ML20085D649
| ML20085D649 | |
| Person / Time | |
|---|---|
| Site: | Saxton File:GPU Nuclear icon.png |
| Issue date: | 03/24/1964 |
| From: | Neidig R SAXTON NUCLEAR EXPERIMENTAL CORP. |
| To: | |
| Shared Package | |
| ML20083L048 | List:
|
| References | |
| FOIA-91-17 1613, NUDOCS 9110170035 | |
| Download: ML20085D649 (11) | |
Text
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e SAXTON NUCLEAR EXPERIMElGAL CORPORATION DOCKET NJ. 50-lh6 LICENSE DPR-h Change Request hl2 l.
Applicant hereby subnits Chan6e Request N
, paragraph 3B of License DPR-h for change of To. 12 in compliance with to be authorized by the Commission echnical as p Specifications rovided in 10 CFR 50 59.
SAXTON NUCLEAR EXPERIMENTAL CORP ,
By _
/s/ R. E. Neidig Attest:
President __
/s/ R. E. Svnher Secretary _
(3 E A-L)
March Sworn and subscribed to before 196h. 2hthme daythisof (S 6 A L) _
/s/ Martin A. Kohr Notary Public 9110170035 PDR 910424 }tr Commission Expires . h, 1966 FebMuhlenberg Tow FOIA DEKOK91-17 PDR 1C13
~_. . _. -. - .. . - . . - . - . . . -
March 2h, 196h
. Docket No. 50-lh6 DPR-b Technical Specifications Change Request #12 (Page 2 of $ pages)
Chenge section G.2.b to read as follows:
- b. Drive mechanism design parameters Normal length of travel, in. 60 Maximam length of travel, in. h2 Design pressure, psig 2500 Design temperature, OF 650 Normal load attached to drive shaft, lbs.
with blade absorber 125 with alternate rodded absorber 108 Maximum load on drive shaf t, lbs. 250 Approximate increment of movement, in. 1/32 Operating coil voltage, d-c 125 1 10%
Positio,n indicating coil voltage for reactor operation, 60-cycle a-c 230 A 100-eycle power supply for position indication may be used for additional accuracy needed in experimental work, but this supply is not necessary for reactor operation.
Change section N.6.d to read as followst
- d. In the case of removal of an individual control rod, the coolant water will be borated to a concentration thc' will insure at least 10% shutdown when all six rods are fully inserted. Then all rods will be withdrawn g approximately eight inches. The rod having the most individual worth is /
then withdrawn from the core and an inverse count rate plot maintained \
during withdrawal to insure that criticality is not achieved. If the inverse count rate indicates that the reactor vill be critical before the rod is fully withdrawn, additional boron will be added. After the highest worth control rod is felly withdrawn and subt ticality is assured, all i control rods are dropped oack into the core, and tae control rod boing changed may then be removed from the core.
- 2. Purpose of Change Experience in other reactors with the type of control rod presently used at Saxton indicates that there is a potential problem due to possible contamination I of reactor coolant with activated silver. Fcr this reason, it is desired to I repiece the present Saxton control rods with a new type rodded abscrber which I will eliminate this potential contamination problem, and in addition, will provide data on the operation of this new design in a PWR environment.
- 3. Safety Coreiderations
- a. Mechanical Design Each of the new absorbers is made up of 22 stainless steel clad silver, indium, cadmium rods. The absorber rods are constructed by inserting silver-
March 2h,196h
- Docket No. 50-lho s DPR-k Technical Specifications Change Request //12 (Page 3 of 5 pages) indium-caumium rods into cold worked stainless steel tubing. A typical rodded control rod is shown on the ermlosed Fig. 203-5c of the Saxton Final Safeguards Report as amended.
The stainless at, eel tubing is 0.bl35-inch 0.D. and 0.3785-inch I.D. The absorber rods are 0.375-inch 0.D. The minimum diametral clearance at room temperature for the rod and tube is 0.002 to 0.005 inch and the minimum clearance between the rod and end plug is 0.350 inch. These clearances are provided to allow for differential thermal expansion between the absorber and the clad and to limit the ultimate pressure rise inside the tube due to heating of air and No measurable swelling of the absorber will result moisture sealed in the tube.
from irradiation.
During reactor cperation, tne maximum calculated absorber temperature is 9600F and the maximum calculated clad temperature is 5650F. Under these conditions the diametral clearance is 0.0005 to 0.0035 inch, and che end plug clearance is The clad and absorber are 0.139 inch. The maximum internal pressure is 595 psi.
given the same acceptance tests, including helium leak testing, as the fuel rod clad and assembly.
