ML19347B527
| ML19347B527 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 10/10/1980 |
| From: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04.A, TASK-02-04.B, TASK-02-04.C, TASK-03-06, TASK-2-4.A, TASK-2-4.B, TASK-2-4.C, TASK-3-6, TASK-RR NUDOCS 8010150291 | |
| Download: ML19347B527 (7) | |
Text
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cag A Consumers o
I j) PoWar Nbwp Company
@ @!F)W7 General Offices: 212 West Michigan Avenue, Jackson, Michigan 49201
- Area Code 517788-05S0 October 10, 1980 Director, Nuclear Reactor Regulation Att Mr Dennis M Crutchfield, Chief Operating Reactors Branch No 5 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - RESPONSE TO STAFF LE' ITER DATED AUGUST 4, 1980 -
PROPOSED SEISMIC EVALUATION PROGRAM AND BASIS FOR CONTINUED INTERIM OPERATION Your letter dated August 4, 1980 referenced NRC letter of January 15,1979 and requested that we submit our plans for proceeding with a seismic evaluation program for the Big Rock Point Plant. The plan was requested to address the scope of the review, evaluation criteria to be used and provide a schedule for completion.
The Big Rock Point Seismic Evaluation Program has been a subject of ongoing discussions with the Staff since January 1979. Your letter of January 15, 1979 requested information which Consumers Power provided ir letters of February 23, 1979 and April 25, 1979. A meeting, as suggested by your January 15, 1979 letter, was held with NRC Staff on July 26, 1979. Our April 25, 1979 letter and the minutes of the July meeting (dated August 7, 1979 and signed by Jack Wetmore) outlined in considerable detail our plans to provide structural evaluations. Contrary to assertions made in your August 4, 1980 letter, this program has been diligently pursued starting in June 1979 with the full knowledge of NRC Staff and at a cost of nearly one million dollars. At this time, the entire scope outlined in the April 25, 1979 letter is nearly complete. We expect final reports to be submitted to us by our contractor by December 31, 1980.
In the July 26, 1979 meeting, the Staff strongly urged us to provide an early analysis of the primary coolant loop.
We, therefore, had our contractor revise his plans and couple a model of the primary loop directly to the reactor building structural model. This technique, although innovative at the time, has been espoused and used in a slightly different version by others. This greatly increased the size and complexity of the model of the reactor building internal structure and re-sulted in an extension of the contractor's schedule of about six months. We 801015 OA7/
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Dennis M Crutchfield 2
Big Rock Point Plant October 10, 1980 expect to have at least'a preliminary analysis of the primary coolant loop (large diameter main piping) in-the structural report'.
In the April 25, 1979 letter and in the July 26, 1979 meeting, we agreed to construct the structural models and exercise them using an example spectra.
'The example spectra is a Reg' Guide 1.60 spectra anchored at 0.12 g.
At that time', it was anticipated that NRC Staff would provide in October 1979 a site seismic response spectra that was acceptable to them for the SEP analysis.
Our intention was to hold the more computational intensive work, eg, floor response spectra, until the final site spectra became available. The final spectra suffered a series of delays and is now promised by December 31, 1980.
In light of the delays, we went ahead with the analysis, including floor response spectra and structural strength analysis, using the example spectra.
The series of delays in obtaining this input spectra did contribute to schedule delays.
Your letter of August 4, 1980 included as Attachment 1 a preliminary version of a ground response spectra which the Staff considers appropriate. We ob-serve that our example spectra envelops this spectra. Since your spectra is still preliminary, we, in general, intend to continue to use the example spectra until yours is finalized. Additionally, the spectra are sufficiently close that for preliminary purposes and, perhaps for final' answers, the differences can be linearly scaled. That is to assume that stress, displace-ment, etc, differences are directly proportional to the differen'ces in acceleration at the resonant frequency of the structure. Although this may not be particularly pleasing on theoretical grounds, in practice it has proven to be conservative in almost every case.
As stated in your letter, we are developing our own site specific spectra.
Our spectra'is also in preliminary stages of completion. The preliminary versions'of our spectra are in agreement with your preliminary spectra within the generally acknowledged uncertainties except at the very low frequency end of the spectra where yours appears to be very conservative. The difference is thought to be due to your use of'very conservative attenuation models. This difference is well known to NRC Staff and is essentially acknowledged in the basis document for your spectra. Our spectra-is intended for uses in addition to SEP such as demonstrating the overall logic of seismic design in Michigan.
We'are greatly encouraged in these efforts by the apparent good agreement between NRC funded work and our own.
In any event, all decisions to provide plant modifications to meet SEP requirements will be based on the spectra provided by NRC.
