NUREG/CR-5732 

ORNL/TM-11861

Iodine Chemical Forms in

LWR Severe Accidents

Final Report

Prepared by 

E. C. Beahm, C. F. Weber, T. S. Kress, G. W. Parker 

Oak Ridge National Laboratory 

Prepared for 

U.S. Nuclear Regulatory Commission
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NUREG/CR-5732 

ORNIJTM-11861 

R3

Jo dine Chemical Forms in

Iodine Chemical Forms in 

LWR Severe Accidents 

Final Report

Manuscript Completed: January 1992 

Date Published: April 1992 

Prepared by 

E. C. Beahm, C. F. Weber, T. S. Kress, G. W. Parker 

Oak Ridge National Laboratory 

Operated by Martin Marietta Energy Systems, Inc. 

Oak Ridge National Laboratory 

Oak Ridge, TN 37831-6285 

Prepared for 

Division of Systems Research 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555 

NRC FIN B0854 

Under Contract No. DE-ACOS-84OR21400
Abstract

Calculated data from seven severe accident sequences 

in light water reactor plants were used to assess the 

chemical forms of iodine in containment. In most of 

the calculations for the seven sequences, iodine 

entering containment from the reactor coolant system 

was almost entirely in the form of CsI with very small 

contributions of I or HI. The largest fraction of 

iodine in forms other than CsI was a total of 3.2% as I 

plus HI. Within the containment, the Csl will deposit 

onto walls and other surfaces, as well as in water

pools, largely in the form of iodide (P). The 

radiation-induced conversion of F in water pools into 

12 is strongly dependent on pH. In systems where the 

pH was controlled above 7, little additional elemental 

iodine would be produced in the containment atmo

sphere. When the pH falls below 7, however, it may 

be assumed that it is not being controlled and large 

fractions of iodine as 12 within the containment 

atmosphere may be produced.

iii NUREG/CR-5732
Contents 

A bstract ............................................................................... iii 

Executive Sum m ary ...................................................................... ix 

A cknowledgm ents ....................................................................... xi 

1 Introduction ........................................................................ 1 

2 Chemical Forms of Iodine Entering Containment from the Reactor Coolant System .................. 3 

2.1 B ackground .................................................................... 3 

2.2 Data Manipulation and Calculational Techniques ........................................ 3 

2.2.1 Adaptation of Data from Source Term Code Package .............................. 3 

2.3 Iodine-Cesium-Steam-Hydrogen Reactions ............................................. 9 

2.3.1 Sam ple Calculations ....................................................... 9 

2.3.2 Overall Results of Calculations ............................................... 9 

2.4 Reaction of CsOH with Surfaces ................................................... 10 

2.4.1 Deposition of CsOH onto Structural Surfaces .................................. 10 

2.4.2 Other Reactions of CsOH .................................................. 10 

2.5 Revaporization of CsI from RCS Surfaces ............................................ 11 

2.5.1 Description of Revaporization Process ......................................... 11 

2.5.2 Assessment of Revaporization as a Source of HI ................................. 13 

2.6 Summary of Iodine Chemical Forms in the RCS ........................................ 13 

3 Iodine Behavior in Containment ....................................................... 15 

3.1 Categorization of Iodine Behavior in Terms of Time Intervals During an Accident 

Sequence ..................................................................... 15 

3.2 Importance of pH in Determining the Chemical Forms of Iodine in Water Pools ............... 15 

3.2.1 Materials That Determine pH in Accident Sequences ............................. 15 

3.2.2 Nitric Acid Formation and pH Control ........................................ 16 

3.3 Processes That Alter the Chemical Forms of Iodine in Containment ......................... 17 

3.3.1 R adiolysis .............................................................. 17 

3.3.1.1 Description of Calculated M odel ....................................... 17 

3.3.1.2 M ass M anipulations ................................................. 20 

3.3.1.3 Gas-Liquid Partitioning .............................................. 21 

3.3.1.4 Gas-Phase Reactions: Formation of Organic Iodides ........................ 21 

3.3.1.5 Overall Behavior ................................................... 22 

v NUREG/CR-5732
3.3.2 Results of Iodine Behavior in Containment ..................................... 

3.3.3 Evaporation to Dryness ....................................................

4 Technical Findings ................................ 

4.1 Perspective and Scope of Study .................. 

4.2 Assessment of Iodine Chemical Forms in the RCS .... 

4.3 Assessment of Iodine Chemical Forms in Containment. 

5 References ...................................... 

Appendixes

.... • ....... .......... •29 

...... ..................... .. .. 29 

... ..... ......... 29 

.. .... • . ......... . . ° ... . .. . .... •.... 29 

S. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 3 1

A Data from Accident Sequence Calculations ............................................. A-1 

B Kinetic and Equilibrium Calculations .................................................... B.1 

B.1 Kinetics of Cs-I-H2-H20 Reactions .................................................. B.3 

B.2 Equilibrium Calculations in the Cs-I-H2-H20 System .................................... B.5 

C Fitting of Radiolysis Data ............................................................ C.1 

D Fission Product Release Tables ....................................................... D.1 

E Fractional Release Tables ............................................................ E.1 

Figures 

2.1 Surry TMLB': temperatures in volumes above core ........................................ 4 

2.2 Flow chart of RCS control volumes and variables. Normal type = known data from STCP 

calculations; italics = quantities to be calculated .......................................... 6 

2.3 Surry TMLB': principal species concentrations in Volume 1 above core ........................ 7 

2.4 Mean residence times in volumes above core for Surry TMLB' . ............................. 8 

3.1 Radiolytic conversion of I to 12 [data from C. C. Lin, J. Inorg. Nucl. Chem. 42, 1101 (1980)] ........ 18 

4.1 Additional atmospheric elemental iodine released ........................................ 30 

C.1 Data fitting for radiolytic conversion of I to 12 (Data from U.S. Nuclear Regulatory Commission, 

Regulation Guide 1.4, "Assumptions Used for Evaluating the Potential Radiological 

Consequences of a Loss-of-Coolant Accident for Pressurized Water Reactors") .................. C.4

NUREG/CR-5732

23

vi
Tables

1.1 LW R accident sequences evaluated .................................................... 2 

2.1 FACT system output of Grand Gulf TQUV example at 8780 s ............................... 9 

2.2 Simulated core-melt tests conducted in the ORNL 1-kg facility (Boric acid addition to water 

injected below the bundle) .......................................................... 11 

2.3 Composition of 10-kg fuel bundle .................................................... 12 

2.4 Estimated upper bound on the fraction of iodine as HI due to revaporization of CsI .............. 14 

3.1 Materials that affect pH in containment water pools ...................................... 16 

3.2 Concentrations of H' and NO 3- in water due to irradiation ................................. 17 

3.3 Effects of irradiation dose on pH in trisodium phosphate solution ............................ 17 

3.4 Nuclide groupings and group-specific energy deposition rates ................................ 20 

3.5 Data for equilibrium analysis of example sequences ....................................... 24 

3.6 Distribution of iodine species for pH controlled above 7 ................................... 26 

3.7 Distribution of iodine species for uncontrolled pH ........................................ 27 

3.8 Iodine volatility of 1 x 104 mol/L CsI solutions during evaporation to dryness ................... 28 

A.1 Grand Gulf TC-MERGE output data from MARCH2 ................................... A.3 

A.2 Grand Gulf TC-MARCH2 output for input to TRAP-MELT .............................. A.5 

A.3 Grand Gulf TC-MARCH2 output for input to TRAP-MELT .............................. A.6 

A-4 Grand Gulf TQUV-MARCH2 output from MARCH2 ................................... A.7 

A.5 Grand Gulf TQUV-MARCH2 output for input to TRAP-MELT ........................... A.9 

A.6 Grand Gulf TQUV-MARCH2 output for input to TRAP-MELT ........................... A.10 

A.7 Peach Bottom AE-MERGE output for input to MARCH2 ............................... A-10 

A.8 Peach Bottom AE-MARCH2 output for input to TRAP-MELT ............................ A11 

A.9 Peach Bottom AE-MARCH2 output for input to TRAP-MELT ............................ A-12 

A.10 Peach Bottom TC2-MERGE output from MARCH2 .................................... A.13 

A.11 Peach Bottom TC-MARCH2 output for input to TRAP-MELT ............................ A.15 

A.12 Peach Bottom TC-MARCH2 output for input to TRAP-MELT ............................ A.16 

A.13 Sequoyah TB-MERGE output from MARCH2 ........................................ A.17 

A.14 Sequoyah TB-MARCH2 output for input to TRAP-MELT ............................... A.18 

A-15 Sequoyah TB--MARCH2 output for input to TRAP-MELT ............................... A.19 

A.16 Surry TMLB'-MERGE output from MARCH2 ................................. A.20 

A-17 Surry TMLB'-MARCH2 output for input to TRAP-MELT ............................... A-21 

A.18 Surry TMLB'-MARCH2 output for input to TRAP-MELT ............................... A.21 

A.19 Surry AB-MARCH2 output for input to TRAP-MELT .................................. A-22 

A-20 Surry AB-MARCH2 output for input to TRAP-MELT .................................. A-22 

A.21 Surry AB-MARCH2 output for input to TRAP-MELT .................................. A-23 

A.22 Grand Gulf-Compartment volumes for sequences TC and TQUV ........................... A-23 

A.23 Peach Bottom--Compartment volumes for sequences TC and AE ........................... A.24 

A.24 Sequoyah--Compartment volumes for sequence TBA ..................................... A.24 

A.25 Surry-Compartment volumes for sequences AB and TMLB ............................... A.24 

B.1 Reaction rate constants ............................................................ B.4 

B.2 Standard free energy of reaction 500 to 1200 K (441 to 17010F) written as AG = a + bT, 

exothermic reaction expressed left to right (Energy in joules) .......... . ................... B.5 

C.1 Radiolysis data for formation of I, .................................................... C.3 

D.1 Fission product inventories for selected plants .......................................... D.3 

D.2 Bounding values for fractions of core inventory released into containment ..................... D.4 

E. 1 Grand Gulf - fractional releases and energy deposition rates ................................ E.3 

E.2 Peach Bottom - fractional releases and energy deposition rates ............................. E.4 

E.3 Sequoyah - fractional releases and energy deposition rates ................................. E.5 

E.4 Surry TMLB' - fractional releases and energy deposition rates .............................. E.6

NUREG/CR-5732
Executive Summary

The analyses in this study were based on quantitative 

(calculated) results of seven severe accident 

sequences for light water reactor (LWR) nuclear 

power plants. These sequences represent a wide 

range of conditions that are significant risks. Both 

high- and low-pressure sequences were chosen for 

three principal plant types; a single sequence was 

considered for the PWR ice condenser. Each 

sequence was evaluated by the Source Term Code 

Package (STCP), and the thermal hydraulics has been 

documented in previous NRC reports.12 The issue 

that has been addressed is the chemical forms of 

iodine in the reactor coolant system (RCS) and in 

containment - not the ultimate disposition of these 

chemical forms. 

In an LWR accident sequence, fission products 

released from the core will undergo changes in 

temperature and concentration as they pass through 

regions of the RCS. A chemical kinetic model used 

20 reactions to determine the control volume where 

an equilibrium of the iodine, cesium, hydrogen, and 

steam species becomes "frozen." This means that the 

temperatures and concentrations of species in 

subsequent control volumes are not sufficient to 

reach an equilibrium in the mean residence time 

available. The "frozen" equilibrium is the species 

distribution entering containment. Separate 

equilibrium calculations were performed, using the 

FACT system,3 to obtain the distribution of iodine 

species. The FACT system was chosen in this study 

because it can be used by anyone who wishes to 

examine the calculations and its data base contains 

only assessed data. 

In six of the seven calculations, iodine entering the 

containment from the RCS was almost entirely in the 

form of CsI; the contributions of I or HI were 

<0.1% of the overall percentage of iodine. 

During the second half of the Surry AB sequence, 

there is a period during which temperatures in the 

core region are predicted to be in excess of 2000 K 

(3141"F) and subsequent volumes of the upper grid 

plates and guide tubes are at temperatures of only 

-500 K (441"F). Under such conditions, the 

equilibrium compositions in the core region would 

be "frozen" by the rapid decrease in temperature.

For this sequence, the overall iodine distribution was 

2.8% as I, 0.4% as HI, with the remainder as CsI. 

Thus, a total of 3.2% as I plus HI was the largest 

fraction of iodine in a form other than CsI calculated 

to enter containment from the RCS in this study. 

Once within the containment, CsI is expected to 

deposit onto interior surfaces and dissolve in water 

pools, forming iodide (I) in solution. The 

dissolution of HI and HNO3 (produced by irradiation 

of N2 in the atmosphere) and the hydrolysis of 12 

tend to acidify films and pools of water. 

Iodine behavior in containment was evaluated during 

the early stage of an accident sequence, up to 

-1200 min. If pH is controlled in containment water 

pools so that it stays above 7, a reasonable value for 

the fraction of I- converted to 12 is 3 x 10'. This 

yields a small production of volatiles for PWRs, but 

virtually none for BWRs. Thus, if pH is maintained 

at 7 or above, only a small additional amount of I2 is 

indicated to enter the gas phase in PWR systems. 

If the pH drops below 7 (assumed uncontrolled pH), 

a larger fraction of aqueous I will be converted to 12. 

Evaporation of this volatile species so as to maintain 

equilibrium partitioning will result in greater 

atmospheric 12, which, in turn, will yield higher 

organic iodide concentrations. As expected, the 

levels of airborne iodine volatiles are much higher 

than in the pH-controlled case, indicating almost 

complete conversion for PWRs. 

The gaseous I2 fraction is considerably higher in 

PWRs than in BWRs because of the large water 

volumes in the latter, which both lower the dose rate 

and retain greater quantities of dissolved 12. 

In addition, organic iodide is present in PWRs at 

about 0.5% of core inventory; in BWRs, this value is 

closer to 0.1%. The 12 generated by the radiolytic 

conversion of I in containment pools dominates the 

amount released directly from the RCS as 12. In 

addition, due to the equilibrium assumption, the 

presence of some 12 already airborne will result in 

less evaporation of 12 formed radiolytically. Hence, 

for the case of uncontrolled pH, the cumulative total

ix N-JREG/CR-5732
is well represented by the equilibrium amount 

formed within containment. 

The production of 12 in containment will be directly 

related to the pH levels of the water pools. There is 

a significant difference in the amount of 12 between 

the uncontrolled-pH and the controlled-pH cases. A

major uncertainty in fixing the production of volatile 

iodine chemical forms in containment involves the 

extent of evaporation to dryness. At a minimum, 2 

to 20% of the iodine in water pools that have 

evaporated would have been converted to a volatile 

form, most likely as I.

NUREG/CR-5732 X1
Acknowledgments

The authors acknowledge the aid of Michael Brown, 

of Thurso, Scotland, who wrote the routine used with 

the FACSIMILE code and performed scoping 

calculations for this study. We also wish to express

gratitude to Betty Drake for preparing the 

manuscript. In addition, we appreciate the assistance 

of Vladimir Kogan of Battelle Columbus 

Laboratories in obtaining data on accident sequences.

xi NUREG/CR-5732
1 Introduction

In the past 10 years, studies of iodine behavior in 

containment under accident conditions have identified 

a variety of chemical and physical interactions that will 

determine the forms of iodine and environments 

where reactions may occur."7 In general terms, the 

ability to predict iodine behavior is now more limited 

by knowledge of the environment in which the iodine 

is present than by deficiencies in understanding what 

iodine will do in a given set of environments. Thus, 

with only a few exceptions, the prediction of chemical 

form or magnitude of iodine released from 

containment is limited by the lack of information on 

the materials and environments involved in iodine 

reactions in the containment, as well as by uncertainty 

in the chemical forms and amounts of iodine that 

enter the containment. For example, it has been 

found that boric acid and borates are important in 

determining the chemical forms of iodine in the RCS 

and in the containment. However, the location, 

amounts, and type of borate are not well defined in 

severe accident sequences. A number of tests were 

performed to examine organic iodide formation with a 

variety of materials. However, it is not known what 

organic material will be present and in what form it 

"will exist for a given reactor plant and accident 

sequence. 