The tubes are combined into an absorber assembly by placing them in a fixture i
and electron beam welding ferrules between the tubes at elevations approyinately l
10 inches apart on a pitch of 0.h615 inch, The upper and icwer end pieces of the l
absorber assembly, identical to those of the present control rods, are fitted over pins extending from the end plugs of each tube and joined to the tubes by electron l
l veam welding.
l-Table 1 gives the maximum expected clad stresses for the worst clad tolerance conditions assuming no contact between the clad and absorber rod.
TABIE I ABSORBER CLAD STRESSES Maximum Circumferential* -49,043 psi Axial **
Dead Weight -18,366 psi 3.7g Deceleration -18,6h2 psi 30.0g Deceleration -21,382 psi The gas pressure in the tube is negligible and is considered zero for these stresses.
- Includes pressure and thermal stresses (p = 2600 psig at max. transient).
March 2k,196h
' Docket No. 50-lh6 DPR-b Technical Specifications Change Request #12 (Page h of 5 pages)
Clad condition: Mean I.D. = 0 3785 in.
Mean 0.D. = 0.L135 in.
Max. Ovality - 10.001 in.
Tensile Yield = 80,000 psi @ 700F Tensile Yield - 50,000 psi e 725oF 3 7g deceleration is for normal scram while 30.0g deceleration assumes partial dashpot failure.
The meting of the rodded control rods and the followers is done in the same manner as with the present bladed control rods.
The rodded absorbers have been designed to be dimensionally essentially the same as the present bladed rods and are therefere subject to the same overall clearances and tolerances. Extensive mechanical and hydraulic tests on absorber sections of a similar design have been conducted by Westinghouse and no operational difficultics were encountered. Since no operational difficulties have been experienced with the present control rods, it is expected that operation of .ne rodded absorbers should be equally trouble free.
- b. Nuclear and Hydraulic Design Because of the smaller absorber volume and mass of the new rods, it is expected that their total worth will be 90% of the measured values of the present rods. The measured worth of the present blade rods, 20 to 21%, was more than sufficient to control the reactor. Therefore, no problems are foreseen in operating the reactor with the rodded absorbers, even though their total worth is only 18-191.
Operation of a completely new core would require the presence of boron in the coolant. Based on chemical shim experience to date, this situction would present no problem.
The cross sectional area of the new-absorber section is slightly smaller than that of the present absorber. This smaller area will not have an adverse effect on the coolant flow characteristics through the control rod channels.-
The flow characteristics will be essentially the same as for the case when the present control rod follower sections are in the core during chemical shim operation.
The overall weight of each rodded absorber is 17 lb. less than the bladed absorber presently in use. Although _it is lighter, the total weight of the absorber plus follower (97 lb.) is still well in excess of the estimated hydraulic lifting forces. Scram time for the new rods is expected to be 10% slower than with the present rods, but still well within the limits imposed by the original safety analyses.
The proposed change of control rod procedure which eliminates removal of the adjacent fuel assemblies requires coolant boration to insure that the reactor is shut down by 10%. Present Saxton shutdown procedures for head removal call for a baron concentration sufficient to keep the reactor 10% shut down so that no special or unusual safety precautions are required when performing the prcpesed rod change.
j
March 2h,196h
' Decket No. 50-lh6 DPR-b Technical Specifications Change Request #12 (Page 5 of 5 pages)
- c. Installation Procedures and Precautions The present Technical Specifications call for the remcval of the four adjacent fuel assemblies before a control rod can be removed. Such a process is unduly conservative from a nuclear standpoint and subjects the reactor to the additional risk of physical damage during all of the fuel movement and handling required, it is therefore proposed that the c, tant be borated so that the reactor is at least 10% suberitical and the control rods be removed and replaced one at a time. The following procedures will be followed for the control rod change.
Following reactor shutdown, head removal and coolant water boration, all rods will be banked at approximately eight inches (corresponding to approximately 7% zik/k held in the rods). The rod having the most individual worth is then withdrawn from the core and an inverse count rate plot maintained during with-drawal to insure that criticality is not achieved. If the inverse count rate indicates that the reactor will be critical before the rod is fully withdrawn, additional boron will be added to suppress criticality. All rods are then --,
dropped back into the fully in position and the rod being replaced, now dis- !
enga gsd from the drive, is removed from the core and taken to the unlatching position in the fuel rack. The present bladed absorber section will be unlatched '
fren the follower and placed in a storage can. A new rodded absorber section .'
will then be latched to the follower. This assembly is then inse-ted into the core in the vacant control rod position. Following installation, the new control'~
rod will be moved in and out of the core to .nsure correct operation.
