ORNL-CF-68-3-38.txt

OAK RIDGE NATIONAL LABORATORY INTERNAL USE ONLY

OPERATED BY

 

UNION CARBIDE CORPORATION

NUCLISION | 0 R N L
CENTRAL FILES NUMBER

OAK RIDGE, TENNESSEE 37830

 

68-3-38

 

 

 

DATE: March 25, 1968 COPY NO.

susJECT: Decay Heat Generation by Fission Products and
£39Pq in a Single-Region Molten Salt Reactor

 

 

TO: M. W. Rosenthal and E. S. Bettis

FROM: W. L. Carter

ABSTRACT

Fission product and 233pg decay heat and concentrations have
been calculated for a single-region MSR for reactor equilibrium con-
ditions and as a function of decay cooling time. The MSR is_a
2000-Mw(e) system containing 2000 ft3 of LiF-BeFo-ThF4-233UF
fuel. Three operating modes were studied: (1) inert gas sparging
to remove noble gases from the fuel, (2) inert gas sparging plus re-
moval of noble metals by reaction with surfaces of the heat exchanger
loop, and (3) removal of all fission products by chemical processing
only. In all three cases the fuel was being processed in a chemical
plant on a 38-day cycle. Tabular and graphic data are presented for
32 fission product elements and 233Pa for decay times up to 11 years.

NOTICE This document contains information of a preliminary nature
and was prepared primarily for internal use at the Oaok Ridge
National Laboratory. It is subject to revision or correction and
therefore does not represent a final report. The information is
only for official use and no release to the public shall be made
without the approval of the Legal and Information Control Depart-
ment of Union Carbide Corporation, Nuclear Division.

 
INTRODUCTION

A primary concern in the design of a nuclear reactor is the removal of the after-
heat when the reactor is shut down. The problem becomes acute when it is assumed
that the shutdown is unscheduled due to an emergency that has disrupted the normal
cooling system of the reactor. In the case of the Molten Salt Reactor, this requires
draining the fuel into a receiver where emergency cooling is provided. Proper design
of this emergency cooling system is therefore essential to safe operation of the reactor.

This study has been carried out to determine the afterheat as a function of time

after fuel has been drained from the reactor. The reactor system considered is a
2000-Mw(e), single-region MSR containing 2000 ft3 of LiF-BeFp-ThF4-233UF4
fuel; the composition of the fuel carrier is respectively 52, 36, 12 mole %. In
addition to sufficient 233U for criticality, the fuel contains about 0.256 g/liter of

3Pq plus fission products. It was assumed that the reactor had been operating long
enough so that fission products were present in equilibrium concentrations for the
chosen processing conditions. Three processing modes were considered in determining
fission product concentrations: (1) all fission products removed on a 38-day cycle
through the processing plant; (2) noble gases removed by sparging and the remaining
fission products removed by chemical processing; and (3) noble gases sparged, noble
metals plated out on reactor surfaces, and the remaining nuclides removed by chemical
processing.

Protactinium is removed on a three-day cycle in a separate processing step.
About 7% of the 233Pa (14.5 kg) is in the circulating fuel; the remainder (190.5 kg)
is held in the processing plant. The system has a breeding ratio of 1.076.

Heat generation and inventory data were calculated for both fission products
and 233Pq from equilibrium to about 11 year's decay. At equilibrium gross fission
products and 233Pq in the fuel are generating about 289.4 Mw and 0.74 Mw,
respectively; an additional 9.7 Mw is being generated by 233Pq in the processing
plant.  When gases are sparged in the reactor, the fission product contribution is
reduced to 257 Mw, and, when both noble gases and noble metals are absent, the
rate is further reduced to 255.8 Mw. The fission product concentrations for these
three processing modes are respectively 3.08, 1.94, and 1.48 g/liter.

The principal source of heat is the short-lived fission products having half-lives
less than a few minutes. Hence, there is an initial large decrease in the heat genera-
tion rate when fissioning ceases. In the first 2 min after shutdown, the rate is down
by a factor of 3, in 18 min by a factor of 4.5, in 1 hr by a factor of 7, and in
10 hr by a factor of 17. Protactinium-233, which has a 27.4-day half-life, does
not show a significant decrease in heat production until about 15 to 20 days after
shutdown,

Extensive tables and graphs in later sections of this memorandum describe more
completely the thermal characteristics of this fuel for cooling times up to about
11 years.
A further interesting result of this study is the importance of just a few fission
products in the total heat generation rate. For example, at equilibrium, Rb, Cs,
and Sb, respectively, account for 22.8, 21, and 17.3% of fission product decay
heat. At 1 hour's decay, the figures are 18.6% I, 13% Kr, 10.5% La, and 9.6%
Y; at 10 hour's decay, the values are 23.8% |, 16.5% Lla, and 11.4% Y. For
much longer decay times (e.g., 125 days), about 80% of the decay heat is due to
Nb, Zr, Pr, and Y.

In the period two days to five months after reactor shutdown, more heat is being
generated by the massive amount of 3Pa in the processing plant than by decay of
gross fission products (see Fig. 2, page 13).

METHOD OF CALCULATION

Equilibrium concentrations of fission products were calculated by the HTGN
code written by Watson.!  This program treats 290 fission product nuclides and
accounts for their removal by chemical processing, neutron capture, decay, gas
sparging, and sorption on reactor surfaces. Production is a function of the fission
rate and characteristic yield. Decay heat and concentrations at equilibrium and
after shutdown were calculated by the CALDRON code written by Carter.2 This
program treats 469 nuclides and was written to describe the behavior of fuel in a
chemical processing plant. Beta heat, gamma heat, and concentration are calcu-
lated for each of the 469 nuclides as a function of time. The program accounts for
branching in the decay chains, and, in the case of chemical processing, allows the
removal and accumulation of specified nuclides in various process operations.

