ML20030A338
| ML20030A338 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 11/14/1961 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| References | |
| NUDOCS 8101090334 | |
| Download: ML20030A338 (13) | |
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V SECTION 3 CONTAINMENT 3.1 GENERAL 3.1.1 Reactor containment is provided by a spherical steel vessel, 130 feet in diameter. The sphere extends 27 feet below grade and 103 feet above grade. Construction requirements are shown in Drawing C-101. Minimum distance from this vessel to the land boundaries of the site is one-half mile, and to the edge of Lake Michigan
.,.s 200 feet.
3.1.2 The containment vessel's primary purpose is to prevent a harmful spread of radioactive material to the environs in the e tent of a rupture in the reactor system, or other accident.
To accomplish this end the vessel is designed to withstand the internal pressure that would result from the most severe rup-ture accident which can reasonably be considered possible. It is built to contain this pressure with the greatest practical de-gree of leak-tightnes s.
3.1. 3 As a secondary, everyday function, the containment vessel also serves as a weatherproof housing for the steam generating system and auxiliaries. Besides the reactor, this includes the steam drum, recirculation piping and pumps, reactor clean-up system, shutdown cooling system, liquid poison system, eme rgenc y cooling system, and stornge and handling facilities for new and spent fuel. Figure 3.1 is a cutaway perspective showing the general arrangement inside the sphere.
3.1.4 The plant is designed so that operating personnel may enter the sphere and remain inside as necessary during normal operation, shutdown and refueling.
3.2 DESIGN CRITERIA
- 3. 2.1 At an early stage in the design of the plant it was necessary to fix the design pressure of the containment vessel in order to pro-ceed with procurement. A value of 27 psig was conservatively chosen in order to accommodate possible increases in reactor i
system volume during the course of design. The final calcu-lated peak pressure in the containment is 23 psig, based on the 3
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i Section 3 Page 3 assr.mption of a nearly instantaneous, complete severance of a z ecirculating pump discharge line, with the reactor in the hot etandby condition at 1500 psia. At this time the reactor system contains its maximum stored energy. The calculation further assumes the release of all pressurized hot water and steam within the reactor, steam drum, recirculation and cleanup loops, e.nd the steam and feedwater piping to the iso-lation valves. The containment pressure transient is shown in the following Figure 3. 2.
3.2.2 Design parameters for the containment vessel are as follows:
TABLE 3.1 Design Pres sure, Internal 27 psig Design Pres sure, External 0.5 psig*
(Coincident with dead load only) t Design Temperature Rise 190 degrees F**
(Coincident with design internal pressure)
Design Maximum Temperature 235 degrees F Wind load ASA Std A58,1 Without Snow Load (Basic wind pressure =
30 psi)
With Snow Load 60 mph t
Snow Load ASA Std A58.1 (max = 40 psf at top) s Lateral Seismic Forc e 5 per cent of gravity (Coincident with dead load and snow load only)
Maximum Leakage Rate at 27 psig....
- 0. 5 per cent per day
- External pressure does not govern; with shell thickness designed to withstand 27 psig internal pressure, safe external pree sure coincident with dec.d load only is 1. 22 psig.
- This value assumes a rise from an initial shell temperature of 45 de-(
grees F, and is structurally more severe than a rise from 100 to 235 degrees F, which is assumed in determining the design maximum temperatur e.
The maximum temperature rise is used in determining secondary stresses due to the structura? discontinuity where the ves-sel shell emerges from the foundation.
These sit esses, when com-bined with primary stresses, are required to be no greater than 1. 5
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times the allowable primary stresses.
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Section 3 Page 4
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CONTAINMENT VESSEL DESIGN PRESSURE BASIS:
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- 3. PARTIALLY CHOKED BLOWDOWN
- 4. THERMAL EQUILIBRIUM IN VESSEL 5.
VESSEL THERMALLY INSULATED a
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10 0.5 1.0 3.0 5.0 10 30 TIME (SECONDS) i
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CONTAINMENT PRESSURE TRANS'ENT l
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en POWER SYSTEM EQUIPMENT - HEAT EXCHANGERS Data Sheet
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0 Shell Design Tube Design Duty Temp F Temp 0F Service Btu / Hr Flow Lb/Hr Psia F
In & Out Flow Lb/Hr Psia CF In & Out 6
Main Condenser 428 x 10 460,000 30 &
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51,600 Gpm 35 50 50 - 70
@ 1-1/2" Hg 1-1/2" Hg 1-1/2" Hg 6
526 x 10
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LP Feed-Water
- 5. 2 x 10 277,400 65 &
200 172 - 105 739,000 290 200 95 - 166 Heater 1-1/2" Hg IP Feed-Water
- 8. 6 x 10 188,700 90 325 286 - 176 739,000 2,240 400 283 - 363 Heater Reactor Cooling 9 x 10 500,000 90 180 86 - 68 500,000 90 180 50 - 68 Water (2) i l
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Section 3 Page 5 3.2.3 Design and construction of the vessel is In accordance with the ASME Boiler and Pressure Vessel Code, sections II, VIII and IX, as modified by the applicable nuclear Code cases. The vessel has been Code stamped. The shell is constructed of SA-201 Grade B, firebox quality steel produced to SA-300 specifications.
