ML20094C224
| ML20094C224 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1975 |
| 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-10.02-01, SRP-10.02-1, NUDOCS 9511020105 | |
| Download: ML20094C224 (7) | |
Text
NUREG 75/087 eQ QEcoq y" )
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U.S. NUCLEAR REGULATORY COMMISSION t'
i STANDARD REVIEW PLAN i
%.*...f OFFICE OF NUCLEAR REACTOR REGULATION SECTION 10.2 TURBINE GENERATOR REVIEW RESPONS!BILITIES Primary - Auxiliary and Power Conversion Systems Branch (APCSB)
Secondary - Reactor Systems Branch (RSB)
MechanicalEngineeringBranch(MEB) l Materials Engineering Branch (MTEB)
Radiological Assessment Branch (RAB)
Electrical. Instrumentation and Ccatrol Systems Branch (EICSB) 1.
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 consists essen-tially of the turbine unit and the automatic devices, alarms, and trips which control and regulate turbine action, and the generator unit and its controls. The turbine control sys-tem and the steam in10t stop and control valves the low pressure turbine steam intercept and in16: control valves, and the extraction steam control valves control the f Deed of the j
turbine under nonnal and abnormal conditions, and are thus related to the overdi safe operation of the plant.
The turbine generator systems installed in nuclear plants are typically equipped with i
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 plan is to verify that such redundancy, in conjunction with inservice inspection and testing of the essential valves, makes 3 turbine overspeed condition above the design overspeed very unlikely.
Assessment of the ri n to essential plant systems and structures from potential turbine missiles is reviewed under SRP 3.5.1.3.
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1.
The APCSB reviews the turbine generator system and the components and subsystems nor-mally provided with this equipment with respect to the following considerations:
The general arrangement of the turbine and associated equipment with respect to a.
safety-related structures and systems and balance of plant.
USNRC STANDARD REVIEW PLAN
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b.
The types and locations of main steam stop and control valves, t ehtat stop and I
I intercept valves, and associated piping arrangements, The capability of the turbine generator control and overspeed protection systems c.
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.
2.
The inservice inspection and operability assurance program for valves essential for overspeed protection is reviewed.
3.
The applicant's proposed technical specifications are reviewed for operating license applications as they relate to areas coverd (a this review plan.
Secondary reviews are performed by other branches and the results used by the APCSB to complete the overall evaluation of the system. The secondary reviews are as follows: the R$8 detennines that appropriate seismic and quality group classifications have been estab-11shed for system components where appropriate. 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 with service conditions. The RAB determines if any radiation shielding is necessary to assure safe access to turbine equip-The EICSB reviews the overspeed protection instrumentation and controls with respect ment.
to capabilities, reliability, and redundancy.
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
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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 operating conditions, and to assure that a full load turbine trip will not cause the turbine to overspeed beyond acceptable limits.
L'nder 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.
2.
Turbine main steam stop and control valves and reheat steam stop and intercept valves should be provided to protect the turbine from exceeding set speeds and to protect the reactor system from abnonnal surges. The reheat stop and intercept valves should be capable of closure concurrent with the main steam stop valves, or of sequential closure within an approp.iate time limit, to assure that turbine overspeed is controlled.
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within acceptable limits. The valve arrangements and valve closure time 3 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.
3.
Extraction steam stop valves should be provided at each extraction connection. The valves shall be capable of closing within an appropriate time limit to maintain stable turbine speeds in the 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:
l At approximately 3-1/3-year intervals Curing refueling or maintenance shutdowns a.
coincicling with the inservice inspection schedule required by Section XI of the ASME CoJe for reactor components, at least one main steam stop valve, one main I
steam control valve, one reheat stop valve, and one reheat intercept valve should be dismantled and visual and surface examinations conducted of valve seats, disks, and stems. If unacceptable flaws or excessive corn. tion are found in a valve, all other valves of that type should be dismantled and in pected. Valve bushings should be inspected and cleaned, and bore diameters should be checked for proper clearance.
b.