CHARACTERISTICS OF THE REACTOR

The molten salt reactor for which these calculations were made has the follow-
ing characteristics:

33

Fuel LiF-BeF-ThF4-2S3UF,
Composition of carrier salt, mole % 52-36-12
Power, Mw(th) 4444
Fuel volume in core, £13 1333
Total circulating fuel volume, 3 2000
Processing cycle time for fission products, days - 38
Processing cycle time for 233pq, days 3
Pa inventory in circulating fuel, kg 14,5
233pg inventory in processing plant, kg 190.5

Breeding ratio 1.076

 
AVERAGE LIFETIMES OF NOBLE GASES AND NOBLE METALS

It is well established that for good breeding performance the fission product
xenon must be quickly removed from the fission zone. This is accomplished by
sparging the circulating fuel with an inert gas; this action also removes krypton.
Competing with sparging for removal of noble gas atoms are radioactive decay,
neutron capture, diffusion into the graphite moderator, and chemical processing.
Studies and experience in MSRE operation indicate that the sparging rate needs to
be sufficiently vigorous that the average residence time of a gas atom in the fuel is
only about 50 sec for maintaining tolerable xenon poisoning. |

Secondly, there is a group of fission products (Se, Nb, Mo, Tc, Ru, Rh, Pd,

Ag, In, Te) whose behavior in the system is not entirely understood, but it is be-
lieved that these elements distribute throughout the circulating fuel loop by reactirg
with or otherwise attaching themselves to surfaces contacted by the fuel. This group
is known as the noble metals. Competing events for the removal of the noble metals
are radioactive decay, neutron capture, and chemical processing. The average life-
time for this "plating out" effect is probably different for each of these elements,
and the data are not available for determining the values very accurately. MSRE
data for fission product distribution in the reactor system were examined by Watson,4
who concluded that a value of 50 hr is reasonable for the average lifetime of the
noble metals. The scatter and paucity of the data did not warrant assigning a charac-
teristic lifetime to each element; so the 50-hr figure was assumed to apply to all.

REACTOR OPERATING CONDITIONS FOR WHICH DECAY
HEAT RATES ARE COMPUTED

Fission Products

The three following situations were considered in the HTGN and CALDRON
computations for determining the equilibrium heat and afterheat rates for decaying
fission products:

1. Gross amounts of fission products in the fuel, that is, no sparging of
noble gases and no plating out of noble metals.

2, Noble gases sparged on 50-sec cycle but no plating out of noble metals.
3. Noble gases sparged on 50-sec cycle and noble metals plated out on
50-hr cycle.

In each case equilibrium concentrations were calculated for a 38-day chemical
processing cycle and the characteristic losses due to neutron absorption and radioactive
decay. However, in the case of the gases, the computer program does not provide

for removal due to diffusion into the graphite.
 

In the computer program freatment of Cases 2 and 3, sparging and plating out
has the effect not only of removing the noble gases and noble metals but also of re-
moving daughter products of these elements. While this treatment is quite proper
for gases which are quantitatively removed from the fuel environment, it is not as
rigorous for noble metal decay products. Noble metals attached to reactor, piping,
and heat exchanger surfaces are always in contact with fuel, and decay products,
which are not noble to these surfaces, might reenter the fuel stream. The calcula-
tions on Cases 2 and 3 include only the daughter products of the noble gases and
metals that are associated with the equilibrium amounts of these gases and metals in
the fuel.

Protactinium

The amount of 233pq present in the system had been determined previously by
Kerr.5 His results stated that for a 3-day processing cycle for protactinium there
would be 14.5 kg 233pq (0.256 g/liter) in the circulating fuel stream and an addi-
tional 190.5 kg in the processing plant. The calculation of 233pPq afterheat was
then straightforward, since the chain terminates with a single decay. The beta and
gamma decay energies are respectively 9.3 and 41.5 w/g, totaling 50.8 w/g.

DISCUSSION OF RESULTS

Comparison of Cases 1, 2, and 3

The heat generation rates as a function of time after reactor shutdown given in
Tables 1, 2, and 3 were calculated for the three assumed reactor operating conditions
described above. A graphic gresen'ration of the total B + y heat generation is
given in Fig. 1. Values for 33Pq in these exhibits are for 233Pa in the fuel stream
only.

The effect on decay heat rate of removing noble gases and noble metals is shown
by the three fission product curves of Fig. 1. At equilibrium the effect of sparging
and plating is to decrease the gross decay heat by about 11.6%. However, the effect
on heat generation after fuel is dumped from the reactor is more pronounced, particu-
larly during the first hour or so. During this period, heat generation for the sparged
and "plated out" fuel is as much as 33% smaller than the gross fission product case
(Table 4). After the first hour of decay, the effect of removing gases and noble
metals is less pronounced but still reduces the decay heat by about 20% on the
average for the next year. After three year's decay there is a considerably larger
difference between the decay curves because the long-lived daughters of krypton and
xenon are absent from the sparged fuel. However, by this time the decay heat gener-
ation rate is small even for gross fission products; so the significance of this difference
is minor.

