ML18235A039

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Aerojet-General Nucleonics Report AN-1527, Aerojet-General Nucleonics Industrial Reactor (Agnir) Reactor Physics Tests.
ML18235A039
Person / Time
Site: Aerotest
Issue date: 09/30/1966
From: Tomlinson R
Aerojet-General Corp, Aerojet-General Nucleonics
To:
Office of Nuclear Reactor Regulation
References
AN-1527
Download: ML18235A039 (36)
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Text

' "

AGN r

Engineering and Development Division AEROJET-GENERAL NUCLEONICS INDUSTRIAL REACTOR (AGNIR)

. *-~' .I

.. ; REACTOR PHYSICS TESTS AN-1527 September 1966 r----------------*- --------- - ~

- NOTICE - ECOPY THE ATTACHED FILES ARE OFFICIAL RECORDS OF THE DIVISION OF DOCUMENT CONTROL. THEY HAVE BEEN CHARGED TO YOU FOR A LIMITED TIME PERIOD AND MUST BE RETURNED TO THE RECORDS FACILITY BRANCH . 016. PLEASE DO NOT SEND DOCUMENTS CHARGED OUT THROUGH THE MAIL. REMOVAL OF ANY PAGE(S) FROM DOCUMENT FOR REPRODUCTION MUST BE REFERRED TO FILE PERSONNEL.

JlEGU.lATORY DOCKET TILE COPI DEADLINE RETURN DATE NUCLEON I CS RECORDS FACILITY BRANCH IFORNIA l-

AGN ENGINEERING AND DEVELOPMENT DIVI.§.!QN AEROJET-GENERAL NUCLEONICS INDUSTRIAL REACTOR (AGNIR)

REACTOR PHYSICS TESTS By R. L. Tomlinson AN-1527 August 1966 t ft N * : * * '* *\ * , .._ ,"" _.., * * ..... ' ** ,,.; * ..~ ~  ; { ;* \a,( { ' " * * \ ,., **..\ *** ' * ' .. i. ,

Approved b y : ~

R. H. Chesworth, Manager Engineering and Development Division AEROJET GENERAL NUCLEONICS 0 A DIVISION OF AEROJET-GENERAL CORPORATION iii

AN-152 7 AEROJET-GENERAL NUCLEONICS INDUSTRIAL REACTOR (AGNIR)

REACTOR PHYSICS TESTS*

by R. L. Tomlinson*

ABSTRACT

_The Aeroj et-General Nucleonics Industr_ial Reactor (AGNIR) achieved initial criticality on 9 July 1965. Following ini.tial criticality, a series c:i.f neutronics and power calibration tests were perfonned to characterize the reactor from both the physics and thermodynamics sta.ndpoints; A description of. th.e. . conduct. .. a.nd significant results of this test program is *presented herein,

  • P.ublished by Aerojet-General .Nucleonics, San Ramo~,. Calif.

V

~-...

AN-1527 CONTENTS Page I. INTRODUCTION 1 II.

SUMMARY

AND CONCLUSIONS 2 III. CONTROL AND SAFETY ROD SCRAM TESTS 5 IV. FUEL LOADING 5 A. INITIAL FUEL LOADING 5 B. SECOND FUEL LOADING 8

v. ISOTHERMAL TEMPERATURE COEFFICIENT 8 VI. REACTIVITY MEASUREMENTS 9 A. TECHNIQUES EMPLOYED 9 B. CONTROL AND SAFETY ROD CALIBRATIONS 9
c. FUEL AND REFLECTOR ELEMENT REACTIVITY MEASUREMENTS 14 D. GLORY HOLE MFASUREMENTS 14 E. DUMMY ELEMENT IRRADIATION CAPSULE MF.ASUREMENTS 17 F. FLUX WIRE HOLDER MEASUREMENTS 18 G. THERMAL COLUMN MEASUREMENTS 18 H. LARGE COMPONENT IRRADIATION BOX 20 I. XENON POISON EFFECTS 20 VII. POWER CALIBRATIONS 20 VIII. POWER COEFFICIENT MEASUREMENT 24 IX. NEUTRON FLUX TRAVERSES 27 REFERENCES 31 vii