3.2.4 Requirements for the closure of normally open penetrations are set forth in paragraph 3. 5.
- 3. 3 FIRE AND FLOOD PROTECTION
- 3. 3.1 Combustible materials are a t a minimum within the sphere. Hose connections are provided and portable fire ex-tinguishers are installed inside the sphere. The external ap-i purtenances are protected oy the plant fire loop.
3.3.2 No special provisions are necessary for flood protecticn since the site is close to Lake Michigan, which has a very stable water level ranging from elev'. 576 to elev 584. The a rea imme-diately surrounding the ephere is at an elevation of 592'-6" and is adequately drained to the lake.
- 3. 4 PENETRATIONS 3.4.1 The spherical shell is penetrated at 100 points. Ninety-five of these penetrations are welded nozzles varying from 3/4 in.
to 24 in. in diameter, to permit pas sage of piping, instrument tubing, and electrical leads. Ample spares are included in this number. Two other penetrations are manholes at the top and bottom of the sphere, which were used during construction and then welded shut. The remaining three are access locks, which in turn are penetrated by doors, shafts and associated piping and cables. Location, size and use of the various sphere penetrations are shown in Drawing C-102.
3.4't2 Each pipe passing through a penetration is sealed externally in a manner appropriate to its service. As shown in Drawing M-217, a pipe which exerts relatively little thermal stress is either welded directly to the ends of the penetration nozzle (Detail C), or in cases where the pipe is smaller than the noz-zie, it passes through a hole in a cap which in turn is welded to the nozzle (Details B and D). Detail E shows a variation of t
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Section 3 Page 6 this method to avoid contact of dissimilar metals. Where thermal movements prohibit a rigid connection, the pipe passes through a nozzle sufficiev.ly large to allow clearance around the pipe and insulation. This space is closed by a bellows seal as shown in Detail A.
t 3.4.3 All electrical conductors are seale? where they pass through t
the containment boundary. For coaxial cables, access lock power and control cables, and instrumented fuel assembly cables, this is accomplished by hermetically sealed bulkhead-type connectors. All other conductors are passed through compound-filled nipples as shown in Drawing E-31. Each pene-tration assembly is tested by the manufacturer at
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1.25 times the design pressure of the containment vessel.
3.4.4 All three of the access locks are cylindrical in shape, but they vary in sin; The equipment lock is 12'-0" inside di-ameter, the personnel lock is 7'-7", and the escape lock, 5'-6".
Each lock has two gasketed doors in series, and the doors are designed and constructed to withstand the design pressure with no leakage detectable by soap bubbles. The doors of the per-sonnel and equipment locks are electrically controlled, hydrau-lically operated, and the two doors of each lock are mechanic-ally interlocked to insure that at least one is locked closed at all times. These are breech type doors commonly used on steam autoclaves. Each opens away from the lock, ca that the inner door opens into the sphere, and the outer door opens out-ward. The doors of the escape lock are mechanically operated and interlocked, and both doors open toward the center of the sphere. Either door of each lock can be operated from inside the sphere, inside the lock, or outside the sphere.
- 3. 5 ISOLATION VALVES
- 3. 5.1 Since many of the pipes piercing the containment shell must i
carry fluids during plant operation, special precautions are taken to prevent the escape of any significant amounts of radio-active material through these lines in the eved of an accider..
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For the purpose of determining the number, type and position of isolation valves required on each pipe line, these lines are
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divided into four categories:
3.5.1.1 Lines which are or may be open to the interior of the containmert shell have two valves in series, at least o..
of which closes
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Section 3 Page 7 automatically whenever necessary to prevent outward flow in event of ron incident. Except for check valves (see par. 3. 5. 2. 2),
both valves can be closed by manual initiation from either the control room or another place that would be tenable after a severe accident.
- 3. 5.1. 2 Lines which are open to the reactor or any portion of the re-actor recirculating loop are treated in the manner described in the previous paragraph, with the added requirement that the two valves are on opposite sides of the containment shell.
- 3. 5.1. 3 Lines that are normally closed have only a single valve. A lock, interlock, or operating rules protect this valve from be-ing opened during reactor operation, or in otherwise potentially hazardous situations.
