ML20009F774
| ML20009F774 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 07/24/1981 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8107310616 | |
| Download: ML20009F774 (13) | |
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IE N SUJJECT:
TRANSNITTAL OF PR.'.I!!INARY SER DRAFT SECTIO?l 5.
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HIDLMD PLANT, tlMITS 1 AND 2 l
b Enclosed for your review and cataent are the following preliminary draft sections of the NRC Staf f's Safety Evaluation Report:
5.4.1 Reactor Coolant Paaps 5.4.2 Steam Generator 5.4.3 Reactor Coolant Piping 5.4.7 Decay Heat Re' oval Systen S.4.10 Pressurizer Your attention is directed in particular to any open iteas contained within these draf t sections. A principal objective of this trans71ttal is to provide l
for tioely identification and resolution of any additional analysis, missing infor1stion, clarifications or other work necessary to resolve outstanding issues.
Please contact the Staff's Project Manager regarding the need for any neetings and telephone conferences to this end.
6 1
l Your coments, including schedules 'for completion of any further analyses or other work associated with resolution of open itcas, are requested within I
I tin weeks of this letter.
l Sincererly, Original signed by l
Robert L. Tedasoo t
Robert L. Tedesco, Assistant Director l
of Licensing Division of Licensing j
cc: See next page
Enclosure:
As stated i
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0FFiCIAL RECORD COPY usem m-.ameo NRC FORM 318 (1HO) NRCM 0240
i MIDLAND i
Mr. J. W. Cook i
Vice President Consumers Power Corpany 1945 West Parnall Road Jackson, Michigan 49201 cc:
Michael I. Miller, Esq.
Mr. Don van Farrowe, chief Ronald G. Zamarin, Esq.
Division of Radiological Health Alan S. Farnell, Esq.
Departrent of Public Health Isham, Lincoln & Beale P.O. Box 33035 Su:',e 4200 Lansing, Michigen 48909 1 eirst National Plaza
- Chicago, Illinois 60603 William J. Scanlon, Esq.
2034 Pauline Boulevard
' Jaces E. Brunner, Esq.
Ann Arbor, Michigan 48103 Consumers Power Company 212 West Michigan Avenue U.S. Nuclear Regulatory Commission Jackson, Michigan 49201 Resident Insoectors Office
]
Route 7 Ayron M. Cherry, Esq.
Midland, Michigan 48640 1 IBM Plaza Chicago, Illinois 60511 Ms. Barbara Stamiris 5795 N. River Ms. Mary Sinclair Freeland, Michigan 48623 5711 Summerset Drive Midland, Michigan 43640 Stewart H. Freeman Assistant Attorney General State of !;icnigan Environmental Prctection Division 720 Law Building Lansing, Michigan 48913 i
Mr. Wendell Marshall Route 10 1
Midland, Michigan 48640 Mr. Steve Gadler 2
2120 Carter Av'enue St. Paul, Minnesota.55108
a MIDLAND OPEN ITEMS SECTION 5.4.7 1.
Manual action outside the control room a.
Manual action outside the control room in the absence of a postulated single
-itsB failure of a safety grade system is not consistent with BTP 5-1.
The.present 3
design requires that the operator leave the control room to open DHR suction valves, restore power to the DHR heat exchanger bypass valves, align the Emergency Boration System, and actuate the Auxiliary Pressurizer Spray.
Provide modifications so that these actions can be perforned within the control room, or propose alternate qualified paths by which these functions can be performed from the control room.
b.
Confirm that core floodtank isolation during the cooldown process can be acconplished from the control room.
I 2.
Provide analyses of boron mixing in the reactor system during the approach to cold shutdown under natural circulatior..
Include calculations of boron concen-tration and shutdown margin as a function of time during cooldown. Address the 1
possibility of bor'on injection into an inactive reactor coolant loop.
3.
Provide a time-dependent calculation of reactor's system p'ressure and temperature for natural circulation cooldown. The calculations should include both two steam generator and single steam generator cooldown.
4.
Provide the details of a natural circulation test program which will demonstrate
. that the Midland Plants can be brought to cold shutdown without offsite power.
Discuss provisions for demonstrating steam voids will not form in the primary system during cooldown.
/
5.
