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Yamamoto, Hisashi*; Sekiguchi, Yoshiyuki*; Hirose, Tadashi*; Sanda, Toshio*; Tamura, Seiji*; *; *
PNC TN941 80-179, 402 Pages, 1980/10
On April 24th, 1977, the initial criticality of JOYO was achieved and on July 5th, 1978, the reactor output reached rated power of 50 MW for the first time. The 75MW power ascension test was started in July, 1979, followed by two cycles of rated power operations, and the 100 hour nominal power continuous operation was completed in February, 1980. Through the tests for the core, plant it self, radiation shield and plant monitoring, the results proved satisfactory operation characteristics at 75MW. This report presents the summary of an the results obtained in the Test of MK-I core.
Sasaki, Makoto; *; Miyakawa, Shunichi; *; Sekiguchi, Yoshiyuki*; *; *
PNC TN941 80-116, 84 Pages, 1980/07
This report contains papers on planning of the Dosimetry Experiment (measurement and analysis) in Exparimental Fast Reactor "JOYO". These papers were distributed for announcement to Dep. of Fast Breeder Reactor, OEC. The preparation of the dosimetry experiment was almost complitely done in 1979. The dosimetry experiment will be excuted in 1980.
*; Miyakawa, Shunichi; *; Sasaki, Makoto; Sekiguchi, Yoshiyuki*
PNC TN908 80-03, 33 Pages, 1980/05
None
*; Sekiguchi, Yoshiyuki*
PNC TN941 80-64, 111 Pages, 1980/04
Although the temperature of the primary system sodium coolant in JOYO is high, the primary heat transport system piping and components are crowded into the in-containment, underfloor areas. For the successful operation of the JOYO reactor, as well as to gain experience for the design of future plants, it is important to obtain an understanding of the thermal behavior in these underfloor areas during reactor operation. The heat load in each cell was observed by measuring its inlet and outlet gas temperatures during the 50MWt and 75MWt start-up tests. Based on observation of the cell layout and the results of these tests, the cell cooling performance for the underfloor areas were divided into three categories as follows : (1)Cooling Condition : Good. Cell is not crowded with piping and components. The arrangement of the cooling gas inlet nozzles is suitable. (2)Cooling Condition : Average. Cell is crowded with piping and components ; however, arrangement of cooling gas inlet nozzles is suitable, and the cooling gas flow rate is sufficient for adequate temperature control. (3)Cooling Condition : Poor. Cell is crowded with piping and component ; and hot areas are produced. Arrangement of cooling gas nozzles is not suitable and the cooling gas flow rate is insufficient. Insulation surface temperature of the PHTS piping and components were measured to obtain the information, which was used for an analysis of the thermal behavior in the underfloor areas. An insulation surface mean temeprature of the hot leg piping is 85
C, and a mean temeprature of the cold leg piping is 77C.
Yamamoto, Hisashi*; Sekiguchi, Yoshiyuki*; Sanda, Toshio*; *; *; *
PNC TN941 80-58, 85 Pages, 1980/04
[Measurement of the Minimum critical Core] Following initial criticality, the reactivities necessary for determining the excess reactivity of the power-up core were measured. Only those measurements necessary to provide the minimum required information were made as follows: (1)One regulating control rod worth was measured by using both the period and subcritical multiplication techniques. (2)The isothermal temperature coefficient was measured between 170C and 250C. (3)Reactivity worth measurements of one core edge fuel assembly were made. In addition to these measurements, the neutron source effects which affect the determination of true critical control rod position were measured. All the measured reactivity. worths described above were in good agreement with design calculations. [Full Core Loading Test] Based on the reactivity worths descrived above, the number of fuel assemblies to be added for the desired excess reactivity was determined. Five fuel assemblies, were added, to the existing core with 65 fuel assemblies (one fuel assembly had already been added to the minimum critical core to measure the edge fuel worth). The initial power-up core with 70 fuel assemblies was achieved after the five assemblies were loaded in three steps, with confirmation of the additional reactivity worth measured after each step. The excess reactivity of the core was measured as 2.2%
k/k at 250C.
