ML20070K682
| ML20070K682 | |
| Person / Time | |
|---|---|
| Site: | Clinch River |
| Issue date: | 12/28/1982 |
| From: | Longenecker J ENERGY, DEPT. OF, CLINCH RIVER BREEDER REACTOR PLANT |
| To: | Check P Office of Nuclear Reactor Regulation |
| References | |
| HQ:S:82:168, NUDOCS 8212300253 | |
| Download: ML20070K682 (6) | |
Text
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Department of Energy Washington, D.C. 20545 Docket No. 50-537 HQ:S:82:168
,DEC 2 8 22 Mr. Paul S. Check, Director CRBR Program Office Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Check:
ADDITIONAL INFORMATION ON. SEISMIC QUALIFICATION The purpose of this letter is to provide additional information to resolve questions asked by the Nuclear Regulatory Commission (NRC) of the Clinch River Breeder Plant project on seismic qualification in Preliminary Safety Analysis Report Section 3.10. is the information requested. Enclosure 1 also contains a revision to NRC Question 270.10 that was requested at the November 23, 1982, meeting on equipnent qualification.
Any questions regarding the information provided or further activities can be addressed to A. Meller (FTS 626-6355) or D. Florek (FTS 626-6188) of the Project Office Oak Ridge staff.
Sincerely, JE.W gr John R. Longenecker Acting Director, Office of Breeder Demonstration Projects Office of Nuclear Energy 3 Enclosures cc: Service List Standard Distribution Licensing Distribution Q&h 821230025'1$0 7
__________-___i
Enclosure (1)
Open Item Margins for non-linear material behavior DESCRIPTION:
The applicant did not address what method or criteria will be used, including reduction of allowable stresses beyond those that are established for pressure boundary integrity, to account for the ef fects of material non-linearity at high temperatures and creep to ensure equipment operability.
Normal operating loads superimposed with seismic and dynamic loads are likely to produce such non-linear - responses in equipment in the presence of high temperatures.
In the case of seismic analysis the applicant did not account for the non-linear ef fects or indicate how the non uniqueness of seismic time history would be considered.
Response
The non-linear material response and analysis methodology are described in RDT F9-4'and RDT F9-5.
In addition, PSAR Section 3.7 Appendix 3.7-A describes the requirements, load combinations and analysis methods for seismic analysis.
It is inappropriate to review these in this response.
However, for illustrative purposes a more detailed answer is provided for permanent reactor internals.
Permanent reactor internals are designed to the appropriate ASME criteria (ASME
- III, including CC N-47) with additional restrictions to assure component operability.
The operability requirements are particularly critical for components related to reactor shutdown, such as the control rods and interfacing equipment.
In general, these restrictions include an upgrade of the seismic events to more stringent requirements such as evalua ting the OBE as ASME Normal (Service Condition A) and the SSE as ASME Emergency (Service Condition C), as well as detailed studies to evaluate the acceptable control rod insertion time.
Normally OBE would be evalua ted to upset (Service Condition B) and SSE to Faulted (Service Condition D) limits.
This upgrade in the seismic loading condition criteria is a significant effect on the critical equipment integrity and operability under these plant loading conditions.
An estimate of this ef fect can be based on the basic seismic input for the plant as the OBE may be as low as 55% of the SSE.
There is also a significant difference in the allowable stresses for the service levels.
In general, seismic and thermal stresses are not critical at the same locations due to the different nature of the loading conditions.
Seismic events are most significant for thin
- sections where primary stresses and stability are critical.
Thermal stresses are generally most significant at thick sections where the thermal inertia of the component produces large thermal stresses.
A typical situation where the thermal and seismic stresses are both important would be the intersection of thin and thick sections.
The seismic stresses in this section may be significant by themselves while the thermal stresses may also be significant due to the difference in thermal response of the two sections at the discontinuity.
In these situa tions, the following general procedures apply.
(1)
One OBE event is combined with the worst upset event at the most critical time in the upset event.
Four OBE events are combined with the worst normal operating condition.
(2)
The SSE event is combined with most adverse normal operating condition.
(3)
In these situa tions, there is generally one stress component (or effective stress / strain is used) that is highly predominate relative to the other components.
The thermal and seismic events are conse rvatively combined to maximize thesa critical stress components.
(4)
The requirements of RDT F9-5 regarding bilinear stress strain curves and 10th cycle kinematic hardening are imposed in the analysis.
The effects of this load uination may be stated for th ree separate cases.
In all cases, the total increased creep and fatique damage due to this loading combina tion is generally relatively small due to the limited number of events considered.
Case 1:
Structure does not yield The loading combination produces larger primary plub secondary and fr tique stress ranges than either event acting alone, but does not result in a residual stress.