AN-1527 FIGURES Figure Number Title Page 1 AGNIR Installation 3 2 AGNIR Core 4 3 AGNIR Core Loading Patterns 6 4 AGNIR Initial Approach to Criticality 7 5 AGNIR Isothermal Temperature Coefficient 10 6 AGNIR In-Hour Equation 11 7 AGNIR Shim Rod Reactivity Calibration 12 8 AGNIR Regulating Rod Reactivity Calibration 13 9 AGNIR Core Component Reactivity Worth as a 15 Function of Core Position 10 Fuel Element Worth Versus Water in the AGNIR .Core 16 11 AGNIR Dummy Element Irradiation Capsule 17 12 Dry Irradiation Tube on Thermal Column 19 13 Large Component Irradiation Box 21 14 Xenon Poison Effects in AGNIR Versus Time 22 15 AGNIR Power Coefficient of Reactivity 23 16 AGNIR Pool Water Heating and Cooling Data 25 (Without Heat Exchanger) 17' AGNIR Calorimetric Power Calibration 26 18 Axial Thermal Neutron Distribution in the AGNIR 28 Core at a Power Level of 230 Watts 19 Radial Thermal Neutron Distribution in the AGNIR 29 Core (230 Watts) 20 Radial Thermal Neutron Distribution in AGNIR Core 30 and Thermal Column viii

AN-152 7 AEROJET-GENERAL NUCLEONICS INDUSTRIAL REACTOR (AGNIR)

REACTOR PHYSICS TESTS I. INTRODUCTION The Aerojet-General Nucleonics Industrial Reactor (AGNIR) achieved i.n-itial criticality at San Ramon, California, on 9 July 1965. It was the twentieth reactor to be built and operated at the San Ramon site. The previous nineteen were AGN-201 and -211 research and training reactors which were sold commercially to research and educational institutions in the U.S. and Europe.

One 20 watt(t) AGN-201 reactor was in use at San Ramon for over eight years until the AGNIR became available for company research activities.

The AGNIR is a 250 kw(t) pool-type reactor; it is fueled with uranium-zirconium hydride; and is water-moderated and water-cooled. The reactor is licensed for general purpose neutron irradiations and isotope production. The open-core design and the 10-ft-diameter, 23-ft-deep water pool was designed to simplify the installation of special purpose irradiation loops, Both wet and dry irradiation facilities are provided within the reactor in addition to special laboratory space for the setup of electronic gear adjacent to the reactor. In-pool storage is provided for 21 irradiated fuel or dummy element irradiation capsules.

The reactor is operated from a control console which permits the oper*

a tor to fully view all operations performed at the top of the reactor po~il..

The facility is served by a 3-ton bridge crane; a mechanically positioned, large component irradiation box can be actuated from the top of the reactor pool.

1

AN-1527 The reactor core consists of zirconium-hydri_de fuel moderator elements surrounded by graphite-filled reflector elements. The inherent safety of this core design simplifies the procedure for obtaining licenses for experi-ments.

Reactor control is maintained by three boron carbide control rods. In-core irradiation facilities include a seven-element central exposure capa-bility; two 3-element exposure facilities; a glory hole; and nrultipurpose dummy element irradiation capsules.

The facility consists of a high-bay metal-framed building 40 by 80 ft, the low-bay portion of which is occupied by a general purpose laboratory; a control room, and a change room. Six shielded pits are provided in the facility for the storage of radioactive components, and a hot cell,which is

'licensed for 500 curie of Co-601 is also located with the reactor building. Non-radioactive storage is provided above the low-bay area within access of the three-ton bridge crane.

The initial physics tests on the reactor are reported herein. A cut-away drawing of the AGNIR installation is shown in Figure l; and a drawing of the AGNIR core is shown in Figure 2. The facility was described earlier (Ref. 1) as were the procedures used in performing the above-mentioned physics tests (Ref. 2),

II.

SUMMARY

AND CONCLUSIONS The initial criticality for the AGNIR was achieved with 63 altnninum-clad TRIGA Mark I fuel elements. These fuel elements contained a total of 2265 gm of U-235 in the form of uranium-zirconium hydrid~. The isothermal temperature coefficient for the system was found to have an average value between 60 and 125°F of -0.15~/°F. All in-core void measurements indicated negative effects.

