW has also been performed [ 53, 54]. The offgas treatment system for the non-radioactive process studied in the HLWIP is shown in Fig.l 1. It consisted of sintered-metal filters at the exit of the calciner, followed by a scrubber, a condenser, a second scrubber and HEPA filters. In the non-radioactive process, the loss (through the sintered-metal filters) to the offgas ranged from 10"3% to 10_1% for ruthenium and from non- detectable to 10_1% for caesium (the contribution from the melter was negligibly small). A significant fraction of the nuclides lost to the offgas was in particulate form. Small decontaminations for ruthenium and caesium across the first scrubber and the condenser have been reported for the non-radioactive process; some values are given in Table X.

31 TABLE XI. DISTRIBUTION OF RADIONUCLIDES IN THE OFFGAS TREATMENT SYSTEM OF THE AVM PLANT [56]

Distribution (%) Nuclide Campaign No. Escaped from Recycled to Condensate Acid recovery Washing the calciner the calciner column column

Ru-106 38.7 22.0 16.7 7 X 10"2 10"4

s 19.7 12.7 7.0 2.3 X 10" 10"4

3 7 Cs-137 11.5 10.1 1.4 3.3 X 10" 1.3 X 10"

6.4 5.2 1.2 3.0 X 10"3 4.3 X 10'7

Ce-144 5.9 4.0 1.9 4.0 X 10"4 5.0 X 10"6 3.9 2.2 1.7 0.2 X 10"4 1.3 X 10"6

Sr-90 5.2 5.0 0.2 3 X 10~s 7 X 10~8 3.0 2.9 0.1 3 X 10"5 7 X lO"'8 TABLE XII. DECONTAMINATION FACTORS ACROSS VARIOUS COMPONENTS OF THE OFFGAS TREATMENT SYSTEM OF THE AVM PLANT [56]

Decontamination factor Nuclide Campaign No. Calciner First Condenser Acid recovery and melter scrubber column

Ru-106 3.2 2.3 255 650 5.7 2.8 306 6 440

Cs-137 9.6 8.4 420 24 600 16.5 5.3 404 7 060

Ce-144 17.6 3.1 5130 72 26.2 2.3 4240 307

Sr-90 20.3 24.7 6000 480 33.8 28.0 3105 475

6.3. ROTARY-KILN CALCINATION Rotary-kiln calcination has been performed since 1978 in the AVM plant, France, on an industrial scale in connection with vitrification of HLLW from re- processing of natural uranium fuel [55, 56]. The offgas treatment system, shown in Fig. 12, consists of the following main components: a scrubber, a condenser, two further scrubbers (columns) and HEPA filters. The liquor of the first scrubber is recycled to the rotary kiln. No ruthenium filter has yet been installed. The distribution of radionuclides in the offgas treatment system of the AVM plant during the first two campaigns is presented in Table XI. For these campaigns the escape of ruthenium from the calciner was 39% and 20%, and that of caesium was 12% and 6%, respectively. Most of the ruthenium and caesium was removed by the first scrubber and recycled to the calciner. The corresponding decontamination factors are listed in Table XII. Overall decontamination factors of greater than 109 have been achieved for ruthenium and caesium. Loss of ruthenium from the rotary kiln can be strongly reduced by the addition of sugar to the feed. In the Atlas plant, which has half-scale AVM equipment, a reduction by a factor of 20 was thus achieved and less than 1% of 106Ru was then found in the condensate.

33 FISSION PRODUCT WASTE 1 s. ® SILICA/BORAX SLURRY , VACUUM EJECTOR ®H Q-

ABSOLUTE FILTER OVENS TO MAINTAIN AT PRIMARY SECONDARY 250°C STIC FILTER/ABSORBER FILTER/ABSORBER CAU SCRU BBER

STAINLESS STEEL^ J CYLINDER

FURNACE WITH 6 INOEPENOENTLY 1 CONTROLLED HEATING ELEMENTS CONDENSER

SPENT FILTER i

1050°C 250° C 250° C

FIG.13. Flowsheet of the Fingal plant offgas treatment system [57], TABLE XIII. DISTRIBUTION OF RUTHENIUM IN PROCESS AND FILTER VESSELS OF THE FINGAL PLANT [57] ;

Distribution (%) Run Duration No. (h) Process, vessel First Second Glass Walls Total filter filter

P33 12 38.8 32.5 71.3 28.7 - P12 14 34.8 37.0 71.8, 22.8 5.4 P17 29 26.0 32.6 58.6 34.9 6.5 P10 34 28.5 29.9 58.4 35.5 5.8 P18 36 46.0 19.6 65.6. , 29.6 4.8 Pll 50 33.3 12.0 ' 45.3 47.1 7.4 P20 50 48.9 10.5 59.4 ' 38.7 1.9 P21 50 47.0 13.5 60.5 ,36.6 2.9 P22 50 47.4 11.8 59.2; 38.3 2.5 P23 50 44.4 12.2 56.6' 42.0 1.4 P24 50 44.6 12.6 57.2 40.2 2.6

P39 45.5 64.0 . 12.1 16.1 23.9 • - P41 48 75.1 6.2 81.3 15.0 3.7

P42 12 77.0 9.9 86.9 13.1 -

P43 46 59.8 9.6 69.4 30.6 ' -

Note: Runs 39 to 43 were carried out at low offgas temperature.

