ML20197C480

Notice of Violation from Inspec on 780822-24

ML20197C480
Person / Time
Site:	Perry
Issue date:	09/29/1978
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20197C469	List: IR 05000440/1978012 ML20197C465 ML20197C480
References
50-440-78-12, 50-441-78-11, NUDOCS 7811210106
Download: ML20197C480 (3)

Text

- . - _ _ . .

4 d &

INTERIM REPORT

, . I 10-2-78 Accession No.

Contract Program or Project Titte:

Subject of this Document: E.xperimental Coaxial ~ Molybdenum-Zircaloy Fuel  !

Rod Cladding Surface Thermocouple Type of Document:

l Author (s): S. C. Wilkins 4

cate of Document

September 1978

! Responsible NRC Individual and NRC Office or Division: R. Van Houten Fuel Behavior Research This document was prepared primarily for preliminary or internal use. It has not f received full review and approval. Since there may be substantive changes, this 2

l document should not be considered final.

s 4

wu i

II. P. Pearson, Supervisor Information Management EGSG Idaho Prepared for U.S. Nuclear Regulatory Commission l

4 Washington, D.C. 20555 flRC Fin #A604l I

INTERIM REPORT l

4 ((Ig#?'hi j

o4 4 TFBP-TR-284 for U.S. Nuclear Regulatory Commission i

I I

l EXPERIMENTAL COAXIAL I MOLYBDENUM-ZlRCALOY FUEL ROD CLADDING SURFACE THERMOCOUPLE S.C. WILKINS l

, BC Researc1 anc "ec1nica N. Assistance Report l

September 1978 h

IDAHO NATIONAL ENGINEERING LABORATORY 1'

O PARTMENT OF fNERGJ . .

IDAHO OPERATIONS OFFICE UNDER CONTRACT EY-76-C-07-1570

. . . : s.

H I

(

TFBP-TR-284 August 1978 l

l l

'\

- AN EXPERIMENTAL C0 AXIAL ,

M0LYBDENUM-ZIRCALOY FUEL ROD- i CLADDING SURFACE THERMOCOUPLE -l By -

S. C. Wilkins APPROVED:

O Mf*WYw l

Cay V. Anderson, Manager RD. Advanced Instrumentation Branch l j

khQ gh{

R. W. Narshall, Jrf Manager PBF D sinn end Fabricafion Division

'P __

RtfiJ. Zeile, Manag g,T ermal . Fuels Behavior Prog m Thermal Fuels Behavior Program -

. .EG&G Idaho,-Inc.

-Idaho National Eng,ineering Laboratory s.

4 .

ACKNOWLEDGEMENTS

?

I' l This work is in behalf of and supported by the Thermal Fuels Behavior Program. -The technical skills of N. G. Boyce and D. R. Collins, which were of substantial importance to this work, are hereby recognized.

4 d

I l

I I

I l

l l

-11 1-

. 2 ,

4 4

. ABSTRACT

] .The results of sa scoping study, intended to determine the feasi-bility of fabricating a useful small diameter' coaxial-type

~

a ' molybdenum-zircaloy thermocouple, are presented. Samples of 0.51 mm diameter.thermocouples and their attachment to zircaloy fuel rod clad-i ding l surf aces, are illustrated. 'The thermoelectricioutput of the molybdenum-zircaloy thermocouple pair is plotted. Comparative rise-time figures are presented for this experimental thermocouple and for l l standard titanium-sheathed cladding surface thermocouples.

. l l

i

I 1

+

1 4

3 4

4 9

i 4

a e

d iii

SUMMARY

4 a The scoping study presented here has danonstrated the feasibility 4'

of producing a small coaxial molybdenum-zircaloy thermocouple for potential use in fuel rod cladding surf ace temperature measurements.

