ML19221B076
| ML19221B076 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-10.2, NUREG-75-87, NUREG-75-87-10.2, SRP-10.02, NUDOCS 7907120359 | |
| Download: ML19221B076 (6) | |
Text
NU R EG-75/087 p Rtog f
s h[$h' STANDARD REVIEW PLAN U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION
+
SECTICN 10.2 TUR3INE GENERATOR REVIEW RESPONSIBILITIES Primary - Power Systems Branch (PSB) l Secondary - Mechanical Engineering Branch (MEB)
Materials Engineering Branch (MTEB)
Radiological Assessment Branch (RAB)
Auxiliary Systems Branch (ASB)
I.
AREAS OF REVIEW Nuclear reactor plants include a turbine generator system (TGS) to convert the energy in steam from the nuclear steam supply system into electrical energy.
The TGS censists essentially of the turbine unit and the automatic oevices, alarms, and trips which control and regulate turbine action, and the generator unit and its controls. The turbine control system and the steam inlet stop and control valves, the low pressure turbine steam intercept and inlet control valves, and the extraction steam control valves control the speed of the turbine under normal and abnormal conditions, and are thus related to the overall safe operation of the plant.
The turbine generator system installed in a nuc1 ear plant is typically equipped with redundant overspeed protection instrumentation and controls and the main steam and reheat steam control and stop valving arrangements typically provide redundancy in the valves essential for overspeed protection. The intent of the review under this SRP section is to verify that such redundancy, in conjunction with inservice inspection and testing of the essential valves, makes a turbine overspeed condition above the design overspeed very unlikely. Assessment of the risk to essential plant systems and struc-tures fcum potential +1rbine missiles is reviewed under SRP Section 3.5.1.3.
1.
The PSB reviews the turbine generator system and the components and subsystems l
normally provided with this equipment with respect to the following considerations:
a.
The general arrangement of the turbine and associated equipment with respect to safety-related structures and systems and balance of plant, b.
The types and locations of main steam stop and control valves, reheat stop and intercept valves, and associated piping ar rangements, k
USNRC STANDARD REVIEW PLAN stand.re review p=no are propered for the evidence of the omce of mucieer seector Reaus. coa steff respor o.wie for the re-w of sepiiceitone to conetruci and operate aveteer power plante These documento are enede evenable to the public es part of the Cornmemon o po6 icy to iriform the nucieer 6ndustry and the generet publ&c of reguletory precedures and po 6c6es Stauderd rev6ew piene are not substitutes for regu6etory guides or the Cornmienson a roguestione and compteence wM feiern le not regw6ced The emenderd review pien occtione are keye1 to Revision 2 of the Stendeed Format and Content of Se ety Anotysee Reporte r
foe newceeer Power Ptente Root.N oectione of the Standard Former heve e correspondmg revsew plan Pubatched etendford review p4ene wsll be rewteed per6pdscalig. es oppropriere to eCCornmodete come ente and to reMett new enformation end caperience Centments Dr.d ewggaettone for improvernent will but conesdered and enould be sont to the U S stocieer Regelstory Commesson. Office of powcieer Reactor Regulet8en. Weefb6ngton. D C 2E46 7907120 N i
c.
The capaoility of the turbine generator control and overspeed protection systems to detect a turbine overspeed condition and to actuate appropriate system valves or other protective devices to preclude an overspeed condition above the design overspeed.
d.
The overspeed protection instrumentation and controls with respect to redundancy, testability and reliability.
2.
The PSB reviews the inservice inspection and operability assurance program for l
valves essential for overspeed protection.
3.
The PSB reviews the applicant's proposed technical specifications for operating l
license applications as they relate to areas covered in this SRP section.
Secondary re'iews are performed by other branches and the results used by the PS3 to complete the overall evaluation of the system. The secondary reviews are as follows:
the ASB determines that appropriate seismic and quality group classifications have been established for system components where appropriate. The ASB and MEB determine that the TGS is in accordance with Branch Technical Positions ASB 3-1 and MEB 3-1 as related to pipe cracks or breaks in high and mod 9 rate energy piping systems outside of contain-meat.