Some information on iodine reactions has not yet 

been put into models and implemented in computer 

codes. The disparity between information on reactions 

and models for a computer code is best illustrated by 

the effect of water radiolysis on iodine chemical forms. 

Experimental data show that radiolysis can control the 

chemical forms of iodine in water. Models were 

developed to calculate water radiation dose rates and 

pH in severe accident sequences. Modeling of iodine 

radiolysis at a pH and dose rate in terms of individual 

reaction rate constants has proven to be extremely 

difficult because it requires expressions for 

(1) radiolysis of water, (2) iodine hydrolysis, and 

(3) the interaction of iodine species with water 

radiolysis products. 

In summary, uncertainties in iodine chemical forms in 

containment stem principally from uncertainties in the

(1) chemical forms and amounts of iodine that enter 

containment, (2) conditions and materials in which 

iodine interacts, and (3) lag between obtaining data 

and implementing it in computer models and codes. 

Regulatory Guides 1.38 and 1.49 state the following: 

(1) Fifty percent of the maximum iodine inventory of 

the reactor core is released to the primary reactor 

containment; 25% is available for leakage. 

(2) Of this 25%, 91% is in the form of elemental 

iodine, 5% is in the form of particulate iodine, 

and 4% is in the form of organic iodide. 

Iodine is assumed to enter containment in the forms 

and amounts stated above with neither physical nor 

chemical changes occurring in containment. However, 

present knowledge may not support this distribution of 

iodine forms and the static state throughout the 

duration of an accident. 

It is anticipated that a more "realistic" representation 

of the chemical speciation of fission product iodine 

would likely have the following characteristics: 

(1) an initial release of some combination of 

particulate iodine (CsI) and gaseous iodine (HI) 

or (I), with the largest proportion being 

particulates 

(2) a continuous re-release of molecular iodine that 

would arise from "revolatilization" from water 

repositories and would include some small 

complement of organic iodine 

Table 1.1 lists the seven calculated LWR severe 

accident sequences considered in this analysis; these 

sequences involve a wide range of conditions that 

represent significant risks. Both high- and low

pressure sequences were chosen for three principal 

plant types; a single sequence was considered for the 

PWR ice condenser. Each sequence was evaluated by 

the STCP and has been documented in previous NRC 

reports.' 2

1 NUREG/CR-5732
Table 1.1 LWR accident sequences evaluated 

Plant Reactor type Accident Accident type Documentation 

Grand Gulf BWR - Mark III TC High pressure BMI-2104, Vol. III 

(ATWS) 

TQUV Low pressure BMI-2104, Vol. III 

(No makeup water) 

Peach Bottom BWR - Mark I TC2 High pressure NUREG-4624, Vol. I 

(ATWS) 

AE Low pressure BMI-2104, Vol. II 

(LOCA, no ECCS) 

Sequoyah PWR - ice condenser TBA Low pressure NUREG-4624, Vol. II 

Surry PWR - large containment TMLB' High pressure BMI-2104, Vol V 

(Station blackout) 

AB Low pressure BMI-2104, Vol. V 

(LOCA, no ECCS) 

(Station blackout)

"See References 1 and 2 for complete reference description.
2 Chemical Forms of Iodine Entering Containment 

from the Reactor Coolant System

2.1 Background

The chemical forms of iodine in the RCS are closely 

tied to the chemical forms of cesium. The relationship 

between cesium and iodine in the RCS can be 

illustrated by the following reaction

CsI + H2O * CsOH + H (1)

The reaction of cesium iodide (CsI) with steam (H20), 

as shown in Equation 1, is the reverse of an acid-base 

reaction and, thus, is unlikely to proceed unless one or 

both products are removed. Reactions of CsOH, 

which tend to lower the partial pressure of CsOH, 

shift the equilibrium to the right and enhance the 

formation of HI. 

At temperatures in excess of 1800 K (2781"F) and at 

low hydrogen pressures, iodine as I, rather than HI, is 

the favored product of the reaction between CsI and 

H20

1 CsI + H20 - CsOH + I + -IH 2 2 (2)

Thus, iodine chemical forms other than CsI are 

favored when steam pressures are much greater than 

cesium hydroxide pressures. 

Fission products released from the core will undergo 

changes in temperature and concentration as they pass 

through regions of the RCS. A chemical kinetic 

model used 20 reactions to determine the control 

volume where an equilibrium of the iodine, cesium, 

hydrogen, and steam species becomes "frozen." This 

means that the temperatures and concentrations of 

species in subsequent control volumes are not 

sufficient to reach an equilibrium in the mean 

residence time available. Separate equilibrium 

calculations were run, using the FACT system,3 to 

obtain the distribution of iodine species. The FACT 

system was chosen for this study because it can be 

used by anyone who wishes to examine the

calculations and its data base contains only assessed 

information. 

2.2 Data Manipulation and 

Calculational Techniques 

2.2.1 Adaptation of Data from Source Term 

Code Package 

In order to evaluate the chemistry in the RCS, it is 

necessary to specify the thermal-hydraulic conditions 

under which reactions would occur. This has been 

undertaken for each of the accident sequences in 

Table 1.1 using data from the STCP calculations. 

Where possible, detailed transient data were taken 

from the original computer output; otherwise, values 

were derived from tables or estimated from graphs in 

the sequence documentation."2 A listing of all the 

data used is contained in Appendix A. 

The chemical equilibrium is calculated in each relevant 

RCS control volume for the individual sequences. 

This requires a description of the thermodynamic 

conditions that occur during various phases of accident 

progression and a measure of the time span over 

which such conditions hold. 

The MARCH2' 0 code generates a special output file 

that provides input for the TRAP-MELT" code. This 

file was used to identify time-varying values of tem

perature and pressure in the RCS. Each control 

volume in the RCS remains constant, and the values 

used are given in Appendix A. Figure 2.1 illustrates 

the temperature history of the first two control 

volumes above core in the Surry TMLB' accident 

sequence, where time 0 is at the start of core melting. 

The figure shows phases of constant or slowly 

changing behavior in addition to periods of large 

swings in magnitude. Other sequences exhibit similar 

patterns. 

In addition to T, P, and V, chemical equilibria are 

dependent on the molar inventories n, of constituent 

species H2, H20, I, and Cs. These inventories also 

vary during the transient and must be obtained for 

each control volume. Such quantities are calculated

3 NUREG/CR-5732
Chemical Forms

ORNL DWG 91A-20

Volume 1

Volume 2

0 5 10 15 20 25 30 35 40

TIME (min) 

Figure 2.1 Surry TMLB': temperatures in volumes above core

NUREG/CR-5732

1800 

1600 

1400 

1200 

1000

Lii c,-"

800 

600

I

I I I I I

4
Chemical Forms

since they are not directly available from STCP results. 

Mass flows of H 2 and H20 and release rates of CsI and 

CsOH from the core are converted into molar flows 

(gi, i = 1, 2, 3, 4) of H2, H20, I, and Cs. These are 

assumed to directly enter the first control volume 

above the core. A simple schematic of the system of 

above-core control volumes is shown in Figure 2.2. 

Known data are given in normal type, and quantities 

to be calculated are shown in italics. Although only 

two control volumes are shown, -additional ones could 

be added (and were for most of the sequences in this 

study); treatment would be analogous to the second 

volume in the figure. 

Within each control volume, temperature and pressure 

are assumed to be uniform spatially and constant over 

computational time intervals (time intervals must be 

specified small enough to make this valid). From the 

ideal gas law, the total molar inventory must then also 

be constant since n = PVIRT. This implies that the 

molar flow (g-mol/s) into a control volume must equal 

the molar flow out

E ,il-- E , -- = g (3)

new old n# = n. + At (g"-1 -g.d (7)

Using this procedure, molar inventories were 

calculated in each control volume downstream from 

the core, as were the molar concentrations C, = n..V'. 

As an example, Figure 2.3 shows the time variation of 

principal species concentrations for the first control 

volume above core in the Surry TMLB' sequence. 

These concentrations, together with temperature and 

pressure values, were subsequently used to estimate 

the equilibrium distributions of chemical species, as 

described in Section 2.3.1. It is important to note that 

the equilibrium chemistry was completely decoupled 

from the mass transfer processes (i.e., no chemical 

reactions were considered in the flow calculations). 

The mean residence time (s) for flow through a 

control volume is simply the inverse of the fractional 

flow

1 j = - (8)

Since the inlet flows gio are known (cf. Figure 2.2), the 

total flow g can be easily obtained. The volumetric 

flow v, from control volume j (m3/s) is, then

RT. (4)

and the volume fractional flow from volume j (s') is

= -j v. RTj 

JJV PI', (5)

Assuming well-mixed control volumes, the flow (mol/s) 

of constituent i from volume j is represented by

(6) g# = f, no

Figure 2.4 shows this quantity for each of the two 

control volumes above core in the Surry TMLB' 

sequence. As described in Section 2.3.1, a mean 

residence time > 1 s is usually sufficient to attain 

equilibrium for regions with a sufficiently high 

temperature. The mean residence time is greater than 

1 s for both volumes, although control volume 1 

approaches this limit briefly at about 30 min. 

The simplicity of this method introduces some 

uncertainty into the results. However, this uncertainty 

is generally far less than that due to the input data 

itself. The time steps were chosen small enough to 

reduce calculational error to relative insignificance 

when compared with other sources of error; hence, 

the chemical reactions may have a slight effect on 

pressure and temperature, but this is not expected to 

be significant in altering the inventory and flow 

patterns. Thus, the results provide a reasonable 

picture of the chemical thermodynamic conditions in 

each control volume as the transients progress.

where the molar inventories n4 are updated at each 

time step by a simple balance equation

5 NUREG/CR-5732
Chemical Forms

ORNL DWG 91A-21

CONTROL 

VOLUME 

1

CONTROL 

VOLUME 

2

Figure 2.2 Flow chart of RCS control volumes and variables. Normal type = known data from STCP 

calculations; italics = quantities to be calculated

NUREG/CR-5732 6
Chemical Forms 

ORNL DWG 91A-22 

10' 

100 

1 H20 

------- ----------

1 C)74 

' 

10-' 

10-,4,6 

10-7 10-61 

II 

10-8 IIJ I ii 

0 5 .10 15 20 25 30 35 40 

TIME (min) 

Figure 2.3 Surry TMLB': principal species concenitrations in Volume 1 above core

NUREG/CR-5732

-j 

0 

E 

0 

z 

w 

0 

U--

7
Chemical Forms

ORNL DWG 91A-23

10 5

U, 

C2) 

LIJ 

12 z 

w•

104 

103

10 

10

2

0 5 10 15 20 25 30 35 40

TIME (min) 

Figure 2.4 Mean residence times in volumes above core for Surry TMLB'

NUREG/CR-5732

III 

I' 

Ole 

V 2 

I 

-"7

Volume 1

I II I II

\

1

I I I 10o

8
Chemical Forms

2.3 Iodine-Cesium-Steam-Hydrogen 

Reactions 

2.3.1 Sample Calculations 

Kinetic and equilibrium calculations were carried out 

at frequent intervals during the seven accident 

sequences. The use of these procedures can be 

illustrated with the Grand Gulf TQUV sequence at 

8780 s. Temperatures of the control volumes are 

shown in Table 2.1. Kinetic calculations, using the 

FACSIMILE1 2 code, indicated that the equilibrium was 

not attained in the upper annulus at 907 K (1173*F). 

However, equilibrium was rapidly attained in the 

higher-temperature regions. The results of the 

equilibrium calculations are given in Table 2.1. In the

core region, some I and HI were indicated along with 

CsI. The predominance of I over HI here is the result 

of reaction 2 being dominant over reaction 1 at the 

relatively high temperature of this region. Very little I 

or HI was indicated in the steam separator volume, 

and essentially only CsI was present in the steam 

dryers. In this example, the equilibrium was "frozen" 

at 1180 K (1665°F) in the steam dryer volume 

because this is the lowest temperature where 

equilibrium could be attained. If the equilibrium had 

"frozen" in the core region by quenching from its high 

temperature without changing composition, then the 

distribution of iodine species would have been 

different (see Table 2.1). Calculational techniques used 

in the seven accident sequences are discussed in 

Appendix B.

Table 2.1 FACT system output of Grand Gulf TQUV example at 8780 s 

Control volumes Percent Percent Percent Temperature 

CsI I HI (K) (aF) 

Core region 91.0 7.5 1.5 2047 3225 

Steam separators 99.96 0.01 0.03 1398 2057 

Steam dryers -100.0 <0.01 <0.01 1180 1665 

Upper annulus Not at equilibrium 907 1173

2.3.2 Overall Results of Calculations 

In six of seven calculations, the iodine was almost 

entirely in the form of CsI; the contribution of I or HI 

was <0.1% of the overall percentage of iodine. 

During the second half of the Surry AB sequence, 

there is a period during which temperatures in the 

core region are in excess of 2000 K (3141"F) and 

subsequent volumes of the upper grid plates and guide 

tubes are at temperatures of only -500 K (441"F). 

Because of this, equilibrium compositions in the core 

region would be "frozen" in by the rapid decrease in

temperature. For this sequence, the overall iodine 

distribution was 2.8% as I and 0.4% as HI, with the 

remainder as CsI. Thus, a total of 3.2% as I plus HI 

was the largest fraction of iodine in a form other than 

CsI in this study. 

These calculations considered only reactions involving 

cesium, iodine, hydrogen, and species, as shown in 

Appendix B, but covered a wide range of 

temperatures, hydrogen concentrations, steam 

concentrations, and fission product concentrations. 

However, deposition on surfaces and reactions with 

surfaces were not included in these calculations. Very 

few specific experimental data about surface

9 NUREG/CR-5732
Chemical Forms

interactions of fission products are available. The 

effect of these interactions on iodine chemical forms 

must be carried out with scoping or bounding 

calculations rather than detailed sequence specific 

evaluations that were performed for the reactions of 

iodine and cesium species with steam and hydrogen. 

2.4 Reaction of CsOH with Surfaces 

2.4.1 Deposition of CsOH onto Structural 

Surfaces 

Of the possible reactions of CsOH in the RCS, the 

reaction with structural surfaces is the most amenable 

to evaluation. Johnson et al.'3 have studied the 

deposition of CsOH on oxidized stainless steel 

surfaces. They used the following simple expression to 

relate the thermodynamic activity of CsOH to the 

surface concentration 

a = 0.5 exp98.5 - 3.84 x 101W - 0.28)} (9) 

x <0.28 

where a and x are the surface activity (atm) and 

concentration (mg/cm2), respectively. The reaction of 

interest with stainless steel may be written as

CsOH (surface) ,. CsOH (gas) (10)

Thermochemical data obtained from the FACT 

system3 give the respective equilibrium constants for 

the reactions in Equations 1 and 9 as 

K - L2 p 1.407 - 1.626 x 10' (11) 

P,2 0 PW T )

K9 = .189 1=ex x 10 _ 1.50 x1 

40 6 T•T 900 •ý T _- 1263

(12)

Calculations using Equations 9, 11, and 12, together 

with mass balances on cesium and iodine, indicate that 

the amount of HI formed due to the CsOH surface

reaction is less than 0.6% for each of the accident 

sequences studied. This is because PQoH must be very 

small if the ratio PHI/Pal is large enough to be 

significant. However, if PCOH is very small, then so is 

x; hence, very little surface reaction could occur. 

2.4.2 Other Reactions of CsOH 

Other reactions of CsOH may also remove it from the 

vapor phase, but there is generally a lack of 

information on the amounts and locations of other 

reactants. For example, several cesium borates may 

form in the reaction of CsOH with boric acid or boron 

oxide. The formation of cesium metaborate (CsBO2) 

may occur by the following reaction 

CsOH + HBO2 . CsBO2 + HO (13) 

At equilibrium at 1000 K (13410F), the pressure of 

CsOH may be written as

Pc,,, = -1.6 x 10 -t1 iP'2 

P HBo02

(14)

If sufficient meta-boric acid (HBO2) were available, it 

could result in a lowering of the vapor pressure of 

CsOH. 