*; *; Sekiguchi, Yoshiyuki*
PNC TN941 80-33, 136 Pages, 1980/04
This report describes the results of the burn-up coefficient test (NT-35) that was planned and performed as a part of the power-up testing of the Experimental Fast Reactor "JOYO". The purpose of this test is to measure the reactivity change against the reactor burn-up (burn-up coefficient). Two measuring methods was adopted properly, one was to measure the critical points at the reactor start-up and the other was to measure control rods' position at rated power operation. This testing was made through 3 periods in 1978 
1979, that is, 50 MW power-up testing, 50 MW duty 1st and 2nd cycle. (1)The measured burn-up coefficient was negative as follows. Burn-up coefficient I (including Np239 effect): -7.9(+1.0,-0.3)
10
%K/K/50MW/DAY Burn-up coefficient II (excluding Np239 effect): -7.7(+0.9,-0.5)10 %K/K/50MW/DAY (2)The reactivity descent by burn-up was rather large in a few-days after reaching the rated power, and it became linear after about a week, resulting in the accumulation of Np239. This effect was measured as -1 -2 cent. (3)The error of burn-up coefficient is estimated as +6 -12 % against absolute value.
*; Endo, Masayuki*; Sekiguchi, Yoshiyuki*
PNC TN941 80-06, 83 Pages, 1980/01
This report describes the results of the power coefficient test (NT-34) that was planned and performed as a part of the power-up testing of the Experimental Fast Reactor "JOYO". The purpose of this test is to measure the reactivity chauge against the power increase (power coefficient) by measuring the reactor thermal power and excess reactivity at steps of the power ascension procedure. This testing was made from July through August in 1978, and the followings were confirmed. (1)The power coefficient was negative in all power range through 50MW rated power, and could be fitted with good reproducibility as follows. Power coefficient f
(%K/K/MW) = -5.93 10
P-6.05 (10. P: Reactor thermal Power (MW) for 11MW ≦ P ≦ 53MW. The power coefficient was linear against the powar and became less negative with range 10MW (-6.610%K/K/MW) through 50MW (-9.010 %K/K/MW). (2)The experimental error was from +4.6% to -9.7%, and the dominant parts were the systematic errors. Particularly, the maximum error was derived from the difference of the thermal expansion between the extension pipes of the control rods and the reactor vessel. The error range was biased to the negative direction because the control rod worth used in this testing was seemed to be a few percent larger than the real worth by reasons of the change of the shadowiug effect, the change of the core fuel arrangement and the burn-up of control rods. (3)There was no significant difference between the results of the power ascent and descent. The reactor attained enough equilibrium of reactivity and thermal condition within about 20 minutes.
Yamamoto, Hisashi*; *; *; Sekiguchi, Yoshiyuki*; *; *
PNC TN941 80-04, 221 Pages, 1980/01
Critical approach test started from March 16, 1977. The core had been loaded with dummy sub-assemblies of 55, blanket sub-assemblies of 203, and reflectors of 48, in the early stage of the functional test period. The neutron source of an antimony-beryllium type was loaded at a position just outside the predicted critical core. The source intensity was of approximate 10
n/sec. Three extra neutron counting channels were provided for monitoring the counting rates during the tests. In the critical approach, the dummy sub-assemblies (and some blanket sub-assemblies) were replaced by core sub-assemblies from the core center with fifteen steps. A criterion was applied to number of fuels to be loaded at each step, which was limited within half the number of fuels to be loaded to the critical core estimated by inverse multiplication curves. The effect which was caused by neutron multiplication of fuels at the in-vessel fuel storage rack was estimated, and the inverse multiplication curve was corrected. The criticality was achieved on April 24 with 64 fuel sub-assemblies, which was predicted as 61 
5.
