ML20138H715
| ML20138H715 | |
| Person / Time | |
|---|---|
| Site: | 07003001 |
| Issue date: | 08/28/1985 |
| From: | Huffman F THERMO ELECTRON CORP. |
| To: | Glenn J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20138H649 | List: |
| References | |
| 104333, NUDOCS 8510290130 | |
| Download: ML20138H715 (5) | |
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MiThermo Electron R&DINew Business Center Post Office Box 459 Telex: 92 3323 101 First Avenue August 28, 1985 Cable: TEECORP Wal tham, Massachusetts 02254 (617) 890-8700 U.S. Nuclear Regulatory Commission Nuclear Material Section B 631 Park Avenue King of Prussia, PA 19406 Attention:
John E. Glenn, Ph. D.
Subject:
Amendment to Special Nuclear Materials License No. SNM-1935
Dear Sirs:
The subject license presently authorizes Thermo Electron's use of Uranium-235 (quantity not to exceed 350 grams) as uranium oxide pellets containing up to 20 percent Uranium-235.
The orientation of our Department of Energy (DOE) Thermionic Technology Program (Contract DE-ACO3-84SF12193) is being shifted to smaller diameter thermionic diodes which will require fabricating emitters containing enrichments of Uranium-235 up to 40 percent.
Except for their smaller size, the basic design of the thermionic diodes will be similar to those now being irradiated in the TRIGA Mark-F Reactor at GA Technologies.
I am enclosing a paper, " Experimental Investigation of Fueled Thermionic Emitter Deformation" by Dunlay et al. which describes the present design of the thermionic diodes.
b eg o.
Therefore, Thermo Electron requests authorization to g
receive, possess, store and use up to 350 grams of Uranium-235 m
with enrichments up to 40 percent at the Company's R&D Center location at 85 First Avenue, Waltham, MA.
Other than the design bk modifications asociated with the reduced size of the thermionic M diode, the material will be used in accordance with Special g Jg Nuclear Materials License No. SNM-1935.
owl I understand that this amendment corresponds to Category 1K mem of Section 170.31, 10 CFR 170 and that the fee is $120.00.
A check for this amount is enclosed.
If you require further information relative to this amendment request, please contact me at (617)890-8700, Ext. 362, 4 ~%2nt htt' 9 I
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"O K RICORD COPY"ElO Received By Paper LPMB 9blsc SEP 0 31985
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c 1985 IECEC Experimental Investigation of Fueled Thermionic Emitter Deformation J.B. Dunlay and E.A. Smith Thermo Electron Corporation 85 First Avenue, Waltham, MA 02254 J.W. Holland and M.H. Horner GA Technologies Inc.
10955 John Jay Hopkins Drive, San Diego, CA 92121 ABSTRACT fuel to the progressively cooler components sur-rounding the fuel. At high temperatures, elec-In-core thermionics is a promising power trons from the emitter flow across the gap to the conversion technology for use in reactor space collector. The energy associated with the elec-power systems. During the past year, new work tron flow represents the dominant mode of both was performed to provide a better understanding the heat removal from the emitter and the heat of the life-limiting characteristics of the tech-input to the collector. Heat is removed from the nology. In-core experimental tests provided data collector by conduction through the ceramic in-for validating deformation models used to predict sulator to the sheath tube and, finally, to the fueled emitter life times up to 60,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />.
surrounding coolant.
The design, fabrication, and initial results of For space power, a representative operating the tests are summarized.
voltage for a converter is 0.5 volt at a current density of 6 amperes per cm2 of emitter area.
Since a TFE may contain 300 cm2 or more of emit-ter ares, the use of a single converter extending EXTENSIVE EXPERIENCE with nuclear-fueled emitters the full length of the TFE results in a high-has demonstrated that UO2 is the preferred fuel current, low-voltage output (e.g.,1800 amperes for long-tern chemical compatibility with tung-at 0.5 volt). To reduce the amount of conductor sten emitters. The thermal properties of UO2, metal required to carry such high currents, typ-however, such as thermal expansion, thermal con-ical TFE designs divide the total converter area ductivity, ed vapor pressure, combine to intro-into a number of smaller, series-connected con-duce stresses at the fuel pellet tungsten emitter verters with TFE outputs in the order of 300 am-interface. The experimental work described in peres at 3 volts (e.g., 6 series-connected con-this paper was undertaken to investigate the verters). Such a configuration is called a long-term dimensional stability of typical fueled flashlight TFE design referring to the f amiliar emitter ccnfigurations.
multi-battery, hand-held light source.