The power coefficient was measured to be -0.47¢/kw, resulting in a $1.17 in-itial reactivity deficit at 250 kw in addition to xenon, samarium, and fuel burnup effects. The total worth of the control and safety rod system was measured to be -$8.51. No data were obtained during these tests that measur-ably differ: from that presented in the AGNIR Hazards Summary Report (Ref. 1).

2

LARGE COMPONENT IRRADIATION BOX FIGURE 1. AGNIR INSTALLATION 3

DUMMY ELEMENT IRRADIATION SPACE 7 ELEMENT EXPOSURE FACILITY 3 ELEMENT EXPOSURE FACILITY CONTROL INSTRUMENT CHAMBERS FIGURE 2. AGNIR CORE 4

AN-1527 III. CONTROL AND SAFETY ROD SCRAM TESTS The experimental tests performed prior to the initial reactor critical-ity, and the four measurements subsequently performed as part of the quarterly maintenance checks, indicate that the control rod drop times fall well within the Technical Specifications of the reactor license. The Technical S.pecifi-cations state that the total rod drop time, including magnet separation time, shall not exceed 600 milliseconds. For the three .control/safety rods the magnet separation varied from 50 to 60 msec, while the total drop time varied from 410 to 430 msec, A special relay rack panel was installed in the con-trol room to facilitate the easy measurement of the rod drop time with the aid of a sweep oscilloscope and a series of microswitches. The panel also has provisions for controlling a BF pulse counting assembly that was used for con-3 trol rod calibrations using the rod-drop technique, described in Section VI.

IV, FUEL LOADING A. INITIAL FUEL LOADING The initial fuel loading followed the reference procedures (Ref.2);

the fuel load consisted of 63 aluminum-clad TRIGA Mark I fuel elements and 23 graphite-filled reflector elements. The loading was purposely skewed toward the control instrumentation to provide the maximum signal to the reactor in-strumentation during the initial critical experiment. The initial loading configuration is shown in Figure 3A.

The nuclear instrumentation used during the initial critical ex-periment consisted of the normal four channels of reactor control instrumenta-tion; i.e., one BF pulse channel; one gamma-compensated ion chamber inter-3 mediate channel; and two uncompensated ion chambers used as power channels, With no appreciable gamma background on the fuel, all four channels were on scale providing useful infonnation. In addition, two additional BF pulse 3

channels and one uncompensated ion chamber were used during the critical ex-periment for a total of seven usable channels of nuclear instrumentation. A plot of the multiplication versus fuel mass for the initial fuel loading (Figure 4) reveals that the ion .chamber data proved more reliable than the pulse counter data for this initial fuel loading. Cr.iticality was achieved for the configuration within 35 grams of the value found in the initial criticality calculation.

5

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~ CONTROL RODS SOURCE FUEL ELEMENTS 9 GRAPHITE ELEMENTS GLORY HOLE AGNIR CORE LOADING FOR S2.70 EXCESS COLD CLEAN AGNIR CORE LOADING FOR CRITICAL+ 20,7~ EXCESS COLD CLEAN (SKEWED LOADING PATTERN)

(SKEWED LOADING PATIERN) .

FIGURE 3A. FIGURE 38.

AGNIR CORE LOADING FOR $1.80 EXCESS COLD CLEAN (SYMMETRIC LOADING PATIERN)

FIGURE 3C.

FIGURE 3. AGNIR CORE LOADING PATTERNS

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.FIGURE 4. AGNIR INITIAL APPROACH TO CRITICALITY

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AN-152 7 The fuel loading proceeded until a total of 69 fuel elements and 23 graphite elements were loaded into the AGNIR core for a total cold, clean excess of $2. 70 (Figure 3B), The initial control rod calibrations were per-fonned during this loading. The final fuel loading for this configuration is shown in Figure 3B. Preliminary coEe component reactivity measurements were made with this configuration.