Swaged zircaloy-sheathed cables with a central molybdenu'm wire were produced .in diameters of 0.51 mm. . Installation'on the coaxial thermo-i~

couple in a. partially embedded configuration of fuel rod cladding was

demonstrated, u' sing a laser-weld attachment ' technique ~ Variations in the attachment configuration can be simply accomplished. 'An approxi-4

' mate curve:of the thermoelectric output of molybdenum-zircaloy was

. determined.up to '1300 C, with a Seebeck coefficient of '18; pV/0C' at 1000 C.' Repeatability using the same lots of material was within 1.3%, butL reproducibility from one lot of material to. another was not examined. Risetime measurements (10-90%) made using a pulsed laser technique yielded values of 8.5 ms for the 0.51 mms diameter coaxial

thermocouple, which compares favorably to 49.4 ms for a 1.2 mm diameter. titanium-sheathed thermocouple and 10.8 ms for an intrinsic Type. X thermocouple with 0.25 mm~ diameter wires. Recommendations for further study. include ' lot-to-lot variations in the calibration of the molybdenum-zircaloy pair, as well as variations due to heat treatment and the effect of oxidation of the zircaloy sheath on the stability of the thermocouple.

a iv E . _ _ _ _ _ _ _ _ _

CONTENTS ACK NOW L EDG EM E NTS . . . . . . . . . . . . . . . . . . . . . . . . . . . ii AB S TR AC T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

SUMMARY

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv l

I. INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 l II. Fi?.3IBILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 l

1. FABRICATION. . . . . . . . . . . . . . . . . . . . . . . . . 2

2. THERMOELECTRIC OUTPUT. . . . . . . . . . . . . . . . . . . . 2 .

3. INSTALLATION ON CLADDING . . . . . . . . . . . . . . . . . . 4 l

4. TIME-RESPONSE TESTS. . . . . . . . . . . . . . . . . . . . . 5 '

III. CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . 10 l l

I V. R EF ER ENC ES. . . . . . . . . . . . . . . . . . . . . . . . . . . 12 j FIGURES

1. Cross section of 0.51 mm diameter coaxial thermocouple with zircaloy sheath and central molybdenum wire . . . . . . . . . . 3

2. Thermoelectric output of molybdenum-zircaloy and molybdenum-zirconium thermocouple combinations . . . . . . . . . . . . . . 4 I

. 3. Diagram and photograph of cross section of installation of coaxial molybdenum-zircaloy thermocouple on fuel rod ' cladding .

surface . . . . . . . . . . . . . . . . . . . . . . .-. . . . . 6

'4. Measuring junction attachment of coaxial molybdenum-zircaloy thermocouple to fuel rod . cladding surf ace . . . . . . . . . . . 7 TABLES I. Comparison Risetimes of Experimental and Standard Cladding Su r f ac e Thermoc ou p l e s . . . . . . . . . . . . . . . . . . . . . 8 y

. s.

AN EXPERIMENTAL C0 AXIAL MOLY 8DENUM-ZIRCALOY FUEL R0D CLADDING SURFACE -THERM 0 COUPLE J

I. INTRODUCTION I

One of the important measurements which must be made during water.

reactor safety research tests is fuel rod cladding surf ace tempera-tures. These measurements are commonly made by attachi.ng a metal-sheathed thermocouple longitudinally to the fuel rod surf ace. The I presence of the thermocouple, however, perturbs the measurement it is

intended to make, and can act as a cooling' fin on'the cladding surf ace l under certain coolant flow conditions. ,

i l

The perturbing influence of a thermocouple can be reduced in proportion.to decreases in the size and mass of the thermocouple. The l present state-of-the-art does not yet permit extremely small sizes in metal-sheathed thermocouples made with materials that are compatible l l with zircaloy fuel rod cladding over a wide temperature range .

j ' The work reported here made use of an alternate approach to standard l

two-wire thermocouples, and was intended primarily to scope the feasi-bility of the method without exhaustive testing and evaluation. The goals were to determine if (a) a small diameter coaxial thermocouple can be fabricated with a zircaloy sheath acting as one thermoelement; (b) the thermoelectric. output of the selected thermocouple pair has a usable output; and (c) a-low profile cladding surface thermocouple-installation can actually'be made with such a configuration.

Data published by Kuhlman indicated that a molybdenum-zirconium ~ thermocouple combination should have a usable emf. Problems

-with material. compatibility on zircaloy-clad fuel ~ rods would be avoided if a zircaloy thermoccuple sheath were used, and the combina-tion would have the added advantages of a good thermal expansion match and . low thermal neutron. absorption cross sections.