The MEB confirms that the components, piping, and structures are designed in accordance with applicable codes and standards. The MTEB verifies that inservice inspection requirements are met for system components, and will verify the compatibility of the materials of construction wi+5 service conditions. The RAB determines if any radiation shielding is necessary to assure safe access to turbine equipment.
II.
ACCEPTANCE CRITERIA There are no general design criteria or regulatory guides that are directly applicable to the design evaluation of the turbine generator. Acceptability of the design of the turbine generator system, as described in the applicant's Safety Analysis Report (SAR),
is based on the specific criteria listed below and on the similarity of the design to that of plants previously reviewed and found acceptable.
1.
A turbine control and overspeed protection system should be provided to control turbine action under all normal or abnormal operat.ing conditions, and to assurn that a full load turbine trip will not cause the turbine to overspeed beyond acceptable limits. Under these conditions, the control and protection system should permit an orderly reactor shutdown either by use of the turbine bypass system and main steam relief system or other engineered safety systems. The overspeed protection system should meet the single failure criterion and should be testable when the turbine is in operation.
2.
Turbine main steam stcp and control valves and reheat s'au stop and intercept valves should be provided to protect the turbine from exceeding set speeds and to protect the reactor system from abnormal surges. The reheat stop and intercept Rev. I 10.2-2 149 062
valves should be canable of closure concurrent with the main steam stop valves, or of sequential closure within an appropriate time limit, to assure that turbine overspeed is controlled within acceptable limits. The valve arrangements and valve closure times should be such that a failure of any single valve to close will not result in excessive turbine overspeed in the event of a TGS trip signal.
L The extraction steam check valves provided at extraction connections shall be l
capable of closing within an appropriate time limit to maintain stable turbine speeds in t' event of a TGS trip signal.
4.
The TGS should be provided with the capability to permit periodic testing of components important to safety while the unit is operating at rated load.
5.
The inservice inspection program for main steam and reheat valves should include the following provisions:
At approximately 3-1/3 year intervals, during refueling or maintenance shut-a.
do ns coinciding with the inservice inspection schedule required by Section XI of the ASME Code for reactor components, at least one main steam stop valve, one main steam control valve, one reheat stop valve, and one reheat intercept valve should be dismantled and visual a.d surface examinations conducted of valve seats, disks, and stems.
If unacceptable flaws or excessive corrosion are found in a valve, all other valves of that type should be dismantled and inspected. Valve bushings should be inspected and cleanod, and bore diam-eters should be checked for proper clearance.
b.
Main steam stop and control valves and reheat stop and intercept valves should be exercised at least ence a week by closing each valve and observing by the valve position indicator that it moves smoothly to a fully closed position. At least once a month, this examination should be made by direct observation of the valve motion.
6.
Unlimited access to all levels of the turbine area under all operating conditions should be provided. Radiation shielding should be provided as necessary to permit access.
7.
Connection joints between the low pressure turbine exhaust and the m3in condenser should be arranged to prevent adverse effects on any safety related equipment in the turbine room in the event of rtpture (it is prefer 1ble not to locate safety-related equipment in the turbine rcom).
8.
Branch Technical Positions ASB 3-1 and MEB 3-1 should be used to determine the l
acceptability of the effects of postulated TGS piping failures on safety related equipment.
149 063 10.2-3 Rev. I
9.
Repslatory Guide 1.68 should be used with regard to preoperational and startup testing of the power conversion system.
For those areas of review identified in sub;ection I of this SRP section as being the responsibility of other branches, the acceptance criteria and their methods of applica-tion are contained in the SRP sections corresponding to those branches.
III. REVIEW PROCEDURES The procedures below are used during the construction permit (CP) review to determine that the design criteria and bases and preliminary design as set forth in the Prelimi-nary Safety Analysic. Report meet the acceptance criteria given in subsection II.
For review of operating license (OL) applications, the procedures are utilized to verify that the initial design criteria and bases have been appropriately implemented in the final design as set forth in the Final Safety Analysis Report.
The review procedures for OL applications include a dete mination that the content and intent of the technical specifications prepared by the applicant are in agreement with the requirements for system testing, minimum performance, and surveillance developed as a result of the staff's review.
The review procedures given are for a typical turbine generator system. Any variance of the review, to take account of a proposc'i unique design, will be such as to assure that the system meets the criteria of subsection II.