 
Table 1. Heat Generation from Fission Products and 233Po in Fuel of One-Region Molten Salt Reactor
With No Sparging' of Noble Gases and No Plating of Noble Metals

 

 

 

Reactor Power = 4444 Mw(th)
Fuel Volume in Reactor Circulating System = 2000 ft
Fuel Processing Cycle Time = 38 days
Pa Processing Cycle Time = 3 days
Equilibrium Pa Concentration = 7.25 g/ft3
Equilibrium Fission Product Concentration = 87.16 g/ff3
Time After Fuel Fission Products in Fuel Stream 233Pa'in Fuel Stream 233Pa + Fission Products
Dumped From Reactor B Heat vy Heat B + y Heat B + y Heat | B + y Heat
(hr) (w/Ft3) (w/Ft3) (w/f13) (w'/ft3) /i) (/)
0 (equilibrium) 0.1194 x 10° 0.2531 x 10° 0.1447 x 10° 368.3  7.250 0.1451 x 10°
0.001 (3.6 sec) 0.7109 x 10° 0.2526 x 10° 0.9635 x 10°  368.3  7.250 0.9672 x 10
0.003  (10.8 sec) 0.4577 x 10° 0.2505 x 10° 0.7082 x 10° 368.3  7.250 0.7119 x 10°
0.01 (36 sec) 0.3309 x 10° 0.2433 x 10° 0.5742 x 10° 368.3  7.250 0.5779 x 10°
0.03 (1.8 min) 0.2686 x 10° 0.2291 x 10° 0.4977 x 10° 368.3  7.250 0.5014 x 10°
0.10 (5 min) 0.2054 x 10° 0.2062 x 10° 0.4116 x 10° 368.2  7.249 0.4153 x 10°
0.30 (18 min) 0.1453 x 10° 0.1729 x 10° 0.3182 x 10° 368.2  7.248 0.3219 x 10°
1.0 . 0.8940 x 10° 0.1240 x 10° 0.2134 x 10° 367.9 7.242 0.2171 x 10°
3.0 0.5917 x 10% 0.8398 x 10° 0.1432 x 10°  367.1  7.227 0.1469 x 10°
10 0.3464 x 10* 0.5127 x 10% 0.8591 x 10% 364.4  7.174 0.8955 x 10*
30 0.1945 x 10* 0.3356 x 10% 0.5300 x 104 356.8  7.024 0.5657 x 10*
100 (4.17 days) 0.1119 x 10* 0.2090 x 10* 0.3209 x 10* 3315 6.525 0.3540 x 10*
300 (12.5 days) 0.6762 x 10° 0.1132 x 10% 10,1809 x 10* 268.5  5.285 0.2078 x 10*
1,000  (41.7 days) 0.2933 x 10° 0.3781 x 10° 0.6714 x 10° 128.4 2,528 0.7998 x 10°
3,000 (125 days) 0.1021 x 10° 0.1161 x 10° 0.2182 x 10° 156 0.3071 0.2338 x 10°
10,000 (1.14 years) 0.2203 x 102 0.9287 x 10" 0.3131 x 10° 0.01 0.000192 0.3132 x 10°
30,000  (3.42 years) 0.4463 x 10" 0.1664 x 10" 0.6127 x 10" 0.6127 x 10"
100,000  (11.4 years) 0.1556 x 10! 0.8611 x 10° 0.2417 x 10’ 0.2417 x 10!

 

Ref: Case JW-9

 
 

Table 2, Heat Generation From Fission Products and 233?0 in Fuel of One-Region Molten Salt Reactor
With Sparging of Noble Gases but No Plating of Noble Metals

 

 

 

 

 

Cycle Time for Noble Gas Sparging = 50 sec

Reactor Power , = 4444 Mw(th)

Fuel Volume in Reactor Circulating System = 2000 £13

Fuel Processing Cycle Time = 38 days

33Pa Processing Cycle Time = 3 days

Equilibrium Pa Concentration = 7.25 g/ft3

Equilibrium Fission Product Concentration = 54,85 g/ Fr3

: — : | /KK 733 —
Time After Fuel Fission Products in Fuel Stream Pa in Fuel Stream Pa + Fission Products
Dumped From Reactor B Heat y Heat | B + y Heat B + y Heat B + y Heat
(hr) (w/ftd) (w/ft) (w/Ft) w/d) (/) (w/Ft3)
o 6 5 6 6

0 (equilibrium) 0.1114 x 10 0.1715 x 10 0.1285 x 10 368.3 7.250 0.1289 x 10
0.001 (3.6 sec) 0.6357 x 10° 0.1710 x 10° 0.8068 x 10° 1 368.3  7.250 0.8105 x 10°
0.003  (10.8 sec) 0.3884 x 10° 0.1692 x 10° 0.5576 x 10° 368.3  7.250 0.5613 x 10°
0.01 (36 sec) 0.2682 x 10° 0.1626 x 10° 0.4308 x 102 368.3  7.250 0.4345 x 10°
0.03 (1.8 min) 0.2129 x 10° 0.1499 x 10° 0.3629 x 10 368.3  7.250 0.3666 x 10°
0.10 (6 min) 0.1609 x 10° 0.1316 x 10° 0.2925 x 10° 368.2  7.249 0.2962 x 10°
0.30 (18 min) 0.1122 x 10° 0.1096 x 10° 0.2217 x 10° 368.2  7.249 0.2254 x 10°
1.0 0.6800 x 10 0.8362 x 10° 0.1516 x 10° 367.9  7.242 0.1553 x 10°
3.0 0.4873 x 10° 0.6650 x 10% 0.1152 x 10° 367.1  7.227 0.1189 x 10°
10 0.3141 x 10 0.4809 x 10% 0.7950 x 10% 364.4  7.174 0.8314 x 10°
30 0.1768 x 10 0.3270 x 107 0.5038 x 10* 356.8 7.024 0.5395 x 10
100 (4.17 days) 0.9729 x 10° 0.2034 x 10* 0.3007 x 10* 3315  6.525 0.3338 x 10*
300 (12.5 days) 0.5662 x 10°  0.1103 x 10 0.1669 x 10% 268.5  5.285 0.1937 x 10
1000 (41,7 days) 0.2286 x 10° 0.3717 x 10° 0.6003 x 10° 128.4  2.528 0.7267 x 10°
3000 (125 days) 0.8058 x 10° 0.1141 x 10° 0.1947 x 10° 15.6  0.3071 0.2103 x 10°
10,000  (1.14 years) 0.2051 x 10° 0.7621 x 10! 0.2814 x 10° 0.01 0.000192 0.2815 x 10°
30,000  (3.42 years) 0.3475 x 10" 0.4481 x 10°  0.3923 x 10’ 0.3923 x 10!
100,000 (11.4 years) 0.7705 0.1218 0.8923 0.8923