THERM 10NIC WEL ELEMENT (TFE) OPERATING u Put of 0.5 volt at 6 am-CONDITIONS peres per em, the operating temperatures of the converter components within a TFE will be approx-A TFE resembles a heat source fuel element imately 1750 K for the emitter and 1000 K for the 4
4 collector. To transfer heat to the emitter, the except for the addition of heat-to-electrical surface temperature of the fuel pellet is about power conversion components within the TFE. The 2000 K; and, to remove heat from the collector, j
TFE may contain one or a number of thermionic the ceramic insulator and sheath tube operate at converters. A central fuel pellet enclosed by a about 950 to 900 K.
metal layer forms the emitter of the thermionic l
converter. Surrounding the emitter, but sepa-FUELED EMITTER DEFORMATION rated by a narrow gap, is a second metal 1syer
)
which is the thermionic collector. Ceramic sur-Two nuclear fuels, UC-ZrC and 00, were ex-2 rounds the collector and is used to electrically i
ate the collector from an external sheath tensively studied ia previous thermionic programs.
The use of a carbide fuel typically resulted in The overall flow of energy in a TFE is Poor thermionic performance due to contamination
-radial, frors the center of the high-temperature and to embrittlement of the emitter early in life DOE Contract No. DE-AC03-84SF12193 caused by interactions between the tungsten and i
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i q,a the fuel. Uranium oxide fuel showed no such ad-fuel simulates the emitter heat generation dis-verse effects and, typically, resulted in stable tribution of a fast reactor. At the 1.5-megawatt a
pe rf,o rmanc e.
Emitter strains greater than 3.5 power level, the f ast neutron fluence (>0.1 Mev) percent were measured and the emitter showed no in the thermionic fuel is the same as the average l
cracking or other signs of embrittlement. UO2 fast fluence in the SP-100 reactor. Hence, the has. consequently, been selected as the fuel f or materials fast neutron damage is also experienced the SP-100 thermionic reactor design. (1)*
in these tests.
There are three possible mechanisms for dis-The Mark 4 f acility provides unrestricted tortion of a UO -fueled emitter. First, the dif-access to capsule instrumentation and control 2
ference in themal expansion of tungsten and UO2 systems during reactor operation, and also has can lead to distortion of the emitter if large the capability to perform periodic neutron radio-temperature changes are made in a " thermal ratch-graphy of the fueled emitter samples. Capsules eting" mode. With a decrease in temperature. the are withdrawn from the core at intervals of 1500 fuel contacts more than the emitter opening a hours, and nondestructively examined in a neutron gap between the two. The hot fuel evaporates and radiography camera placed adjacent to the Mark-F i
condenses on the inner diameter of the emitter, reactor core. Analyses of periodic neutron radi-4 filling the gap. With a return to the original ographs provide measureaents of real-time defor-higher temperature, the larger expansion of the mation rates. Emitters are radiographed prior to U02 stresses the emitter, resulting in a perma-initiation of testing to provide baseline data nent strain.
for later comparison. Equipment and techniques A second potential emitter deformation mech-were developed and evaluated during an earlier anism is the build-up of fission gas pressure program.(3) within the central void of the fuel. Fission gas bubbles formed in the fuel rigrate to this void.
IN-CORE CAPSULE REQUIREMENTS If the fission gas is not vented, sufficient pressure can build up to strain both the fuel and Containment of the fission products produced emitter.
in the UO2 fueled thermionic emitters is insured The dominant deformation mechanism is be-by using a double enclosure. The first or pri-lieved to be fuel swelling caused by the buildup mary section is a hermetically sealed container of fission product gases within the UO. Small, totally surrounding the test converters. The 2
widely dispersed bubbles of gas cause a volumet-primary containment is filled with helium for ric expansion which stretches the emitter. Fuel ef fective heat transfer to the surrounding cool-swelling is rapid during initial operation, but ant. All electrical connections for voltage and reduces to a slower rate with continued operation current leada, and cesium reservoir temperature i
due to gas bubble migration and venting at the control heaters penetrate the primary wall central void, through a hard seal plate containing ceramic-to-Emitter deformation, due to fuel swelling, metal lead-throughs. Since the seal plate is is being studied using the LIFE-4 Computer located close to the reactor core and is adjacent Code.(2) LIFE 4 is the national reference code to the high temperature test components, the for the integral modeling of fuel pins for fast lead-throughs must be both radiation resistant breeder reactors. Validation of the deformations and capable of operation at elevated temperatures predicted by the code includes comparisons with (200 to 300 C).