- 3. 5.1.4 Certain lines enter and leave the sphere without any openings to the containment interior. Others leave and return to the sphere without any openings to the atmosphere. Such lines do not require isolation valves, provided the lines are not in danger of being broken as a result of a reactor system rupture.
These lines will be routinely checked to insure leak-tightness.
- 3. 5. 3 For pipe lines in the first two categories (par. 3. 5.1. I and
- 3. 5.1. 2) the type of isolation valves on each line, and the con-ditions which initiate their operation are dependent on the ser-vice and in most cases by the direction of normal flow in the line.
- 3. 5. 2.1 Normally open lines which carry fluids out of the sphere are closed automatically upon a signal indicating high sphere pres-sure or low water level in the reactor ves sel. Either of these two signals means that a rupture may have occurred in the re-l actor system. These automatic isolation valves also close upon air or power failure, and upon manual trip in the control room.
- 3. 5. 3. 2 Normally open lines which carry fluids into the sphere are each equipped with a check valve to prevent backflow upon loss of inward prope11ent force. In addition, operating per-sonnel can secure these lines by manually operated gate valves or by air operated control valves. The latter close upon air or power failure, with exception of the supply lin~ to the con-e trol rod drive hydraulic system. Control valves in this line
Secti:n 3 Page 8
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Rev i (3/12/62) fail open to insure continuous water supply, and back-up isola-A-
tion is provided by integral. spring-seated valves in the control rod drive pumps.
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3.5.2.3 The two 24-inch ven+!!ation openings, one for supply and one for exhaust, would present the greatest avenue of escape for
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contaminants in the event of an accident. For this reason, these openings are closed within six seconds after any scram signal.
This will assure that the initial release of radioactive material to the atmosphere prior to completion of closure would be a negligible quantity co'mpared to the total permissible leakage in the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following an accident. The valves for these openings are described in paragraph 6.8.4.4.
In order to prevent the possibility cf excessive external pressure on the sphere due to atmospheric changes or other causes, at an external pressure of 3/4 psig an alarm sounds and the safety system contacts are bypassed, thus permitting the operator to manually open the inlet ventilation valves. At an external pressure of 1 psig, the valves will open auto-matically. At an external pressure still slightly positive, the valves will again close. To assure continued operation of the inlet ventilation valves in the event of air failure, an accumulator with a capacity for approximately 50 operations is located in close proximity to the valves.
3.5.3 The provisions described in this section deal only with the con-tainment of potentially radioactive material in the event of an accident. For a description of measures taken to limit release of fission products from the off-gas system to the ventilation stack during normal operatiori, see Sections 7 and 9.
3.6 MISSILES 3.6.1 No special design measures are considered necessary to pro-tect the enclosure against missiles. Safety of the enclosure against damage by missile effects that could conceivably ac-company a severe boiling water reactor accident has been con-sidered. The conclusions of these considerations are:
3.6.1.1 There is no indication in this boiling water reactor design of an energy source with sufficient magnitude to create a signifi-cant danger from missile effects. Specific items considered 1
in this respect were the metal-water reactions and nuclear excur sions.
3.6.1.2 In the unlikely event of a reactor system rupture, the rupture would be of the ductile type not cond ive to the development of penetrating missiles.
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Section 3 Page 9 l
3.6.1.3 Failure of enough head-closure bolts to permit the whole re-actor head to fly off, dislodge the reactor top shielding plug,
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and possibly break the enclosure is not considered credible.
l 3.6.1.4 Even if missiles were in some manner generated, the concrete shielding and other structures surrounding the reactor and I
other components of the primary loop would protect the enclo-(
sure shell'and penetrations from any substantial missiles for 4
any' plausible missile path. The concrete structures them-selves are designed to prevent portions therefrom'becoming 3
i mis sile s.
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3.6.2 In designing the shielding around the nuclear steam supply system, it was necessary to restrict openings to such an ex-4 tent that the pressure immediately following a rupture accident could cause the shield walls around the recirculating loop to 2
collaps e.
To prevent this, a blowout panel has been provided to relieve such a sudden pressure buildup. The blowout panel consists of high density sand and. gravel confined in place by light gauge metal siding. If the panel were blown free, it would separate into six sub-panels, each about 90 square feet in area and 4-1/2 feet thick. The gravel would no longer be confined at the edges, and each unit would immediately begin to fall apart. The trajectory would bring the panels down onto the floor directly over the reactor. From there some of the i
gravel might roll or bounce far enough to reach the shell of l
the sphere, but the maximum size missile would be 1-1/2 inch and would not have sufficient ene,,rgy to be damaging. The blow-j out panel is held in place sufficiently that it would not be dis-j lodged by blowing of the steam drum safety valves.