Two simulated core-melt tests were run at ORNL to 

assess boric acid volatility and the potential for vapor 

interactions with CsI. Two different sized simulant 

fuel bundles were used-nominally 1 and 10 kg. The 

smaller, 1-kg, fuel simulant bundle consisted of 12 

zirconium tubes (10.16 cm long) with 0.247 kg end 

caps, 0.093 kg stainless steel grids, 0.0185 kg Inconel 

grids, and 0.585 kg UO pellets. There were no added 

Cs or I species in the small bundle test. The test was 

performed by inductively heating the fuel bundle while 

injecting feedwater containing 2000 ppm boric acid 

into the bottom of the bundle. In this test, it was 

found (see Table 2.2) that during the lower

temperature heating steps up to 1600' C, -10% of the 

boron was transported through the bundle and was 

captured downstream as boron oxide. As the tempera

ture was increased to partial melting of the bundle, 

the collected B20 3 decreased. This decrease was

NUREG/CR-5732 10
Chemical Forms

Table 2.2 Simulated core-melt tests conducted in the ORNL 1-kg facility 

(Boric acid addition to water injected below the bundle)

Boron collected as B20 3 

Heating step Total boron present (g) Filter (%) Wash (%) 

A (1600' C) 0.034 10.37 0.0 

B (1800- C) 0.088 5.5 0.68 

C (2400' C) 0.142 0.024 0.009 

As boric acid in water used for steam generation.

attributed to increased reactivity of the boron oxide 

with the hot fuel and clad oxides. 

The composition of the 10-kg fuel bundle is shown in 

Table 2.3. Note that in this test, CsI was added to 12 

of the 60 simulant fuel rods in a limited region near 

the bundle centerline. Excess cesium was not added. 

The 10-kg test was conducted at a bundle centerline 

temperature limit of 1600"C, which was reached in 

-30 min and maintained for an additional 30 min. 

During this time, 365 mL of boric acid solution 

containing 3.83 g of H 3B0 3 was added to the steam 

generator porous media below the fuel bundle. 

Hydrogen release measured 326 L, which would be 

equivalent to 72% conversion of the water and -30% 

reaction of the Zircaloy in the bundle. 

Analytical results from X-ray diffraction showed that 

white solids observed plated out on the quartz 

chimney were nearly pure CsI with no detectable B20 3. 

Chemical analysis of the washings from the system 

indicated that nearly half of the CsI had vaporized and 

that no boron-containing materials were present. This 

complete failure to find any B20 3 downstream of the 

bundle was somewhat unexpected since the 1-kg test 

had resulted in some penetration of boron oxide. It is 

likely that the extra length of the 10-kg system 

prevented penetration by the reaction of B20 3 with 

ZrO2. A sample analysis of a white oxide (a thin ring 

of mixed ZrO2 and B20 3) in a very highly refractory 

solid solution on the oxidized clad surface was 

estimated to account for about one-third of the total 

boron added. The remainder of the boron oxide

appeared to be associated with the porous ZrO2 steam 

generator base at the bottom of the bundle. A test 

scrubber that had been operated continuously on a 

diverted part of the hydrogen/steam flow showed no 

evidence of volatile (nonparticulate) iodine. 

Similar results were subsequently obtained in a test 

with silver vaporized in a 10-kg bundle containing Ag

In-Cd alloy control rod simulants. In the latter case, 

cadmium vapor was observed downstream, but the 

silver did not penetrate out of the bundle-presumably 

because of interactions with Zircaloy. 

Based on these results, it is highly likely that boric 

acid covaporized from residual water below the core in 

severe accidents will be tied up by the Zircaloy in the 

lower regions of the core and will not be available 

airborne to affect the chemical form of the released 

iodine. 

2.5 Revaporization of CsI from RCS 

Surfaces 

2.5.1 Description of Revaporization Process 

During an accident sequence, CsI may condense on 

RCS surfaces. If the temperature increases later in 

the sequence, the CsI may revaporize into a gas with 

very little cesium hydroxide. The revaporization of 

CsI can be expressed as

11 NUREG/CR-5732
Chemical Forms

Table 2.3 Composition of 10-kg fuel bundle

60" - Zircaloy tubes 

120 - Zircaloy end caps 

3 - Stainless steel grids 

1 - Inconel grid 

4 - Stainless steel supports and screws 

2 - Stainless steel lifts and screws

2181.0 

503.6 

342.0 

112.0 

58.5 

9.0

(N.W.) 7464.0 

(E.W.) 6739.9 

(N.W.) 1201.9 

(E.W.) 1059.5 

3.00

4.05 

2.28 

0.21 

1.12 

4.87 

4.70 

0.82 

5.16 

0.85

".N.W. = net weight; E.W. = uranium element weight. "'Twelve of these tubes had three horizontal slits each, 0.010 in. wide x 1 in. long, and 120(apart in their midsection. 

tCsI mixed with 300 g UO2 , rare earths, and metal powders was added to the -1-in. section of the 12 tubes.

NUREG/CR-5732

Item Weight* 

(g)

U0 2 pellets 

UO2 powder

SrCO3 

BaCO 3 

La203 

Eu 203 

Sm 203 

CeO 2 

Mo

Te 

Ru

Cs•t

12
Chemical Forms

CsI (liquid) - CsI (gas)

The vapor pressure of CsI, calculated with data 

obtained from the FACT system,3 is 

Pc= e -2.021x 10' + 1.307 x 101 

T = 1000 - 1553 K

(15)

(16)

In Equation 1, a mole of CsOH would be produced 

for every mole of HI. Assuming that this is the only 

CsOH (gas) in the system for the sake of a bounding 

calculation, the equilibrium constant for reaction 1 

may be arranged as

p = PcaC. *PO exp{( 1.622x 104+ 1.467J} 

T - 1000 - 1553 K

(17)

2.5.2 Assessment of Revaporization as a 

Source of HI 

From Equation 17, P. may be calculated if PH2 is 

known or assumed and P0,1 is calculated from 

Equation 16. The calculated percentages of iodine as 

HI when PnH = 1 atm varied from 0.5% at 1000 K to 

0.25% at 1553 K. At higher steam pressures, 

proportionately higher percentages as HI may occur. 

To assess an upper bound on the extent of HI 

formation by revaporization of CsI, the following 

assumptions are made: 

(1) The temperature of revaporization is the 

temperature where equilibrium was "frozen." 

(2) The steam pressures are those obtained from the 

seven accident sequences. 

(3) The only CsOH (gas) in the system is that 

produced by Equation 1 and is, mole for mole, the 

same as HI. All other cesium was somehow 

removed (i.e., vented).

(4) All of the iodine deposited on the surface and was 

subject to revaporization as described by 

Equations 15 and 16. 

Table 2.4 indicates the estimated upper bounds on the 

fraction of iodine as HI that results from these 

assumptions. The highest percentages as HI were 

obtained from those accidents in which steam 

pressures were >1 atm for a significant time during 

the sequence. These upper bounds probably 

overestimate the formation of HI in several ways: 

(1) It is not likely that all iodine would deposit as CsI 

and be subject to later revaporization. 

(2) The steam pressures used in the calculations were 

those of the accident sequences. Revaporization 

could occur after steam pressures had decreased. 

(3) The cesium hydroxide pressure would most likely 

be greater than the HI pressure. As described in 

Section 2.4.1, it would be difficult to reduce CsOH 

pressures low enough to influence HI formation 

by deposition of cesium on stainless steel. 

2.6 Summary of Iodine Chemical 

Forms in the RCS 

Iodine entering containment from the RCS should be 

predominantly in the form of CsI. The examination of 

Cs-I-H.O-H. interactions for seven accident sequences 

gave a maximum of 3.2% iodine as I plus HI, with the 

remainder as CsI. There are some uncertainties in the 

reactions of CsOH with oxides, as well as in the 

revaporization of CsI, that produce uncertainties in 

the extent to which iodine may exist in a form other 

than CsI. Cesium needs to be removed from reactions 

involving iodine if very much iodine is to be in a form 

other than CsI. 

Based on this analysis, the chemical forms of iodine 

entering containment from the RCS may reasonably 

be described as a maximum of 5% as elemental iodine 

and HI, with not less than 1% as either elemental 

iodine or HI. The remaining 95% would be CsI.

13 NUREG/CR-5732
Chemical Forms

Table 2.4. Estimated upper bound on the fraction of iodine as HI 

due to revaporization of CsI 

Accident sequence Estimated percentage of iodine as Hr 

Grand Gulf TC 0.3 

Grand Gulf TQUV 0.4 

Peach Bottom AE 0.6 

Peach Bottom TC2 3.1 

Sequoyah TB 2.4 

Surry TMLB' 3.8 

Surry AB 0.03 

*Note: See Section 2.5.2 for a list of assumptions used in calculating these estimated values.

NUREGICR-5732 14
3 Iodine Behavior in Containment

3.1 Categorization of Iodine 

Behavior in Terms of Time 

Intervals During an Accident 

Sequence 

Based on TRENDS models, calculations of iodine, 

behavior for NUREG-0956,14 and information from 

large-vessel tests'" 8 as well as from the accident at 

TMI-2, the iodine behavior may be separated, by time, 

into three categories: (1) from initial release into 

containment up to 1000 to 1200 min following 

initiation of the accident, (2) from 1000 to 1200 min 

to -2 to 3 weeks, and (3) for times greater than 

-3 weeks. 

Category 1. Iodine Behavior. In this time interval, the 

uncertainty in the amount and chemical forms that 

enter containment is most important. The upper time 

limit for this category is the time when airborne 

aerosol concentrations have been substantially reduced 

from their peak values. The source term calculations 

in previous reports12 stopped in the range of 1000 to 

1200 min. 

All of the chemical and physical interactions of HI are 

expected to occur during this time interval. Events 

leading to the formation of 12 by radiolysis would also 

occur in this interval and the next time interval as 

well. Thus, during this period, all material of 

importance to iodine reactions is expected to deposit 

in water pools or onto surfaces, all gaseous iodine

aerosol interactions are expected to take place, and all 

HI effects, except for those related to pH, are expected 

to occur. 

Category 2. Iodine Behavior. In this time interval, 

vapor-phase iodine will consist of 12 produced by 

radiolysis and partitioned between aqueous solution 

and the gas, as well as organic iodide. Iodine will also 

be found in aqueous solution in forms that are 

determined both by radiolysis and by pH and 

deposited on structural surfaces. In this time interval, 

the chemical forms of iodine should not be closely 

related to the chemical forms that entered 

containment from the RCS because the iodine would

have interacted with a surface and/or dissolved in 

water. 

Category 3. Iodine Behavior. At long times after a 

severe accident, gas-phase iodine is expected to be 

dominated by organic iodide with a small contribution 

from 12. Approximately 15 months following the 

accident at TMI-2, the concentration of 1291 in 

containment gas was 3.3 x 10-12 ± 8.9 x 10-11 mol I/L.19 

Methyl iodide is an *ubiquitous" halocarbon that is 

present in the atmosphere at concentrations which 

vary somewhat with distance from the ocean. In a 

study of eight locations in the United States, the 

overall mean concentration was -2 x 10-12 mol 

CH3I/L-2 Thus, the long-term organic iodide 

concentration in containment will probably be on the 

order of 10-12 mol I/L Iodine behavior and 

distribution, in the long term, are expected to have 

little relationship to the chemical forms or amounts 

released into containment because the iodine would 

have had time to deposit on surfaces or in water pools 

and the environmental conditions in containment 

would prevail in determining the chemical forms. 

3.2 Importance of pH in 

Determining the Chemical Forms 

of Iodine in Water Pools 

3.2.1 Materials That Determine pH in 

Accident Sequences 

Results of various experiments have shown that 

solution pH is the major factor in determining the 

amount of 12 and organic iodide formation in 

solution.' Materials that can determine pH in 

containment water pools are given in Table 3.1. This 

list includes both acidic and basic materials. In 

situations in which no chemical additives are present 

to control pH, the amounts of HI, cesium borate or 

hydroxide, and boron oxides reaching a sump will 

initially determine pH. In some sequences, the core

concrete interaction would produce aerosols that 

contain the basic oxides K.0, Na2O, and CaO. The 

influence of these oxides on pH will depend on the 

amount that has entered the water pool, the initial pH 

and buffering capacity of the solution, the quantity of

is NUREG/CR-5732
Iodine Behavior

Table 3.1 Materials that affect pH in containment water pools 

* Boron oxides (acidic) 

* Basic fission product compounds such as cesium hydroxide or cesium borates (basic) 

* Iodine as HI (acidic) 

* pH additives (basic) 

* Atmospheric species such as carbon dioxide or nitric acid (acidic) 

* Core-concrete aerosols (basic) 

0 Pyrolysis and radiolysis products from organic materials (acidic)

water, and the extent of dissolution of the aerosol 

material. One of the TRENDS models calculates the 

pH in water pools. 

3.2.2 Nitric Acid Formation and pH Control 

Water that is exposed to air absorbs CO2 to form 

carbonic acid, which lowers pH. The pH of water 

approaches a limiting value of -5.65 due to this 

process. In addition, nitric acid can be produced by 

the irradiation of water and air. Table 3.2 shows the 

relationship between the formation of nitrate ions and 

hydrogen ions from the irradiation of an air-water 

system. Table 3.3 shows the decrease in pH for an 

irradiated solution that contained trisodium phosphate 

with an initial pH of 9.0. During the irradiation, nitric 

acid and atmospheric CO2 decreased the pH as shown. 

Phosphate solutions have their maximum pH buffer 

capacity at a pH near 7. This buffer capacity is 

reflected here in the length of time that the pH 

remained near 6.5. Once the buffer capacity was 

exceeded, the pH continually decreased. 

Because of CO, and nitric acid, the pH is not likely to 

remain at some preadjusted value. A buffer system to 

retard changes from the desired pH is expected to 

provide a more stable pH level.

Two different buffer systems could be used in 

containment water pools: a phosphate buffer and a 

borate buffer. The phosphate buffer has a maximum 

capacity near pH 7, while the borate buffer has its 

maximum capacity near pH 9. Buffer capacity is often 

evaluated in terms of its buffer value B, which is 

defined by 

B db 

dpH 

where db is an increment of strong base in mol/L. 

With the addition of strong acids, a negative 

increment -db is used. Bates2

' has shown that the 

relationship between the maximum buffer value, B,,, 

and concentration of a buffer, C, can be written as: 

B. = 0.576 C 

Thus, a given concentration of phosphate would have 

the same buffer value at a pH near 7 that the same 

concentration of borate would have at a pH near 9. 

The selection of the buffer system is important in 

determining the pH to be maintained. From a strictly 

chemical standpoint, selecting a borate for the buffer 

to maintain a pH near 9 is just as simple as selecting a 

phosphate to maintain a pH near 7.

NUREG/CR-5732 16
Iodine Behavior

Table 3.2 Concentrations of H+ and NO3 in water due to irradiation 

Irradiation time [H+I [NO3 ] 

(h) from pH from ion electrode 

6 3.2 x 10-. 6.5 x 10s 

12 6.3 x 10"' 6.7 x 10' 

22 1.0 x 104 1.0 x 104 

65 2.5 x 104 1.8 x 104 

114 5.0 x 104 4.0 x 104

"100 mL in closed 200-mL container at rate of 0.6 Mrad/h.

Table 33 Effects of irrradiation dose 

on pH in trisodium phosphate solution 

Time 

(h) pH 

0 9.0 

4 6.4 

7 6.5 

23 6.5 

41 4.7 

63 3.9

"Dose rate, 0.53 Mrad/h. 

Recently, a patent was issued for a method of pH 

control and gettering of iodine species which employs 

well-dispersed silver carbonate.'

3.3 Processes That Alter the 

Chemical Forms of Iodine in 

Containment 

3.3.1 Radiolysis 

33.1.1 Description of Calculated Model 

In the presence of radiation, the equilibrium formation 

of 12 from I is strongly dependent on pH and weakly 

on temperature and concentration. Ignoring the last 

two effects,4 this dependence can be written as

F(pH) = equilibrium fraction = - 2____ 

['2] - [P]

(18)

where [x] is the concentration of 12 or I (g-atom/L). 