6.4. POT CALCINATION Pot calcination has been investigated within the WSEP programme (see Section 6.2). It has also been used or is being used in plants such as Fingal, Harvest and Piver. The distribution of ruthenium in the WSEP offgas treatment system (see Fig. 10) for the pot calcination (PC) runs is contained in Table IX. The loss of ruthenium to the offgas was some 20% on an average, most of which was removed by the first condenser. The overall ruthenium DFs amounted to about 1010. The Fingal plant operated from 1962 to 1966. Vitrification of Magnox HLLW was carried out [57], The Fingal process featured a peculiarity in so far as a primary ruthenium filter (Fe203) was operated in a pot which in the subsequent Text continued on p.44.

35 TABLE XIV. DECONTAMINATION FACTORS IN THE FINGAL PLANT [57]

Run Duration / Feed Overall DF Total DF ( No. (h) activity (P,y) \ Condensate ) ( Feed \ processed / a \ Effluent gas J (Ci) Ru-106 Sr-90 Cs-137 Ce-144

4 7 7 7 A13 50 55 1.9 X 10 1.0 X 10 1.0 X 10 1.6 X 10 — A14 35 1 018 7.8 X 104 1.5 X 108 2.0 X 108 2.1 X 107 1.5 X 1013 A25 20 428 2.8 X 10s 1.4 X 10s 4.6 X 108 6.9 X 107 1.6 X 1013 A26 36 937 2.6 X 102 1.2 X 108 1.6 X 108 9.6 X 109 11 9 10 A27 30 639 8.2 X 10s 4.0 X 108 1.2 X 10 8.9 X 10 A34 6 s 8.6 X 107 3.0 X 107 1.4 X 1013 15 507 2.2 X 10 AA35 6 6 1.0 X 1010 2.6 X 10'° 3.8 X 1014 4 5 650 1.0 X 10 10 15 AA44 43 14 500 8.0 X 104 4.4 X 1010 3.8 X 10 2.3 X 1010 8.0 X 10

a 1 curie (Ci) = 3.70 X 1010 Bq. u> -J FIG. 14. Flowsheet of the inactive Harvest plant [5S], FIG.15. Loss ofRu and Cs to the offgas in the Piver plant as a function of time during the second campaign. Maximum loss: Ru-106 15%; Cs-137 0.1% ' (1 curie = 3.70X 10l0Bq ) [32].

TABLE XV. DISTRIBUTION OF RUTHENIUM AND CAESIUM IN LIQUORS OF THE OFFGAS TREATMENT SYSTEM OF THE PIVER PLANT [32]

Distribution (%) Liquor Ru Cs

Condensate 15 0.1 Liquor of first column 0.05 0.005 Liquor of second column 0.01 0.001

Note: No Ru filter used.

38. MELTING CONDENSATION TRAPPING ADSORPTION WASHING WASHING FILTRATION

(Ru) (N0X) FD = 7 FD = 103 FD = 25 FD = 4 FD = 3 FD = 5 FD = 10J * I + it* I 1 Ci Ru-106 i-6 1.5 X 10" Ci 6X10 1.5 X 10 5X10'' 10"' L_££ li i SPECIAL \ I I MELTING 0.15 Ci \ V \ \ 1.5X10"4

:'0.1 5 Ci: :0.85 Ci

i jiiiiyj \

10"6Ci 5 X 10"6Ci 10-10 Ci

INTERMEDIATE- INTERMEDIATE- OFFGAS LEVEL EFFLUENT LEVEL EFFLUENT

FIG. 16. Distribution of Ru in a plant of the Piver type (1 curie -• 3.70 X lO10 Bq) [32], o i—J CONDENSER DF= r~ Hgh TOTAL POT CONDENSER CONDENSER

FRACTIONATOR r---(Wy SPRAY

LOW-LEVEL EFFLUENT TREATMENT PROCESS LIQUID I • PROCESS OFFGAS

-A ACID X- DF : DECONTAMINATION _|J KILLING El FACTOR (ESTIMATED TANK J~ VALUES)

FIG.17. Flowsheet of the Tarapur Waste Immobilization Plant offgas treatment system. INTO THE ATMOSPHERE

FIG.18. Flowsheet of the offgas treatment system for a vitrification process with a liquid- fed ceramic melter (USSR) [43, 62]. 1. Melter 4. Fine particulate filter 2. Bubbler-condenser 5. Ru adsorber