Sanda, Toshio*; *; *; *; *; Muramatsu, Toshiharu; Sekiguchi, Yoshiyuki*
PNC TN941 79-218, 99 Pages, 1979/12
As part of dynamics tests in the experimental fast breeder reactor "JOYO", reactor noise tests were carried out. At some power levels, up to 50MW, fluctuations of the flux, the outlet, temperatures of fuel assemblies and temperatures of primary and secoudary main cooling loops were measured. The power spectral density, correlation function, transfer function and coherence function of these signals were obtained and reactor characteristics were analyzed. The major results are as follows. (1)It was confirmed that no unstable phenomenon exists in JOYO. (2)At low frequency region, fluctuations of these signals are larger and give better correlations. At this region, the primary contributors to fluctuations of the flux and the reactor outlet temperature were investigated. (3)In power spectral density of the flux, the noticeable peaks exist at about 1.8Hz and 0.025Hz. The former peak is due to control rod vibration effect and the latter peak has reactor power dependency and the neutron detector position dependency. (4)By the correlation functions of the secondary cooling loop temperatures, coolant transport delay times were obtained, which showed good agreement with the times calculated by flow velocity and the pipe length.
Sanda, Toshio*; *; *; *; *; Sekiguchi, Yoshiyuki*
PNC TN941 79-191, 78 Pages, 1979/10
For the initial core (70-fuel subassembly core), control rod worths for 6 rods were measured by means of critical methods (period and substitution methods). And rod worths of safety rods were measured with a rod drop method. As consequences, (1)Obtained reactivity stroke curves for 6 control rods were in good agreement with design curve. The total worth of 6 control rods was 10% greater than design worth. (2)It was confirmed that one rod stuck margine is sufficient. (3)Scram time of safety rod and reactivity change on scram was observed with a rod drop method (an inverse kinetics method), and scram time of 0.66sec was obtained. Reactivity change was completed within 0.4sec, from biginning to the end. (4)Intereference of rod worth due to adjacent other control rod pattern was observed and found to be in good agreement with design value.
*; Endo, Masayuki*; *; *; *; Sekiguchi, Yoshiyuki*
PNC TN941 79-179, 198 Pages, 1979/10
This report describes the results of the thermal power calibration test (PT-11) that was planned and performed as part of the power-up testing of the Experimental Fast Reactor "JOYO". The purpose of this test is to calibrate the Power Range Monitors (PRM) and Intermediate Range Monitors (IRM) by measuring the reactor thermal power at several levels from low power through the rated power of 50 MWt. The reactor thermal power was determined by measuring the inlet and outlet temperature and the flow rate of the primary main coolant. After this procedure, PRM and IRM were adjusted to coincide with the reactor thermal power by regulating the electronic amplifiers. Thes testing was made from April through August 1978, and followings were confirmed. (1)The PRM indicators show good linearity with the reactor thermal power. (2)The PRM indicators overlap with the IRM indicators over more than three decades. (3)The PRM indicators changes depending on the operating histry of the reactor. The PRM indicators is lower than the reactor thermal power immediately after start-up. Then that increases gradually and comes to stable in about one week after start-up. The maximum drifting value is about 6 per cent.
Yamamoto, Hisashi*; Sekiguchi, Yoshiyuki*; Tamura, Seiji*; *; *; Sasaki, Makoto; *
PNC TN941 79-164, 185 Pages, 1979/09
The 75MW power ascension test of "JOYO" was started in July, 1979, followed by the successful 50MW power ascension test and two cycles of rated power operations. In the 75MW test reactor power was raised up to 65MW at first in order to confirm the characteristics of the plant stability and safety. On July 16th, 1979, the reactor out put reached the rated power of 75MW for the first time. Through the tests for the core, plant it self, radiation shield and plant monitoring, the results proved satisfactory operation characteristics at 75MW. The power ascension test was completed, except for the 100 hour nominal power continuous operation which is scheduled in January, 1980. This report presents the summary of the main results obtained in the test conducted untill August 1979.