 

Ref: Case JW-9R
Table 3. Heat Generation from Fission Products and 233Pa in Fuel of One-Region Molten Salt Reactor
With Sparging of Noble Gases and Plating of Noble Metals

Cycle Time for Sparging of Noble Gases =

Cycle Time for Plating of Noble Metals = 50 hr
Reactor Power = 4444 Mw(th)
Fuel Volume in Reactor Circulating System = 2000 f13

 

 

 

Fuel Processing Cycle Time = 38 days
Pa Processing Cycle Time = 3 days
Equilibrium Pa Concentration = 7.25 g/ft3
Equilibrium Fission Product Concentration = 41,85 g/ft3
Time After Fuel Fission Products in Fuel Stream 233Pa in Fuel Streom 233Pa + Fission Products
Dumped From Reactor B Heat Y Heat B + y Heat B + y Heat B + y Heat
(he) (w/ft3) (w/ftd) (w/ft) w/f)  @/fd) (w/ft°)

0 (equilibrium) 0.1113 x 10° 0.1658 x 10° 0.1279 x 10° 368.3  7.250 0.1283 x 10°
0.001 (3.6 sec) 0.6348 x 10° 0.1654 x 10° 0.8002 x 10° 368.3  7.250 0.8039 x 10°
0.003  (10.8 sec) 0.3875 x 10° 0.1635 x 10° 0.5510 x 10° 368.3  7.250 0.5547 x 10°
0.01 (36 sa2) 0.2624 x 10° 0.1570 x 10° 0.4193 x 10° 368.3  7.250 0.4230 x 10°
0.03 (1.8 min) 0.2122 x 10° 0.1443 x 10° 0.3565 x 10° 368.3  7.250 0.3602 x 10°
0.10 (6 min) 0.1601 x 10° 0.1258 x 10° 0.2859 x 10° 368.2  7.249 0.2896 x 10°
0.30 (18 min) 0.1111 x 10° 0.1034 x 10° 0.2145 x 10° 368.2  7.249 0.2182 x 10°
1.0 06638 x 107 0.7654 x 10% 0.1429 x 10° 367.9  7.242 0.1466 x 10°
3.0 | 0.4631 x 10* 0.5821 x 10 0.1045 x 10° 367.1 7.227 0.1082 x 10°
10 0.2880 x 10°% 0.3963 x 10° 0.6843 x 10% 364.4  7.174 0.7207 x 10*
30 0.1552 x 10 0.2543 x 10% 0.4095 x 10 356.8  7.024 0.4452 x 10*
100 (4.17 days) 0.8577 x 10° 0.1610 x 10* 0.2468 x 10* 3315 6.525 0.2800 x 10
300 (12.5 days) 0.5410 x 10° 0.9729 x 10° 0.1514 x 10° 268.5  5.285 0.1782 x 10*
1000 (41.7 days) 0.2226 x 10° 0.3285 x 10° 0.5511 x 10° 128.4  2.528 0.6797 x 10°
3000 (125 days) 0.7826 x 10° 0.1050 x 10° 0.1833 x 10° 156 0.3071 0.1989 x 10°
10,000  (1.14 years) 0.1971 x 10° 0.7514 x 10" 0.2722 x 10° 0.01 0.000192 0.2723 x 10°
30,000  (3.42 years) 0.3310 x 10" 0.4346 0.3745 x 10" 0.3745 x 10’
100,000 (1.4 years) 0.7698 0.1218 0.8916 0.8916

 

Ref: Case JW-9RP

 
 

ORNL DWG 68— 2106

 

   
 
   

   
    
 
  

 

 

 

 

     
  

 

 

 

" 2 4 6 810 2 4 6 8102 2 4 6 810 2 4 6 B810* 2 4 6 8 .o
C T T T T T T7TT7 T T 1T TTTT17 T T T T I r T T TTTT7 Y —TT1TT1711 0
8 - 7 8
6 I 46
= -
q9 - -4
~ -
er ~2
"
I0%} < 0%k ~i0%
— ~ GROSS FISSION PRODUCTS —
8 : 8 48
6 6 de
o F —
e -— 4
4 :tJ 4
- L NOBLE GASES SPARGED
: ON 30-SEC CYCLE
2 GROSS FISSION PRODUCTS S 2 2
o Ssec 10sec 30sec Imin S min 15 min
|o‘_ '00 1 LAt 1l 1 1 L 111111 i 1 1 114 |04
8 F 6° 2 4 6816 2 4 6810 2 4 6878
6 I ‘ TIME AFTER DISCHARGE FROM REACTOR (hours) 46
L NOBLE GASES SPARGED —
4 - ON 30- SEC CYCLE i
- F NOBLE GASES SPARGED AND —
= NOBLE METALS PLATED ON
S, b REACTOR SURFACES 4
a
©°
3
- 10%E ~10°
:t.l 8 - 8
Te n 36
2.0 -
O 4 L PROTACTINIUM =233 44
o | -
2 F 2
0% —10?
8 - -8
6 I —{6
4 - -' 4
2 F 2
REACTOR POWER = 4444 MW ( Thermol)
FUEL VOLUME « 2000 13
10 EQUILIBRIUM 233pg s 0.256 g/liter To)
- FUEL PROCESSING CYCLE e 38 doys '8
8 I 233p, PROCESSING CYCLE = 3doys
6 6
. 4
2 2
id 5d 204d 2mo
| ] i 1 1 1111l lll llllllll 1 1 llllllll 1 1 lllllll I.
| 2 4 6 810 2 4 6 8102 2 4 6 810 2 4 6 810* 2 4 6 810