The January 1,-1980 NRC letter from D G Eisenhut to D P Hoffman required Consumers Power Company to take certain actions to verify anchorage and support of safety-related electrical equipment.
As required by your letter, Consumers Power Company responded on February 13, 1980 with an action plan and on March 31,'1980 with the results of our investigation. These-letters promised action on a best efforts basis and plans were formulated to install
- any needed remedies during the refueling outage that is scheduled to start this month. This effort was further discussed in a meeting between SEP Owners and.NRC Staff on May 14, 1980 and in the Owaers Group letter to the NRC of J
Dennis M Crutchfield 3
Big Rock Point Plant October 10, 1980 July 3, 1980. On July 28, 1980, we received a letter providing additional
' guidance to the expected scope.of our investigations.
In our view, this letter ignored the Owners' pcsition in the May 14 meeting and July 3 letter and expanded the scope well beyond the bounds of the January'1, 1980 letter, thereby leading to significant problems in meeting-the NRC desired schedule of December 31, 1980. The Owners Group letter of August 28, 1980 responded taking exception' to Items 1, 3c and 5 of Attachment 1 to the NRC's July 28
' letter. The Owners' position was that Items 1 and 3c have traditionally been accomplished by test rather than by structural analysis and were, therefore, more logically handled along with seismic qualification of the electrical equipment (functional qualification similar to IEEE 344).
Item 5 is being handled by an Owners Group program to test cable trays and extend the results by simplified engineering analysis to the cable trays in each plant. The above efforts require the use of floor response spectra resulting from the structural analysis and can proceed only after they become available. Our present plan to meet the requirements is to assure by December 31, 1980 that the major floor and wall mounted electrical equipment is anchored so that it will remain in place when subjected to preliminary floor response spectra from the ongoing structural program, that it will not be significantly damaged by nonsafety-related equipment in the vicinity and that the anchor bolting to the equipment is at appropriate structural locations on the equipment and will not pull out of the equipment steel.
In addition to those activities noted above which are scheduled to be complete by December 31, 1980, the following will be required to complete the Big Rock Point Seismic Program:
1.
Seismic analysis of safety-related piping other than the major reactor coolant system piping. This analysis uses as input the floor response spectra and/or time histories from the building analysis. Assuming major structural modifications will not be required, this can begin soon after January 1, 1981. By this time, the site specific ground response spectrum will be finalized and there will be some confidence that the input will be acceptable. Unless extensive piping revisions are required, this effort can be completed by January 1, 1982.
2.
Seismic qualification of mechanical equipment. This includes pumps, valves, heat exchan.ers and drivers (motors, engines).
Since the valves are excited by the piping, they will have to be qualified as a part of the piping program. For the remaining equipment, normal operating loads are typically higher than seismic loads. An engineering analysis of the anchorage of this equipment should be sufficient.
If questionable appen-dages are noted on the basic, equipment packages, additional analysis or qualification by similarity will be employed. The effort scoped above can be completed by January 1, 1982.
3.
Seismic qualification of electrical equipment. As stated in the August 28, 1980 letter from R E Schaffstall to D M Crutchfield, the SEP Owners Group'is. conducting an electrical equipment qualification program which will address methodology, acceptance criteria and that equipment which is reasonably common to more than one plant.
It is envisioned that w
Dennis M Crutchfield-4 Big Rock Point Plant.
October 10, 1980 certain plant unique equipment will have to be handled outside this program. The Owners Group methodology and acceptance criteria will be employed if applicable. Present intentions are to make maximum use of existing test data and equipment similarity.
If an appreciable amount of testing is required to verify any of the methodology, acceptance criteria, or special pieces of equipment, it will not be possible to complete this task by January 1, 1982. We are willing to discuss possible ways of shortening this program with the Staff.
It is intended that this program will address Items 1 and 3c of Attachment 1 of the NRC's July 28, 1980 letter as well as the issue of completeness of all required IE equipment also. raised in the July 28 letter.
4.
Seismic qualification of cable tray and conduit raceways. As stated in the August 28, 1980 letter, the Owners Group is conducting a cable tray test program. This program was presented to NRC Staff in some detail during a meeting with the Owners Group.on October 3, 1980.
It is expected to last approximately 18 months. At the conclusion of this program, some plant specific work may be required to demonstrate the applicability of the tests or to handle plant specific configurations.which may be beyond the scope.of the test program and its derived methodology. The Owners Group intends to be receptive to NRC Staff input in conducting the program.
Interim results may give some confidence that the raceways can withstand seismic forces and provide additional justification for allowing the program to continue beyond January 1, 1982 particularly since it is envisioned that remedial designs will be tested if they appear to be required.
In this sense, perhaps the January 1, 1983 deadline date may be the more applicable one.
It is understood that the equipment to be qualified in Items 1 through 4 above is that which is required for safe shutdown.