B. SECOND FUEL LOADING On completion of the preliminary physics tests the AGNIR core loading was adjusted to a nearly symmetric pattern with the "glory hole," a dry exposure tube, located at the geometric center of the reactor (Figure 3C),

With 71 TRIGA Mark I fuel element.s and 23 graphite elements, the reactor had a cold, clean excess reactivity of $1.80. The control rod calibrations, core component reactivity measurements, neutron flux traverses, and power calibra-tions were performed with this basic core configuration.

V. ISOTHERMAL TEMPERATURE COEFFICIENT The water-filled pool, which serves as~ radiation shield and coolant reservoir for the AGNIR, contains approximately 13,000 gallons of water, The water tank was used as a low-grade calorimeter for two thermal measurements:

1) power calibration of the reactor (see Section VII), and 2) the isothermal temperature coefficient and cooling characteristics of the reactor pool tank.

Nineteen 220-volt immersion heaters, with a total measured power rating of 23.9 +/-. 0.1 kw, were inserted into the reactor grid using the fuel element positions, while water was continuously circulated through a purification loop at the rate of R:i 6 gpm. While maintaining the reactor. critical, the water tem-perature was monitored at five locations within the reactor pool tank. During the tests, the water temperature was varied from 69°* to 125°F. The control rods were calibrated, using both period and rod-drop techniques (see Section VI), prior to measuring the temperature coefficient. As the water temperature of the pool tank is changed, the actual position of the poison section of the control and safety rods differs from the control/safety rod position indica-tors, because of thermal expansion of the rods. The discrepancy is appreci-able since the submerged portion of the control/safety rods is 20.5 +/- 0.5 ft during normal reactor operation, the uncertainty in length being due to the 8

AN-152 7 allowable l ft variation in the water level within the reactor pool tank, The average value of the isothermal temperature co.efficient from 60° to 130°F is

-0.15¢/°F (Figure 5), The insertion of controi .rod poison as a: function of bulk water temperature due to the linear expansion o.f the aluminum hanger rods accounts for the entire coefficient within. the acci:lr~cy of the experimental

  • measurements.

VI. REACTIVITY MEASUREMENTS A. TECHNIQUES EMPLOYED A series of reactivity measurements we~e pe'rformed,. using positive period and rod-drop techniques, The circuitry. Ufled in performing

\ ' '

these*

measurements is similar to that used ai: ~ther* :reacto~. i~stallauons; however, an AGN-developed neutronics code* was used in r~ducing the data front the rod-drop measurements.

  • The range of positive periods meastir~d; using ,* . *,.

thifl technique, varied between 100 and 10 seconds, which. corresporid~ ,.tci :excess reacti vitie~

from 10 .to 40 cents. The reference pro,cedures (R~f'. *2.)**were' used during the measurements. The In-Hour Equation used in the period measurements is plotted in Figure. 6.

B. CONTROL AND SAFETY ROD CALIBRATIONS*

The la~ge reactivity worth of the AGNIR control ~nd safety rod system ($8. 51 total) does not allow complete posit*i~e p~i;-iod calibration of

  • the *sh~ and safety rods (appro~imately $3.80 and $3.75~* respectively), due to the $3.00 license limitation

. and the safety.. inte~lock

. . o~ ~he . .

safety rod. The

. safety rod is maintained in the "full "'-out" position ,du~ing *reactor operation; therefore, total worth measurements on all rods w~re 'obtained~. using rod;.drop techniques. Intermediate points on the shi,;n . and regulating rods were also ob- -

tained with rod-drop techniques and were ,found .

to ,be in:.,. good '

  • agreement

. ' . w:i. th*

the period measurements. The calibr~tion, curves* obtai~ed u~in*g these tech-niques are presented in Figures 7 and 8 ..

In all reactivity measurements, .the accurat'e*determination of criticality is very important. To assist in this' determinati~n, an expanded scale was placed on the Channel 4 line~r power reco~d~r.: Using this recorder,

    • Internal Communication: T.P. Wilcox, DROP -* An IBM*Code to Solve for Reactor Power L~vels* After a Step Change in System ReactivHyJ AN.-COMP-134.

9

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AN-152 7 with its full-range zero suppression and 100-to-l amplification, minute drifts in power can be readily detected and exact criticality accurately determined.