TIME AFTER DISCHARGE FROM REACTOR (hours)

1. Fission Product and Protactinium Decay Heat in One-Region MSR Fuel.

 
10

Table 4. Relative Decrease in Fission Product Decay Heat Generation Rate
When Noble Gases Are Sparged and Noble Metals Are Plated Out in Reactor

 

Time After Percent of Gross Heat Generation

 

 

Reactor Shutdown Noble Gases - Noble Gases Sparged Plus
(hr) Sparged® ~ Noble Metals Plated Out®

O (equilibrium) 88.8 88.4

0.001 (3.6 sec) 83.7 83.1

0.003 (10.8 sec) 78.7 /7.8

0.01 (36 sec) 75 73

0.03 (1.8 min) 72.9 71.6

0.10 (6 min) 71.1 69.5

0.30 (18 min) 69.7 67.4

1.0 /1 67

3.0 80.4 | 73

10 92.5 80.5

30 95 77.3

100 (4.17 days) 93.7 77

300 (12.5 days) 92.3 83.7

1,000 (41.7 days) - 89.4 82. 1

3,000 (125 days) 89,2 ‘ 84

10,000 (1.14 years) 89.9 86.9

30,000 (3.42 years) 64 61.1

100,000 (11.4 years) 36.9 36.9

 

9 Also includes the decay heat of daughters of removed gases or noble metals.

 
11

The extreme right columns of Tables 1, 2, and 3 give the total of 233pq and
fission product decay heat in the fuel stream. These heat generation rates govern
the design of the afterheat cooling system for dumped fuel. Decay heat of 233pq,
which is present at equilibrium at about 7.25 g/f'r3 for a 3-day processing cycle,
is only a small portion of the total decay heat except in the one- to three-month
period after discharge from the reactor.

233Pa Inventory and Heat Generation

For a 233pq processing cycle of three days the total 233pq inventory in the
system is 205 kg, of which 14.5 kg are in the circulating fuel and 190.5 kg in the
processing plant. The inventory and heat generation rate as a function of time after
the reactor stops operating are given in Table 5 and Fig. 2. The equilibrium heat
generation in decay storage is 9.7 Mw, and, unlike the fission product decay heat,
this rate does not show a significant decrease until about three weeks after shutdown.
In fact, in the decay period of two days to five months more heat is being generated
by 233pg than by gross fission products.

Distribution of Decay Heat Among Fission Products

Tables 6 and 7 have been prepared to show the distribution of decay heat
among the fission products. Values are given for equilibrium and for selected decay
times. Each entry for an element gives the summation of the decay heat rates for
all isotopes of that element. The noble gases and noble metals are exhibited sep-
arately as the two bottom rows of the tables. These particular values are for the
noble gases and noble metals only, that is, they do not include the decay energies
of the daughter products of these nuclides.

The columns of Table 7 are arranged in descending order of heat generation
rate. |t is interesting to note that over 50% of the total decay energy is associated
with only three or four elements. In the immediate period after shutdown, iodine
has the largest decay energy; for longer decayed fuel, lanthanum, zirconium, and
niobium have the most energy.

Additional Data

The data reported herein are a small portion of the data that are available in
the CALDRON output. This summary should satisfy most of the needs for decay heat
data. However, complete inventory plus beta and gamma decay energies are avail-
able for all fission product nuclides for each of the three cases. For example, if
one is interested in information on selected nuclides or a particular mass chain as a
function of their decay time, the data can be easily obtained.

 
Table 5. Inventory and Heat Generation Rate of 23

Reactor Power

Fuel Volume in Reactor Circulating System
Pa Processing Cycle Time

Breeding Ratio

4444 Mw(th)
2000 13

3 days
1.076

3Pa in @ One-Region Molten Salt Reactor

 

 

 

 

 

Time After Shutdown ‘ 233Pa in Fuel Stream 233Pa in Decay Tank Total 233Pa
 of Reactor Inventory B + y Heat Inventory B + YV Heat Inventory B + y Heat
(hr) (@) (w) () (w) ) (w)