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l 3.7 POST-INCIDENT COOLING
- 3. 7.1 To mitigate the effects of an accident resulting in loss of cool-ant, a core spray system brings water from the plant fire pro-tection system to a sparger ring within the reactor, and sprays water directly on the core. This system is described more fully in paragraph 5. 9.
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3.7.2
.A branch line from this system leads to a set of post-incident spray nozzles in the upper part of the sphere as shown in i
Drawing M-123. This line is normally dry, but its supply valve is automatically opened on high sphere pressure after a 4
15 minute time delay. This delay is provided to allow the oper-j-
ator to override a possible spurious actuation.
In addition, the time delay feature may be manually overridden to actuate the sprays prior to the expiration of the 15 minute period.
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If the core spray system could be relied upon to be fully effect-ive under all accident conditions, the post-incident sprays would probably not be needed. However, it is possible that a rupture
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in the reactor coolant loop could damage or destroy the core spray supply line. In Sat event, the sphere sprays would serve to prevent a further rise in sphere pressure due to decay heat
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after the initial peak has passed, and would bring this pressure down to less than 5 psig within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, thus materially limit -
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ing the quantity of leakage from the containment. The sprays would also tend to wash out airborne fission products which might be released from a damaged core. This washing would
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reduce the intensity of direct radiation, and minimize the leakage of fission products from the containment vessel.
3.7.4 As a back-up in the event of failure of the automatic system, an independent line leads from the fire protection system to a second
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set of post-incident sprays. These sprays can be turned on by opening a manual gate valve located in the machine shop at a point which is shielded from the containment sphere and is accessible
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after an incident.
3.7.5
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Each set of sprays has a total capacity of 400 gpm, which is supplied automatically by the motor-driven fire pump, with i
back-up by the diesel-driven fire pump.
k' 3.7.6 If the sprays should operate for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the
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water in the containment vessel would rise to a level near grade.
j Further addition cf water from the fire, protection system must be stopped, as a water level higher than three feet above grade
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would over-stress the vessel shell. In order to effectively con -
trol containment vessel pressure in the event of a severe rupture accident, the post incident system using the back-up sprays may
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be manually operated intermittently after the sphere pressure is reduced to slightly above atmospheric pressure, thus conserving C' -
the vessel capacity for prolonged accumulation of spray water.
If the core spray system is operative, it is desirable to continue this in order to keep the core below the melting point. This is
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accomplished by recirculating the water from the bottom of the sphere through the core spray pumps and cooler as described in pa rag raph 5. 9
- 3. 8 INSULATION The exposed exterior surface of the sphere is insulated with
,l a cork mastic coating sprayed to a dry thickness of 3/8", and r
protected by two coats of acrylic resin base emulsion. The insulation is provided for the following reasons: a) To prevent
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excessive temperature inside the containment vessel due to I
solar radiation; b) To reduce heat loss in winter; c) To provide
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atmospheric corrosion protection; and d) To reduce inside sur-face condensation. Although temperature control is primarily for operational purposes, it will also tend to maintain ductility L
of the metal shell.
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3; 9 CONSTRUCTION AND TESTING 3,9.1 After excavation for the below-ground portion of the sphere, steel columns were erected for support of the vessel during construction. The shell was then welded together and all seams were radiographically examined.
3,9.2 Nozzle penetrations were closed by temporary steel caps, and l
the sphere was pressurized to 5 psig. All welds and door gas-kets were soap-bubble tested for leaks, then the sphere was pneumatically tested at 1-1/4 times design pressure.
3.9.3 An integrated leakage rate test was made at just under 27 psig, using the reference vessel method. This test demonstrated a r
leakage of less than 0. 05% per 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. day. Test air was then released from the spYere.
3.9.4 A large opening approximately 24 x 22 feet was cut in the shell 4
for construction access. Concrete was placed between the sphere and the ground, and congurrently the inside concrete structure was brought up to grade level. A portion of the weight of the sphere was removed from the steel columns by adjusting jacks at their base. It is intended to remove the entire weight from the columns upon closing of the construc-tion opening, and column bracing will be removed.
3.9.5 The interior structure was erected above grade and major I
pieces of equipment are now being installed. Piping and elec-trical leads are being run through the nozzles and the permanent seals are being made. Near the end of construction the shell plate will be re-welded into the construction access opening.
All new welds will be radiographed.
I 3.9.6 Prior to initial loading of fuel, a final test will be made of the containment ves sel. Welds and seals added or disturbed since the previous test will be soaped at 5 psig. A second integrated leakage rate test of the vessel will then be made at a pressure not exceeding 10 psig.
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3.9.7 Means are provided for introducing compressed air into each i
i of the three access locks and the space between each pair of ventilation isolation valves, so that these appurtenance's may
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readily be tested for leak-tightness at design pressure at suit-able intervals during the life of the plant. ~ The first set of i
i these tests will be run prior to initial fuel loading.
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