C. FUEL AND REFLECTOR ELEMENT REACTIVITY MEASUREMENTS The reactivity worth of the AGNIR fuel elements, dry glory hole, and dummy element irradiation capsule were evaluated as a function of ring position, starting at the geometric center of the reactor grid plate. The fuel measurements and dry glory hole measurements both were made with refer-ence to water, The actual worth measurements are plotted as a function of ring position in Figure 9.

It can be seen that a fuel element in the center of the loading, ring A, is worth less than that in rings Band C, which are almost identical in worth. Since the AGNIR grid structure is basically a TRIGA grid with a few minor modifications, this effect is not what might be expected, LP.riori;,.

however, in most TRIGA reactors the central core position is occupied with a pulse rod or a norunovable glory hole and are therefore not available for the placement of fuel, The TRIGA grid is undermoderated in the center and over-moderated at the edge. Starting at the center of the core, the hydr~gen/

uranium (235) ratio increases approximately linearly with radius. Multigroup neutron transport calculations (Ref. 3, 4) performed on the actual AGNIR core loading indicate a definite depression of thermal neutron flux in the center of the core with a fuel element in the central location. With the central fuel position flooded with water, the standard loading pattern for TRIGA reactors, a normal thermal neutron distribution across the core is obtained (Figure 10), Therefore, the shape of the fuel element reactivity curves shown in Figures 9 and 10 are wqat would be expected from an analytical basis for the AGNIR with and without a fuel element in the central position.

Graphite reflector elements were evaluated in the F and G rings of the AGNIR core, The average value for these elements were found to. be 9 cents for the F ring, and 4 cents and for the G ring.

D. GLORY HOLE MEASUREMENTS A special dry glory hole is available for various radiation ex-periments, This glory hole is equipped with an internal shield plug that is used to reduce the radiation streaming in the vicinity of the control rod 14

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FIGURE 9. AGNIR CORE COMPONENT REACTIVITY WORTH AS A FUNCTION OF CORE POSITION I * ' * '

15

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AN-1527 drives at the top of the AGNIR pool. The glory hole can be positioned in selected locations in each of the seven rings of the reactor core. The reactivity of water versus the voided glory hole for these locations are shown in Figure 9.

E. DUMMY ELEMENT IRRADIATION CAPSULE MEASUREMENTS To facilitate special short irradiations of a general nature, an irradiation capsule was designed that could be adapted for a variety of irradiations (Figure 11), It can be located in most fuel element positions and has provisions for bringing instrumented tubes to the surface, A shielded transfer cask is available for transporting the capsule within the AGNIR building to the hot cell area for remote disassembly. The worth of the dummy irradiation capsule versus water in the reactor core was found to be identical in reactivity with the glory hole within the experimental error of the measure-ments.

SEAL IRRADIATION VOLUME FIGURE 11. AGNIR DUMMY ELEMENT IRRADIATION CAPSULE 17

AN-1527 F, FLUX WIRE HOLDER MEASUREMENTS The AGNIR core was designed t o allow flux traverses to be rea di ly per f ormed. A total of 22 holes, 0.313 in. in diameter, penetrate the up pe r and lower reactor grid plates to allow the use of flux measuring wires, or 0 . 25 - i n.-diameter (or smaller) neutron-sensitive chambers to be placed in th e reactor core. Special aluminum holders for flux measuring wires have bee n fabr ica ted for use in these holes. The reactivity of these holders, wit h respect to water, is so low as not t o be a consideration in any flux mea sur e -

ments ; howev er, special cadmium tubing used with many flux wire measuremen t s (0 .050-in. ID by 0.090-in. OD) has an appreciable effect on the reactivi t y o f the AGNIR. Cadm i um tubes, with a l e ngth of 26 in. and a weight of 6.63 gm, were inserted in t he flux wire hold ers and their r eactivity worth deter mi ned .

Thes e da ta ar e plott ed in Figure 9 as a function of core position.