3. Coarse particulate filter 6. NOx absorber

TABLE XVI. INFLUENCE OF ADDITION OF SUGAR ON LOSS OF NUCLIDES TO OFFGAS IN A LIQUID-FED CERAMIC MELTER (USSR) [62]

Amount of added sugar

None 150 g-L"1 Feed rate (L-h~l) 100 100 Melted mass temperature (°C) 1100 1000+ 50 Offgas temperature (°C) 500-550 300 ± 25 Loss of Ru (%) 70-80 4-5 Loss of Sr (%) 0.4-0.6 0.05-0.1 Loss of Cs (%) 0.6-1.0 0.2-0.3 Loss of particulates (%) 0.3-0.4 0.05-0.1

41 FIG.19. Flowsheet of a vitrification process with a liquid-fed ceramic melter (USA) [63]. Ventilation Compressed air Steam Cold vi Cold water outlet-

.Freeze collars

Oust removal NOy absorber wet scrubber

FIG.20. Flowsheet of the offgas treatment system for a liquid-fed ceramic melter (FRG) [55]. u> 10 30 50 70 90 110

OPERATING TIME (h)

FIG.21. Ru loss to the offgas system (without deposition in the offgas pipe) of a liquid-fed ceramic melter (FRG) as a function of operating time and pool coverage [66], Curve 1: pool coverage 100%. Curve 2: pool coverage 70 - 90%. Curve 3: pool coverage 50%. Denitration: none. campaign was used as the calcining/melting pot. The spent ruthenium filter was thus incorporated into the glass (this is illustrated in Fig.l 3). A secondary ruthenium filter (Fe203) was operated in another pot. Further offgas cleanup was performed with a condenser, two scrubbers and HEPA filters. Table XIII contains data on ruthenium volatilization and retention in the Fingal process. With a high offgas temperature, the ruthenium loss to the offgas (including the part trapped by the ruthenium filters) was some 40%; with a low offgas temperature it was lower by about a factor of 2. Most of the volatilized ruthenium was retained by the primary ruthenium filter. The decontamination factors across pot and ruthenium filters ranged from about 104 to 106 for ruthenium and from about 107 to 1010 for caesium (see Table XIV). The inactive Harvest plant, a scale-up of the Fingal plant, started operation in 1975 [58]. The offgas treatment system of the inactive Harvest plant is shown in Fig. 14. It is similar to that of the Fingal plant except for the ruthenium filters, which have not been incorporated in the Harvest plant. Loss of ruthenium to the offgas of the Harvest plant has averaged 40% with slurry feed and 10% with crizzle feed. Loss of caesium was about 1% with crizzle feed. Decontamination factors across the condenser and the scrubbers of the Harvest plant were 50 to 100 for each unit for 'soluble' ruthenium and 5 to 40 for 'insoluble' ruthenium. The Piver plant operated from 1963 to 1973 for vitrification of HLLW from natural U fuel reprocessing [32, 59], The offgas treatment system is identical

44 OPERATING TIME (h)

FIG.22. Ru loss to the offgas system (without deposition in the offgas pipe) of a liquid-fed ceramic melter (FRG) as a function of operating time and denitration [66], Pool coverage: 70 -90%. with that of the AVM plant (see Fig. 12) except for the first scrubber, which was dispensed with in the Piver plant. A ruthenium trap consisting of Fe203-based material was tested when installed between the condenser and the acid-recovery column. The losses of ruthenium and caesium to the offgas as a function of time during the second Piver campaign are shown in Fig. 15. The maximum losses of ruthenium and caesium were 15% and 0.1%, respectively (the contribution from the glass-pouring process was negligibly small). A typical distribution of these elements in the liquors of the offgas treatment system is given in Table XV; they were collected almost entirely in the liquor of the condenser. The DF for ruthenium across the ruthenium trap was estimated to have been 25. This low value was attributed to poorly controlled face velocity and temperature within the ruthenium trap. The overall ruthenium and caesium decontamination factors were on the order of 1010 and 1011, respectively. Figure 16 shows a complete ruthenium balance for a solidification plant of the Piver type. The waste immobilization plant under construction at Tarapur, India, will employ a semicontinuous pot-glass process to solidify high-level waste arisings from the fuel-reprocessing plant at that site [60, 61 ]. The offgas treatment system for the Waste Immobilization Plant, Tarapur, is shown in Fig. 17. Part of the ruthenium volatilized from the process pot during solidification is deposited in the vertical water-cooled offgas line and is periodically washed back to the process pot. This helps to avoid offgas-line choking and reduces the escape of volatilized ruthenium from the system. The offgases are condensed in a packed tube condenser. Both condensate and non-condensates are recycled to the evaporator. Volatilization of ruthenium from the evaporator is controlled by maintaining the acidity level with the help of recycling fractionator condensate, which is poor in nitric acid. The closed loop and acidity control,

45 TABLE XVII. DISTRIBUTION OF RUTHENIUM AND CAESIUM IN THE OFFGAS TREATMENT SYSTEM OF A LIQUID-FED CERAMIC MELTER (FRG) [65]

Distribution (%) Component3 Ru Cs

Offgas pipeb 4.3 0.3 Dust scrubber 12.1 2.5 Condenser 0.8 0.6

NOx scrubber 0.1 0.5 Total 17.3 3.9

a No Ru filter used. b Connecting melter and dust scrubber.