0 (equilibrium) 14,500°  0.7366 x 10° 190,500°  0.9677 x 10" 205,000°  0.1041 x 10°
0.03 (1.8 min) 14,499  0.7365 x 10° 190,490  0.9677 x .10’ 204,989  0.1041 x 10°
0.10  (6min) 14,498 07364 x 10° 190,480  0.9676 x 10’ 204,978  0.1041 x 10°
030 (18 min) 14,495  0.7363 x 10° 190,440  0.9674 x 10° 204,935  0.1041 x 10°
1.0 14,485  0.7358 x 10° 190,300  0.9667 x 10” 204,785  0,1040 x 10°
3.0 14,454 0.7343 x 10° 189,900  0.9647 x 10” 204,354  0,1038 x 10°
10 14,348 0.7289 x 10° 188,500  0.9576 x 107 202,848  0.1030 x 10°
30 14,049 07137 x 10° 184,570 0.9376 x 107 198,619 0.1009 x 10°
100 (4.17 days) 13,050  0.6629 x 10° 171,450 0.8710 x 10 184,500  0.9373 x 10’
300 (12.5 days) 10,570 0.5370 x 10° 138,860  0.7054 x 10 149,430 0.7591 x 107
700 (29.2 days) 6,934  0.3522 x 10° 91,100  0.4628 x 10 98,034  0.4980 x 107
1000 (4.7 days) 5,055  0.2568 x 10° 66,420  0.3374 x 10’ 71,470 0.3631 x 107
2000 (83.3 days) 1,766 0.8971 x 10° 23,200 0.1178 x 107 24,966  0.1268 x 107
3000 (125 days) 614 0.3119 x 10° 8,070  0.4100 x 10° 8,684  0.4411 x 10°
4000 (167 days) 215 0.1092 x 10° 2,819 0.1432 x 10° 3,034  0.1541 x 10°
5000 (208 days) 75  0.3810 x 10% 981  0.4983 x 10° 1,056  0.5364 x 10°
7000 (292 days) 9 0.4572 x 10° 18 0.5994 x 10° 127 0.6452 x 10
10,000  (1.14 years) 0.38  0.1930 x 10° 5 0.2540 x 10° 538  0.2733 x 10°

 

9These values are the equilibrium amoun‘s of 233
correspond to a breeding ratio = 1.076 (Ref. Case G-04).

Pa present in the system when the processing cycie time is three days. These numbers

4
13

ORNL DWG 68-—2107

 

 
  
 

 

 

 

   
  

 

 

 

     
    

 

 

[ 2 4 6 810 2 4 6 810% 2 4 6 810° 2 4 6 810* 2 4 6 810°
00— NIRRT I.IH,'O’.: L | IIII_I___L,O.
8 — 8 — :8
© o s GROSS FISSION PRODUCTS + GROSS 222 pg S [= snoss misgion eaooucs == :
4 GROSS FISSION PRODUCTS §4 : GROSS FISSION PRODUCTS ]
\ e
2 | — - - W, | imin Smin 1Smin  30min __|5
o7 \\\ o7k, '}” Po INDECAY TANK 0"
8 — L L 1 1]ll5+ds
6 — 233pg IN DECAY TANK 2 4 6 80l 2 4 6 6
— TIME ( hours)
— 4q
2 — 2
10— '/'." PaINFUEL STREAM 10®
8 — ‘ | 8
6 — | 6
T4 4
S e
3
=2 2
-
&
q |O.: IO,
Q8 — 8
= e
& —
5 ‘[ 4
e
;: 2 — 2
10— 10
8 — 8
6 . 6
4 [ 4
2 — 2
FUEL 233y
REACTOR POWER 4444 MW (thermal)
3 FUEL VOLUME 2000 f13 s
10" — FUEL PROCESSING CYCLE 38 DAYS —10
8 — Po PROCESSING CYCLE 3 DAYS ] 8
6 — —{ 6
4 |— — 4
2 t— —2
Id 44d 10d 30d 3mo 6é mo 2yr Syr
St v e b sl e e
2 4 6 8I0 2 4 6 8107 2 4 6 810° 2 4 6 810% 2 4 6 810°
TIME AFTER DISCHARGE FROM REACTOR (hours)
Fig. 2. Total Heat Generation Rate in One-Region MSR from Gross Fission

Products and 233Pa.

 
14

Table 6. Distribution of Decay Heat Among the Fission Product Elements
"With No Sparging of Noble Gases and No Plating of Noble Metals

Reactor Power = 4444 Mw(th)
Fuel Volyme = 2000 f3
Fuel Processing Cycle Time = 38 doys

B + y Heat Generation Rate (W/ft3 fuel).

&

 

 