earlier TFE test results plus information f rom The high operating temperature of the UO2 the present in-core capsule tests.
fuel pellets plus thermal cycling which occurs during periodic shutdowns of the test reactor re-TEST REACTOR sult in release of the gaseous fission products (krypton and xenon) from the pellets. Since the Testing of the fueled emitters is performed void volume within an emitter is small, the fis-in GA Technologies' TRICA Mark-F Reactor. The sion gas pressure wculd increase to about 1 x 106 i
burt.able poison-containing core used in this re-Pa (10 atm) within 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> of operation. This actor limits thermi cycling of the test emitters pressure level is the threshold pressure at which since very little centrol rod motion is required, some emitter deformation would begin to occur as and the core can operate as a constant neutron a result of internal pressure (a bladder mechan-source without refueling for extended per'iods.
ism). To prevent this type of deformation, a The reactor configuratian provides four test po-relatively large volume trap is connected through sitions near the center ef the core. Each posi-a tube to the emitter fuel volume. The trap and tion accepts a 2.37-inch-diameter experimental the connecting tube become an integral part of capsule. The fueled region of the core is 15 the primary containment. The minimum volume of inches deep.
the trap is determined by the requirement not to Operating the reactor at a maximum power of exceed the threshold deformation pressure during 1.5 megawatts permits' the use of 10 to 15 percent the operating life of the experiment. The maxi-U-235 enrichment in the fueled ealtters. The mum volume of the trap is established by the de-resulting thermal neutron penetration into the sire to use the pressure buildup in the trap as a means of monitoring the rate of fission gas re-lease from the UO2 fuel.
- Numbers in parentheses designate references at The secondary containment totally encloses the end of paper.
all components of the primary containment section.
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Electrical penetrations to the secondary contain-and the seal plate. The capsule also includes ment use a soft seal design (plastic potting) thermocouples for temperature measurements of the since the seals are approximately 3 and 4 meters emitter flange, the collector and the cesium above the core section. The secondary void vol-reservoir; voltage taps for the emitter and col-use located between the soft seal plate and the lector; and power leads for cesium reservoir hard seal plate is filled with helium at a pres-heaters. As the collectors and seal plate run at sure that is positive with respect to the helium ground potential, the emitter electrical leads, within the primary containment. This insures fission gas tubuhr tan and cesium reservoir heater that aay small leakage will be into the primary leads are insulatet. Gas gaps between the col-and that the gas will be helium. The gas content lector electrical lead and primary tube compen-of the annular section of the secondary directly sate for different Seat rejection loads from surrounding the test converters is independently collectors.
controlled f rom the remainder of the secondary.
A mixture of inert gases (helium and argon) is used in the annular gap to control the operating g]
temperatures of the primary wall and, hence, the s
s temperature of the internal converter components.
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Design of test converters for temperat -
stat oms <
s s
control must consider internal heat ger _,stion in s\\
the nonfueled components. At a reace,r power of 1.5 megawatts, gamma heating varie-from about
' cmanac renomaouce 0.75 watt / gram in the center of '..e core to 0.40
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watt / gram near the edge. Heat Anput to all con-Sg N
verter components is directionally proportional p# 'f i
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to reactor power. Reactor power level is, there-h j' fore, a very convenient and ef f ective overall EWNSeou sECrpo temperature control parameter. For a given power 7
'6 level, the operating temperature of the emitter depends on the thermionic current flowing from
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Y the emitter. The magnitude of the current can be controlled remotely by varying the electrical
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f load connected to the converter. For given re-f 1 m*I actor power and current output values, the col-hh I
lector temperature is dependent on the thermal l
brwrita necimcamas conductance of the surrounding secondary contain-fl
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ment gas gap.
nascm cons sacmm <
J Independent temperature control is desirable for the cesium reservoirs to insure adequate cesium pressure in the converters under all pos-unaeues onee runro sible converter operating conditions. The pres-J l
menim ac connntans m ence of cesiwn in the converters affects the current output of the converter and, hence, the temperature of the emitter. Control is provided i
by establishing excess cooling in the reservoir censuis nes:nvon sacros <
design and then using electrical heaters in com-C'l bination with the available gamma heating to ad-just the temperature to the desired value.
CAPSULE DESIGN AND FABRICATION FEATURES Figure 1.