G, THERMAL COLUMN MEASURE11ENT S The AGNIR thermal column consi s ts of a large block of graphi te containing five rows of 1.5-in. diameter holes arranged at increasing radii from t he core. The rows are placed 6 in. apart, and each row contains seven irrad i ation positions (Figure 12). Flux wire holder positions are located near the centerline of each row to facilitate performing neutron flux traverses of the thermal column assembly. Four slotted beams, two on each side, are pro-vided to allow experiments to be attached directly to the thermal column. Ex-tensions of these beams allow experiments to be placed inunediately adjacent to t he reactor core. The assembly is located adjacent to the reactor core on ta pered pins and remotely bolted to the bottom of the reactor pool tank. In-stallation and removal of the whole assembly is accomplished with the facility crane and remote handling tools on a routine basis. Figure 12 also shows a 6-in. dry irradiation tube in one of the rear positions of the thermal column.

When the thermal column was installed, the worth of the column was measured to be less than one cent positive with respect to water, due to the 2-in. gap between the reactor core structure and the thermal column which ef-fectively separates the reactivity effects of the thermal column from that of the reactor core. Neutron flux traverses performed in the thermal column are described in Section IX.

18

FIGURE 12. DRY IRRADIATION TUBE ON THERMAL COLUMN 19

AN-1527 H. LARGE COMPONENT IRRADIATION BOX The large component irradiation box (Figure 13) consists of an aluminum box with an internal volume of 8 cu ft. The walls of the box are r e latively thin to eliminate excessive parasitic neutron absorption. The box is pressurized with CO 2 to 0.5 psi above the water pressure with the aid of a relief valve attached to the top of the box. The CO 2 is supplied thro ugh aluminum and plastic tubing from a supply at the top of the reactor poo l . Another tube is available for bringing electrical leads to the top of t be pool if required for any experiment. The box is weighted with lead to el iminate buoyancy. The box is remotely installed and bolted to a movable t a ble at the bottom of the AGNIR pool. Similarly, the movable table is re-mot e ly positioned on tapered locating pins and bolted to the bottom of the AGNIR pool.

When the void box was installed, a reactivity loss of 9 cents was measured for the voided box with respect to water. The box is designed to handle the irradiation of components and subsystems up to 2 ft in diameter.

I. XENON POISON EFFECTS Since AGNIR operates at an average thermal neutron flux of about 12 2 13 2 4 x 10 n/cm -sec and peaks at about 10 n/cm -sec at the center of the r eactor core, the effects of xenon poisoning on the operation are appreciable.

A test was run on the cold, clean reactor core to determine more specifically the magnitude of these effects. The reactor was held at a constant power level o f 250 kw an d a constant poo~1 temperature o f 8S°F f or 50 h ours d uring

. t h e test.

Using the control rod calibrations, the effect of xenon poisoning as a function of operating time was determined (Figure 14). Similarly, the poison worth of xenon was measured following shutdown by making criticality determinations at low power level and correcting for the power coefficient (Figure 15) and iso-thermal temperature coefficient effects (Figure 5). The results of these data are also plotted in Figure 14.

VII. POWER CALIBRATIONS An accurate method of reactor power level determination for pool-type reactors is electrical heat substitution (Ref. S). The reactor pool tank (containing 13,000 gallons of water) was determined to be a fair calorimeter between 70 and 95°F. As previously discussed in Section rv, nineteen 220-volt immersion heaters (with a total measured power rating of 23.9 +/-. O.l_kw) were 2.0

FIGURE 13. LARGE COMPONENT IRRADIATION BOX 21

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. REACTOR POWER LEVEL, kw FIGURE 15. AGNIR POWER COEFFICIENT OF REACTIVITY 23

AN-1527 inserted into the reactor grid, using the fuel element positions, while the water was continuously circulated through a purification loop at~ 6 gpm.

Sirtce the inlet to the purification loop is near the top of the reactor pool tank and the discharge nea_r the bottom, this flow slowly .stir s the pool water, thereby reducing temperature stratification within the tank. The water temperature was monitored at five locations within the reactor pool tank. Plots of the heating and cooling characteristics of the pool water tank are shown in Figures 16 and 17. Once the 23.9 kw electrical heating curve was obtained, the reactor was flux-mapped at low power* and the corresponding read-ings of the Channels 3 and 4 ion chambers were made. The flux traverses were made at an estimated power level _of 160 w, based on thermal flux integration techniques. Using this estimated power as a ba*sois, a scale factor was applied to the ion chamber readings corresponding to a power level of 23.9 kw. A 24-hr nuclear heating run was performed at these ion chamber readings. The actual pow~r level was found to be 34.32 +/- 0.93 kw, based on the previously performed electrical heating data; therefore, the initial flux mapping was performed at 230 watts instead of the estimated 160 watts (Figure 17).