Main steam stop and control valves and reheat stop and intercept valves should be exercised at least once 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 main condenser.
should be arranged to prevent adverse effects on any safety-rela ted equipment in the turbine room in the event of rupture (it is preferable not to locate safety-related equipmentintheturbineroom).
8.
Branch Technical Position APCSB 3-1 should be used to determinie the acceptability of the effects of postulated TGS piping failures on safety-relatead equipment.
II'I. REVIEW PROCEDURES The procedures below are used during the construction permit (CP) review to detennine that the design criteria and bases and preliminary design as set foriti in the preliminary safety analysis report meet the acceptance criteria given in Section II of tMs plan. For review 10.2-3 11/24/75 a
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of operating license (OL) applications, the procedures are utilised to verify that the initial design criteria and bases have been appropriately implemented in the final cesign as set forth in the final safety analysis report.
The review procedures for OL applications include a deter ination 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, s
The review procedures given are for a typical turbine generator system. Any variance of the review, to take account of a proposed ur.ique design, will bo suca as to assure that the system meets the criteria of Section 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 material from this review plan, as may be appropriate for a particular case.
1.
The SAR is reviewed to detennine that the system description and piping and instrumenta-tion diagrams (PID's) show the turbine generator system. The general arrangement of the TGS and associated equipment with respect to safety-related structures, systems, and components is noted.
2.
The reviewer consults with the EICSB to verify the adequacy of the control and over-speed protection system and to detennine that:
a.
Support systems, subsystems, control systems, and alarms and trips will function for.all abnormal conditions, including a single failure of a'ny component or sub-I system, and will preclude an unsafe turbine c<erspeed. The indepth defense that is provided by the turbine generator protection system to preclude excessive overspeeds should be designed with diverse protection means.
b.
For normal speed-load 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.
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c.
A mechanical 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 syitem may utilize the same sensing techniques as the electro-hydraulic cor' ol system. However, the circuitry is reviewed to determine that the control signals from the two systems are isolated from and independent of one, another.
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3.
The main steam stop and control and tha rsheat stop and intercept valving arrangements and valve closure times are reviewed to insure that no single valve failure can disable the overspeed control function.
4.
The extraction steam valving arrangements and valve closure times are reviewed to see that stable turbine operation will result after a TGS trip.
5.
The capability for testing of essentail 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 Section II.
7.
The reviewer 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 that protection has been pro-vided from the ef#ects of high and moderate energy TGS piping failures or failum of the connections from the low pressure turbine section of the main condenser. The means of providing such protection will be given in Section 3.6 of the SAR, and the procedures for reviewing this information are given in the corresponding review plans.
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:
"The tu.bine generator system includes all components and equipment normally provided including turbine main steam stop and control valves and reheat steam stop and inter-cept valves. The scope of review of the turbine generator system for the plant included layout drawings, piping and instrumentation diagrams, and descriptive infonnation for the system and for control and supporting systems that are essential to its operation. [The review has detennined the adequacy of the applicant's pro-posed design criteria and bases for the turbine generator system and the requirements for safe operation of the system during normal, abnormal, and accident conditions.
(CP)] [Thereviewhasdeterminedthatthedesignoftheturbinegeneratorsystemand supporting systems is in conformance with the design criteria and design bases. (OL)]
"The basis for acceptance in the staff review has been ;onformance of the applicant's designs, design criteria, and design bases for the turbine generator system and supporting systems to applicable staff technical positions and industry standards.
"The staff concludes that the design of the turbine generator system conforms to all applicable staff positions and industry standards, and is acceptable."
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V.
RE"EflENCES 1.
Branch Technical Position APCSB 3-1 " Protection Against Postulated Piping Failures in Fis:'u Systems Outside Containment " attached to Standard Review Plan 3.6.1.
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