Data from Lin,23 as shown in Figure 3.1, illustrate this 

effect for several initial concentrations and pH values 

using solutions that were at ambient temperature and 

had been irradiated for 1 h at 4.5 Mrad/h. The final 

pH values were not indicated but probably decreased 

slightly since no mention is made of buffering in the 

experiment. The values of pH >6 may not be quanti

tatively useful since the very small conversion fractions 

are probably incorrect due to measurement error. As 

seen in Figure 3.1, F is near 0 for pH >7 and near 1 

for pH <2 but experiences a drastic change in the

17 NUREG/CR-5732
Iodine Behavior

ORNL DWG 91A-47

Z 

0 

0 

w 

Z 

0 

II

1.00

0.75 

0.50 

0.25

Il_

0

1 2 3 4 5 6 7

pH 

Figure 3.1 Radiolytic conversion of I to 1I [data from C. C. ln, J Inorg. NucL CJem. 42, 1101 (1980)]

NUREG/CR-5732 18
Iodine Behavior

range 3 < pH < 4. As discussed in Appendix C, this 

can be effectively modeled by the functional form

F = [1 + e PH P+P]- (19)

Equation 19 was fit to Lin's data by minimizing the 

sum of least-squares residuals, which yields

a = 1.72 P = -6.08 (20)

Similar data are given by Naritami et al.24 for 

5 < pH < 9. They subjected borated I solutions of 

10-4, 105, and 10W mol/L to much lower dose rates 

(6°Co gamma rays of 0.1 Mrad/h) for 1 h. The model 

of Equations 19 and 20 gives a good match to these 

data for concentrations of 10-4 mol/L, although the 

model overestimates conversion for the lower 

concentrations. 

If the pH is maintained sufficiently high through 

buffering or addition of sufficient basic material, very 

little conversion will occur. In this case, most iodine 

remains dissolved as L. Lin's data generally indicate 

<1% conversion at pH = 7. This value declines as 

the total iodine concentration decreases. The data of 

Naritomi show a conversion of 0.2% for iodide 

concentrations of 10.4 mol/L and 0.01% at lower 

concentrations. Data measured for this study indicate 

that for a dose rate of 0.35 Mrad/h, an iodine 

concentration of 10.4 mol/L conversion was 0.003% 

after 4 h irradiation and 0.03% after 24 h. The last 

value, 0.03%, has been used in the present work. 

If the pH level is not deliberately controlled, it may 

decrease sufficiently to allow considerable conversion 

of I to I2. The primary mechanism is radiolytic 

generation of nitric acid (see Section 3.2.2). If the pH 

is neutral initially, then this effect soon dominates, 

resulting in

[H] = 10g g(HNO3) VLNo (21)

where 

[H÷] = concentration of H' (mol/L),

g(HNO3) = rate of HNO3 production due to irradiation (molecules/100 eV), 

E•i = total energy deposition due to fission 

product decay (MeV), 

VL = volume of water (L), 

No = 6.022 x 103 (molecules/mol). 

The data in Table 3.2 indicate that at 30"C (860F) 

g(HNO) = 0.007 molecudes/l00 eV (22) 

This relationship is based on radiation absorption by 

the aqueous phase. The actual mechanism for the 

formation of nitric acid is not known. It may occur in 

the aqueous phase, in the gas phase, or at the gas

surface interface. The containment water volume, VL, 

is usually constant over the period during and 

subsequent to significant fission product releases. 

The energy deposition over a time At is

E~,h= iE,, At = At Em k (23)

where

At 

k4 

Mi,

time (h), 

total energy deposition rate (MeV/h), 

mass of nuclide group j in pool (g), 

energy deposition rate per unit mass of 

nuclide group j (MeV/h-g).

Various groupings of fission products and actinides 

have been considered in past safety studies. A 

grouping compatible with that used in STCP accident 

studies was selected for this study (see Table 3.4). The 

specific energy deposition rate 4 for each group 

depends on the relative distribution of radioactive 

nuclides, which, in turn, depends on such factors as 

fuel enrichment, power history, and additives or other 

materials in the fuel or reactor. 

A detailed analysis of Browns Ferry (a large BWR 

with Mark I containment) accident sequences has been 

performed by ORNL staff members. Using the 

ORIGEN2 code,25 nuclide inventories were determined 

for the highest and lowest power of each type of fuel

19 NUREG/CR-5732
Iodine Behavior

Table 3.4 Nuclide groupings and group-specific energy deposition rates

Group Energy deposition rate, 

index, Characteristic • x 10-19 

element Included nuclides (MeV/h-kg) 

1 I I, Br 425.0 

2 Cs Cs, Rb 3.971 

3 Te Te, Se, Sb 20.06 

4 Sr Sr 31.25 

5 Ba Ba 8.900 

6 Ru Ru, Tc, Rh, Mo, Pd 6.613 

7 Ce Ce, Pu, Np 1.540 

8 La La, Am, Cm, Y, Pr, Nd, Pm, Sm, 25.46 

Eu, Zr," Nb 

9 Xe Xe, Kr 2.902

*Includes only fission products.

assembly in the cycle 6 fuel loading. Nuclide 

inventories for every assembly in the reactor were then 

determined by interpolation based on power history, 

using the high and low cases for that assembly type. 

These inventories were subsequently combined to 

obtain a total core inventory for every fission product 

nuclide of significance either in mass or decay energy 

at 5 h after shutdown. Assuming all decay energy is 

absorbed, the total inventories were used with decay 

energy data for each nuclide to obtain energy 

deposition rates q. for each fission product group, 

which are also shown in Table 3.4. Complete details 

of this calculation can be found in Reference 26. 

The group energy deposition rates for the Browns 

Ferry BWR are applied to all sequences considered in 

the present study. This is a very legitimate assumption 

for the Peach Bottom plant, which is also a BWR

Mark I nearly identical to Browns Ferry in size and 

design. A similar assumption is also made for Grand 

Gulf, also a BWR. These assumptions are analogous 

to those made in previous reports"2 using ORNL 

calculations for the Browns Ferry cycle 4 loading. 

While PWRs have many characteristics different from 

BWRs, the fission process results in the same 

distribution of fission products. Although the final 

distribution is somewhat affected by geometry and 

additives, the group energy deposition rates are

assumed to be sufficiently similar to BWR values to 

permit use of the values in Table 3.4 for Sequoyah and 

Surry sequences. 

3.3.1.2 Mass Manipulations 

The group masses mn are obtained by multiplying the 

total core inventory m-, by the estimated fractional 

release into containment

Mi = fi 1i (24)

Total core inventories for the plants are those 

identified in previous reports, 2 and are given in 

Appendix D. Various estimates of the fractional 

releases f can be obtained from Nourbakhsh. 27 He has 

compiled results from many STCP accident 

calculations (including those mentioned in this study) 

and has stated bounding estimates for the fractions of 

core inventory released into containment due to the 

following effects:

(1) 

(2) 

(3)

release from RCS prior to vessel failure 

release at vessel breach 

ex-vessel release due primarily to core-concrete 

interactions

NUREGICR-5732 20
Iodine Behavior

(4) late revolatilization from the RCS. 

Categories 1, 2, and 4 can be combined to yield a total 

release into the containment from the primary system. 

The release fractions adopted from Nourbakhsh and 

used in this study are shown in Table D.2 of 

Appendix D. 

Finally, At in Equation 23 is the time needed to reach 

the approximate steady state. In general, the first 

phase of an accident can be considered to reach steady 

state in 10 to 15 h (see Section 3.1), and this is the 

time range considered for At. The pH can be 

calculated from 

pH = -log, 0 [H'] = -An [Hi]/'n 10 

and the fractional conversion in Equation 18 then 

takes the form 

F = Ii + eF[Hl hRO] 0-1 1i + 5.55 X loll (25) 

Thus, when pH is not controlled, fractional conversion 

is directly dependent on the liquid volume VL in which 

radiolysis occurs; the energy deposition E4, which 

itself depends on the amounts of radioactive species in 

water; and the time At allowed for the radiolysis 

process to reach steady-state conditions. 

3.3.1.3 Gas-Liquid Partitioning 

The equilibrium distribution of a single volatile 

species, such as 12, is represented by the partition 

coefficient

(26)

[12 (-

This quantity is inversely related to the Henry's Law 

constant K (i.e., P = 1/K) and should not be confused 

with the overall iodine partition coefficients often used 

in reactor safety studies. Partition coefficients for 12 

were calculated from

loglo P = 6.29 - 0.0149 T 

T(KQ

(27)

This relationship gives the experimental value reported 

by Eguchi et al.2' and by Sanemasa et al.29 at 298 K 

(770 F). Extrapolation of the experimental results of 

these investigators to 373 K (2120F) yielded a 

partition coefficient of 3. Furrer et al0 reported a 

calculated partition coefficient at 373 K (212"F) of 9. 

Some of the data used in this calculation was based on 

estimated parameters. Equation 27 gives a partition 

coefficient of 5.3 at 373 K (2120$), the approximate 

average of the calculated value, and the extrapolation 

of the measured values. 

While it may take considerable time to approach such 

equilibration in a large system such as a reactor 

containment, Equation 26 can still be used to estimate 

12 volatility. In fact, instant equilibration is a 

conservative assumption since considerable holdup 

could be expected in real-life situations. A rigorous 

analysis would consider the delay associated with the 

evaporation of volatile species from water pools. This 

phenomenon is not well understood, and only crude 

models are available. Thus, the escape of 12 from 

water pools will be modeled by assuming that 

Equation 26 holds continuously as 12 is produced 

radiolytically. 

33.1.4 Gas-Phase Reactions: Formation of Organic 

Iodides 

The process of converting 12 into organic iodides 

(chiefly CH3I) is still not fully understood. Postma 

and Zavodoski3

' reviewed production rates from about 

70 containment tests and determined that the 

asymptotic steady-state conversion to CH 3I was

-026 percent 12 converted = 0.19 C.,

(28)

where C,, = initial 12 concentration (mg/m3). This 

equation was based on 69 containment experiments. 

In a more recent review, Beahm et al.' described 

formation using the rate equation

21 NUREG/CR-5732
Iodine Behavior

dCo " - C) (29)

where 

a = formation rate constant (s 1), 

C0 = organic iodide concentration 

(mg iodine/m3

), 

C" = steady-state organic iodide concentration 

(mg iodine/M3

). 

They assigned the constant value a = 0.0051 based on 

empirical evidence and used

C. = 0.0189 C,"

c1 = 12 (aq)], C2 = [V2 (8)], C3 = [V- (aq)], 

C4 = [CH3I (9)] 

Equations 26, 18, and 31 can be rewritten as

C1 = PC2 

C3_ = G FF C1 

(30)

in place of Equation 28. This equation was based on 

containment experiments performed with irradiated 

fuel rather than simulated materials. The percent 

conversion to organic iodide when irradiated fuel was 

used was somewhat greater than that obtained from 

simulant materials (cf. Figure 4, Reference 5). 

By converting units to g-atom/L, Equation 30 can be 

rewritten as

[CH31] = [1 I10U (31)

where P = 0.0189 (106 - MW)41 , MW being the 

molecular weight of I. For MW = 130, then P3 = 6.55 x 104, which indicates that generally < 1% of 

gaseous iodine will be organic.

C-- 0 8 2

(32a) 

(32b)

(32c)

In addition, the total iodine inventory NT (g-atom) is 

equal to the initial I- entering the containment and 

remains constant throughout the distribution process: 

NT = VL (C, +C 3) + V,(c2 + C4 ) (32d) 

There are four equations (Eqs. 32a-32d) and four 

unknowns (C,, C2, C3, and CQ); all equations except 

Equation 32c are linear, and its nonlinearities are very 

mild. 

To obtain solutions to the system, Equations 32a-32c 

are substituted into Equation 32d, yielding

VL ,NT=-PC On)~ F 2 + Vg (C +PC 2 (33)

33.1.5 Overall Behavior

As described in the previous sections, the distribution 

of species throughout the gas and liquid phases can be 

estimated from models for three basic processes: 

radiolytic conversion of r to 12 in water, evaporation 

of I., and gas-phase formation of organic iodides. 

Defining the desired quantities as concentration 

variables (g-atom/L)

which can be arranged into the form

(34)

This represents a convenient form for fixed-point 

iteration, which usually converges to a relative error of 

10-4 within three to five iterations. Once C2 has been 

determined from Equation 34, the other concentra

tions are obtained from Equations 32a-32c.

NUREG/CR-5732 22
Iodine Behavior

Because organic iodide is such a small part of the 

total, it is helpful to examine the distribution behavior 

without considering organic iodide. By ignoring 

Equation 32c, Equation 33 becomes 

NT = PC2 + vC 2 F 

which can be rearranged to obtain

N2 + L 

N - +

(35)

where N2 = VgC 2 = g-atom of I2 in gas. Equation 35 

is a convenient expression of the fraction of iodine 

that is volatilized. (Consideration of organic iodide 

will increase this fraction very slightly.) For the case 

of uncontrolled pH, substitution of Equation 25 into 

Equation 35 yields

N2P1+ 5.55 x10'(VO77I 

TN t . 0~,747 (36)

which is an expression for the fraction of volatile 

iodine (as 12). To use Equation 35 or 36, it is 

necessary to estimate the characteristics or 

approximate values for each of the following 

quantities: 

VL, Vs = liquid and gas volumes (L), 

T = air-water interface temperature (which 

permits computation of the partition 

coefficient P by Equation 27). 

For the case of uncontrolled pH, it is also necessary to 

obtain 

mi = masses of fission products in the 

containment (from which the dose 

term Ed, is calculated by 

Equation 24), 

At = approximate duration of the radiolysis 

phase(s) in category 1 (see 

Section 3.1). 

If Equation 35 or 36 is used instead of solving the 

nonlinear Equation 34, then a good approximation to 

the airborne organic iodide inventory can be obtained

by simply using Equation 32c. Furthermore, 

Equations 35 and 36 are in particularly convenient 

form not only to estimate iodine volatility, but also to 

estimate the individual phenomena and their impact 

on overall behavior. 

33.2 Results of Iodine Behavior in 

Containment 

The analysis described in Section 3.3.1 has been 

applied to each of the seven accident sequences listed 

in Table 1.1. Using whole core inventories from 

previous reports,"2 the release fractions of 

Nourbakhsh2V (including both vessel and core-concrete 

releases), and the nuclide group energy deposition 

rates in Table 3.4, the energy deposition rate P,•, can 

be calculated for each plant using Equations 23 and 

24. The results are shown in Appendix E. 

Once the energy deposition has been computed, the 

remaining quantities can be calculated by solving the 

system of equations 32. Liquid and gas volumes and 

temperatures were obtained from sequence 

documentation."'2 The gas volumes used for BWRs 

include all primary containment space, although it may 

sometimes be appropriate to use only wetwell airspace, 

depending on sequence considerations. Partition 

coefficients were calculated as functions of 

temperature from Equation 27. The total iodine 

inventory initially deposited in water as I* was 

calculated using previously mentioned mass inventories 

and release fractions and assuming a molecular weight 

of 130. 

These various data and the quantities calculated from 

them are listed for each accident sequence in 

Table 3.5. From the table, it appears that PWRs 

exhibit dose rates considerably higher than do BWRs, 

contributing to the much higher conversion fractions. 

The presence of extremely large water volumes is a 

distinct advantage for BWRs in this regard. The 

conversion data of Lin23 were taken at a dose rate of 

4.5 Mrad/h in the range of PWR rates. The data 

taken at ORNL are generally in the range of BWR 

dose rates (i.e., 0.35 to 0.6 Mrad/h). Both sets of data 

indicate that conversion is dominated by pH effects. 

In this study, two scenarios were evaluated: 

(1) control of pH above 7 and (2) uncontrolled pH 

with resulting drops below 7 due to nitric acid. For

23 NUREG/CR-5732
I1

Table 3-5 Data for equilibrium analysis of exnmple sequences 

Volume (m3

) Aqueous 12 MY 

Temperature Partition E Dose rate- Total I 

Plant Accident Liquid Gas (0 c) coefficient (MeV/h)" (Mrad/h) (g-mol) At = 10 h At = 15 h 

X 10-23 

Grand TCy 4550 39650 102 5.0 1.2778 0.45 122.5 14 18 

Gulf TQUVy 5171 39650 60 21.2 1.3020 0.40 136.2 13 18 

Peach AEy 4000 7873 54 26.0 1.2223 0.49 127.7 16 21 

Bottom TC2 4500 7873 118 2.9 1.1997 0.43 114.9 14 19 

Sequoyah TBA 1465 36404 112 3.6 0.9267 1.01 105.2 24 30 

Surry TMLB' 115 51000 93 6.8 0.5136 7.16 57.2 59 67 

AB 172 51000 112 3.6 0.6912 6.44 85.8 58 66 

"Calculated from Equation 23. "Calculated from the expression: dose rate (Mrad/h) = 1.60219 x 10"20 F&(pVL), where p = 1 kg/L is assumed. 

tCalculated from Equation 19.

