. on . : get . . I OF ORNL P 2179 1 " : C . - - ISO S6 V 1 I MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS - 1963 URNK € - 299 2199 Conf-660511-6 CFS93 PICES JON 27 1966 { 1, i iilis H.C. $ 6.00 MN 50 :*I * .charter MASTER A DILATOMETER FOR MEASURING AXIAL DISPLACEMENT OF FUEL DURING IRRADIATION* F. R. McQuilkin T. L. McLean V. A. DeCarlo R. L. Senn Oak Ridge National Laboratory Cak Ridge, Tennessee RELEASED FOR ANNOUNCEMENT IN NUCLEAR SCIENCE ABSTRACTS 1 LEGAL NOTICE Thle roport ms preporod HS 1D accurnt of Government sponsorod work. Noithor the United Statos, por the Commission, por any person acting on beball of the Commission: A. Makes any warranty or representation, exprousad or implied, with respect to the accu- racy, completeness, or usofilnost of the information contained in this roport, or that the uso of any information, apparatus, mothod, 07 procoas disclosed in this roport may not Infringe privaloly owned rights; or B. Assumes may Habilites with respect to the use of, or for damagou resulting from the uno of any information, apparatus, mothod, or procosa disclosed in this report. As usod in the abovo, "person acting on baball of the Commisolon" includes any on- ployoo or contractor of the Commission, or omplryoo of such contractor, to the axtant tout such omployee or contractor of the Commission, or omployee of such contractor propards, dienomiosion, or providos accoss to, may information purnuant to his employment or contract with the Commission, or his omployment with such contractor. . 2 Prepared for Presentation at the International Symposium on Capsule Irradiation Experiments Pleasanton, California May 3, 4, and 5, 1966 .. : AL *Research sponsored by the U. S. Atomic Energy Commission under con- tract with the Union Carbide Corporation. . - - - - - . - .. - - . . A DILATOMETER FOR MEASURING.. AXIAL DISPLACEMENT OF FUEL DURING IRRADIATION . . . . . . F. R. McQuilkin T. L. McLean V. A. DeCarlo R. L. Senn . - . . - - - - - - Axial displacement of U02 fuel pellets during irradiation has been . - -en-*- *** . - - --- mura - measured with a dilatometer employing a commercial pneumatic linear motion, - - - - - - - transducer. A unit similar to one used by Notleyl and others for measure- ments of the change in cladding length was redesigned to fit a modified EGCR type fuel irradiation capsule assembly. A bellows sealed push-rod, : : coupling the fuel stack to the transducer, provided a unique arrangement for penetrating the fuel encapsulating can. The transducer, near the top of the test assembly shown in Fig. 1, . ; consists of three chambers separated by two small sharp-edged orifices. A precision-tapered pin moves in the second orifice. The pin, attached to the tip end of the push-rod, moves axially with fuel displacement and thus .... . .. is. n e - - - varies the flow area of the second orifice. Nitrogen flow to the trans- i' - - . A INI upper orifice (AP12). The differential pressure across the second orifice (AP23) is then a function of the position of the tapered pin and hence the in length of the fuel stack To insure repeatability the exhaust pressure . - (P3) is held constant. The thin-wall (0.0016 inch) nickel bellows which provides the fission gas seal between fuel can and push-rod is lightly compressed. The push- .. l'od is thereby held against the insulator on top of the fuel stack and follows axial moverent of the fuel. The lower end cap of the fuel can, the Nak-filled primary containment tube, and the gas-filled secondary tube - - . L - ORNL-OWO 65-63JR THERMOCOUPLES STATIC PRESSURE TUBES- JON, GAS FOR TRANSDUCER INI.ET - TRANSDUCER BODY "FIXED" ORIFICE PRESSURE TAPS "VARIABLE" URIFICE TAPERED TRANSDUCER PIN Im NICKEL BELLOWS- N, GAS FROM TRANSDUCER . NOK BLANKET GAS INLET -NOK BLANKET GAS OUTLET CONTROL GAS OUTLET er NICKEL BELLOWS Carr... m CONTROL GAS INLET. Nok NICKEL BELLOWS SESSO 22.594 in. NOK CONVECTION FLOW DAM PUSH- ROD TO TRANSDUCER- INSULATOR -END CAP STAINLESS STEEL THERMOCOUPLE BAND AND DOSIMETER- SECTION A-A 10% in. CONTROL GAS ANNULUS SPACER WIRE FUEL CAPSULE VOZ PELLETS- CONTROL GAS CONTAINMENT TUBE INSULATOR -- THERMOCOUPLE PITULO DAN Urus NOK VESSEL END CAP UW. IL CAPSULE LOCATING PIN WELDED TO FUEL CAN, INNER AND OUTER TUBES AFTER TRANSDUCER CALIBRATION Pneumatic Dilatometer Transducer for Determining Axial Movement of UO, Pellets During irradiation. ............. are rigidly attached to provide a stable reference plane against which the fuel movement is related. The differential thermal expansion of the fuel can and NaK tube is accommodated by a separate nickel bellows for parh. MEN Measurements are taken by manually adjusting the nitrogen flow and is exhaust pressure to the salues used during calibration and observing the differential pressure (AP23). The differential pressures (AP 12 and AP23) pressure gages. Complete instrument system calibration during assembly enabled us to obtain an accuracy of 10.00.1 inch over a range of 0.290 inch. Two capsules so instrumented have performed well in irradiation tests c at conditions similar to EGCR test requirements.3 Measured values ,of the fuel stack heights at design temperatures agree well with expected thermal expansion of the 9-in. fuel stack. Repeatability at lower temperatures during imposed thermal cycles is excellent (+0.0005) and the values clearly demonstrate that the overall height of the fuel stack decreases during ir- radiation. Consecutive measurements at zero reactor power, which dupli- cates the initial temperatures, produce the most interesting results. The fuel stack height in unit No. I had shrunk 0.031 inch at 96 days exposure: when it was removed because of a failure in another part of the capsule; i . . and unit No. 2, still operating in mid-February after 108 days, had shrunk 0.045 inch without indication of leveling off. The contributions of G. R. Samuels and the helpful discussions with . .. . J. R. MacEwan of AECL are gratefully acknowledged. ... .. . . .... . ... - NOD311 REFERENCES : CHAPTE18 111:. 1. M. J. F. Nistley and A. Harvey, "The Length Changes of Zircaloy Sheathed UO2 Fil Elenents During Irradiation," CRFD-1174 (AECL-1876), Atomic Energy of Canada, Liunited, August 1963. 2. D. B. Trauger, "Some Major Fuel-Irradiation Test Facilities of the Oak Ridge National Laboratory," USAEC Report ORNL-3574, Oak Ridge ileticnal Laboratory, April 1964. 3. D. }. Trauger, "Irradiation Testing of Fuel Materials for EGCR," Nu- clear Sc!ence and Engin aring, Vol. 14, No. 1, pp. 69-82, September 1962. i i!!!!.. ? . .. ., . . . ... . . . ... . .. . . . . . . .. .. . . . .. .. .. UU .. NOMAT MOM 0 20 END ? - . USAJ DATE FILMED 7/27 / 66 .