KTA_2201_4_english

Safety Standards of the Nuclear Safety Standards Commission (KTA) KTA 2201.4 (6/90) Design of Nuclear Power Plants against Seismic Events Part 4: Requirements for Procedures for Verifying the Safety of Mechanical and Electrical Components against Earthquakes (Auslegung von Kernkraftwerken gegen seismische Einwirkungen; Teil 4: Anforderungen an Verfahren zum Nachweis der Erdbebensicherheit für maschinen- und elektrotechnische Anlagenteile) If there is any doubt regarding the information contained in this translation, the German wording shall apply. Editor: KTA-Geschaeftsstelle c/o Bundesamt fuer Strahlenschutz (BfS) Willy-Brandt-Strasse 5 � 38226 Salzgitter � Germany Telephone +49-1888/333-(0) 1621 � Telefax +49-1888/333-1625 KTA SAFETY STANDARD June 1990 Design of Nuclear Power Plants against Seismic Events;Part 4: Requirements for Procedures for Verifying the Safety of Mechanical and Electrical Components against Earthquakes KTA 2201.4 CONTENTS Basic Principles............................................................................................................................................................1 1 Scope...............................................................................................................................................................1 2 Definitions ........................................................................................................................................................1 3 Basic Requirements .........................................................................................................................................2 3.1 Design..............................................................................................................................................................2 3.2 Verification Procedure ......................................................................................................................................2 3.3 Verification Methods.........................................................................................................................................2 3.4 Superposition of Loads.....................................................................................................................................3 3.5 Seismic Excitation at the Site ...........................................................................................................................3 3.6 Determination of Excitation at the Place of Installation .....................................................................................3 3.7 Mechanical System Analysis ............................................................................................................................3 3.8 Loading Analysis ..............................................................................................................................................3 3.9 Combination of several verification steps .........................................................................................................4 3.10 Relative Displacements....................................................................................................................................4 4 Verification by Analysis ....................................................................................................................................4 4.1 General ............................................................................................................................................................4 4.2 Determination of Excitation at the Place of Installation .....................................................................................4 4.3 Mechanical System Analysis ............................................................................................................................5 4.4 Loading Analysis ..............................................................................................................................................8 4.5 Combination of Several Verification Steps .....................................................................................................10 5 Verification by Experiments ............................................................................................................................10 5.1 Verification Objective......................................................................................................................................10 5.2 Requirements Regarding the Test Object.......................................................................................................10 5.3 Requirements for the Excitation of Oscillation ................................................................................................11 5.4 Mechanical System Analysis ..........................................................................................................................12 5.5 Experimental Loading Analysis ......................................................................................................................15 5.6 Combination of Several Verification Steps .....................................................................................................15 5.7 Documentation ...............................................................................................................................................16 6 Alternative Methods of Verification .................................................................................................................16 6.1 General ..........................................................................................................................................................16 6.2 Verifications by Analogy Considerations ........................................................................................................16 6.3 Plausibility Analysis ........................................................................................................................................16 Appendix A Cranes and their Steel Structures.................................................................................................17 Appendix B List of Symbols and Abbreviations Used.......................................................................................18 Appendix C Regulations Referred to in this Safety Standard ...........................................................................19 PLEASE NOTE: Only the original German version of this safety standard represents the joint resolution of the 50-member Nuclear