Operating time: 100 h. Pool coverage: 70-90%. Denitration: none. described above, minimizes the loss of ruthenium from the system. This is followed by the conventional offgas treatment cycle of heating, filtration and scrubbing. The process incorporates an optional ruthenium trap with suitable adsorbents in front of the caustic scrubber. To minimize the volatility of ruthenium, the effect of adding the reducing agents, sodium thiosulphate, sodium sulphide, and sodium hypophosphite, to selected melt formations was studied [31]. A general decrease in volatilization loss with an increase in the ratio of reducing agent to ruthenium was observed, and more than 99.9% of the ruthenium could be retained using a high ratio of reducing agent. However, the product quality is adversely affected. Of the three reducing agents, sodium sulphide was found to suppress ruthenium volatility best.

6.5. LIQUID-FED CERAMIC MELTER This section contains results of investigations with liquid-fed ceramic melters (LFCM) performed in the USSR, the USA and the Federal Republic of Germany. The offgas treatment system used with the Soviet LFCM is shown in Fig. 18. The main components are a bubbler-condenser, two particulate filters, a ruthenium adsorber (pyrolusite) and a NOx adsorber.

46 TABLE XVIII. VOLATILIZATION AND RETENTION OF RUTHENIUM IN VARIOUS HLLW SOLIDIFICATION PROCESSES (ROUNDED AVERAGE VALUES)

Solidification Plant/ Country HLLW Ru loss to the DF of Ru Total Ru DF process project offgas (%)a filter if used (feed-stack)

Fluidized-bed WCFb USA Actual non-LWR 50c 102 —103 d 103-106 calcination

Spray calcination WSEP USA Sim. LWR 60e Not used 1010 HLWIP USA Sim. LWR lO^-lO"1 Not used n.d.

Rotary-kiln AVM France Actual non-LWR 30 Not used >10* • calcination

Pot calcination . WSEP USA Sim. LWR 20 Not used 1010 Fingal UK Actual non-LWR 30 n.d. n.d. Harvest UK . Sim. non-LWR 40f Not used n.d. Piver France Actual non-LWR 15 25 1010

- India 20 n.d. n.d.

Liquid-fed _ USSR Sim. LWR 80 n.d. n.d. ceramic melter 1 - USA Sim. rion-LWR 10" Not used n.d. • - FRG Sim. LWR 20 n.d. n.d. a Including gaseous and particulate forms; without addition of reductants. For in-can melting runs 1%. b No vitrification. f With slurry feed; with crizzle feed about c With indirect heating; with in-bed combustion lower by a factor of about 10. n.d. = no data available; sim. = simulated. d With indirect heating; with in-bed combustion about 10. Data on the loss of ruthenium and caesium to the offgas, obtained with simulated commercial HLLW, are given in Table XVI. The ruthenium loss of about 80% can be reduced by a factor of 20 by the addition of molasses up to a con- centration of 150 grams per litre. The caesium loss can also be reduced in this way. Data on the behaviour of ruthenium and caesium within the offgas cleanup system are not known. The offgas treatment system used for the US LFCM is shown in Fig. 19. Its components are, essentially, HEPA filters, two scrubbers and a condenser between the scrubbers. The losses of ruthenium and caesium to the offgas were 0.2% and 10%, respectively, with simulated non-commercial HLLW. The low loss of ruthenium was attributed to the fact that the HLLW was neutral, but the high loss of caesium could not be accounted for. The losses of antimony and tellurium were 0.1% and 0.4%, respectively. The behaviour of the semivolatiles within the offgas cleanup system has not been indicated. The LFCM from the FRG, which is to be used in the Pamela plant [64], has an offgas treatment system as shown in Fig.20. The main components are a scrubber with a demister, a condenser, two further scrubbers and HEPA filters. Two ruthenium filters of silica gel have also been provided, as shown in Fig.20, but they have not yet been tested. Results obtained with simulated commercial HLLW are presented in and 22 and in Table XVII. From Figs 21 and 22 it can be seen that coverage of the pool with feed and denitration of feed strongly influence the ruthenium loss of the offgas. At a coverage of 70% to 90%, the ruthenium loss (without deposition in the offgas pipe) ranged from about 10% to 15% with undenitrated feed and from about 1% to 5% with denitrated feed. The loss of caesium was much lower under these conditions, as shown by the data in Table XVII. Most of the ruthenium and caesium was removed by the first scrubber. Average ruthenium decontamination factors of about 10 were indicated for the first scrubber and about 5 for the condenser.