Time After
Reactor Shutdown o
(hr) Equilibriym 0.0} C.03 0.1 0.3 1 3 i0 30 10 3720 1000 3000 19,000 30,000
Ge 4.365 4,350 4.321 4,222 3.955 3.186 1.921 0.817 0.232  0.003 -—-- ——=- === === ----
As 832.4 409.5 116,9 J1.18 24,56 18.98 11.94 1.449 0.320 0.096 0.003 -——— == ---= ===
Se 182.0 1716 146.2 83.80 33.79 6.551 0.092 0.0007 0.0005 ~---- -—== - o= ——-- --=-
Bc 4721 2720 142.7 653.8 457.5 199.7 31.08 3.233 0.616 0,154 0,003 - === - ===
Kr 7055 4972 4525 4071 3610 2776 1349 155.1 0.823 0.003 0.003 0.003 0.003 0,003 0.002
Rb 32,963 6322 5766 4641 2999 1342 698.2 123.4 0.920 0.04} 0.030 0.010 === ——-- ———-
Se 3838 3526 an 2587 2208 1839 1377 654.5 2219 108.4 96.10 64.56 20.84 0.690 0.295
Y 3634 3617 3561 3300 2723 2040 1733 974.1 266.2 113.7 102.3 73.01 28,27 2,193 1.247
Zr 571.2 571.0 570.7 569.6 566.3 555.0 524.5 435.1 283.6  166.4 145.9 106.9 43.99 1,963 ----
Nb 714 857.1 1014 127 1131 1116 1054 818.8 404.1 97.56 89.36 102.9 69.18  4.065 ----
Mo 1403 1172 961.5 777 .4 554.3 314.4 273.8 254.6 207.1 100.4 12,70 0.009 ——-- ———- -—-=
Te 305 357.9 447.6 590.3 486.6 81.51 15.73 34.33 41.07  20.80 2,630 0.002 -—-- .- -~
Ru 128.6 125.8 121.2 110.3 99.82 92.54 78.50 52.73 39.58 37.06 32,08 19.36 4,583 0.039 0.002
Rh 453.2 220,5 75.00 39.45 34.32 25,52 21.63 17.86 1290 6.715 4.276 3.228 1.912  0.916 0.188
Pd 4,084 4.101 4,052 3.777 3.142 2,094 1.583 1.120 0.428 0,018 ---- ~—-- ——— eees eeee
Ag 13.94 13.50 12,74 11.28 10.25 9.045 7.903 5.689 2.892 0.838 0.300 0.020 ——-- -——- -—--
Cd 2,870 3.443 4.090 4,530 4,256 3.394 2,116 1.026 0.6481 0.282 0.023 ——— ——— -——- -———-
In 10.07 9.800 9.311 8.006 5.970 3.143 1.199 0.497 0.487 0.204 0.017 ——— -———- -——— ———-
6167 5911 5431 4042 1753 138.9 28.27 2,982 0.131  0.021 —— ——— —— -—-- -——
Sb 25,052 2484 2083 1334 802.6 476.2 278.0 126.6 46.30 24.83 6.220 0.318 0.138  0.111  0.062
Te 5492 3213 1663 939.5 741.0 483.2 225.6 135.4 88.23  46.09 8.414‘ 0.656 0.362 0.074 0.015
l 7045 5140 4802 4477 4356 3961 2948 2040 1359 640.7 138.1 4,346 0.003 ---- -—--
Xe 3426 2506 1934 1230 623.6 292.3 247.6 250.4 157.5 71,42 24,07 0.555 -———- ——— ———
Cs 30,373 4399 3789 3060 2393 1132 102.5 3.585 3.485 3.206 2,607 1.745 1.437 1,173 0.708
Bo 4565 2972 2637 231 1677 869.8 431,2 235.0 219.0 187.2 119.6 25,52 1,327 1,038 0.985
Lo 3413 3400 3345 3164 2791 2244 1805 1416 1312 1210 800.9 165.5 1.82 -—-- -——-
Ce 1099 1041 944.7 748.0 597.6 532.7 507.1 449.4 323.4 1347 68.43 38.58 10.00 2,170 0.285
Pr 1002 1000 997.3 978.5 889.0 568.9 330.1 228.6 176.5 159.4 120.9 58.87 34.04 16.62 2,192
Nd 169.2 167.4 164.0 153.8 133.4 105.4 80.44 61.51 57.31 47.77 28.39 4,597 0.025 ---- ———-
Pm 104.0 104.0 104.0 104.0 104.0 103.4 101.1 91.82 69.25  28.59 4,441 0.374 0.297 0.240 0.130
Sm 5.332 5.331 5.330 5.324 5.309 5.254 5.102 4,601 3.427 1,222 0.064 ——— ——— —— ——
Eu 1.242 1.262 1.262 1.262 1.262 1.260 1.255 1.239 1,193 1,047 0.722 0.205 0.023 0.017  0.014
Total 144,700 57,420 49,770 41,160 31,820 21,340 14,320 8591 5300 3209 1809 671.4 218.2 3.3 6.127
Kr + Xe° 10,481 7478 6459 5301 4234 3068 1617 405.5 158.3 71.42 24,07 0.558 0.003 0.003 0.002
Noble Mefolsb 8706 6145 4455 3691 3101 2134 1680 ' 1321 797 309.7 149.8 126.2 76.04 5094 0.205

 

aDoughfer proudcts of Kr and Xe are not included.

bEIemenl’s included are Se, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Te. Daughter products of thes= elements are not included.

i
Table 7. Relative Amounts of Decay Heat Associated With Fission Products in One-Region MSR Fuel

Equilibrium Concentrations

 

15

With No Sporging of Noble Gases and No Plating of Noble Metals

Reactor Power

- Processing Cycle Time

Fuel Volume

4444 Mw(th)
38 days
2000 13

Time After Fuel is Drained From Reactor

 

 

 

 