1

t J

II. FEAS:31LITY

1. FABRICATI0h To f abricate the smallest possible thermocouple, the smallest available' starting materials were used. This was limited by the size

. 'of single-hole Be0 insulation preforms comercially available:

0.56 m outside diameter (00) by 0._18 m inside diameter (ID). . Zirc-aloy tubing of '0.64 m-ID,.with a wall thickness of about 0.13 mm, and

{

comercial purity.(99.9%)' molybdenum wire of 0.13 m diameter were l . also used. Standard solvent cleaning techniques were used on the

. tubing and wire, and the Be0 insulators were vacuum outgassed to re-move' moisture and gase' Js . impurities.- The tubing had a thin protec-tive oxide. layer built 'up on .the inside surf ace as a precaution b against materials reactions at high temperatures b1 .

j Af ter : loose assembly, the thermocouple cable was swaged with a i rotary swager in steps.of 0.1-0.15 mm, down to a final diameter of

0. 51 m. The~ cable was annealed between swage passes at 6500 C in

argon for 15 minutes to restora ' ductility to the zircaloy sheath. ,

< Figure 1 shows a cross section of the cable-and illustrates the heavy sheath wall that results. The condition of the central molybdenum l wire was still good, and further reduction of the cable diameter may l have been possible. For purposes of the scoping study, however, the 0.51 m diameter was satisf actory.

2. THERM 0 ELECTRIC OUTPUT i'

As pointed out previously, data reported by Kuhlman offered hop +

that 5; usable thermoelectric ' output could be obtained from a

, molybdenum-zirconium combination, and the extension to molybdenum and z'ircaloywasnatural..Schley,et.al,[43'alsoreportedsomedataon the. Mo-Zr pair, but it was aidently dropped in f avor.of a combination with a higher temperature limit, Mo-Nb. Thus, there was evidence I supporting investigation.of. molybdenum-zircaloy as a possible thermo-couple _ pair.;

2.

h- 6

i~

g i

l i ,

7

('

l l -

l j

I i .

o

~ '

h  ; * .

l

a

=

l l .

l e

I

[ ,

- 'j f.

4

[ . _ _ . . .

l Fig. 1 Cross .section of 0.51 mm. diameter coaxial thermococole with

zircaloy sheath and central molybdenum wire.

1 With a junction formed by welding the sheath and wire at the cable tip, test thermocouples were operated in a helium atmosphere in a resistively-heated furnace. Data was collected only up to 1300 C, l

and an emf-temperature curve representing the average of a number of

cycles is shown on Figure 2. The output was repeatable to within 1.3%

l for the units-tested. For comparison the curve found for a molybdenum-

! zirconium pair is plotted on the same figure.

y This 'est showed that the thermoelectric output of the molybdenum-zircaloy pair is large enough to be pcocessed without special equipment (similar to the output of.W-Re alloys), it is repeatable, is 'ot double-valued, and is'close to that indicated in 3

l

a- -

t .,; .o 25 , i i

.i i .

4. cM t i20 -

g60 2 /.

3 <

s

8. 15 - -

.sO o - /

b /

f 10 f' -

'i

g. -

-s o.

f . '.  !

s -

I Reference junction at 0* C

.g 1 l- i- i i 0- 200' 400- 600 800 1000 1200' :1400 1

Temperature ('C) INEL A-9366

. , - . . - . -. -. = - - . - -- - -- - -

l Fig. 2. Thermoelectr'ic output of molybdenum-zircaloy and molybdenum- 1 zirconium thermocouple _ combinations. _

1

.the.two references above,'in1the case of molybdenum-zirconium. It did' not . indicate the~ reproducibility of the output when various lots of--

wire 'and tubing .are used,' nor did it . indicate the long-term stability or the effect of oxidation of. the.zircaloy sheath. There is. no ap - -

. parent' effect of.the a.- S ph'ase' transformation in zircaloy'and 0

-zirconium at:870 C. l

. 3..'INSTALLATI0N'0F CLADDING g 't'ith the feasibility of cable fhb'rication established, and with.-

aniapproxiinate: knowledge of' the thermoelectric output of the

.4 7

. s

,. .,,; s ,. .,

n A

molybdenum-zircaloy combination, the question of thermocouple instal-lation on fuel rod cladding surfaces was addressed. Several options were available 'as installation configurations: the round cable could

~

be attached to the cladding surf ace by a standard laser-welding technique  ; it could be flattened'over perhaps 20.-40 mm at the tip, further reducing its profile on the cladding, then laser-welded to the cladding; or it could be installed in a groove on the cladding surface.