6.6. SUMMARY The experience with HLLW solidification processes with respect to volatilization and retention of semivolatiles can be summarized as follows: (1) Without addition of reductants, volatilization of ruthenium has often been higher than 10%. (2) Feed-to-stack ruthenium decontamination factors of higher than 109 have been obtained even without ruthenium filters. Silica gel seems to have per- formed best in ruthenium filters with decontamination factors of about 102 to 103. (3) Volatilization of caesium has usually been lower than 10%.

48 (4) Feed-to-stack caesium decontamination factors of higher than 109 have been observed. (5) There are nearly no data on volatilization and retention of other semivolatiles. Some data on volatilization and retention of ruthenium are listed in Table XVIII.

7. SAMPLING AND MONITORING

Measurements of the semivolatiles at different locations in the offgas cleanup system are important in assessing volatilization, efficiency of retention systems, and releases to the environment. The measurement of the semivolatiles has frequently been performed by taking samples of the liquors formed or used in offgas treatment components such as condensates and scrub solutions. Moreover, samples of the offgas have been drawn through a condenser and then through acidic or caustic scrubbers. By placing a HEPA filter upstream of this system it has been possible to distinguish between particulate and gaseous forms. Such an arrangement is shown in Fig.23. It has also been proposed to differentiate between gaseous and particulate forms of ruthenium by using a series of acidic scrubbers followed by a series of caustic scrubbers [41 ] (gaseous ruthenium would be trapped in the acidic scrubbers; particulate ruthenium in the caustic scrubbers).

FIG.23. Ru sampling system [49],

49 In future it might be necessary to monitor ruthenium routinely in the offgases of HLLW solidification plants and reprocessing plants [61]. In this case a system consisting of a HEPA filter followed by a ruthenium adsorbent might be more convenient. Such a system, with polyethylene as the ruthenium adsorber, has already been successfully employed [68],

8. CONCLUSIONS

Ruthenium is the most significant semivolatile contaminant in gaseous effluents at nuclear facilities. In high-level liquid waste solidification plants it may be significant both for its impact within the plants and for its influence on the environment because of its high volatilization potential, high mass and activity in the waste. It may cause plugging of pipes and create high radiation fields within the plants. A feed-to-stack decontamination factor on the order of 108 may be required to reduce the environmental burden to an acceptable level. In present light-water-reactor fuel reprocessing plants, ruthenium may be significant in terms of the in-plant impact only. In future, however, it may cause problems in reprocessing plants for fast-breeder reactor fuel. In other nuclear facilities the control of volatilized ruthenium is insignificant under normal conditions. Volatilization of ruthenium can be reduced by various means, in particular by adding reductants. Volatilized ruthenium can be retained by adsorbents such as silica gel and ferric-oxide-based materials. Decontamination factors on the order of 103 have been obtained with these adsorbents under optimum conditions. Volatilized ruthenium can also be removed by other equipment such as condensers and scrubbers. Experience with high-level liquid waste solidification plants has shown that, in general, ruthenium volatilization is on the order of 10% or more unless special treatment is undertaken. There is little experience with ruthenium adsorbers in plants. Silica gel seems to have performed best, with ruthenium decontamination factors of about 102 to 103. However, feed-to-stack ruthenium decontamination factors of 109 or more have been obtained even without ruthenium adsorbers. Other semivolatiles are relatively insignificant under normal conditions because of a low level of volatilization potential or mass or activity in the inventory. Moreover, owing to particulate formation, they can be easily removed without specific equipment.

50 REFERENCES

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51 McELROY, J.L.,etal., Waste Solidification Program Summary Report, Vol.11, Evaluation of WSEP High Level Waste Solidification Processes, Battelle Pacific Northwest Labs Rep. BNWL-1667 (1972). ORTINS de BETTENCOURT, A., JOUAN, A., VolatUit6 du ruthenium au cours des operations de vitrification des produits de fission: II - Fixation sur un tube d'acier, decomposition du peroxyde, CEA Rep. CEA-R-3663(2) (1969) [English translation: AEC-tr-7575]. HOLDOWAY, M.J., The Volatilisation and Deposition of Ruthenium Dioxide in Relation to the FINGAL Process, UKAE Atomic Energy Res. Estab., Harwell, Rep. AERE-R6418 (1971). Idaho Chemical Programs Annual Technical Report, Fiscal Year 1973 (BOWER, J.R.,Ed.), Allied Chemical Corp., Idaho Falls, Rep. ICP-1047 (1974). MAAS, E.T., LONGO, J.M., "Confinement of volatilized ruthenium oxides", Scientific Basis for Nuclear Waste Management (McCARTHY, G.J., Ed.), Vol.1, Plenum Press, New York (1979) 487. MAAS, E.T., LONGO, J.M., Confinement of ruthenium oxides volatilized during nuclear fuels reprocessing, Nucl. Technol. 47 (1980) 451. NAKHUTIN, I.E., POLJAKOV, A.S., et al., USSR Patent N. 565430. Bui. Isobret. (1978) N12. NAKHUTIN, I.E., POLJAKOV, A.S., et al., Catalytic reduction of ruthenium tetroxide, At. Ehnerg. 45 2(1978). KLEIN, M., et al., "Filtration and capture of semi-volatile nuclides", Management of Gaseous Wastes from Nuclear Facilities (Proc. Symp. Vienna, 1980), IAEA, Vienna (1980)91. KEPAK, F., et al., "Removal of nitrogen oxides, volatile radionuclides and aerosols formed in laboratory-scale denitration, calcination and solidification of simulated high- level wastes", ibid., 101.