Provide the details of a test progran designed to demonstrate that boron injected into the primary system during natural circulation cooldown will be, adequately mixed within the primary system.
MIDLAND RSB SAFETY EVALUATION (5.4.1,5.4.2,5.4.3,5.4.7,5.4.10) 5.4.1 Reactor Coolant Pumos The reactor coolant pumps are sized to provide adequate core cooling flow to maintain the departure from nucleate boiling ratio above 1.30 under normal and transient operating conditions.
Pump rotational inertia is provided ty a flywheeel for acceptable flow coastdown characteristics following a loss of power to the pump motor.
Our review of such events is reported in Chapter 15 of this SER.
i The reactor coolant pumps will be single stage, single suction, constant speed, vertical centrifugal pumps.
Each of these pumps employs a sealing system consisting of mechanical seal assemblies arranged in a removable l
cartridge contained in a seal leakage chamber to prevent reactor coolant fluid leakage.
The component cooling water system provides cooling to the coolant pump f
motor and to the seal coolers. The seals are also cooled by seal injection water provided by the dual purpose liakeup, High Pressure In-jection System.
These systems are discussed in Chapter 9 of inis SER.
l l
5.4.2 Steam Generators The two steam generators are vertical, straight tube and shell heat exchangers producing superheated steam which is controlled to maintain 4
a constant throttle pressure over the power range.
. Reactor coolant enters the upper hemispherical head through a single inlet nozzle, flows downward through the tubes, and disenarges through two outlet nozzles in the lower immispherical head.
The steam generators provide a heat sink for the reactor coolant system during normal, transient, and accident conditions.
Our review of this capability is evaluated in Section 5.2.2, 5.4.7, and 15 of this report.
5.4.3 Reactor Coolant Piping The reactor coolant piping is arranged in two transport loops, each which con-tains two reactor coolant pumps and one steam generator.
Included as part of the reactor coolant piping is the surge line, which transports reactor coolant be. tween the pressurizer and the reactor outlet piping, and the spray line, w'hich connects the reactor inlet piping and the pressurizer and which provides pressurizer spray for pressure control.
5.4.7 Decay Heat Renoval System The decay heat removal function is accomplished in two phases: the initial cooldown phase utilizing the steam generators, and the decay heat removal (DHR) system operation phase.
The decay heat removal system is dedgned to remove decay heat and sensible heat from the reactor coolant system and core during the latter stages of cooldown.
The system also provides auxiliary spray to the pressurizer for complete depressurizatign, maintains the reactor coolant temperature during refueling, a'nd provides the meant g
for filling and draining the refue' ling cavity.,In the event of a f
.9 loss-of-coolant accident, the decay heat remova'l pumps are used i,
for low pressure injection of borated water into the reactor vessel for emergency core cooling.
?
. The decay heat removal system is normally placed into operation accroxi-mately six hours after initiation of olant shutdown when the temoerature and pressure of the reactor coolant system are below 280 degrees Fahrenheit and 300 pounds per square inch gauge, respectively.
Assuming that two pumps and coolers are in service, and that each
' cooler is supplied with component cooling water at design flow and temperature, the decay heat removal system is designed to reduce the reactor coolant system temperature to 140 degrees Fahrenheit within 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />.
If one of the two pumps or one of the two coolers is not operable, safe cooldown of the plant is not compromised; however, the time required for cooldoe. is ex*. ended. Assuming only one train is available, the plant can be cooled from 280 degrees to below 212 degrees Fahrenheit within two and one-half hours.
The decay heat removal system for each Midland unit has a single suction connection fron one hot leg in the reactor coolant system which splits inside containnent to provide two parallel sets of redundant isolation valves, and which may be operated from the control room.
The DHR suction again solits outside of containment to two redundant trains consisting of a decay heat renoval pump, heat exchanger, and associated throttling valves.
When the decay heat removal system is aligned to cool the plant, the decay heat removal pumps take suction from the reactor coolant system hot leg, discharge through the cecay heat renoval exchangers, and then back into the reactor coolant 'ystem through their respective core flood nozzles.
We s
l have reviewed the DHR system and have determined that the single failure' l
l criterion of Appendix A of 10 CRF 50 is met.