Yamamoto, Hisashi*; Sekiguchi, Yoshiyuki*; *; *; Kawashima, Masatoshi*; *; *
PNC TN941 79-112, 156 Pages, 1979/07
This report describes the results of the Nuclear Power Calibration test and the Power Distribution measurements made on the core center axis by micro fission chambers. The nuclear power leve1 was determined from the relationship between the calculated reaction rates and the count rates obtained by the Pu239 micro fission chambers which were inserted in the Joyo core. The Pu239 chambers used in this test were previously calibrated in the known neutron field of a thermal reactor. The principal results of this test are as follows: (1)It was confirmed that the relationship between the SRMS count rates and nuclcar power level is linear in the range of 0.1KW 10 KW. (2)The SRMS and IRMS indicators overlap in the range of 1KW 10 KW. The IRMS indicators show, linearity with the power level a above 1 KW. (3)Five fission reaction rates, Pu239, Pu240, U235, U238 and Th232, were measured along the center axis of the core using micro fission chambers. The axial power peaking factor was 1.19. The measured value of axial peaking factor agreed with the one predicted by design. (4)The SRMS count rates increase about 8% when temperature of primary sodium increases by 100C. (5)The core fuel assemblies stored in the in-vessel fuel rack affect the count rates of the neutron monitoring system. When one core fuel assembly is loaded in a fuel rack position on a line connecting the core center and SRMS counters, the count rates increase about 25%. The additional nuclear characteristics determined in this teat are: (6)Isothermal temperature coefficient was -3.65 10 % 
/
/C (190C 250C) (7)The reactivity change due to the replacement of a normal core assembly at the core center with a special subassembly for this test was -0.085% /k.
Hirose, Tadashi*; Endo, Masayuki*; Nanashima, Takeshi*; Doi, Motoo*; Enomoto, Toshihiko*; Suzuki, Yukio*; Sekiguchi, Yoshiyuki*; Yamamoto, Hisashi*
PNC TN941 79-91, 81 Pages, 1978/12
This system is used to remove reactor decay heat in cases where the main cooling system is inoperable for unexpected reasons, a lower than normal sodium level exists in the R/V or during in-service inspection in the R/V. The purpose of this test is to verify that the design heat removal rate (2.6MWt) can be achieved by the Auxiliary cooling system. With the sodium level lowered below main cooling system outlet nozzles and the coolant temperature (DHX outlet temperature) controlled at 250 C, the reactor power was increased first to approx. 1MW (1.16 MWt actual) and then to 2 MW (2.16 MWt actual) to provide the "decay heat". At both steps, steady-state conditions were verified and test data were recorded, from which the heat removal rate at design conditions was calculated. (Testing was terminated after the second step to maintain the calculated distortion of the partially-filled R/V within prescribed limits.) Test Results : At the second test condition (reactor power = 2.16 MWt) the R/V inlet Na temperature of 267 C corresponded to a 72% open DHX inlet vane setting. Extraporating this to the design condition (R/V inlet temperature = 370C), a 100% DHX vane opening would permit the removal of 3.1 MWt decay heat.
*; *; *; *; Muramatsu, Toshiharu; Sekiguchi, Yoshiyuki*
PNC TN941 79-127, 236 Pages, 1978/12
A plant stability test of JOYO has been conducted in the period of JOYO Power Up Test. The plant stability test consists of two kinds of tests. One is a test of changing set point of DHX (Dump Heat Exchanger) outlet sodium temp. (PT-22), and the other is a small reactivity disturbance test (PT-21). In JOYO, reactor inlet sodium temperature is kept constant (370C) by a coolant temperature controller, which is provided for each DHX (Each loop has two DHXs). The plant stability test has been conducted at the reactor power levels of = 20MW, 25MW, 40MW, 50MW, and the test results are as follows ; (1)The plant is sufficiently stable for set point change of DHX outlet sodium temperature through the reactor power range, and damping ratio of main response variables are less than 0.25 (aiming value as design) for sub-optimal controller's parameter. (2)The plant is also sufficiently stable for small reactivity disturbances of 3cent 5cent, and main response variables change monotomously even if the coolant temperature controllers are manual condition.