NIKOLIC, R., VUJISIC, L., "Adsorption of gaseous Ru04 by various sorbents", Proc. KTG/DAtF Jahrestagung Kerntechnik, Dusseldorf, March 1981, p.323. ELLIOTT, M.N., et al., Fixation of Radioactive Waste in Glass, UK Atomic Energy Res. Estab., Harwell, Rep. AERE-R4098 (1962) Part 3. NEWBY, B.J., BARNES, V.H., Volatile Ruthenium Removal from Calciner Off-gas Using Solid Sorbents, Allied Chemical Corp., Idaho Falls, Rep. ICP-1078 (1975). RASTOGI, R.C., et al., Investigation of Materials and Methods for Fixation of Low and Medium Level Radioactive Waste in Stable Solid Media, Final Report, Bhabha Atomic Research Centre, Bombay, BARC-400 (1969) 78-128. JOUAN, A., et al., "Traitement des effluents gazeux dans les installations de vitrification des produits de fission", Proc. CEC Seminar on Radioactive Effluents from Nuclear Fuel Reprocessing Plants, Karlsruhe, 1977, p.621. POSTMA, A.K., HILLIARD, R.K., Nucleation and Capture of Condensible Airborne Contaminants in an Aqueous Scrubbing System, Hanford Engineering Development Lab., Richland, Rep. HEDL-TME 78-82 (1978). MAY, C.E., et al., Ruthenium Behavior in a Nitric Acid Scrubber, USAEC Idaho Operations Office Rep. IDO-14448 (1958). WILDS, G.W., "Volatilization from borosilicate glass melts of simulated Savannah River Plant waste", Proc. 15th DOE Nuclear Air Cleaning Conference, Boston, 1978, Vol.1, CONF-780 819 (1980) 95. LORENZ, R.A., et al., Fission Product Release from Highly Irradiated LWR Fuel, Rep. NUREG/CR-0722 (1980). GHATTAS, N., et al., Some studies of nuclides losses: I - Vitrification of high activity waste, J. Appl. Chem. Biotechnol. 28 (1978) 523. GHATTAS, N., et al., Some studies of nuclides losses: II - Cold finger, J. Appl. Chem. Biotechnol. 28 (1978) 847. GODBEE, H.W., KIBBEY, A.H., Source Terms for Radioactive Gaseous Effluents from a Model High-Level Waste Solidification Facility, Oak Ridge Natl. Lab. Rep. ORNL/NUREG/TM-67 (1976). MENDEL, J.E., et al., Annual Report on the Characteristics of High-Level Waste Glasses, Battelle Pacific Northwest Labs Rep. BNWL-2252 (1977). RIMSHAW, S.J., et al., Volatility of Ruthenium-106, Technetium-99 and Iodine-129, and the Evolution of Nitrogen Oxide Compounds during the Calcination of High-Level, Radioactive Nitric Acid Waste, Oak Ridge Natl. Lab. Rep. ORNL-5562 (1980). USERDA, Alternatives for Managing Wastes from Reactors and Post-Fission Operations in the LWR Fuel Cycle, Rep. ERDA-76-43, Vol.2 (1976). INTERNATIONAL ATOMIC ENERGY AGENCY, Techniques for the Solidification of High-Level Wastes, Technical Reports Series No. 176, IAEA, Vienna (1977). HANSON, M.S., KASER, J.D., "Design of off-gas cleaning systems for high-level waste vitrification", Proc. 14th USERDA Air Cleaning Conference, Sun Valley, 1976, Vol.1, CONF-760822 (1976) 102. THEODORE, L., BUONICORE, A.J., Industrial Air Pollution Control Equipment for Particulates, CRC Press, Cleveland (1976). BUONICORE, A.J., THEODORE, L., Industrial Control Equipment for Gaseous Pollutants, CRC Press, Cleveland (1975). LAKEY, L.T., WHEELER, B.R., "Solidification of high-level radioactive wastes at the Idaho Chemical Processing Plant", Management of Radioactive Wastes from Fuel Reprocessing (Proc. Symp. Paris, 1972) OECD-NEA, Paris (1973) 731. CHRISTIAN, J.D., RHODES, D.W., Ruthenium Containment during Fluid-Bed Calcina- tion of High-level Waste from Commercial Nuclear Fuel Reprocessing Plants, Allied Chemical Corp., Idaho Falls, Rep. ICP-1091 (1977). SCHINDLER, R.E., et al., Development of a Fluidized-Bed Calciner and Post-Treatment Processes for Solidification of Commercial Fuel-Reprocessing Liquid Wastes, Allied