I 

C 

LA

I I
Iodine Behavior

this calculation, it was not necessary to specify the 

material that was used to control the pH at 7 or 

above. 

If the pH is controlled so that it stays above 7, a 

reasonable value for the fraction of I converted to 12 is 

3 x 10-' (Section 3.3.1.1). Using this and the other 

computed quantities in Table 3.5, the system of 

equations 32 is solved to yield the species distributions 

in Table 3.6. It should be noted that data in 

Tables 3.5 and 3.6 refer to the total iodine in contain

ment, not the core inventory of iodine. Table 3.6 

indicates a small production of volatiles for PWRs but 

virtually none for BWRs. 

Such results are strongly dependent on the aqueous 

conversion fraction of F = 3 x 10-', which represents a 

best estimate of the maximum from ORNL data. 

Thus, if pH is maintained at 7 or above, only a small 

additional amount of 12 is expected in the gas phase in 

PWR systems. 

If the pH falls below 7, a system for conrolling pH is 

not being used and the decreased pH results in a 

larger fraction of aqueous I being converted to 12. 

Evaporation of this volatile species so as to maintain 

equilibrium partitioning will result in greater 

atmospheric I. This, in turn, yields higher organic 

iodide concentrations. The aqueous conversion 

fraction itself is determined from Equation 25, which 

requires a value for the equilibration time At. As 

discussed in Section 3.3.1, a value of At = 15 h is 

appropriate and yields the results shown in Table 3.7 

for the equilibrium species distributions. As expected, 

the levels of airborne volatiles are much higher than 

in the controlled case, indicating almost complete 

conversion for PWRs. 

The gaseous 12 fraction is considerably higher in PWRs 

than in BWRs because the large water volumes in the 

latter both lower the dose rate and retain greater 

quantities of dissolved I2. This last effect also depends 

on the gas volume and the ratio of gas to liquid 

volumes. It is ironic that the relatively small gas space

in the Peach Bottom reactor (generally a safety 

liability) permits noticeably less evaporation than 

other reactors, resulting in the lowest gaseous 1I 

fractions. 

The other principal effect is due to temperature - the 

12 partition coefficient changes markedly over the 

range of temperatures used. This is most noticeable in 

the BWR sequences where different sequences at the 

same plant show large differences in the airborne 12 

fraction. Thus, an increase in containment 

temperature (at the gas-liquid interface) from 60 to 

115"C (140 to 239"F) produces nearly an order of 

magnitude increase in the airborne fraction. 

The organic iodide is present in PWRs at about 0.5% 

of core inventory; in BWRs, this concentration is 

closer to 0.1%. The 12 generated by the radiolytic 

conversion of I dominates the amount released as 12 

from the RCS. Further, based on the equilibrium 

assumption, the presence of some 12 already airborne 

will result in less evaporation of 12 formed 

radiolytically. Hence, for the case of uncontrolled pH, 

the cumulative total is well represented by the 

equilibrium amount formed within containment. 

3.3.3 Evaporation to Dryness 

Water pools or condensate puddles may evaporate in 

containment and provide a mechanism for the release 

of dissolved aqueous iodine to the gas. As with all 

processes involving aqueous iodine, the extent of 

volatile iodine produced is related to pH. Table 3.8 

gives percentages of volatile iodine produced when 

1 x 104 mol/L CsI solutions were evaporated to 

dryness at 95"C. Radiation increased the percentage 

of volatile iodine by about an order of magnitude. In 

solutions where the initial pH was 7 or below, there 

was a rapid decrease in pH just before dryness. 

The overall impact of evaporation to dryness will 

depend on the extent to which it occurs in 

containment.

25 NUREG/CR-5732
F

Table 3.6 Distribution of iodine species for pH controlled above 7

Fraction of total iodine in containment (%) 

Plant Accident 12 (g) 12 (f) r (0) CH3I (g) 

Grand Gulf TC y 0.05 0.03 99.92 0.001 

TQUV y 0.01 0.03 99.96 0.0003 

Peach Bottom AE y 0.002 0.03 99.97 0.0001 

TC2 y 0.02 0.03 99.95 0.0004 

Sequoyah TBA 0.21 0.03 99.76 0.004 

Surry TMLB' y 1.9 0.03 98.0 0.03 

AB y 2.4 0.03 97.5 0.03

I,
Table 3.7 Distribution of iodine species for uncontrolled pH 

Fraction of total iodine in containment (%) 

Plant Accident 12 (g) 12 M) I (Q) C1- 31 (g) 

Grand Gulf TC y 26.6 15.3 58.0 0.2 

TQUV y 6.6 18.3 75.1 0.06 

Peach Bottom AE y 1.6 21.6 76.8 0.01 

TC2 y 10.9 18.0 71.0 0.07 

Sequoyah TBA 69.2 9.9 20.5 0.4 

Surry TMLB' y 97.1 1.5 0.7 0.7 

AB y 97.6 1.2 0.6 0.6

N 

-JU'
N F

Table 3.8 Iodine volatility of 1 x 10- mol/L CsI solutions during evaporation to dryness 

Test conditions Percent volatile 

Initial Borate Without With radiation Fimal pH just 

pH (M) radiation (total dose, 2.1 MR) before dryness 

4.4 0.2 7.2 >99 1.8 to 2.0 

4.4 0* 2.0 3.6 

6.0 0.2 6.8 55 2.0 to 2.2 

7.0 0.2 32 3.0 

Pure water 0 1.6 21 

9.0 0.2 1.8 22 8.5

"Phosphoric acid added to adjust the pH to 4.4.
4 Technical Findings

4.1 Perspective and Scope of Study 

This study assumed that iodine forms in containment 

can be delimited by an examination of the seven 

severe accident sequences in LWR plants, along with 

an evaluation of associated processes. The associated 

processes include the deposition of CsOH on RCS 

surfaces and the effects of radiolysis. The issue is the 

chemical form of iodine that may be produced in the 

RCS and in containment - not the ultimate 

disposition of the various chemical forms. For 

example, it is likely that much of the gaseous 12 in 

containment would be removed by engineered safety 

features or would deposit on painted or metal 

surfaces. 

4.2 Assessment of Iodine Chemical 

Forms in the RCS 

The maximum iodine as I plus HI calculated for the 

seven severe accident sequences is 3.2%. Iodine in all 

forms other than I, HI, and CsI is estimated to be less 

than 1%. Although this analysis only considered seven 

sequences at four plants, it is reasonable to consider 

that a maximum of 5% of the iodine would be present 

as elemental iodine and HI for all accident sequences. 

A minimum value would not be expected to be less 

than 1%. The remaining 95% of the iodine would be 

as CsI. 

The gaseous forms of iodine that entered containment 

from the RCS were given in terms of both elemental 

iodine and HI. There is a fundamental reason for this. 

The two forms of iodine are related by

1+ H2 -M 

2

(37)

In the temperature range of 1000 to 2000 K, thermo

chemical data for this reaction were fit to give

f7e4 .2x14- 5.6451 (38) P, T 

Lower temperatures and higher hydrogen pressures 

tend to favor HI over I, with the opposite conditions 

favoring I over HI. Five percent of iodine as I plus 

HI, with not less than 1% in either form, means that 

the Po-to-P1 ratio in Equation 38 would range from 

0.25 to 4. With a hydrogen pressure of 1 atm, this 

would occur in the temperature range of 1456 to 

2404 K (2161 to 38680 F); with a hydrogen pressure of 

10 atm, it would occur in the temperature range of 

1251 to 1893 K (1792 to 29480F). These conditions 

are reasonable for situations that lead to the 

formation of I or HI. 

The major uncertainty is the extent to which CsOH 

will react with oxide materials and reduce its vapor 

pressure. If the reaction of CsOH is to have a major 

impact on the iodine chemical forms, most of it 

(certainly more than 90%) must be fixed at a very low 

vapor pressure. 

4.3 Assessment of Iodine Chemical 

Forms in Containment 

The production of 12 in containment will be directly 

related to the pH levels of the water pools. As illu

strated in Figure 4.1, failure to control the pH at or 

above 7 could result in an increase of 12 in the 

atmosphere of between 4,100 and 33,000% as com

pared with the case where pH is controlled for PWRs. 

Essentially all of the 12 could become gaseous in the 

PWRs without pH control. For BWRs, the increase is 

between 53,000 and 80,000%, with about 25% of the 12 

becoming gaseous. The dramatic difference in the 

amount of 12 between the cases where pH was uncon

trolled below 7 and the controlled cases speak for 

themselves. A major uncertainty is the extent of 

evaporation to dryness. From 2 to 20% of the iodine 

in water pools that have evaporated could be 

converted to a volatile form, most likely as I2.

29 NUREG/CR-5732
ORNL DWG 91A-683R

AE TC2 TQUV TC TBA TMLB AB

PEACH BOTTOM GRAND GULF SEQUOYAH

Figure 4.1 Additional atmospheric elemental iodine released

._J 

0 

I

LU 

z 

z 

0 

U 

0 

CL 

U) 

0 I100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0

SURRY
5 References

1. Gieseke, J. A. et al., "Radionuclide Release 

Under Specific LWR Accident Conditions," 

BMI-2104, Battelle Columbus Laboratories, 

1984. 

2. Denning, R. S. et al., "Radionuclide Release 

Calculations for Selected Severe Accident 

Scenarios," NUREG/CR-4624 (BMI-2139), 

Battelle Columbus Laboratories, 1986. 

3. FACT, a copyrighted product of 

THERMFACT Ltd., 447 Berwich Ave., 

Mount-Royal, Quebec, Canada, H3R 1Z8. 

4. Wisby, S. J. et al., "Iodine Behavior in 

Containment Under LWR Accident 

Conditions," pp. 6-29 in Proceedings of the 

Symposium on Chemical Phenomena 

Associated with Radioactivity Releases During 

Severe Nuclear Plant Accidents, Anaheim, 

Calif., September 1986. 

5. Beahm, E. C., W. E. Shockley, and 0. L. 

Culberson, "Organic Iodide Formation 

Following Nuclear Reactor Accidents," 

NUREG/CR-4327, Oak Ridge National 

Laboratory, 1985. 

6. Lemire, R. J. et al. "Assessment of Iodine 

Behavior in Reactor Containment Buildings 

from a Chemical Perspective," AECL-6812, 

1981. 

7. Burns, W. G. et al., "The Radiolysis of 

Aqueous Solutions of Caesium Iodide and 

Caesium Iodate," AERE-R-13520, 1990. 

8. U.S. Nuclear Regulatory Commission, 

Regulatory Guide 1.3, "Assumptions Used for 

Evaluating the Potential Radiological 

Consequences of a Loss-of-Coolant Accident 

for Boiling Water Reactors," June 1974. 

9. U.S. Nuclear Regulatory Commission, 

Regulation Guide 1.4, "Assumptions Used for 

Evaluating the Potential Radiological 

Consequences of a Loss-of-Coolant Accident 

for Pressurized Water Reactors," June 1974.

10. Wooten, R. 0., P. Cybulskis, and S. F. Quayle, 

"MARCH2 Meltdown Accident Response 

Characteristic Code Description and User's 

Manual," NUREG/CR-3988 (BMI-2115), 

Battelle Columbus Laboratories, 1984. 

11. Jordan, H. and M. R. Kuhlman, "TRAP

MELT User's Manual," NUREG/CR-4205 

(BMI-2124), Battelle Columbus Laboratories, 

1985. 

12. Chance, E. M. et al., "FACSIMILE: A 

Computer Program for Flow and Chemistry 

Simulation, and General Initial Value 

Problems," AERE-R-8775, AERE Harwell, 

December 1977. 

13. Johnson, I. et al., "Downstream Behavior of 

Volatile Iodine, Cesium, and Tellurium 

Fission Products," EPRI NP-6182, 

January 1989. 

14. Silberberg, M. et al., "Reassessment of 

Technical Bases for Estimating Source Terms," 

NUREG-0956, U.S. Nuclear Regulatory 

Commission, July 1986. 

15. Megaw, W. J. and F. G. May, "The Behavior 

of Iodine Released in Reactor Containers," J. 

Nucl. Energy, Pts. A/B, 16, 427 (1962). 

16. Croft, J. F. and R. S. Isles, "Experimental 

Release of Radioiodine in the Zenith Reactor 

Containment," AEEW-R-172, 1962. 

17. Parker, G. W., G. E. Creek, and W. J. Martin, 

"Fission Product Transport and Behavior in 

the Stainless Steel-Lined Containment 

Research Installation," ORNL-4502, 1971. 

18. Hilliard, R. K. and L. F. Coleman, "Natural 

Transport Effects on Fission Product Behavior 

in the Containment Systems Experiment," 

BNWL-1457, 1970.

31 NUREG/CR-5732
References

19. Cline, J. E. et al., "Measurements of "2I and 

Radioactive Particulate Concentrations in the 

TMI-2 Containment Atmosphere During and 

After the Venting," GEND-009, April 1981. 

20. Lillian, D. et al., Environ. ScL Technol. 12, 

1042 (1975). 

21. Bates, R. G., Determination of pH, p. 99, 

Wiley, New York, 1964. 

22. Beahm, E. C. and W. E. Shockley, "Method 

for Gettering Organic, Inorganic, and 

Elemental Iodine in Aqueous Solutions," 

Patent ESID 518-X (April 1989). 

23. Lin, C. C., "Chemical Effects of Gamma 

Radiation on Iodine in Aqueous Solutions," 

J. Inorg. Nucl. Chem. 42, 1101 (1980). 

24. Naritami, M. et al., "Batch-Type Tests on 

Formation of Volatile Iodine Species from 

Aqueous Iodide Solutions Under 6OCo y-Ray 

Irradiation," Proceedings of the Third CSNI 

Workshop on Iodine Chemistry in Reactor 

Safely, Sept. 11-13, 1991, Toaki-mura, Japan. 

25. Croff, A. G., "ORIGEN2 - A Revised and 

Updated Version of the Oak Ridge Isotope 

Generation and Depletion Code," ORNL

5621, Oak Ridge National Laboratory, 

July 1980. 

26. Weber, C. F., "Calculation of Absorbed Doses 

to Water Pools in Severe Accident 

Sequences," ORNL/CSD/TM-274, Oak Ridge 

National Laboratory, 1991. 

27. Nourbakhsh, H. P., "Estimate of Radionuclide 

Release Characteristics into Containment 

Under Severe Accident Conditions (Draft for 

Comment)," NUREG/CR-5747, Brookhaven 

National Laboratory, December 1991.

28. Eguchi, W., M. Adachi, and M. Yoneda, J. 

Chem. Eng. Jpn. 6, 389 (1973). 

29. Sanemasa, I. et al., Bull. Chem. Soc. Jpn. 57, 

1352 (1984). 

30. Furrer, M., R. C. Cripps, and R. Gubler, Nucl. 

Technol. 70, 290 (1985). 

31. Postma, A- K. and R. V. Zavodoski, "Review 

of Organic Iodide Formation Under Accident 

Conditions in Water-Cooled Reactors," 

WASH-1233, U.S. Atomic Energy 

Commission, 1972. 

32. Wren, D. J., "Kinetics of Iodine and Cesium 

Reactions in the CANDU Reactor Primary 

Heat Transport System Under Accident 

Conditions," AECL-7781, April 1983. 

33. Frost, A- and B. Pearson, Kinetics and 

Mechanism, 2nd ed., p. 104, Wiley, New York, 

1961. 

34. Lorenz, K, H. Wagner, and R. Zellner, Ber. 

Buns. Phys. Chem. 83, 556 (1979). 

35. Kondrat'ev, V., Kinetics of Chemical Gas 

Reactions, AEC-tr-4493, 1958. 

36. Chase, M. W., Jr. et al., JANAF 

Thermochemical Tables, 3rd ed., American 

Chemical Society, Washington, D.C., 1986. 

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Properties of Inorganic Substances, Springer

Verlag, Berlin, 1973.