The above outlined procedure will be followed for the replacement of each of the six control rods. The can housing the six old absorber sections will be stered in the pool.
Following installation of the new rods, a ccntrol rod test sequence including rod worth, all rods out boron concentration, rod drop time, and scram tests will be conducted.
In our opinion, the proposed change does not present significant hazards considerations not described or implicit in the Final Safeguards Report.
- 4. Health and Safety It is our conclusion that the health and safety of the public will not be endangered by this change.
SAXTON FINAL SAFEGUARDS REPORT The following new and revised pages for the Saxton Final Safeguards Report are enclosed to bring that publication up to date.
- 1. New page 203.5A to be inserted after page 203.5
- 2. Revised page 203 7 to replace the present page.
- 3. Revised page ? 3.S Le replace the present page.
- h. Revised page 203<12 to replace the cresent page.
- 5. New Figure 203-$c to be inserted after present Figure 203-5b.
Dated: March 2h, 196h 9
4 1C1s ;
. . - _ _ _ _ _ _ _ _ _ _ \
New . go: March 2b, 196h 203 5A The control red absorber assembly may be replaced with an absorber assembly containing an alternate center portion as follows:
The center portion is the silver-indium-cadmium alloy (80% Ag,15% In, 5% cd) absorber section which is in proximity with the fuel Each absorber section will contain whe,1 the control rod is fully scrammed.Each rod is inserted in a Type 30h 22 alloy rods 0 375 inch in diameter. The tubes will stainless steel tube of 0.3785-inch I.D. and 0.hl35-inch 0.D.
be joined together on a pitch of 0.bl65 inch by stainless steel ferrules welded between tubes at elevations approximately 10 inches apart.
l 4
vised: March 24,196h 203 7 4
The following is a descriptior i a typical lift cycle of the mechanisms (1) The moveable gripper coils are energized causing the drive ro,d bundle to expana magnetically against the bore of the moveable gripper pole. The magnetic force exerted by the rods on the pole multiplied by the coefficient of friction between rods and pole represents the gripping capacity of the mechanism.
(2) The lift coil is energized raising the moveable gripper pole, along with the drive rod bundle, upwerd until stopped by contact with the bottom of the stationary gripper pole. The stroke length is approximately 1/,R of an inch.
(3) The stationary gripper coils are energized causing the drive rod bundle to expand magnetically against the bore of the stationary gripper pole.
(h) The moveable gripper coils are de-energized allowing the drive rod bundle to contract in the bore of the moveable gripper pole thus leaving the drive rod bundle held by the stationary gripper pole.
(5) The lift coil is de-energized and the pull down coil is energized to pull the moveable gripper down against the top of the pull down pole ready for the next stroke.
J An auxiliary dash pot is incorporated in the lower end of the mechanism rod 5
travel housing to assist the main shock absorber located in the reactor vessel bottom head adapter.
i
- c. Design Basis t
The pressure containing shell of the mechanism is designed and fabricated in accordance with the recommendations of the ASME Boiler and Pressure Vessel Code,Section I, Power Boiler, Special Rulings 1270N,1273N and 127hN, and bears a Pennsylvania Special Number.
Upon loss of power or in the event of a scram, all coils are de-energized, allowing the drive rod bundle to contract and fall freely by the effect of gravity only. Release of the drive rod bundle will occur within a maximum of 0.150 seconds following interruption of the current to the operating coils.
The design parameters are given in Table 203-1, below.
TABLE 203-1 ROD DRIVE MECHANISM 3 DESIGN PARAMETERS Normal length of travel, in. h0 Maximum length of travel, in, h2 2500 Design pressure, psig Design temperature, OF 650 Normal load attached to drive shaft, lbs.
125 with blade absorber 108 with alternate rodded absorber 250 Maximum load on drive shaft, lbs.
N Res sd: March 2h,196h 20308 r .
Operatingspeed,in./ min.
1)
Approximate increment of movement, in. 1/32 125 1 10%
Operating coil voltage, DC 230 Position indicating coil voltage, 60 cycle, AC E. Reactor Physics Calculations In the nuc'. ear design of the Saxton core, a multigroup diffusion theory technique has been employed to compute the neutron multiplication.