Thus the fatique damage is increased, but the creep damage is not ef fected by the load combination.
1 Case 2:
Structure yields only during loading The loading combination produces larger primary plus secondary and f a tique stress ranges than either event i
3-acting alone, and results in a residual stress that may produce creep damage in the structure.
The residual stress and resultant creep damage increment is dependent on the maximum strain produced by the loading combina tion.
Case 3:
Structures yield during loading and unloading This loading combination produces a larger primary plus secondary and fatique stress and strain range than either event alone and results in a residual stress that contributes to creep damage at elevated steady state temperatures.
This residual stress is somewhat dependent upon the total strain in the event combination because of the bilinearized stress strain curve (and resultant variations in yield stress and plastic modulus) approach specified by RDT F9-5.
The non-uniqueness of the seismic time history is considered by developing a synthetic motion whose response spectrum envelops the design response spectrum.
The design response spectrum is a conservative definition of the floor motion since it is obtained by 1) enveloping spectra for the upper and lower bounds of soil modull, 2) widening the peaks to take care of uncertainties, and
- 3) smoothing to eliminate valleys and spectral fluctuations.
i 1
_4 Open_ Item seismic Testing Ma gins IEEE Standard 344-1975 requires that the Test Response Spectrum have a margin over the required Response Spectrum.
The applicant did not address what method will be used to establish the total margin consisting of an input envelope over a number of similar equipment, differences between the initial input and final design input, and the test input versus the required input.
Response
For testing of Class 1E equipment, any margin required by IEEE S t-d. 344 is initially added to the Required Response Spectrum (RRS).
This includes a 10% margin required by IEEE Std. 323.
l The RRS is derived at the mounting of the equipment for the worst l
location of the equipment on the supporting structure, that is, l
the location which gives the highest response spectrum.
l Therefore, testing to this highest RRS conservatively qualifies equipment mounted at other, less severe loca tions.
The test motion is synthesized such that the test response spectrum (TRS) conservatively envelops the RRS.
The margin, based on proof testing, is that given by the initial margin in the RRS and the amount by which the TRS exceeds the RRS.
Additional margin exists to fragility which is not determined.
The qualification testing is perf ormed for the seismic responses obtained f rom the latest seismic analyses.
If the final design input should be different from that for which the test was performed, a comparison is made between the TRS and the final design RRS to ensure that the TRS also envelops the new RRS.
A combination of test and analysis may also be used if the final design of the equipment is modified.
Open_ Item Load _ Frequency Combinations The applicant did not address the procedure that will be use d to combine the equipment loading from earthquake, generally in the O to 33 Hz range, and from anticipated dynamic loadings with a f requency range to 60 to 100 Hz.
Response
Mechanical equipment which may be subjected to the simultaneous occurrence of seismic and other dynamic loads is analyzed for the combination of both loadings.
The more conservative absolute or linear summation methodology is in general used for this combina tion.
The squa re root of the sum of the squares me thodology is used where appropriate for deriving the total seismic loads given by the three components of the earthquake.
_5 CBBRP_RESEQHSE_DOCUMENTATIQN Question _CS110.dQ.
The equipment qualification program at CRBR involves several parties:
the Department of
- Energy, Project Management Corporation, and various vendors.
When the plant is fully licensed and operational, it will be turned over to the plant i
operator.
It is essential for the ope rator of the plant to l
maintain all relevent documentation on equipment qualification in an auditable manner at a central location.
Regarding equipment
)
qualification, the de tails of the interactions of the I
organizations and locations of the central file should be I
provided by amending appropriate sections of the PSAR.
I Ecaponse:
CRBRP will maintain all relevant documentation on equipment qualification in an auditable manner at a central location.
The documentation requirements for Class lE equipment qualification are described in Reference B as specified in PSAR Section 3.11.2,
" Qualification Tests and Analysis".
The documentation for mechanical equipment will be contained with the Equipment Specification data package.
The overall system for collection, storage, and maintenance of this documentation is described in PSAR Chapter 17, Appendix A, paragraph 17.1, " Quality Assurance Records: Owner Implementation," and paragraph 17.2,
" Quality Assurance Records:
Requirements of Other Participants".
Briefly stated, this quality records management system specifies that all data packages which are to be declared as lifetime quality records by each responsible participant are to be transmitted to the Project Office for collection, storage, and maintenance by teh owner at the Owners Level III Quality Records Center, Oak Ridge, Tennessee.
Pursuant to the CPBRP Project implementation of the records storage requirements of ANSI N45.2.9, a duplicate file of these records is to be maintained for security purposes at the regional federal records center established for the CRBRP Project.
.