Subsequent nuclear heating runs were performed at 200 kw and 250 kw (Figure 16). Due to the increased heating rate over the initial calibration runs, the heating curves at these power levels are practically linear and do not show the effects of water evaporation that occurs at the lower heating 0

rates. At pool temperatures of 70 F, the water evaporation was found to be about 0.5 gallons/hr; while at 125°F, the rate increased to 5 gallons/hr. The cooling curve in Figure 16 clearly shows the operating limitations of the AGNIR without its 250-kw heat exchanger.

VIII ~WER COEFFICIENT MEASUREMENT The power coefficient (i.e., the reactivity loss as a function of reactor power) was measured at constant water temperature without xenon in the core. Using the control rod calibration curves, the reactor power was increased in 25-kw steps above delayed critical and the reactivity loss de-termined. A plot of the data is shown in Figure 15. The measured average reactivity coefficient was found to be approximately -0.47¢/kw, for a total

.._g_activity loss at 250 kw of $1.17.

  • Internal Communication: V .R. Forgue, Gold Wire Flux Mapping of AGNIR, AGN Chem Tech Memo No, 887, October. 1965.

24

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.\ .

AN-1527 IX. NEUTRON FLUX TRAVERSES The thermal neutron flux mapping of the AGNIR core and thermal column was performed using 0.010 in. diameter gold wires inserted into the AGNIR flux wire holders and irradiated in the AGNIR. core and thermal column, using the 28 flux wire positions (22 in the core and 6 in the thermal column - see Section VI-F). Epicadmium measurements were made, using 0.050 in. ID by 0.090 in. OD cadmium tubes with the 0.010 in. gold wires running axially down the tubes. The 26Pin. long gold wires were cut into 2-in. increments and wrapped around a dowel to form an 0.32 in. diameter ring and counted on a scintillation counter that had been previously standardized with 0.002 in.

by 0.50 in. diameter gold foils by reference to a National Bureau of Standards calibrated neutron flux. In regions of the AGNIR core where the neutron flux changes rapidly with position, 1/2-in. long wires were used.

The 0.010 in. gold wire and the standard 0,002 in., 0.5-in. diameter gold foils were cross-calibrated, using the AGN 201M reactor (basic AGN-201 reactor modified for 20-watt operation). A typical axial thermal flux plot performed in the Band G rings of the AGNIR is shown in Figure 18, The B ring represents the flux plot at the center of the core, while the G ring represents the flux distribution in the reflector region. Figure 19 shows the thermal neutron distribution radially across the AGNIR core at the center-line of the fuel, Figure 20 shows the thermal neutron distribution radia,lly across. the centerline of the AGNIR. core and thermal column. The details of the thermal neutron flux measurements.were documented earlier*.

  • Internal Communications: V.R. Forgue, Gold Wire Flux Mapping of AGNIR, AGN Chem Tech Memo No, 887, October 1965.

V.R. Forgue, Flux Traverse in AGNIR Thermal Column~ AGN Chem Tech Memo No, 952, March 1966.

27

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..30

AN-1527 REFERENCES

1. R. L. Newacheck, tl al., Aerojet-General Nucleonics Industrial Reactor, Hazards Summary Report, AN-1193, Aerojet-General Nucleonics, San Ramon, California, September 1964
2. R. L. Tomlinson, Aerojet-General Nucleonics Industrial Reactor (AGNIR)

Critical Experiments and Power Calibration, AN-1406, Aerojet-General Nucleonics, San Ramon, California, April 1965

3. L. D. Connolly, Los Alamos Group-Averaged Cross Sections, LAMS-2941, IASL, July 1963
4. B. G. Carlson, e. E. Lee, and W. J, Worlton, The DSN and TDC Transport Codes, LAMS-2436, LASL, October 1959 5, R, L. Tomlinson, SNAP Shield Test Experiment Reactor Physics Tests, NAA-SR-7368, Atomics International, Canoga Park, Calif,, July 1962 31
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