Inadvertent opening of the decay heat removal system while the reactor coolant system is at a high pressure is precluded through the use of interlocks which prevert opening of the suction line isolation valves when the reactor coolant system is above the decay heat removal design pressure and will ensure that all
. isolatic s valves are closed when the reactor coolant system is at high
~
pressure.
The review of these interlocks is described in Chapter 7 of this SER.
Each discharge line will be isolated from the reactor coolant system by two check valves located inside containment and by a motor-operated valve located outside the containment. Thus, two independent and redundant barriers exist whenever the reactor coolant system pressure is above decay heat removal system design pressure.
(See Section 3.9.6 of this SER for a discussion of intersyster leak detection).
The decay heat removal system is provided with a safety valve sized to handle the worst case credible pressure excursion which could occur while in the decay heat removal system operating mode and which will also be used to protect the reactor vessel while operating at low temperatures. The NRC staff evaluation of this aspect of RRR and primary system overpressure protection is contained in Section 5.2.2 of this SER.
The decay heat removal system is designed to protect the decay heat removal pumps from damage due to loss of suction or any other system malfunction resulting in loss of flow.
A flow element located in each pump discharge will stop the decay heat removal pumps if flow decreases to 900 gallons per minute.
This feature is overridden by the emergency core cooling systen actuation signal such that is will not interfere with enr gency core cooling system performance.
The pumps are protected by a miniflow bypass line while in the ECCS mode of operation.
The comaliance of the DHR with applicable codes and standaru and the -
adequacy of the DHR with respect to the ability of the system to withstand the effects of natural phenomena, fire, adverse environmental conditions and missiles to demonstrate compliance with General Design Criteria (GDC)
)
~
- e 1, 2, 3, and 4 is c'.iscussed in Chapters 3 and 5 of this SER.
Components-of the DHR are not shared between the units and therefore the design complies with GDC 5.
The compliance of the DHR with the requirements 'of GDC 19 involving operability from the control room is addressed in Chapter 7 of this SER and in the dhscussion below involving the ability of the Midland Units to reach cold shutdoun.
The NRC is conducting generic studies of the required reliability and capability of shutdown heat removal systems under TMI Action Plan Item
'2 II.E.3.2 of NUREG-0660.
Another NRC study described in action Plan Item II.E.3.3 of NUREG-0660 involves the desirability and possible requirements for deverse heat removal systems. Midland is subject to the results of our generic review of these items.
The applicant has addressed the requirements of Tl11 action Item III.D.1.1 of NL' REG-0737 for leakage reduction of primary coolant from systems outside containment.
Compliance with the NUREG-0737 requirements is discussed in the i
Appendix to this SER.
The NRC staff required that the original Midland design be modified so that the plant could be brought to cold shutdown from the control room utilizing only safety grade equipment.
These requirements are contained in Branch Technical Position RSb 5-1 attached to Section 5.4.7 of the Standard Review Plan.
The applicprd. has committed to modify the plant design as follows:
a) Reactivity Control Following a reactor trip, the safety rods are designed to bring the reac-tor to a subcritical condition with at least a 1% delta K/K shutdown l
margin.
To naintain this shutdown margin during cooldown, boron must be l
l
added to the reactor system to overcome the reactivity additions from xenon decay and decreased reactor temperature.- Boron is normally added by the chemical addition,wem (CAS) via'a Makeup, pump. Alternately, boron may be added from the E,cated Water Storage Tank.
Both these sources of borated e ~
are sufficiently dilute so that the letdown system must be operated to permit the required amount of boric acid to be injected.
Since the letdown system is not safety grade, the appli-i cant has committed to install a safety grade Emergency Boration System (EBS) utilizing a boron concentration sufficient to maintain a 1% delta k/k shutdown margin without letdown.
The EBS design is discussed in Chapter 9 of this SER.
b) Heat Removal In order.for the RHR system to be brought into operation, the reactor system temperature and pressure must be reduced to below a maximum of 325 F and 300 psig, respectively. Temperature reduction is accomplished-l by cooling the reactor system throuah the steam generators which are lowered in temperature and pressure on the secondary side by operator control of steam relief.