Safety Standards Commission (Kerntechnischer Ausschuss, KTA). The German version was made public in Bundesanzeiger No. 194a on October 14, 2000. Copies may be ordered through the Carl Heymanns Verlag KG, Luxemburger Str. 449, 50939 Koeln (Telefax +49-221-94373-603). All questions regarding this English translation should please be directed to: KTA-Geschaeftsstelle c/o BfS, Willy-Brandt-Strasse 5, 38226 Salzgitter, Germany Comments by the editor: Taking into account the meaning and usage of auxiliary verbs in the German language, in this translation the fol- lowing agreements are effective: shall indicates a mandatory requirement, shall basically is used in the case of mandatory requirements to which specific exceptions (and only those!) are permitted. It is a requirement of the KTA that these exceptions - other than those in the case of shall normally - are specified in the text of the safety standard, shall normally indicates a requirement to which exceptions are allowed. However, the exceptions used, shall be substantiated during the licensing procedure, should indicates a recommendation or an example of good practice, may indicates an acceptable or permissible method within the scope of this safety standard. KTA 2201.4 Page 1 Basic Principles (1) The safety standards of the Nuclear Safety Standards Commission (KTA) have the task of specifying safety related requirements which shall be met with regard to precautions to be taken in accordance with the state of science and technol- ogy against the hazards arising from the construction and operation of the facility (Section 7 para. 2 No. 3 Atomic Energy Act), in order to attain the protective goals specified in the Atomic Energy Act and the Radiological Protection Ordinance (StrlSchV) further detailed in the “Safety Criteria for Nuclear Power Plants” and in the “Guidelines for the Assessment of the Design of Nuclear Power Plants with Pressurized Water Reactors against Incidents pursuant to Section 28 para 3 of the Radiological Protection Ordinance - Incident Guidelines”. (2) In order to attain these protective goals, safety standard KTA 2201.4 - as part of KTA 2201 entitled ‘Design of Nuclear Power Plants against Seismic Events’ - deals with require- ments to be met by methods for the verification of the aseis- mic safety of mechanical and electrical plant components. KTA 2201 is comprised of the following parts: KTA 2201.1: Principles KTA 2201.2: Subsurface Materials (Soil and Rock) KTA 2201.3: Design of Structural Components KTA 2201.5: Seismic Instrumentation KTA 2201.6: Post-Seismic Measures (3) In KTA 2201.4, the required verifications for mechanical and electrical plant components are subdivided into individual verification steps: a) Determination of the excitation at the place of installation b) Mechanical system analysis ba) determination of characteristics bb) modeling bc) determination of loads c) Loading analysis ca) determination of loadings cb) verification of admissibility These verification steps are dealt with in each of the three possible verification methods, i.e. a) verification by analysis b) verification by experiments c) alternative methods of verification (verification by analogy considerations, plausibility analysis). The aseismic safety of a component can be verified on the basis of a single verification method or on the basis of a com- bination of verification methods. (4) The requirements for verification methods are specified for the following plant components in accordance with KTA 2201.1: a) Class I plant components b) those Class II plant components which could jeopardize Class I plant components (5) The safety-related tasks comprise: a) in case of Class I plant components: support stability, integrity and functional capability b) in the case of those Class II plant components which could jeopardize Class I plant components: support stability and integrity. (6) With regard to the mechanical limitation of stress, refer- ence is made to the following KTA safety standards: KTA 3201.2 Components of the Primary Circuit of Light Water Reactors; Part 2: Design, Construction and Analysis KTA 3201.4 Reactor Pressure Vessel Internals KTA 3205.1 Component-Support Structures with Non-Inte- gral Connections; Part 1: Component-Support Structures with Non-Integral Connections for Primary Circuit Components. 1 Scope (1) This safety standard applies to mechanical and electrical plant components of nuclear power plants. With respect to nuclear power plants with light water reactors, this safety standard applies in its entirety. With respect to nuclear power plants with other types of reactors, this safety standard applies in its entirety to those mechanical and electrical plant compo- nents which are not specific to the type of reactor concerned; for plant components specific to the reactor type, it applies only to the verification of the loads. (2) This safety standard deals with requirements for the methods used in verifying the aseismic safety of mechanical and electrical plant. components. The task-specific safety-related purposes of support stability, integrity and func- tional capability (see Section 3.8) shall be specified separately for each component and are not dealt with in this safety stan- dard. (3) In this safety standard, the term mechanical plant com- ponents refers to components such as vessels, heat exchang- ers, pumps, valves, lifting gear and pipes, as well as their supporting structures; crane runways, platforms and scaffold- ings are not included. Individual specifications are required with respect to whether supporting and fastening structures shall be treated in accor- dance with this safety standard or in accordance with KTA 2201.3 (currently in preparation). (4) In this safety standard, the term electrical plant compo- nents refers to the combination of electrical equipment, in- cluding all electrical connections and their supporting struc- tures (such as cabinets, frames, consoles, brackets, suspen- sions or supports). (5) This safety standard does not apply to liners (i.e. those steel linings on concrete for the purpose of achieving a par- ticular leak tightness, where the stresses are primarily deter- mined by the deformations of the concrete). 