The third alternative above was selected, such that the ocasuring junction on the coaxial cable could be located at the same elevation as the actual' cladding surface. Ttis was done by laying the cable in j a rounded groove to a depth of half the cable diameter. Attachment r was accomplisned by laser-welding the cable to the cladling, uring small diameter zircaloy filler wire. A cross section of the thermo- 4 couple installation is'shown in the diagram,and photograph of Fi gu re 3. A photograph of the weld attachment near the mea:uring junctioi, is shown in Figure 4. The end product of this technique is a cladding surf ace thermocouple which is still substantial 'enough to be rugged, p t protrudes above the surface only 0.25 mm.

It would have been a simple matter-to flatten the tip of the cable and install it in a rectangular surface groove, but this was considered to be unnecessary since the 0.25 m depth of the rounded groove is not considered to be excessive.

4. TIME-RESPONSE TESTS Pimough not envisioned as a part of the scoping study, it was a simple matter to use a sample of the coaxial molybdenum-zircaloy thermocouple in a test apparatus used with other cladding surface thermocouples. The apparatus is described elsewhere '

, and allows the risetime (10-90% of the total transient response) for the thermocouple installation to be determined in response to a' laser beam pulse impinging on the inside surface of the cladding, beneath the location of the thermocouple measuring function.

5

t.

, c !

i  !

i

\

l I

, Molybdenum wire

! l 0d Zircaloy sheath I a

Laser weld u. I i

, %N< &"Q. l l Zircaloy cladding 7 s'$

x.' +

%'2 ' t

, I

{.

i  % vx ;dg;s

! NS$3'c($'8Sy#

l '%S'3 '

4 4 > ,

t 0.51 mm i

- 0.61 mm 0.25 mm n

(

i l

l lNEL-A-9367 i

i i

4 .

!. l 1

s

1 i

l i

1 l t

' 1 i ,

l . -/ '

i  ? l i ' ' '

I i

'i .+ -

'I A

.., S[ ' -

l Bi$N4/%-)I$ dih ahMNF.;

f h bhIh ; h[k If '.

i j9/ If$~H j

.i k,i%-[$q$jA64(g$Is)k>/8h.

@ gw

r '

. . ,; 2 p:

.:l 4, , g .

'y * ) e '

~,

< - .2 ;y ..

i i

i . ._

t m 4

4 1

Fig. 3 Diagram and photogr.aph of cross section of installation of l- coaxial molybdenum-zircaloy thermocouple on fuel rod cladding surf ace.

i 6

j .

i i

I l

R*Jp:;

k  ; 4 , ;p? <

l+ '

i A $ 8 &yy W{li%p k , $ py,, & '

l lIs}hNh$hh hl bhp,;,h j

m.-,,.%,pwg k- 5 L g .'

s l

2 nod %.qj5hggyjgg 3j&hb{kj. i i

1 I

f Fig.- 4 Measuring Junction attachment of coaxialy molybdenum-zirculoy

thermocouple to fuel .od cladding surface.

I I

f Tests were performed with static air surrounding the thermocouple junction, and then, in an attempt to further simulate actual operatina

conditions, also with static water. Facilities for flowing water past 4

the thermocouple were not available at the time. The results in

! static media are given in Table I, showing an avorage risetime in

j. water of 8.5 ms.

4 i

]- .Although this' result cannot be taken as an absolute measurement, since coolant flow and' temperature conditions will influence the L: result, as well as the pulsed' nature of the test, it ir/ interesting to i

l..

.- 7

. _ , -=

TABLE I COMPARATIVE RISETIMES OF EXPERIMENTAL AND STANDARD

! CLADDING SURFACE THERM 0 COUPLES Average Standard Transient Average Thermocouple Risetime Deviation Response Peak b Type Medium (ms) (ms) '(UC/ms) (UC)

^

0.51 mm diameter Water 8.5 0.3 19.0 144 coaxial molybdenum-j zircaloy Air 25.2 1.0 9.3 218 1.2 mm diameter Water 49.4 1.7 2.7 114 titanium-sheathed Type K Air 72.3 1.7 2.4 161 3

Intrinsic Type K Water 10.8 0.7 53.7 387

' with 0.25 nm-i diameter wires Air 11.8 0.9 41.2 564

[a] The average of a sampling of laser pulse energies was 3.7 joules, i

)

i s

6 4

1 8

.- . .-= , . - . - . . - - . , . . --

- . ls; ' ,

4 C

[L  ;

' compare Lit with measuremen'ts made zon > other: cladding surf ace thermo-coup 1Es. The table shows that~ the average risetime in static' water

for a' standard ~ titanium-sheathed surf ace-mounted thermocouple asJused Lat'the Idaho National Engineering Lab' oratory (INEL).was 49.4 ms, and.

for a bare-wire intrinsic 1 Type-K' thermocouple,10.8 ms.