Steam generator pressure reduction may be accomplished by means of redundant safety grade Power Operated Atmospheric Vent (POAV) valves in each steam line. The Midland plants are provided with a safety grade Auxiliary Feedwater System as discussed in section l
10.4 of this SER.
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c) Primary System Pressure Reduction Primary system pressure is maintained by the steam bubble in the pressurizer.
This steam must be condensed or vented if the primary system is to be brought to the DHR cut in pressure. Since the normal l
, pressurizer spray is only operable if the primary coolant pumps are in operation, the applicant has conmitted to install an auxiliary pressurizer spray which can be connected to the safety grade HPI pumps.
The pressurizer relief valve which is connected to an emergency power source may also be utilized to vent the steam bubble.
We reviewed the Midland emergency shutdown design for compliance with the
. % 5 !-
requirements of BTP; 5-1 for "' ass 2 plants *, We conclude that Midland meets these requirements with the following exceptions.
a) Manual action outside the control room in the absence of a postulated single failure is not consistent ~with BTP 5-1.
The present design of the DHR system requires that the operator leave the control room at 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> into the cooldown to open DHR suction valves and restore pcwer to the DHR heat exchanger bypass valves locatti in the auxiliary building before the system can be brought into service.
i Also, local manual action is required for alignnent of the Emergency Boration System and Auxiliary Pressurizer Spray to an HPI pump. We l
require that modifications to the above systems be made so that these actions can,be performed from the control room, or that the applicant propose alternate qualified means by which these functions can be performed in the control room in the absence of a postulated single #ailure of a l
safety grade system.
l l
- Class 2 are plants for which CP or PDA application. are c::keted before i
January 1,1978 and for which an-OL issuance is expected on or after January 1,1979.
r
. Consumers Power has stated that they are currently reviewing the manual actions performed by the operator outside the control room during the approach to cold shutdown and plans to complete this review in September, 1981.
b) Consumers Power has not submitted analyses of boron mixing in the reactor system during the approach to cold shutdown under natural circulation.
We require that such analyses be submitted and that calculations of boron concentration and shutdown margin b'e submitted as a function of time durino cooldown.
c) We require that time dependent calculations of reactor systen pressure and temperature for natural circulation cooldown be submitted for our review..The calculations should include both two steam generator and single steam generator cooldown.
d) Consumers Power has agreed to perform a natural circulation test which demonstrates the ability to cooldowa the reactor system.
The scope and detailed criteria of the natural circulation test program have not yet been subnitted for our review. We require that the test program cover a sufficient reactor temperature range to demonstrate that the reactor can be brought to cold shutdown without local void formation within the reactor vessel or hot leg piping.
e) ConsumersPowerhasnotcommittedtoperformtests5fboronmixingduring natural circulation. We require that such a test be performed which meets the requirements of Regulatory Guide 1.68.
We will report on the resolution of these open items in a supplement to this SER.
With the exception of the noted deficiencies in the design of the DHR
. v. 5?
in meetina the cold shutdown requirements of Branch Technical Position,.5-1, we conclude that the DHR system complies with the requirements of GDC 5,19
&,'. n vils C and 34 and is the.rafer.e acceptable.
A 5.4.10 Pressurizer The pressurizer maintains the reactor coolant system pressure during steady-state operation and limits pressure changes during transients and accidents electric heater bundles in the lower se.ction and a water spray nozzle in the upper head maintain the steam and water at the saturation temperature corres-ponding to the desired reactor coolant system pressure.
Two of the heater bundles will be connected to emergency power supplies and will be available to the operator in the event of a loss of offsite power.
Pressurizer spray is provided by a line from one reactor coolant cold leg at the pump discharge and will be available so long as the reactor coolant pumps are in operation.
Auxiliary pressurizer spray can be made available by the operator opening valves in a path from the HPI pumps.
Below the Decay Heat Removal System cut in pressure, auxiliary pressurizer spray will be made available utilizing the Decay Heat Removal, LPI pumps.
Two safety valves are connected to the pressurizer for reactor coolant system overpressure protection.
A safety grade power-operated relief valve is also provided. The safety and relief valves discharge to the pressurizer quench tank inside containment. The sizing of the safety valves is discussed in Section 5.2.2.
Control of reactor system pressure during approach to cold shutdown utilizing only safety grade systems is discussed in section 5.4.7.