NUREG/CR-5732 32
Appendix A. Data from Accident Sequence Calculations
Appendix A

Table A-1 Grand Gulf TC-MERGE output data from MARCH2 

Flow rate from core (b/s) Core exit 

Time temperature Pressure 

(s) Hydrogen Total (c F) (psia)

5381 

5498 

5504 

5522 

5552 

5588 

5612 

5642 

5678 

5726 

5756 

5822 

5858 

5924 

5978 

6032 

6080 

6122 

6182 

6218 

6284 

6326 

6380 

6446 

6512 

6578 

6647 

6691 

6742 

6836 

6911 

6974 

7075 

7126 

7176 

7252 

7327 

7390 

7478 

7617

0.0 

0.0 

0.319E-06 

0.109E-05 

0.656E-05 

0.399E-04 

0.1 12E-03 

0.348E-03 

0.110E-02 

0.370E-02 

0.669E-02 

0.177E-01 

0.181E-01 

0.212E-01 

0.251E-01 

0.303E-01 

0.360E-01 

0.420E-01 

0.525E-01 

0.601E-01 

0.772E-01 

0.901E-01 

0.110E+00 

0.139E+00 

0.172E+00 

0.212E+00 

0.251E+00 

0.270E+00 

0.301E+00 

0.302E+00 

0.308E+00 

0.320E+00 

0.308E+00 

0.300E+00 

0.294E+00 

0.286E+00 

0.280E+00 

0.274E+00 

0.269E+00 

0.257E+00

0.543E+03 

0.591E+02 

0.560E+02 

0.480E+02 

0.394E+02 

0.333E+02 

0.301E+02 

0.270E+02 

0.242E+02 

0.208E+02 

0.193E+02 

0.138E+02 

0.115E+02 

0.996E+01 

0.936E+01 

0.884E+01 

0.841E+01 

0.822E+01 

0.762E+01 

0.724E+01 

0.643E+01 

0.611E+01 

0.579E+01 

0.527E+01 

0.472E+01 

0.412E+01 

0.410E+01 

0.361E+01 

0.310E+01 

0.190E+01 

0.162E+01 

0.135E+01 

0.119E+01 

0.113E+01 

0.107E+01 

0.983E+00 

0.886E+00 

0.809E+00 

0.692E+00 

0.569E+00

363 

565 

578 

600 

641 

685 

710 

738 

768 

803 

825 

849 

851 

867 

884 

902 

920 

934 

963 

978 

1004 

1021 

1042 

1069 

1094 

1120 

1144 

1159 

1176 

1206 

1231 

1252 

1283 

1298 

1313 

1334 

1355 

1374 

1402 

1444

146 

117 

117 

116 

115 

113 

112 

111 

110 

109 

108 

106 

105 

103 

102 

101 

100 

99 

98 

97 

96 

95 

94 

93 

92 

91 

90 

89 

89 

87 

87 

86 

85 

84 

84 

83 

82 

82 

81 

80

A-3 NUREG/CR-5732
Appendix A

Table A1 (Continued) 

Flow rate from core Obis) Core exit 

Time temperature Pressure 

(s) Hydrogen Total (a F) (psia)

7705 

7831 

7995 

8159 

8260 

8398 

8474 

8600 

8688 

8827 

9129 

9356 

9734 

10409 

10484 

10514 

10559 

10574 

10769 

10784 

10814 

10874 

10904 

10915 

10924 

10931 

10962 

10969 

10975 

10987 

11000 

11027 

11871 

13251 

13257 

13277 

15067 

15095 

15115 

15410

0.245E+00 

0.230E+00 

0.218E+00 

0.206E+00 

0.199E+00 

0.190E+00 

0.180E+00 

0.168E+00 

0.160E+00 

0.149E+00 

0.127E+00 

0.108E+00 

0.920E-01 

0.578E-01 

0.639E-01 

0.525E+01 

0.796E+00 

0.0 

0.0 

0.206E+01 

0.436E+01 

0.480E+01 

0.107E+02 

0. 176E+ 02 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0

0.539E+00 

0.502E+00 

0.467E+00 

0.431E+00 

0.408E+00 

0.377E+00 

0.347E+00 

0.302E+00 

0.270E+00 

0.218E+00 

0.127E+00 

0.108E+00 

0.920E-01 

0.578E-01 

0.639E-01 

0.989E+01 

0.796E+00 

0.0 

0.0 

0.206E+01 

0.745E+01 

0.958E+01 

0.166E+02 

0.278E+02 

0.513E+01 

0.0 

0.0 

0.837E+02 

0.201E+03 

0.219E+03 

0.318E+02 

0.420E+02 

0.468E+02 

0.470E+02 

0.318E+03 

0.453E+02 

0.481E+02 

0.181E+01 

0.0 

0.0

1469 

1504 

1550 

1595 

1622 

1657 

1676 

1703 

1720 

1745 

1823 

1874 

1953 

2079 

2094 

2216 

2286 

721 

727 

2306 

2347 

2588 

2874 

306 

308 

891 

891 

315 

312 

304 

304 

305 

303 

303 

309 

303 

303 

302 

345 

345

79 

78 

77 

76 

75 

75 

74 

74 

73 

73 

72 

71 

70 

70 

70 

70 

70 

70 

70 

70 

70 

71 

125 

119 

113 

107 

83 

79 

75 

72 

72 

72 

70 

71 

70 

71 

70 

70 

70 

70

NUREG/CR-5732 A.4
Appendix A

Table A.2 Grand Gulf TC-MARCH2 output 

for input to TRAP-MELT 

Flows from core (g/s) 

Time 

(s) CsI CsOH 

0 41.5 414 

96 9.81 59.3 

276 11.7 70.6 

444 12.3 74.6 

612 11.8 73.9 

780 12.0 72.5 

960 11.0 66.5 

1150 10.4 62.7 

1340 9.69 58.6 

1550 8.57 51.8 

1780 8.08 48.9 

2070 7.10 43.0 

2440 6.17 37.3 

2810 5.70 34.5 

3111 12.5 75.6 

3290 15.9 96.0 

3490 7.06 42.7 

3760 0.98 5.93 

4020 0.27 1.63 

5350 0.08 0.5

A-5 NUREG/CR-5732
Appendix A

Table A-3 Grand Gulf TC-MARCH2 output for input to TRAP-MELT

Average gas temperature ( F) 

Time Pressure 

(s) (psia) Volume 1 Volume 2 Volume 3 Volume 4 

0 1370 640 597 590 582 

135 1420 640 597 590 582 

405 1520 640 597 590 582 

675 1620 651 603 590 582 

945 1720 651 603 590 582 

1230 1830 651 603 590 582 

1530 1930 661 608 590 582 

1830 2030 661 608 590 582 

2160 2120 661 608 590 582 

2490 2210 669 612 590 582 

2810 2300 679 615 583 585 

3100 2960 1040 730 768 664 

3360 1740 1830 1420 1420 1170 

3630 568 1290 1420 1120 1240 

3930 567 860 1080 836 1040 

4250 567 686 812 697 832 

4580 603 669 764 668 800 

4890 613 675 755 667 805 

5400 613 675 755 667 805

NUREG/CR-5732 A-6
Appendix A

Table A.4 Grand Gulf TQUV-MERGE output from MARCH2 

Flow rate from core (lb/s) Core exit 

Time" temperature 

(s) H2 Total (aF)

0 

120 

180 

300 

360 

420 

480 

543 

605 

664 

725 

843 

901 

1087 

1200 

1260 

1382 

1566 

1622 

1809 

1874 

2222 

2281 

2642 

2704 

3020 

3064 

3346 

3603 

3661 

3904 

3969 

4287 

4335 

4550 

4910 

5280 

5650

0.0441 

0.0661 

0.0799 

0.114 

0.136 

0.162 

0.156 

0.132 

0.118 

0.109 

0.104 

0.103 

0.0966 

0.0750 

0.0703 

0.0701 

0.0748 

0.0957 

0.109 

0.225 

0.285 

0.756 

0.812 

0.863 

0.0 

0.647 

0.604 

0.638 

0.506 

0.296 

0.0802 

0.0 

0.0547 

0.0127 

0.0 

0.0 

0.0 

0.0

11.6 

9.95 

9.26 

8.30 

7.79 

7.01 

131 

110 

93.8 

83.5 

76.1 

62.5 

58.4 

44.7 

37.2 

34.4 

28.8 

22.9 

21.5 

16.0 

15.0 

7.73 

6.70 

3.30 

0.0 

1.42 

1.31 

1.20 

0.719 

0.377 

0.0802 

0.0 

0.0547 

0.0127 

7.5 

24.7 

67.8 

79.0

1255 

1315 

1346 

1411 

1444 

1476 

1765 

1848 

1902 

1945 

1980 

2047 

20731 

2123 

2148 

2159 

2190 

2250 

2272 

2413 

2514 

2794 

2846 

3053 

0 

3064 

3072 

3150 

3197 

3202 

3219 

0 

3135 

3130 

3120 

3100 

2980 

2920

A-7 NUREG/CR-5732
Appendix A

Table A-4 (Continued) 

Flow rate from core Qb/s) Core exit 

Time" temperature 

(s) H 2 Total (

0 F) 

6010 0.0 47.3 2800 

6350 0.0 10.3 2740 

6720 0.0 3.0 2650 

6843 0.0 1.4 2604 

7090 0.0 0.95 500 

7440 0.0 0.49 500 

"Note: All entries after t = 4335 are from TRAP-MELT input, with H2 = 0 assumed, and most temperatures assumed 

(exception is point at t = 6843).

NUREG/CR-5732 A-8
Appendix A

Table A.5 Grand Gulf TQUV-MARCH2 output for input to TRAP-MELT 

Flows from core (g/s) 

Time 

(s) csl CsOH 

0 36.1 337 

130 8.76 54.1 

325 15.5 93.2 

451 17.6 106 

577 18.1 110 

704 17.8 108 

886 10.3 64.2 

1090 11.6 70.4 

1230 16.1 97.6 

1380 12.5 75.6 

1590 10.5 63.3 

1860 8.08 48.9 

2670 4.67 28.2 

3040 7.07 42.8 

3340 6.85 41.4 

3630 1.33 8.0 

3940 0.35 2.1 

4300 0.18 1.1 

6840 0.03 0.21

A-9 NUREG/CR-5732
Appendix A

Table A-6 Grand Gulf TQUV-MARCH2 output for input to TRAP-MELT 

Average gas temperature (*F) 

Time Pressure 

(s) (psia) Volume 1 Volume 2 Volume 3 Volume 4 

0 100 2510 1690 1430 1050 

204 81.9 2680 1730 1460 1050 

619 56.4 2880 1800 1520 1040 

1040 45.8 2970 1840 1550 914 

1470 36.3 3150 1900 1580 1040 

1890 32.4 3210 1940 1600 995 

2300 31.0 3170 1948 1610 744 

2690 78.2 3240 2090 1680 1300 

3050 210 2670 2390 1920 1510 

3420 327 422 2180 2150 1500 

3790 345 431 1320 1740 1130 

4150 261 407 936 1290 871 

4490 84.6 321 931 1210 839 

4860 39.0 268 935 1190 829 

5230 31.0 253 937 1180 819 

6300 26.0 240 938 1170 816 

6900 25.0 240 938 1170 816 

Table A-7 Peach Bottom AE-MERGE output for input to MARCH2 

Flow rate from core Qb/s) Core exit 

Time temperature 

(s) H2 Total (

0 F) 

0 0 0 1363 

510 0.227 0.354 1363 

690 0.219 0.337 1476 

930 0.140 0.175 1568 

1170 0.196 0.226 1746 

1410 0.142 0.145 1865 

1650 0.710 0.833 3141 

1890 1.02 161 2610 

2130 0.232 173 1178 

2325 0.028 1.03 1606 

2370 0 0 0 

7000 0 0 0

NUREG/CR-5732 A-10
Appendix A

Table A8 Peach Bottom AE-MARCH2 output 

for input to TRAP-MELT 

Flows from core (g/s) 

Time 

(s) L&I CsOH

0 

270 

660 

870 

1050 

1230 

1410 

1560 

1680 

1890 

2340 

3390 

4500 

5250 

6300 

6990

1.53 

2.59 

11.0 

17.2 

18.5 

16.8 

14.8 

27.0 

28.9 

4.13 

1.92 

0.89 

1.56 

3.04 

1.47 

0.055

49.4 

32.5 

73.8 

116 

124 

113 

99.6 

181 

194 

27.9 

12.9 

5.9 

10.5 

20.4 

9.9 

0.37

A.11 NUREG/CR-5732
Appendix A

Table A.9 Peach Bottom AE-MARCH2 output for input to TRAP-MELT 

Average gas temperature (OF) 

Time Pressure 

(s) (psia) Volume 1 Volume 2 Volume 3 

0 38.2 930 265 265 

60 34.6 930 707 366 

180 31.8 930 504 471 

300 30.9 930 496 376 

420 30.5 1220 517 398 

600 30.5 1445 544 432 

780 30.5 1550 554 430 

960 30.5 1645 560 425 

1140 30.5 1750 567 442 

1260 30.5 1820 582 451 

1380 30.6 1900 613 475 

1500 34.2 2290 1040 954 

1620 68.5 3210 1990 1900 

1740 104 3250 2330 2220 

1880 122 2340 2200 2120 

2030 44 1270 1580 1550 

2180 25.2 957 1270 1250 

2300 15.4 1240 1340 775 

2360 15.4 1240 1340 775 

7000 15.4 1240 1340 775

NUREG/CR-5732 A-12
Appendix A

Table A.10 Peach Bottom TC2-MERGE output from MARCH2 

Flow rate from core Qb/s) Core exit 

Time temperature Pressure 

(s) Hydrogen Total (

0F) (psia)

3514 

3736 

3742 

3778 

3814 

3850 

3871 

3881 

3896 

3913 

4066 

4072 

4108 

4144 

4162 

4174 

4186 

4222 

4258 

4294 

4301 

4313 

4328 

4351 

4356 

4523 

4529 

4565 

4601 

4612 

4622 

4638 

4657 

4661 

4701 

4707 

4743 

4748 

4759 

4778

0.0 

0.0 

0.180E+00 

0.257E+00 

0.524E+00 

0.174E+01 

0.482E+01 

0.680E+01 

0.411E+01 

0.0 

0.0 

0.116E+00 

0.395E+00 

0.142E+01 

0.637E+00 

0.0 

0.277E+00 

0.347E+00 

0.391E+00 

0.826E+00 

0.414E+01 

0.932E+01 

0.916E+01 

0.378E+01 

0.0 

0.0 

0.418E+00 

0.146E+01 

0.120E+01 

0.414E+01 

0.826E+01 

0.835E+01 

0.475E+01 

0.0 

0.0 

0.617E+00 

0.174E+01 

0.728E+01 

0.716E+01 

0.754E+01

0.0 

0.0 

0.544E+00 

0.841E+00 

0.188E+01 

0.665E+01 

0.255E+02 

0.396E+02 

0. 189E+ 02 

0.0 

0.0 

0.211E+00 

0.117E+01 

0.515E+01 

0.206E+01 

0.0 

0.642E+00 

0.854E+00 

0.957E+00 

0.250E+01 

0.153E+02 

0.167E+03 

0.418E+02 

0.141E+02 

0.0 

0.0 

0.877E+00 

0.406E+01 

0.266E+01 

0.134E+02 

0.127E+03 

0.375E+02 

0.149E+02 

0.0 

0.0 

0.132E+01 

0.385E+01 

0.231E+02 

0.397E+02 

0.391E+02

690 

690 

1690 

1815 

1843 

1939 

2059 

2225 

2149 

736 

736 

2089 

2180 

2276 

2258 

765 

2136 

2257 

2270 

2294 

2416 

2940 

2998 

3031 

883 

883 

2859 

3061 

3104 

3146 

3720 

3748 

3910 

1063 

1063 

3651 

3812 

3800 

3955 

4079

1105 

1104 

1104 

1108 

1111 

1124 

1118 

1109 

1079 

1099 

1098 

1098 

1100 

1111 

1116 

1116 

1117 

1121 

1125 

1131 

1099 

1120 

1101 

1111 

1111 

1110 

1110 

1121 

1132 

1110 

1120 

1090 

1123 

1123 

1120 

1121 

1138 

1112 

1122 

1090

A-13 NUREG/CR-5732
Appendix A

Table A.O (Continued) 