Fueled Emitter Deformation Capsule The test capsule allows the operation of three thermionic converters whose outputs can be A more detailed view of the thermionic con-measured individually. The measured parameters verter design is shown in Figure 2.
The cylin-are collector temperature, cesium reservoir tem-drical emitter is 27.9 mm (1.10 in.) in diameter perature, output voltages and currents, and fis.
and has an emitting surface area of 4.9 x 103 2 mm sion gas trap pressure. The emitter temperature
( 7.6 in. 2). A 1.02-mm (0.040-in.) gap exists be-is inferred by comparing the output characteris-tween the emitter and collector. The emitter is tics to those of a similar out-of-core converter.
tungsten made by CVD (WF ) and the collector is 6
A diagram of the capsule's lower section is niobium. Approximately 100 to 130 grams of ura-shown in Figure L.
The three converters are me.
nium oxide fuel are loaded into each emitter.
chanically supported from the surrounding collec.
The emitter flange rejects heat from the emitter tor power lead. Cesium reservoirs with heaters and supports the emitter lead and the fission gas for temperature control are located beneath the tubulation.
converters. The emitter electrical leads and Prior to assembly of the converters, all ma-fission gas tubulatio. contain flexible members chined components vere chemically cleaned and to accommodate expansion between the converters vacuum fired. Most components were assembled by
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o Three fueled deformation gapsules were fab-vo,issios w -c ricated for testing. Table I summarizes the de-oas assana sign temperatures and emitter thicknesses being e
co,,
.eannan evaluated. Three of the nine emitters will be m
operated at 1750 K with 1.78-ma wall thickness representing present SP-100 design conditions.
eE The remaining anitters will be operated at 1650, g
"08 1750 or 1850 K with wall thicknesses of 1.02, 1.78 or 2.54 sun.
i vaavatuu 4
>5 M"
Table 1
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L Fueled Emitter Test Parameters
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Caps e Te ure Th k ess p
j unanium oses y (K) on (inch)
J,v 1
run esuits N
runosta.
1 Top 1750 2.54 (0.100)
Middle 1850 2.54 (0.100)
Botton 1750 2.54 (0,100)
,,,osium-coLLECfon 2
Top 1650 1.78 (0.070)
Middle 1850 1.78 (0.070) i U
j Botton 1750 1.78 (0.070) cowia as son A
- ruse l
couIcYo7asE h
Es E 3
Top 1750 1.02 (0.040) i Middle 1750 1.78 (0.070) vase cu=Le mesaum eno cap Botton 1750 1.78 (0.070)
Figure 2.
Uranium Oxide Fueled Thermionic Converter Design INITIAL OPERATION Testing was initiated January 13,1985 with Capsule No. 2.
Capsule No. 2 has accumulated 3
electron beam welding. All vacuum-tight joints 1954 hours0.0226 days <br />0.543 hours <br />0.00323 weeks <br />7.43497e-4 months <br /> and Capsule No. I 1125 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.280625e-4 months <br /> as of I
were checked by a He mass-spectrometer leak de-April 9, 1985. Capsuls No. 3 is being prepared j
tector. Af ter fabrication, the converters were for installation.
outgassed with ion pumps. Cesium was loaded by Radiography of Capsule No. 2 emitters at 8 30 i
l double distillation and the converter was pinched hours of test time revealed no significant emit-off. Before loading with fuel, an operational ter deformation and only limited amounts of fuel test was performed. The loaded converters were redistribution. The radiographs are of high then ready for assembly into the primary quality.
l containment.
The primary containment was assembled by REFERENCES mounting the subassemblies into a fixture. The fixture facilitated brazing and welding opera-1.
SP-100 Program, Proceedings of the First i
tions used to coa. sine componiats into a unit Program Integration Meeting, Danvers, l
while maintaining alignments and protecting deli-Massachusetts, June 13-15. 1984.
cate assemblies during fabrication. After the 2.
" LIFE-4 (Rev. 0) Users and Prograsmers assembly was completed, the collector lead and Manual " Westinghouse Corporation Report, primary containment tube were welded to the seal WARD-0X-9400-12 Vol. 1 and 2.
plate. The primary containment and fission gas 3.
D.E. Schwarzer and C.O. Fitzpatrick. " Equip-tubulation were outgassed with ion pumps while ment and Techniques for the Utilization of the assembly was heated to 300 C.
The outgassed
, outron Radiography with Thermionic Fuel primary was then backfilled with 200 mmHg of re-Elements " CCA Report Gulf-CA-Al2521 search grade helium.
March 26, 1973.
6 L
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