The basic assumption of this technique ,'s the separability of the energy and spatial dependence of the neutron population within a multiplying region.
- 1. Fast Neutron Constants Few group constants are obtained for nonthermal neutrons from the 5h group IBM-70h spectral code MUFT[1. For a given homogeneous mixture of infinite extent, this code computes the spectrum of neutrons from the energy of fissi_n down to the thermal cut-off which is usually selected to be 0.625 ev.
The effects of leakage on the neutron spectrum are approximated by +Ue inclusion of a geometric buckling. From this spectrum, neutron-flux-averaged cross sections are obtained for as nany as three fast groups which can later be used in neutron spatial distribution calculations.
For nonthermal neutrons, the effect of heterogeneity is negligible in a light water moderated lattice except for the occurrence of absorption resonance bearing materials. The principal contributors to resonance absorption are U-238 and U-23S although the structural material of the core does contribute appreciably. The MUPI code does contain all the important resonance parameters and, for homogeneous mixtures, computes the proper absorption rate. .The only account which can be taken by the MUFT code of heterogeneity effect of resonance absorption is through the inclusion of an L factor which is analogous to a disadvantage factor in thermal utilization calculations. This factor is an t
input constant and must be determined by some means external to the MUFT f calculation.
WAPD has modified tre MUF7 code so that an input parameter o could be used, e is the ratio vi resonance absorptions in a given material to the neutron thcrmalizations in a mixture containing that material. The modified form of MUFT thus searches for the value of L which will reproduce l
l this ratio.
I The input value of m for U-238 absorption is obtained from a semi-empirical hand calculation of the resonance escape probability in U-238 which l
1s in good agreement with Monte Carlo calculations.
l For all other resonance absorbing materials in the core, the l
value of the L factor is taken.to be unity.
- 2. Thermal Neutron Constants The thermal neutron spectrum (E <<0.625 ev) is obtained by the IBM-70h code SOFOCATE /2 which contains a solution to the slowing down equations for a hydrogen gas in the presence of absorbing materials. In this manner, the hardening of the spectrum in the presence of heavy absorption is considered.
Neutron-flux-averaged cross sections are 'obtained from this spectrum. Although
4 i rtised: March 26,196h 203.12 Average film drop 5h Maximum surface (at nominal system pressure) 6h2 Outlet of hot channel 570 Inlet to vessel $20 Outlet from vessel $h0 Fuel Rod Outside diameter, in. 0.391 Tube wall thickness, in. 0.015 Pellet diameter, in. 0.357 Pellet length, in. 0.732 Number per cross section 1569*
Fuel length per red, in. 36.6 Rod lattice, in. 0 580 Equivalent diameter of unit cell, ft. 0.0587 Rods per assembly 72 Rows per assembly 9 21 Total number of fuel assemblies Control Rods: 6 Number of slots in 21-assembly core Center-to-center distance, in. 7.6622 Span, in. 5.616 Fuel rods in follower:
Outside diameter, in. 0.h05 Cap, in. 0.00h Clad thickness, in. 0.022 Pellet diameter, in. O.357 Fuel length per rod (pellet stack), in. 36.6 Rods per follower 16 Total rods per six followers 108 Control Characteristics: (Calculated)
Keff, cold and clean 1.250 Ke rr, hot and clean 1.168 Ke rr, full power & equilibrium Xe and Sm 1.12h Average negative temperature coefficient, (F )-1 See Subsection 503 Control rod worth, % (Average 3 Boron Concentrations; (Calculated)
Cold shutdown (k-0.97), no rods, ppm 2700 Hot shutdown (k-0.97), no rods, ppm 2500 Delayed neutron fraction, % 0.63 1.6 x 10-5 Prompt neutron lifegime, sec. h.3 Total core area, ft Equivalent core diameter, ft. 2 35 Maximum core diameter, ft. 2,6h Length to diameter (equivalent) ratio of core 1.3 Water to uranium ratio (unit cell) h.6 Water to uraniun ratio, actual 5.0 Weight of UO 28 Fuel assemblies, lb. 2092 Control rod follower, lb. 136 Initial conversion ratio (Calculated) 0 31 Initial enrichment, wt % 57 Full power lifetime, hr. 7800 Average discharge burnup, L'D/MTU 7300
- Includes el rods in 9 stationary L-shaped subassemblies and omits 23 rods removed for flux wire thimbles.-
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