Flow rate from core (lb/s) Core exit 

Time temperature Pressure 

(s) Hydrogen Total (0 F) (psia) 

4790 0.500E+01 0.124E+02 4120 1129 

4794 0.0 0.0 1238 1129 

4821 0.0 0.0 1238 1127 

4827 0.564E+00 0.118E+01 3865 1128 

4863 0.213E+01 0.470E+01 3983 1146 

4869 0.787E+01 0.441E+02 3998 1124 

4878 0.670E+01 0.328E+02 4053 1139 

4890 0.0 0.0 2101 1119 

4905 0.713E+01 0.124E+03 4004 1132 

5028 0.131E+01 0.282E+01 3967 1150 

5033 0.567E+01 0.171E+02 3970 1122 

5041 0.645E+01 0.920E+02 4016 1141 

5055 0.738E+01 0.608E+02 4014 1106 

5071 0.408E+01 0.112E+02 4040 1135 

5075 0.0 0.0 1644 1135 

5106 0.0 0.0 1644 1133 

5112 0.870E+00 0.184E+01 3868 1135 

5142 0.150E+01 0.324E+01 3989 1150 

5148 0.662E+01 0.232E+02 3985 1122 

5156 0.650E+01 0.786E+02 4025 1150 

5169 0.673E+01 0.300E+02 4028 1116 

5186 0.776E+01 0.231E+02 3153 1135 

5193 0.256E+02 0.548E+02 559 1166 

5195 0.0 0.219E+02 560 1149 

5209 0.0 0.303E+03 558 1122 

5246 0.0 0.124E+03 563 1161 

5673 0.0 0.466E+02 562 1154 

5709 0.0 0.145E+03 563 1156 

6904 0.0 0.246E+02 561 1138 

7589 0.0 0.117E+02 564 1168

NUREGICR-5732 A.14
Appendix A

Table A.11 Peach Bottom TC2--MARCH2 output for input 

to TRAP-MELT 

Flows from care (g/s) 

Ti'me 

(s) CSi CsOH 

3500 0 0 

3504 72.5 667.1 

3548 24.6 163.4 

3676 13.0 87.0 

3833 15.0 100.7 

3968 17.3 116.3 

4132 10.7 72.3 

4295 18.0 122.7 

4425 15.9 108.5 

4585 11.9 83.4 

4735 18.0 126.4 

4859 16.5 113.0 

5027 10.3 70.9 

5173 22.8 171.6 

5248 31.2 227.7 

5361 2.7 19.6 

6516 0.11 0.83 

7587 0.007 0.05

A.15 NUREG/CR-5732
Appendix A

Table A.12 Peach Bottom TC2-MARCH2 output for input to TRAP-MELT 

Average gas temperature ( I

0

F) 

Time Pressure 

(s) (psia) Volume 1 Volume 2 Volume 3 Volume 4 

3500 1290 1090 884 740 671 

3700 1290 1090 884 740 671 

3706 1290 1090 884 740 671 

3913 1490 1190 921 779 697 

4114 1470 1190 895 790 672 

4315 1710 1540 1300 913 816 

4523 1940 1600 1200 936 793 

4725 2380 1830 1250 1020 802 

4923 2490 2140 1470 1240 955 

5130 2480 2210 1640 1340 978 

5329 567 968 1260 1420 1290 

5535 567 764 1060 1250 1200 

5738 567 651 859 1040 1100 

5938 567 607 741 887 986 

6547 568 576 601 649 718 

7360 569 591 607 615 703 

7600 569 591 607 615 703

NUREG/CR-5732 A.16
Appendix A

Table A-13 Sequoyah TB-MERGE output from MARCH2 

Flow rate from core (lb/s) Core exit 

Time temperature 

(s) H2 Total (aF) 

19356 0.112 12.6 2460 

19656 0.607 4.44 2637 

19956 0.627 2.23 3010 

20256 0.730 0.812 3352 

20556 0.687 0.728 3505. 

20856 0.825 0.900 3617 

21162 1.525 2.02 3772 

21366 0 75.85 3288 

21426 0 115.2 3210 

21498 0 123.7 3135 

21558 0 124.7 3070 

21636 0 142.6 2991 

21720 0 128.3 2904 

21804 0 128.3 2813 

21894 0 126.8 2728 

21954 0 130.85 2667 

22014 0 131.75 2602 

22086 0 111.7 2528 

22176 0 106.1 2440 

22260 0 118.4 2355 

22338 0 117.6 2280 

22416 0 100.65 2203

A-17 NUREG/CR-5732
Appendi A

Table A.14 Sequoyah TB-MARCH2 output 

for input to TRAP-MELT

Flows from core (g#s) 

Time 

(s) CsI CsOH

19400 

19643 

19748 

19913 

20033 

20145 

20250 

20355 

20460 

20565 

20685 

20828 

20985 

21163 

21307 

21481 

22012 

22414

0 

16.39 

10.00 

17.00 

20.0 

20.9 

22.0 

22.5 

21.6 

20.3 

16.5 

15.0 

12.9 

10.4 

20.4 

0.67 

0.045 

0.002

0 

146.2 

64.3 

103.8 

114.9 

121.9 

128.0 

132.3 

127.3 

119.6 

98.2 

88.9 

78.1 

63.8 

133.1 

4.3 

0.28 

0.01

NUREG/CR-5732 A-18
Appendix A

Table A.15 Sequoyah TB-MARCH2 output for input to TRAP-MELT 

Average gas temperature ( F) 

"Time Pressure 

(s) (psia) Volume 1 Volume 2 Volume 3 Volume 4 

19400 1223 1830 1100 1050 671 

19782 1223 1830 1100 1050 671 

19923 1254 1910 1120 1070 675 

20063 1282 1990 1150 1090 680 

20198 1305 2090 1170 1110 676 

20337 1327 2150 1210 1140 679 

20475 1345 2180 1240 1170 681 

20614 1360 2220 1280 1200 685 

20753 1370 2240 1310 1240 690 

20891 1407 2280 1370 1310 694 

21030 1485 2310 1430 1370 706 

21167 1588 2360 1500 1440 714 

21306 1911 605 1010 1040 730 

21444 2102 613 758 779 727 

21584 2043 611 667 680 721 

22419 1999 608 619 620 664

A-19 NUREG/CR-5732
Appendix A

Table A-16 Surry TMLB'-MERGE output from MARCH2

Flow rate from core (b/s) Core exit 

Time temperature Pressure 

(s) Hydrogen Total (0F) (psia) 

0 O.OOOE+00 0.298E+04 580 2250 

2640 O.OOOE+00 0.667E+02 564 1599 

2670 O.OOOE+00 0.369E+02 564 1619 

2820 0.OOOE+00 0.802E+01 573 1816 

5835 0.000E+00 0.784E+02 660 2369 

5850 0.668E-07 0.782E+02 660 2369 

5955 0.567E-06 0.691E+02 669 2369 

6060 0.246E-05 0.518E+02 703 2369 

6135 0.779E-05 0.409E+02 746 2369 

6195 0.236E-04 0.335E+02 766 2369 

6270 0.963E-04 0.266E+02 836 2369 

6330 0.288E-03 0.224E+02 889 2369 

6345 0.378E-03 0.216E+02 900 2369 

6390 0.840E-03 0.191E+02 935 2369 

6405 0.109E-02 0.184E + 02 945 2369 

6495 0.436E-02 0.149E+ 02 1009 2368 

6570 0.105E-01 0.129E+02 1063 2368 

6645 0.207E-01 0.110E+02 1116 2368 

6705 0.327E-01 0.997E+01 1162 2368 

6810 0.668E-01 0.786E+01 1241 2367 

6900 0.121E+00 0.665E+01 1315 2367 

6975 0.205E+00 0.543E+01 1380 2367 

7020 0.302E+00 0.420E+01 1413 2366 

7050 0.461E+00 0.252E+01 1426 2366 

7185 0.434E+00 0.140E+01 1527 2366 

7335 0.330E+00 0.526E+00 1638 2366 

7545 0.202E+00 0.202E+00 1745 2365 

7965 0.876E-01 0.876E-01 1892 2364 

8235 0.OOOE+00 0.OOOE+00 663 2363 

8340 0.OOOE+00 0.OOOE+00 663 2343 

8400 0.799E+00 0.829E+00 2059 2354 

8595 0.159E+01 0.202E+01 2689 2363 

8625 0.508E+01 0.206E+02 3413 2363 

8685 0.387E+01 0.705E+02 3852 2366 

8700 0.675E1+00 0.106E + 03 660 2366 

8715 0.OOOE+00 0.107E+03 660 2367 

9045 0.OOOE+00 0.OOOE+00 944 2370

NUREG/CR-5732 A.20
Appendix A

Table A.17 Surly TMLB'-MARCH2 output for input to TRAP-MELT 

Fows from core (gfs) 

Time 

(s) CsI 

0 40.5 368 

60 25.8 130 

150 32.3 163 

240 26.2 132 

360 20.8 105 

480 16.1 80.9 

630 13.3 66.8 

810 11.4 57.3 

1020 8.1 41.0 

1320 6.1 30.6 

1650 7.2 36.1 

2070 1.7 8.3 

2340 0.7 3.7

CsOH

Table A-18 Surry TMLB'-MARCH2 output for input to TRAP-MELT 

Average gas temperature (

0F) 

Time Pressure 

(s) (psia) Volume 1 Volume 2 

0 2370 1470 862 

45 2365 1500 866 

143 2360 1560 873 

248 2358 1640 878 

368 2356 1690 881 

488 2354 1740 883 

645 2353 1800 888 

833 2352 1850 891 

1020 2351 900 891 

1240 2350 788 887 

1470 2340 1780 930 

1570 2360 2240 1090 

1680 2365 3090 1730 

1770 2370 1230 1200 

1900 2370 660 758 

1980 2370 660 719 

2010 2370 660 756 

2340 2370 660 784

A.21 NUREG/CR-5732
Appendix A

Table A.19 Surry AB-MARCH2 output for input to TRAP-MELT 

Flow rate from core Qhbs) Core exit 

Time temperature 

(s) H2 Total ( IF) 

0 0 0 1228 

246 0.392 0.392 1228 

312 0.353 0.353 1280 

576 0.270 0.270 1471 

906 0.233 0.233 1701 

1170 0 40.3 3688 

1230 1.393 40.7 3661 

1470 6.083 40.25 3571 

2070 0 40.7 3731 

2706 0 0 3500 

5000 0 0 3500

Table A.20 Surry AB-MARCH2 output 

for input to TRAP-MELT 

Flows from core (g/s) 

Time 

(s) csT CsOH

0 

36 

96 

156 

228 

300 

384 

480 

588 

720 

900 

1180 

1450 

1630 

1880 

2520 

4030 

5190

162 

35.1 

37.6 

34.0 

29.0 

26.7 

22.9 

19.7 

16.5 

13.3 

8.68 

4.4 

1.1 

0.62 

0.35 

0.21 

0.04 

0

1100 

178 

190 

172 

146 

135 

115 

99.3 

83.3 

66.9 

43.8 

22.3 

5.3 

3.2 

1.8 

1.1 

0.22 

0

NUREG/CR-5732
Appendix A

Table A-21 Surry AB-MARCH2 output for input to TRAP-MELT

Time 

(s)

0 

198 

330 

462 

726 

858 

990 

1120 

1250 

1390 

1520 

1650 

2040 

2280 

2340 

5120

Pressure 

(psia)

35.6 

34.6 

34.0 

34.0 

32.5 

32.1 

31.9 

33.6 

34.5 

35.5 

36.8 

37.6 

39.6 

40.9 

41.1 

41.1

Average gas Temperature (CF)

Volume 1

1040 

0 

1300 

1400 

1580 

1670 

1920 

1010 

258 

260 

262 

263 

266 

267 

257 

257

Volume 2

724 

803 

863 

920 

1010 

1060 

1200 

974 

517 

419 

374 

352 

327 

321 

323 

323

Table A-22 Grand Gulf-Compartment volumes for sequences TC and TQUV 

Volume (ft3

) 

Control volume TC TQUV 

Core 1728 1728 

Steam separators 3357 3357 

Steam dryers 3335 3335 

Upper annulus 2030 2030 

Relief line 208 208

A.23 NUREG/CR-5732
Appendix A

Table A-23 Peach Bottom-compartment volumes for sequences TC and AE 

TC AE 

Control volume Volume Control volume Volume 

(ft~) (ft3

) 

Core 1360 Core 1728 

Shroud head 1170 Steam separator 580 

Pipes and separators 582 Upper outer annulus 2030 

Steam dryers 3000 

Upper outer annulus 1000 

Lower outer annulus 1000 

Steam lines 1080 

Relief lines 622 

Table A.24 Sequoyah-Compartment volumes for sequence TBA 

Control volume Volume (ft) 

Core 1020 

Grid plate 70.01 

Guide tubes 85.70 

Upper support plate 511 

Core barrel 857 

Table A.25 Surry-Compartment volumes for sequences AB and TMLB 

AB TMILB 

Control volume Volume Control volume Volume 

No. (ft) No. (ft) 

1 589 1 589 

2 100 2 100 

3 506 3 506 

4 79 4 230 

5 150 6 1301

NUREG/CR-5732 A-24
Appendix B. Kinetic and Equilibrium Calculations
B.1 Kinetics of Cs-I-H2-H20 

Reactions AGP; = a + bT 

rxn

Twenty reactions (ten reversible equations) were 

chosen to represent the kinetic behavior of cesium and 

iodine species. In a more comprehensive study of the 

rates of formation of CsOH and CsI under accident 

conditions, Wren used 152 reactions.' In that study, 

he concluded that in a CANDU reactor primary heat 

transport system under accident conditions, CsI and 

CsOH would form in < 10.2 s. In the present study, 

the kinetic calculations are used only as a guide in 

determining which control volumes reached 

equilibrium (i.e., those control volumes in which the 

residence times of cesium and iodine species were 

sufficiently long that the species concentrations did 

not vary with time). 

The data on equilibrium thermodynamics are generally 

more reliable than data on rate constants. For this 

reason, equilibrium thermochemical calculations were 

performed in addition to the rate calculations. 

The rate constants for the 20 reactions given in 

Table B.1 is the Arrhenius form

where

AGF = rxn a,b=

standard free energy change of reaction, 

constants fit over the same temperature 

interval.

If we adopt this means of expressing AGO, then rxnK

G; =a+bT = RT In K., = --RT In -K 

,', KR, (B-3)

where

K~q = equilibrium constant, 

KF, KR = rate constant for the forward and reverse 

reactions. 

Equation B.3 can be rearranged as

KF = ex[( a + KR (B.4)

K = A exp(- R) 

where 

K = rate constant, 

A = preexponential or frequency factor, 

E,, = activation energy.

The rate constant equation written in this way assumes 

that there is little or no temperature dependence of A 

or E, over the temperature range of interest. 

In reactions of the type C + D o E + F, the rate 

constants for the forward and reverse reactions can 

satisfy the requirements of the equilibrium constant. 

The requirements of the equilibrium constraint to 

maintain A and E,, independent of temperature can 

be obtained as described in the following 

manipulation. The standard free energy change can 

often be fitted over a temperature interval by the 

simple linear relation

(B.1)

The rate constants for the forward and reverse 

reactions are expressed as

K, = A e4_ RT ) 

KR A ex, -

(B-5)

(B.6)

Inserting Equations B.5 and B.6 into B.4 gives

A *4 - E-1)~ - j- )] -A'4 ) (B.7)

or

NUREG/CR-5732

Appendix B

(B-2)

B.3
Appendix B

Table B.1 Reaction rate constants

Reaction Rate constant* at 1000 K Frequency References 

(1341' F) factor

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20.