Chemical Corp., Idaho Falls, Rep. ICP-1136 (1977). NEWBY, B.J., RHODES, D.W., Ruthenium Behavior during Calcination, Allied Chemical Corp., Idaho Falls, Rep. ICP-1164 (1978). BLASEWITZ, A.G., RICHARDSON, G.L., "The high-level waste solidification demonstration program", Management of Radioactive Wastes from Fuel Reprocessing (Proc. Symp. Paris, 1972), OECD-NEA, Paris (1973) 615. WHEELWRIGHT, E.J., et al., Technical Summary, Nuclear Waste Vitrification Project, Battelle Pacific Northwest Labs Rep. PNL-3038 (1979). HANSON, M.S., Spray Calcination/In-Can Melting: Effluent Characterization and Treatment, Battelle Pacific Northwest Labs Rep. PNL-3109 (1980). HANSON, M.S., et al., "Behaviour of selected contaminants in spray calciner/in-can melter waste vitrification offgas", Management of Gaseous Wastes from Nuclear Facilities (Proc. Symp. Vienna, 1980) IAEA, Vienna (1980) 371. CHOTIN, M.M., et al., "Operational experience of the first industrial HLW vitrification plant", Proc. ACS/USDOE Int. Symp. Ceramics in Nuclear Waste Management, Cincinnati, 1979, CONF. 790420 (1979) 73. PAPAULT, C., et al., "Vitrification of fission product solutions at Marcoule", Trans. ENS European Nuclear Conf., Hamburg, 1979, p. 528, TANSA031 1-666 (1979) (Summary of the paper). [57] GROVER, J.R., et al., "The FINGAL process", Proc. USAEC Symp. Solidification and Long-Term Storage of Highly Radioactive Wastes, Richland, 1966, CONF-660208 (1966) 427. [58] MORRIS, J.B., CHIDLEY, B.E., "Preliminary experience with the new Harwell inactive vitrification pilot plant", Management of Radioactive Wastes from the Nuclear Fuel Cycle (Proc. Symp. Vienna, 1976) Vol.1, IAEA, Vienna (1976) 241. [59] BONNIAUD, R., et al., "Experience acquise en France dans le traitement par vitrification des solutions concentrees de produits de fission", Management of Radioactive Wastes from Fuel Reprocessing (Proc. Symp. Paris, 1972), OECD-NEA, Paris (1973) 555. [60] SUNDER RAJAN, N.S., et al., "Waste immobilisation plant at Tarapur - a survey of process and design features", ibid., 683. [61 ] SUNDER RAJAN, N.S., et al., "Long term planning for management of aqueous wastes from fuel reprocessing", Management of Radioactive Wastes from the Nuclear Fuel Cycle (Proc. Symp. Vienna,1976) Vol.1, IAEA, Vienna (1976) 15. [62] KONSTANTINOVICH, A.A., et al., "Features of a process for vitrifying radioactive waste without precalculation and radionuclide behaviour in the process", ibid., p.385 (in Russian). [63] BROUNS, R.A., et al., Immobilization of High-Level Defense Waste in a Slurry-Fed Electric Glass Melter, Battelle Pacific Northwest Labs Rep. PNL-3372 (1980). [64] HEIMERL, W., "Solidification of HLW solutions with the PAMELA process", Proc. ACS/USDOE Int. Symp. on Ceramics in Nuclear Waste Management, Cincinnati,1979, CONF. 790 420 (1979) 97. [65] WEISENBURGER, S., SEIFFERT, H., "Off-gas cleanup system designed for HLLW- vitrification in a liquid-fed ceramic waste melter", Management of Gaseous Wastes from Nuclear Facilities (Proc. Symp. Vienna, 1980),IAEA, Vienna (1980) 531. [66] WEISENBURGER, S., WEISS, K:, "Ruthenium volatility behavior during HLLW vitrification in a liquid-fed ceramic melter", Scientific Basis for Nuclear Waste Manage- ment (NORTHRUP, C.J.M., Ed.), Vol.2, Plenum Press, New York (1980) 901. [67] HOWER, R.B., et al., Radioactive Airborne Effluent Measurement and Monitoring Survey of Reprocessing and Waste Treatment Facilities, USAEC Chicago Operations Office Rep. COO-3049-9 (1977). , [68] JENSON, D.K., Sampling calciner off-gas for radioactive ruthenium using a polyethylene absorber, Health Phys. 12 (1966) 923.