I F

Since:the junction of the coaxial 1 thermocouple was welded.to the cladding,.the'~ central molybdenum wire could'be: considered to approach heing an. intrinsic' thermocouple when considered 'in combination with h

i theLcladding.itself. When considered;in this way, using the zircaloy

cladding ~as one thermocouple'

leg, the:risetime.inistatic water was

f. 6 ms. Again,- comparative measurements have the' greatest significance',

[ considering- the type of. test and the conditions, but these~ results, 4 serve to illustrate the reduction.in time. response corresponding to reductions in thermocouple size. *

[:

B 4

kE f

d n

s' i -

r t

i j'

..I

. t

,g.

t

- ,s  ;

. . , , s ,.. _ . - - -

Y

? ~

III. CONCLUSIONS AND RECOMMENDATI0'SN This scoping study has demonstrated the following~with regard to j

coaxial molybdenum-zircaloy thermocouples.

(1) A coaxial configuration, using a zircaloy sheoth and a j central molybdenum wire, can readily be fabricated t.o as j small as 0.51 mm in diameter- l (2) The -Seebeck coefficient of the molybdenum-zircaloy combina-tion is similar to magnitude to that of the W-Re alloys (3) ine' molybdenum-zircaloy output was repeatable to within 1.3%

during a series.of temperature' cycles (4) Installation of 0.51 mm diameter zircaloy-sheathed thermo-couples on fuel rod cladding surf aces can readily be done by laser-weld attachment,. in either a surf ace-mounted configur-ation or in a surf ace groove (5)- A 0.51 mm diameter coaxial cladding thermocouple.installa-tion had a risetime (10-90%) of about 9 ms in static water.

Further work on Ethis type of thermocouple should include investi-gation of the following:

(1) The repeatability and reproducibility of the thermoelectric output for different lots of zircaloy and molybdenum (2) Long-term stability and the effect of heat treatment, such as annealing. state, on the thermoelectric output of the pair i

l s.

t '.

10

.(3) The effect of progressive oxidation of zircaloy on the thermoelectric output and stability of the molybdenum-zircaloy pair l 1

(4) Either splicing and extension cable techniques, or of ca'ble penetration methods into~.an in-pile loop.

l l

> 1

\

l l

l l

I l

l i

l l

4 l

J l

. l 11

g 4

IV.

• REFERENCES

! i

~

4

[ 1. S..C.' Wilkins,; Miniature Zircaloy-Sheathed Fuel Rod Cladding- l

- - Surface Thermocouples, TFBP-TR-286 (September 1978). ]

~

I 2. W. - C. Kuhlman, Thermocouple Research at GE-NMP0, GE-TM 65-2-15

.(February.1965)pp.26-29.

! '3. Y. S.. Youlookian, editor, Thermophysical Properties of High

-Temperature Solid Materials, Volumes 1 and 2, .New York: The j- McMillan Company,1967.

'4? R. Schley, J. Liermann, G. Metauer, J. Gentil, " Nouveaux thermocouples pour la mesure des temperatures superieures a i i 10000C, " International Colloquium on High-Temperature In-Pile j~ Thermometry," J. R. C. Petten, Netherlands, December 12-13, 1974,

EUR-5395, pp 325-342.

l- 5. R. H. Meservey, Temperature Measurement on Zircaloy-Clad Fuel j Pins During High Temperature Excursions, ANCC-NUREG-1303 ( April 8

1976).

i

6. S. C. Wilkins, Embedded Cladding Surface Thermocouples on-g 'Zircaloy-Sheath'ed Heater Rods, TREE-NUREG-1072 (June 1977).

I  ;

I i

l-i E

1 12'

.u-