CsI + H 20 - CsOH + HI 

CsOH + HI - CsI + H 20 

2HI - 12 + H 2 

12 + H2- 2HI 

1 + 1 + M -12 + M 

M + 12 - I + I + M 

I + H2 - HI + H 

HI + H - I + H2 

HI + I - H + 12 

H + 12 - HI + I 

H + H + M -. H 2 + M 

M + H2 H + H + M 

Cs + I + M - CsI + M 

M + CsI -. Cs + I + M 

Cs + HI -. CsI + H 

CsI + H - Cs + HI 

Cs + H 20 -. CsOH + H 

CsOH + H -. Cs + H 20 

Cs + 12 -Csi + I 

CsI + I -. Cs + 12

2.12 x 10.23 

1.00 x 10is 

2.42 x 10.20 

3.01 x 10`9 

1.15 X 10.31 

2.56 x 10-17 

2.19 x 10-17 

5.54 x 10-11 

4.66 x 10"18 

6.0 x 10`10 

1.25 x 10"31 

1.9 x 10"20 

3.7 x 10"3 

1.6 x 10"" 

2.00 x 10." 

2.53 x 10" 

1.70 x 10.16 

1.00 x 10.10 

8.81 x 1010 

8.66 x 1020

1.57 x 10.12 

1.00 x 10-11 

1.00 x 10.10 

1.66 x 10.10 

3.17 x 10-m 

3.14 x 10.10 

2.64 x 10.10 

7.4 x 1011 

3.59 x IWO 

6.0 x 10.10 

2.31 x 10.3 

4.98 x 10.' 

6.44 x 10"31 

5.37 x 10-9 

2.00 x 10-11 

2.82 x 10-13 

1.11 x 10.9 

1.00 x 10.10 

8.81 x 10.10 

7.43 x 10-12

M, the collision molecule, is

NUREG/CR-5732

32 

33 

33 

34 

34, 35 

32, 35 

32 

32

Units are s-1, cm 3

-molecule-1 s-1

, and cm6.molecule-2 s"1 for first-, second-, and third-order reactions, respectively. 

the total of the H2 and H 20 molecular concentrations (molecules/cm 3

).

B.4
Appendix B

ln A - - = In A'- .a + RT 

RT tRT _R) eRT 

then

InA - InA = E., -E_ 

RT SRT R) (

(

(I

Assuming that In A - In A' = - bIR, then 

Equation B.9 becomes 

In A -In A's! .,~~cga' + 

R RT RTR 

which yields

E,,F- Eaa, = a

Thus, fitting the standard free energy change of 

reaction to a linear form with temperature and 

assuming the difference in the natural log of the 

frequency factor for the forward and reverse rea 

is equal to -bIR, then rate constants can be expr 

in the Arrhenius form and satisfy the equilibriul 

constraint. Standard free energies of reaction ii

form of AGO = a + bT are given in Table B.2. These 

data were obtained from the FACT system.' The 

(B.8) FACSIMILE computer program was used to perform 

the rate calculations. 

B.2 Equilibrium Calculations in the 

Cs-I-H2-H20 System 

13.9) 

The species considered in the equilibrium calculations 

include (gases) H2, H20, CsOH, CsI, Cs, H, HI, I, and 

12; and (liquids) CsI, CsOH, Cs, and 12. The calcula

tions were performed with the EQUILIB routine of 

the FACT system. This method of calculation was 

chosen because it is readily accessible to anyone in 

B.10) North America and because the thermochemical data 

base of FACT comes from standard assessed sources 

such as JANAF06 and Barin and Knacke.37 Thermo

chemical data for CsOH are not part of the FACT3 

data base, and values from JANAF were inserted into 

a user's data base for these calculations. 

The 13 species used in the equilibrium calculations are 

the same as those used in the kinetic calculations. 

Iodine ratios such as HI/CsI are very similar in the 

equilibrium calculations and in the kinetic 

e calculations, primarily because the bimolecular rate 

ctions constants are consistent with the equilibrium 

essed constants. 

m 

i the

Table B.2 Standard free energy of reaction 500 to 1200 K (441 to 17010 F) written as 

AGO= a + bT, exothermic reaction expressed left to right 

rx F(Energy in joules) 

Reaction a b 

CsOH + HI -- CsI + H 20 -1.31368 x 105 -1.54100 x 101 

12 + H2 " 2HI -1.30038 x 104 -1.48455 x 10' 

HI + H -- I + H2 -1.37991 x 1W5 +1.05761 x 101 

H + 12 . HI + I -1.50995 x 105 -4.26918 x 100 

Cs + HI ,* CsI + H -8.80264 x 102 -3.54386 x 10' 

CsOH + H * Cs + H 20 -1.30488 x 10i +2.00288 x 101 

Cs + 12 '0 CsI + I -1.51875 x 10' -3.97080 x 101

B.5 NUREG/CR-5732
Appendix C. Fitting of Radiolysis Data
Appendix C

Data from Lin"4 are listed in Table C.1 and shown in 

Figure C.1. The fraction of I converted by radiolysis 

to 12 must satisfy

lim F=O 

pH -

JIM F = I 

pH - -cc (C.la,b)

which are identical to the conditions

As shown in Figure C.1, there is a highly linear 

relationship between In(! - 1) and pH. Using the data F 

in Table C.1, a linear least-squares fit of the form 

F{1) = a) pH + 1 

yielded the values a = 1.72 and 13 = -6.08 with a 

correlation coefficient of 0.94.

pH - - )

Table C.1 Radiolysis data* for formation of 12

Initial 

concentration Initial Conversion 

(mol/L) pH (%) 

10-3 2 88.2 

3 81.8 

4 8.6 

5 2.4 

6 2.4 

104 3 93.8 

5 8.0 

6.6 1.7 

10-1 2 89.1 

3 77.9 

4 44.4 

5 6.9 

6.3 0.3

".Taken from C. C. Lin. 14

NUREG/CR-5732

0 l 1 1 )= -

M_
Appendix C

6 

4 

2

0

-2 

-4

ORNL DWG 91A-24

1 2 3 4 5 6 7

pH 

Figure C.1. Data fitting for radiolytic conversion of Y to I1 (data from U.S. Nuclear Regulatory 

Commission, Regulation Guide 1.4, "Assumptions Used for Evaluating the Potential 

Radiological Consequences of a Loss-of-Coolant Accident for Pressurized Water Reactors')

NUREG-CR-5732 C-.4
Appendix D. Fission Product Release Tables
Table D.1. Fission product inventories for selected plants*

Total core inventory (kg) 

Nuclide group Grand Gulf Peach Bottom Sequoyah Surry 

1 I 17.7 16.6 15.2 12.4 

2 Cs 244.8 230.3 184.7 145.7 

3 Te 37.1 34.9 31.7 25.4 

4 Sr 66.7 62.7 60.9 47.6 

5 Ba 112 105 77.7 61.2 

6 Ru 621 584 470 369 

7 Ce 221 208 167 131 

8 La 1724 2404 1313 855 

9 Xe 439 413 347 273

*Taken from References 1 and 2.

-J
I•

e

Table D.2. Bounding values for fractions of core inventory released into containment*

PWR releases into containment BWR releases into containment 

From primary symem' From care-concetc interaction Frm primary systern From core-concrete interaction Fission __________ ___________ __________ _____________ 

product group High RCS Low RCS Limestone Basaltic High RCS Low RCS Limestone Basaltic 

pressure pressure concrete concrete pressure pressure concrete concrete 

I 0.45 0.77 0.15 0.15 0.70 0.77 0.15 0.15 

Cs 0.42 0.77 0.15 0.15 0.65 0.76 0.15 0.15 

Te 0.27 0.51 0.40 0.30 0.17 0.17 0.50 0.30 

Sr-Ba 0.013 0.01 0.40 0.15 0.013 0.01 0.70 0.30 

Ru 0.053 0.01 0.005 0.005 0.053 0.01 0.005 0.005 

La-Ce 0.01 0.0015 0.05 0.05 0.01 0.0015 0.10 0.10 

Xe 1.0 1.0 0 0 1.0 1.0 0 0 

"Adapted from H. P. Nourbakhsh, "Estimate of Radionuclide Release Characteristics Into Containment Under Severe Accident Conditions 

(Draft for Comment)" NUREG/CR-5747, Brookhaven National Laboratory, December 1991. 

".Includes releases due to in-vessel melting, vessel breach, and late revaporization.

'0
Appendix EK Fractional Release Tables
Table El1 Grand Gulf - fractional releases and energy deposition rates

Nudide Whole core Total fraction released into containment" Energy deposition rate, ldep (MeV/h x 10-) 

group inventory" 

(kg) Low RCS pressure High RCS pressure Low RCS pressure High RCS pressure 

1 17.7 0.92 0.85 6.921 6.394 

Cs 244.8 0.91 0.80 0.885 0.778 

Te 37.1 0.67 0.67 0.499 0.499 

Sr 66.7 0.71 0.713 1.480 1.486 

Ba 112 0.71 0.713 0.708 0.711 

Ru 621 0.015 0.058 0.062 0.238 

Ce 1055 0.1015 0.11 0.165 0.179 

La 890 0.1015 0.11 2.300 2.493 

Total 13.020 12.778 

"From J. A. Gieseke et al., "Radionuclide Release Under Specific LWR Accident Conditions," BMI-2104, Battelle Columbus Laboratories, 1984, and R. S. Denning et al., 

"Radionuclide Release Calculations for Selected Severe Accident Scenarios," NUREG/CR-4624 (BMI-2139), Battelle Columbus Laboratories, 1986. 

"*Adapted from H. P. Nourbakhsh, "Estimate of Radionuclide Release Characteristics into Containment Under Severe Accident Conditions (Draft for Comment)," 

NUREG/CR-5747, Brookhaven National Laboratory, December 1991, assuming limestone concrete.

M1

-3
Table E.2 Peach Bottom - fractional releases and energy deposition rates 

Nudide Whole core Total fraction released into containment- Energy deposition rate, Edep (MeV/h x 10z) 

group inventoiy 

(kg) Low RCS pressure High RCS pressure Low RCS pressure High RCS pressure 

1 16.6 0.92 0.85 6.491 5.997 

Cs 230.3 0.91 0.80 0.833 0.732 

Te 34.9 0.67 0.67 0.469 0.469 

Sr 62.7 0.71 0.713 1.391 1.397 

Ba 105 0.71 0.713 0.664 0.667 

Ru 584 0.015 0.058 0.058 0.224 

Ce 992 0.1015 0.11 0.155 0.168 

La 836.6 0.1015 0.11 2.162 2.343 

Total 12.223 11.997 

"From I. A. Gieseke et al., "Radionuclide Release Under Specific LWR Accident Conditions," BMI-2104, Battelle Columbus Laboratories, 1984, and R. S. Denning et al., "Radionuclide Release Calculations for Selected Severe Accident Scenarios," NUREG/CR-4624 (BMI-2139), Battelle Columbus Laboratories, 1986. 

"Adapted from H. P. Nourtakhsh, 'Estimate of Radionuclide Release Characteristics into Containment Under Severe Accident Conditions (Draft for Comment)," NUREG/CR-5747, 

Brookhaven National Laboratory, December 1991, assuming limestone concrete.

N 

LA t1
Table F.3 Sequoyah - fractional releases and energy deposition rates

Nuclide Whole core Total fraction released into containment- Energy deposition rate, Edep (MCV/h x 1-u) group inventory" (kg) Low RCS pressure High RCS pressure Low RCS pressure High RCS pressure 

I 15.2 0.92 0.60 5.943 3.876 

Cs 184.7 0.91 0.57 0.675 0.418 

Te 31.7 0.92 0.67 0.579 0.426 

Sr 60.9 0.41 0.413 0.780 0.786 

Ba 77.7 0.41 0.413 0.284 0.286 

Ru 470 0.015 0.058 0.046 0.180 

Ce 796 0.0515 0.06 0.063 0.074 

La 684 0.0515 0.06 0.897 1.045 

Total 9.267 7.091 

"From J. A. Gieseke et al., "Radionuclide Release Under Specific LWR Accident Conditions," BMI-2104, Battelle Columbus Laboratories, 1984, and R. S. Denning et al., 

"Radionuclide Release Calculations for Selected Severe Accident Scenarios," NUREG/CR-4624 (BMI-2139), Battelle Columbus Laboratories, 1986. 

"*Adapted from H. P. Nourbakhsh, "Estimate of Radionuclide Release Characteristics into Containment Under Severe Accident Conditions (Draft for Comment)," 

NUREG/CR-5747, Brookhaven National Laboratory, December 1991, assuming limestone concrete.

0T1

L4

(!A
N t1ý

Table F.4 Surly TMLB' - fractional releases and energy deposition rates

Nuclide Whole core Total fraction released into containment- Energy deposition rate, Ed (MeV/h X 1-2) 

group inventory 

(kg) Low RCS pressure High RCS pressure Low RCS pressure High RCS pressure 

I 12.4 0.92 0.60 4.848 3.162 

Cs 145.7 0.92 0.57 0.532 0.330 

Te 25.4 0.81 0.57 0.413 0.290 

Sr 47.6 0.16 0.163 0.238 0.242 

Ba 61.2 0.16 0.163 0.087 0.089 

Ru 369 0.015 0.058 0.037 0.142 

Ce 626 0.0515 0.06 0.050 0.058 

La 539 0.0515 0.06 0.707 0.823 

Total 6.912 5.136 

"From I A. Gieseke et al., "Radionuclide Release Under Specific LWR Accident Conditions," BMI-2104, Battelle Columbus Laboratories, 1984, and R. S. Denning et al., 

"Radionuclide Release Calculations for Selected Severe Accident Scenarios," NUREG/CR-4624 (BMI-2139), Battelle Columbus Laboratories, 1986. 

"'Adapted from H. P. Nourbakhsh, "Estimate of Radionuclide Release Characteristics into Containment Under Severe Accident Conditions (Draft for Comment)," 

NUREG/CR-5747, Brookhaven National Laboratory, December 1991, assuming basaltic concrete.

: I

M'
NUREG/CR-5732 

ORNL/TM-11861 

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2. TITLE AND SUBTITLE ORNL/TM-11861 

Iodine Chemical Forms in LWR Severe Accidents 3 DATE REPORT PUBLISHED 

Final Report MONTH YEAR 

April 1992 4. FIN OR GRANT NUMBER 

B0854 

5. AUTHOR(S) 6. TYPE OF REPORT 

E. C. Beahm, C. F. Weber, T. S. Kress, and G. W. Parker Technical 

7. PERIOD COVERED onclusive Dates)

8. ILRFORMI1NG UORGANIZA IUN - NAME AND ADUDH S f NRC, provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address;ifcontractor, provide name and mailing address)

Oak Ridge National Laboratory 

Oak Ridge, TN 37831-6285

9. SPONSORING ORGANIZATION NAME AND ADDRESS (1/ NRC type "Saneas above' 'I contractor. provide NRC Ovison Of/ice or Regoo, US. Nselear Regulatory Cortrnsson

9. SPODNSO R ING 0OR GAN IZAT ION - NAM E AN D AD D RESS tIf NRC, type "'Same as above",' it contractor, provide NRC Division, Office or Region, U-S Nuclear Regulatry Commisin, 

and mailing address.) 

Division of Systems Research 

Office of Nuclear Regulatory Research 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555

1U. SUPPLEMENTARY NOTES

11. ABSTRACT (200rood or less; 

Calculated data from seven severe accident sequences in light water reactor plants were used to assess the chemical 

forms of iodine in containment. In most of the calculations for the seven sequences, iodine entering containment 

from the reactor coolant system was almost entirely in the form of CsI with very small contributions of I or HI. 

The largest fraction of iodine in forms other than CsI was a total of 3.2% as I plus HI. Within the containment, 

the CsI will deposit onto walls and other surfaces, as well as in water pools, largely in the form of iodide (I). The 

radiation-induced conversion of I in water pools into 12 is strongly dependent on pH. In systems where the pH 

was controlled above 7, little additional elemental iodine would be produced in the containment atmosphere. 

When the pH falls below 7, however, it may be assumed that it is not being controlled and large fractions of iodine 

as 12 within the containment atmosphere may be produced.

12. KEY WORDS/DESCRIPTORS (List words or phrases that will assist researchers in locating the report-) 13. AVAILABILITY STATEMENT 

iodine unlimited 

fission product behavior 14. SECURITY CLASSIFICATION 

reactor containment (This Page) 

severe accidents -unclassified 

LWRs (his Report) 

unclassified 

15. NUMBER OF PAGES 

16 PRICE

NRC FORM 335 12-89)
THIS DOCUMENT WAS PRINTED USING RECYCLED PAPER
IODINE CHEMICAL FORMS IN LWR SEVERE ACCIDENTS

UNITED STATES 

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APRIL 1992

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