in Reactor 1 hr 10 hr 100 hr 1000 hr
% of % of % of % of % of
Element Total Heat g/fr3 Element Total Heot Element Total Heot Element Total Heat Element Total Heot
Rb 22.8 2.238 | 18.6 1 23.8 Lo 37.7 Lo 24.6
Cs 21,0 5.872 Kr 13.0 Lo 16.5 l 20.0 Zr 15.9
Sb 173 0.114 La 10.5 Y 1.4 Ba 5.83 Nb 15.3
Kr 4.9 2,010 Y 9.56 Nb 9.54 Zr 5.18 Y 10.9
| 4.86 1.525 Sr 8.62 Sr 7.63 Pr 4.97 Sr 9.62
Sn 4.26 0.078 Rb 6.29 Ce 5.24 Ce 4.20 Pr 8.77
Te 3.79 2.022 Cs 5.30 Zr 5.07 Y 3.54 Ce 5.75
Br 3.26 0.140 Nb  5.23 Mo 2,97 Sr 3.38 Ba 3.80
Bo 3.15 4,844 Ba 4,08 Xe 2.92 Mo 3.13 Ru 2.88
Sr 2,65 5.358 Pr 2.67 Bo 2.74 Nb  3.04 Nd 0.68
Y 251 2,236 Zr 2.60 Pr 2.66 Xe 2.22 i 0.65
Xe 2,37 13.14) Ce 2.50 Kr 1.81 Nd 1.49 Rh 0.48
Lo 2.36 3.592 Te 2.26 Te 1.58 Te 1.47 Cs 0.26
Mo 0.97 6.006 Sb 2.23 Sb 1.47 Ru 1.15 Te 0.10
Ce 0.76 10.027 Mo 1.47 Rb 1.44 Pm 0.89 Xe 0.08
Pr 0.9 2.492 Xe 1.37 Pm 1.07 Sb 0.77 Pm 0.06
As 0.58  0.0004 Br 0.94 Nd 0.72 Te 0.65 Sh 0.05
Nb 0.49 0.376 Sn 0.65 Ru 0.61 Rh 0.21 Eu 0.03
Zr 0.39 11.380 Nd  0.49 Te 0.40 Cs 0.10 Ag )
Rh 0.31  0.215 Pm 0.48 Rh 0.21 Sm 0.04 Rb
Te 0.21  1.626 Ru  0.43 Ag 007 Eu  0.03 Mo ) 0.01
Se 0.12 0.387 Te 0.38 Sm 0.05 Ag 0.03 Kr
Nd 0.12 6.826 Rh 0.12 Cs 0.04 Cd 0.01 Tc
Ru 0.09 2.757 As 0.09 Br 0.04 In 0.01 Sm <
Pm 0.07 0.554 Ag 0.04 Sn 0.03 Br In
Ag 0.016 Se 0.03 As 0.02 Sn ~ Sn
In 0.005 Sm 0.02 Eu 0.01 As Cd
Ge 0.03  0.0001 cd  0.02 Pd 0.0 Rb Y 0.01 Pd $ Negligible
cd 0.042 Ge Cd_ 0.0 Kr Be
Sm 0.841 Pd 0.05 Ge Pd As
Eu 0.080 In In 0.02 Ge Ge
Pd 0.350 Eu Se Se Se _
Total Weight 87.16
Kr + Xe® 7.27 1515 14.37 4,73 2.22 0.08
Noble Metals® 5.9 13.76 9.98 15.4 9.69 18.77

 

°Dcmghfer products of Kr and Xe are not included.

Elements included are Se, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Te. Daughter products of these elements are not included.
16

REFERENCES
J. 5. Watson, Chemical Technology Division, unpublished data.
W. L. Carter, Chemical Technology Division, unpublished data.

H. F. Bauman, Reactor Division, personal communication; original data

identified as Case G-04.

J. 5. Watson, Chemical Technology Division, personal communication.

H. T. Kerr and H. F. Bauman, Reactor Division, calculations on the physics
of the system; identified as Case G-04.
17

DISTRIBUTION
M. W. Rosenthal 45,
L. G. Alexander 46,
C. F. Baes 47,
S, J. Ball 48,
C. E. Bamberger 49,
H. F. Bauman 50.
S. E. Beall 51.
M. Bender 52.
C. E. Bettis 53.
E. S. Bettis 54.
R. E. Blanco 55.
J. O. Blomeke 56.
R. Blumberg 57.
E. G. Bohlmann 58.
G. E. Boyd 59.
R. B. Briggs 60.
S. Cantor 61.
W. L. Carter 62,
C. W. Collins 63.
E. L. Compere 64,
W. H. Cook 65,
D. F. Cope, AEC-ORO 66.
J. L. Crowley 67.
F. L. Culler, Jr. 68.
J. M. Dale 69.
D. G. Davis 70.
C. B. Deering, AEC-ORO 71.
S. J. Ditto 72,
W. P. Eatherly 73.
J. R. Engel 74,
D. E. Ferguson /5.
L. M. Ferris 76.
A. P. Fraas /7.
J. H. Frye, Jr. /8.
C. H. Gabbard 79.
R. B. Gallaher 80.
H. E. Goeller 81.
W. R. Grimes 82.
A. G. Grindell 83.
R. H. Guymon 84.
J, P. Hommond 85.
B. A. Hannaford - 86.

P. H. Harley
P. N. Haubenreich
J. R. Hightower
H. W. Hoffman
W. H. Jordan
P. R. Kasten
R. J. Kedl
M. J. Kelly
H. T. Kerr
J. W. Koger
A. |. Krakoviak
J. A. Lane
R. B. Lindaver
G. H. Llewellyn
M. |. Lundin
R. N. Lyon
H. G. MacPherson
R. E. MacPherson
H. McClain

H. E. McCoy

H. F. McDuffie
C. K. McGlothlan
L. E. McNeese

J. R, McWherter
R. L. Moore

H. A. Nelms

J. P. Nichols

E. L. Nicholson
L. C. Oakes

A. M. Perry

T. W. Pickel

G. L. Ragan

J. T. Roberts

R. C. Robertson
H. C. Savage

W. F. Schaffer, Jr.
C. E. Schilling
Dunlap Scott

J. H. Shaffer

A. N. Smith

O. L. Smith

|. Spiewak
DISTRIBUTION, continued

87.
88.
89.
90.
91.
92,
93.
94,
93.
96.
97.

D. A. Sundberg
J. R. Tallackson
E. H. Taylor
W. Terry

R. E. Thoma

D. B. Trauger

Wa’rts

18

98.

99.

100.

101,

102,

103.
104-1005.
106-107.
108-110.
111,

112,

fl

. Young

E L. Youngblood

Central Research Library
Document Reference Section
Laboratory Records
Laboratory Records, RC
ORNL Patent Office

)