2 Definitions (1) Response spectrum for mechanical systems A response spectrum for mechanical systems is the graphical display of the maximum amplitudes (depiction of the maximum values of displacement, velocity or acceleration) as a function of the eigenfrequencies of oscillators with a single degree of freedom and constant damping; it constitutes the time history of the response of these oscillators to the base point excita- tion. Note: A distinction is made between free field response spectra (primary spectra), floor response spectra (secondary spectra) and compo- nent spectra (tertiary spectra). In their smoothed form, they are used as design spectra. (2) Required design response spectrum for mechanical systems KTA 2201.4 Page 2 A required design response spectrum for mechanical systems is a response spectrum on which the certification of the aseismic safety of the plant component shall be based. (3) Critical damping for mechanical systems The critical damping for mechanical systems is that value of the (velocity-proportional) damping at which the movement of the oscillator represents the aperiodic limit case. (4) Modal damping for mechanical systems Modal damping for mechanical systems is the damping in the respective characteristic mode. (5) Damping ratio for mechanical systems The damping ratio for mechanical systems is the ratio be- tween the existing and the critical damping in an oscillating system with a single degree of freedom. (6) Characteristic frequencies for mechanical systems The characteristic frequencies of the test sample for mechani- cal systems are its eigenfrequencies as well as frequencies at which particular effects occur. Note: Particular effects are, e.g., noise transients. (7) Functional capability Functional capability is the qualification of a system or part of a system (e.g. component, subsystem, loop), including neces- sary auxiliary, supply, and energy systems, to fulfill specified tasks. Note: In this safety standard functional capability, is understood to be the capability of fulfilling the specified task beyond those of sup- port stability, and integrity, in the case of an earthquake. (8) Upper frequency limit for mechanical systems The upper frequency limit for mechanical systems is the fre- quency above which no significant increase to seismic re- sponse occurs (rigid body behavior). Note: The nipper frequency limit is considered to be that frequency above which the acceleration in the response spectrum falls below 1.1 times the zero period acceleration with increasing frequency, or above which the relative displacements are no longer relevant with regard to failure. (9) Lower frequency limit for mechanical systems The lower frequency limit for mechanical systems is the fre- quency below which no significant seismic response occurs. Note: The lower frequency limit equals one half of the lowest eigenfre- quency of the component. (10) Zero period acceleration for mechanical systems (syno- nym rigid body acceleration) The zero period acceleration for mechanical systems is the maximum value, determined over time, of the excitation accel- eration at the place of installation of the respective compo- nent. (11) Test response spectrum for mechanical systems A test response spectrum is a response spectrum determined on the basis of the actual motion of the vibration platform. 3 Basic Requirements 3.1 Design (1) The mechanical and electrical plant components shall be designed for seismic loading in such a way that a) the shutdown of the reactor and the long term mainte- nance of subcriticality is ensured, b) the residual heat removal from the reactor core and the fuel pool is ensured, c) any inadmissible radiological exposure of the environment is prevented. (2) All Class I plant components in accordance with KTA 2201.1 shall be designed in such a way that their safety-related function (see Section 3.8) is preserved in the event of a design basis earthquake. 3.2 Verification Procedure A verification procedure that is subdivided into steps in accor- dance with Figure 3-1 shall be used. Figure 3-1: Flow chart for the verification of the aseis- mic safety of mechanical and electrical plant components 3.3 Verification Methods (1) The following verification methods are admissible either individually or in combinations: a) verification by analysis (in accordance with Section 4), b) verification by experiments (in accordance with Section 5), c) alternative methods of verification (in accordance with Section 6). (2) The verification methods to be applied shall be specified in a component-specific and task-specific manner. For electri- cal equipment (e.g. connectors, circuit breakers), verification by experiments shall be given preference. KTA 2201.4 Page 3 3.4 Superposition of Loads Basically, the loads caused by a design basis earthquake shall be superposed with the loads of stationary full-power opera- tion of the entire plant and, in addition, with the post-incident loads caused by the earthquake, under consideration of their time history. If, in other stationary conditions of normal opera- tion, loads occur in individual plant components which are higher by more than 10% of the loads of stationary- full-power operation, then these loads shall be used as a basis. This applies to both Class I components and those Class II compo- nents which, in the event of failure, could jeopardize Class I components. 3.5 Seismic Excitation at the Site (1) The seismic excitation at the site may be specified in the form of free-field response spectra or free-field time histories. (2) The excitation shall be specified as acting in a resultant in the horizontal direction and the vertical direction, respec- tively. A superposition of the excitation may also be effected in three orthogonal directions. In this case, the horizontal excita- tion may be split into two orthogonal directions. (3) If free-field time histories are used, these may also be spectrum-compatible artificial time histories. All artificial time history is considered as being spectrum compatible if the spectrum it generates envelopes the specified response spectrum for a sufficient number of frequencies. This shall be verified as follows: a) The number of check points is sufficient if the check fre- quency step width does not exceed 10%, of the respec- tively preceding frequency. The lowest check frequency shall not be higher than 0.4 Hz, and the highest check fre- quency shall at least be equal to the upper frequency limit. b) The spectrum generated may fall below the specified spectrum by no more than 10% at a maximum of 10% of the check frequencies mentioned. This requirement should be verified for the damping values D = 0.01 and D = 0.1. (4) The site-specific duration of excitation shall be used for the period of excitation. 3.6 Determination of Excitation at the Place of Installation (1) The excitation at the place of installation shall be deter- mined on the basis of the seismic excitation a