54 LIST OF PARTICIPANTS

Technical Committee Meeting on Retention of Semivolatile Radionuclides at Nuclear Facilities Vienna, 27-31 October 1980

BELGIUM

Klein, M. (Chairman) Departement de Chimie, Centre d'etudes nucleaires Mol, Boeretang 200, B-2400 Mol

CSSR

Urbanek, V. Ministry of Fuel and Energy, Prague

FRANCE

Vigla, D. Departement de protection, Service de protection technique, Centre d'etudes nucleaires Fontenay-aux-Roses, B.P. 6, F-92260 Fontenay-aux-Roses

Leudet, A. Departement de genie radioactif, Service des etudes de procedes, Centre d'etudes nucleaires Fontenay-aux-Roses, B.P. 6, F-92260 Fontenay-aux-Roses

Roux, J.P. Departement de genie radioactif, Service de l'atelier pilote, Etablissement de la Vallee du Rhone, B.P. 171, F-30200 Bagnols-sur-Ceze

55 GERMANY, FEDERAL REPUBLIC OF

Deuber, H. Laboratorium fur Aerosol und Filtertechnik, Kernforschungszentrum Karlsruhe, Postfach 3640, D-7500 Karlsruhe 1

UNITED KINGDOM

Cains, P.W. Chemical Technology Division, UK Atomic Energy Authority, Harwell, Didcot, Oxon. 0X11 ORA

IAEA SECRETARIAT

Tsyplenkov, V. Division of Nuclear Fuel Cycle Scientific Secretary

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ARGENTINA Comisidn Nacional de Energi'a Atomica, Avenida'del Libertador 8250, RA-1429 Buenos Aires AUSTRALIA Hunter Publications, 58 A Gipps Street, Collingwood, Victoria 3066 BELGIUM Service Courrier UNESCO, 202, Avenue du Roi, B-1060 Brussels CZECHOSLOVAKIA S.N.T.L., Spalena 51, CS-113 02 Prague 1 Alfa, Publishers, Hurbanovo namestie 6, CS-893 31 Bratislava FRANCE Office International de Documentation et Librairie, 48, rue Gay-Lussac, F-75240 Paris Cedex 05 HUNGARY Kultura, Hungarian Foreign Trading Company P.O. Box 149, H-1389 Budapest 62 INDIA Oxford Book and Stationery Co., 17, Park Street, Calcutta-700 016 Oxford Book and Stationery Co., Scindia House, New Delhi-110 001 ISRAEL Heiliger and Co., Ltd., Scientific and Medical Books, 3, Nathan Strauss Street, Jerusalem 94227 ITALY Libreria Scientifica, Dott. Lucio de Biasio "aeiou". Via Meravigli 16, 1-20123 Milan JAPAN Maruzen Company, Ltd., P.O. Box 5050, 100-31 Tokyo International NETHERLANDS Martinus Nijhoff B.V., Booksellers, Lange Voorhout 9-11, P.O. Box 269, NL-2501 The Hague PAKISTAN Mirza Book Agency, 65, Shahrah Quaid-e-Azam, P.O. Box 729, Lahore 3 POLAND Ars Polona-Ruch, Centrala Handlu Zagranicznego, Krakowskie Przedmiescie 7, PL-00-068 Warsaw ROMANIA llexim, P.O. Box 136-137, Bucarest SOUTH AFRICA Van Schaik's Bookstore (Pty) Ltd., Libri Building, Church Street, P.O. Box 724, Pretoria 0001 SPAIN Diaz de Santos, Lagasca 95, Madrid-6 Diaz de Santos, Balmes 417, Barcelona-6 SWEDEN AB C.E. Fritzes Kungl. Hovbokhandel, Fredsgatan 2, P.O. Box 16356, S-103 27 Stockholm UNITED KINGDOM Her Majesty's Stationery Office, Agency Section PDIB, P.O.Box 569, London SE1 9NH U.S.S.R. Mezhdunarodnaya Kniga, Smolenskaya-Sennaya 32-34, Moscow G-200 YUGOSLAVIA Jugoslovenska Knjiga, Terazije 27, P.O. Box 36, YU-11001 Belgrade

Orders from countries where sales agents have not yet been appointed and requests for information should be addressed directly to: # ^ Division of Publications $ International Atomic Energy Agency Wagramerstrasse 5, P.O. Box 100, A-1400 Vienna, Austria I

INTERNATIONAL SUBJECT : II ATOMIC ENERGY AGENCY Nuclear Safety and Environmental Protection/Waste Management VIENNA, 1982 PRICE: Austrian Schillings 130,-