The reviewer evaluates the TGS, subsystems, and components of the unit that are considered essential for the safe integrated operation of the reactor facility. The reviewer will select and emphasize caterial from this SRP section as may be appropriate for a particular case.
Upon request from the primary reviewer, the secondary review branches will provide input for the areas of review stated in subsection I.
The primary reviewer obtains and uses such input as required to assure that this review procedure is complete.
1.
The SAR is reviewed to determine that the system description and piping and instru-mentation diagrams (P& ids) show the turbine generator system. The general arrange-ment of the TGS and associated equipment with respect to safety-related structures, systems, and components is noted.
2.
The reviewer verifies the adequacy of the control and overspeed protection system and determines that:
a.
Support systems, subsystems, control systems, and alarms and trips will function for all abnormal conditions, including a single failure of any component or subsystem, and will preclude an unsafe turbine overspeed. The indepth defense that is provided by the turbine generator protection system to preclude excessive overspeeds should be designed with diverse protection means.
P,e y. I 10.2-4 l k Q' Or n
b.
For normal speed-loaa control, the speed governor action of the electro-hydraulic control system fully cuts off steam at approximately 103 percent of rated turbine speed by closing the control, stop, and intercept valves.
c.
A mechanit.al overspeed trip device is provided that will actuate the control, stop, and intercept valves at approximately 111 percent of rated speed.
d.
An independent and redundant backup electrical overspeed trip circuit is provided that senses the turbine speed by magnetic pickup and closes all valves associated with speed control at approximately 112 percent of rated speed. This backup electrical overspeed trip system may utilize the same sensing techniques as the electro-hydraulic control system. However, the circuitry is reviewed to determine that the control signals from the two systems are isolated from and independent of one another.
3.
The main steam stop and control and the reheat stop and intercept valving arrange-ments and valve closure times are reviewed to ensure that no single valve failure can disable the overspeed control function.
4.
The extraction steam valving arrangements and valve closure times are reviesed to see that stable turbine operation will result after a TGS trip.
5.
The capability for testing of essential components during TGS operation is reviewed.
6.
The proposed inservice inspection program for essential speed control valves is reviewed to verify that it includes the provisions of item 5 of subsection II.
7.
The reiiewer consults with RAB with regard to expected radiation levels around the TGS and the degree of access to TGS components during operation.
8.
If there are safety related systems or portions of systems located close to the TGS, the physical layout of the system is reviewed to assure + hat protection has been provided frem the effects of high and moderate energy TGS piping failures or failure of the connections from the low pressure turbine section of the main condenser. The mears of providing such protection will be given in Section 3.6 of the SAR, and the procedures for reviewing this i. formation are given in the corresponding SRP sections.
IV.
EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided and his review supports conclusions of the following type, to be included in the staff's Safety Evaluation Report:
149 065 10.2-5 Rev. 1
"The turbine generator system includes all components and equipment normally provided including turbine main steam stop and control valves and reheat steam sicp and intercept valves.
The scope of review of the turbine generator system for the plant included layout drawings, piping and instrumentation diagrams, and descriptive information for the system and for control and supporting systems that are essential to its operation (The review has determined the adequacy of the applicant's proposed design criteria ana bases for the turbine generator system and the requirements for safe operation of the system during normal, abnormal, and accident conditions (CP).] [The review has determined that the design of the turbine generator syste.n and supporting systems is in conformance with the d~ sign criteria and design bases (OL).]
"The basis for acceptance in the staff review has been conformance of the appli-cant's designs, design criteria, and design bases for the turbine generator system dnd supporting systems to 10plicable staff technical positions and industry standards "The staf f concludes that the design of t he turbine generator system conf orms to all applicable staff positions and industry standards, and is acceptable."
V.
qcFERENCES 1.
Branch Technical Positions ASB 3-1, " Protection Against Postulated Piping failures in fluid Systems Outside Containment," attached to SRP Section 3.6.1, and MEB 3-1,
" Postulated Break and leakage Locations in fluid System Piping Outside Containment,"
attached to SRP Section 3.6.2.
2.
Regulatory Guide 1.68, " Initial Test Programs f or Water-Cooled Reactor Po.er Plants."
Rev. I 10.2-6
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