Evaluation criteria being used in the seismic program include in addition to those in the Reg Guides and Standard Review Plan:
1.
Newmark and Hall " Development of Criteria for Seismic Review of Selected Nuclear Power Plants," NUREG/CR-0098.
2.
Methodology and criteria used by the Senior Seismic Review Team put forth in NUREG/CR-0981, " Seismic Review of Dresden Unit 2 for the Systematic Evaluation Program."
3.
Stress limits are taken from the applicable industry code under which the structure,. equipment or piping was originally designed or any subsequent edit' ion of the Code; eg, ACI-318, ANSI B31.1, etc.
The version used depends on the design of the component and the calculation procedure used in the present seismic analysis.
If not included in the code used, the material properties (yield stress, ultimate strength, allowable stress) from the ASME B&PV Code,Section III, are used.
4.
Structural responses both modal and directional are combined by SRSS or the NUREG/CR-0098 equivalent; eg, 1, 0.4, 0.4 coefficients.
i l
Dennis M Crutchfield.
5 Big Rock Point Plant October 10, 1980 5.
Load combinations used were:
U2D+L+E'+T+P a
where:
U = Allowable load capacity of the system being analyzed; D = Dead load of the structure; L = Live loads that may be expected to be present during the operation of the plant.
In the absence of any data, such live loads may be assumed to be equal to 25 percent of the design floor live loads and 25 percent of design roof snow loads. For purposes of dynamic analyses, the mass contrib-uted by such live loads may be neglected if it is found in-significant with respect to the dead load of the structures; E = Loads generated by the Safe Shutdown Earthquake (SSE);
T = Thermal effects and loads during normal operation based on the most critical condition, but excluding loss of coolant accident or high energy pipe rupture; and P,= Earth pressures generated against embedded concrete structures including increases due to earthquake loading conditions.
Note that LOCA loads are not applied simultaneously with earthquake loads.
LOCA/HELB loads are handled by entirely different methods and use different criteria. These loads are handled under the SEP HELB topics.
6.
Damping values consistent with NUREG/CR-0098 and NUREG/CR-0981 are used.
Values up to 15% are considered under certain circumstances.
7.
Acceptance criteria for equipment and' cable tray qualification generally relate to maintaining function. Equipment distortion is allowed. Analyt-ically, " ductility" factors will be considered if required. It is antici-pated that additional guidance from NRC Staff may be required during these programs to ensure results are acceptable.
As a result of the SEP Program, the seismicity of the Big Rock Point vicinity has been recently reviewed by experts employed by the NRC, the SEP Owners Group and'by Consumers Power Company (see NUREG/CR-1582 and " Eastern United States Tectonic Structures and Provinces Significant to the Selection of a Safe Shutdown Earthquake," Weston Geophysical, /9 gust 1979). Based on approx-imately 200 years of reasonably reliable eart' c.ake history and the known geological and tectonic structure of the area, the experts seem to agree that a design basis earthquake with a return period of one to ten thousand years would be 0.05 to 0.07 g.
Earthquakes of this size do not cause major damage to even poor quality construction.
Dennis M Crutchfield 6
' Big Rock Point Plant-October 10, 1980.
If, in addition to the above, a minimum design earthquake is assigned for the entire-eastern United States without regard to structure or lacation, the design earthquake increases as in Attachment 1 to the August 4 letter to approximately 0.10 g.
Typical industrial construction is not usually damaged by this level of earthquake. Steel and reinforced concrete construction as used at Big Rock might, at worst, suffer minor cracking.
Finally, preliminary calculated results from the Big Rock structural evalua-tion indicate that major structural elements of all safety-related structures will remain below code allowable stress when subjected to an earthquake of the-type shown in Attachment 1 to your letter.
In summary, earthquakes are not very probable at Big Rock Point. Even for long return periods, the earthquake is not predicted to be large enough to cause major damage to quality industrial construction. Preliminary calcula-tions for Big Rock structures show no significant damage occurs to the struc-tures from earthquakes of the size proposed in your letter.
Independent work being done for the Big Rock Probabilistic Risk Assessment indicates very long return periods for earthquakes of this size. We conclude that continued operation of the Plant while the seismic analysis is completed is entirely acceptable for the above enunciated reasons.
David P Hoffman (Signed)
David P.Hoffman Nuclear Licensing Administrator CC Director, Region III, USNRC NRC Resident Inspector-Big Rock Point
CONSUMERS POWER COMPANY Big Rock Point Plant Proposed Seismic Evaluation Program and Basis for Continued Interim Operation Docket No 50-155 License No DPR-6 At the request of the Commission and pursuant to the Atomic Energy Act' of
-1954, and the Energy Reorganization Act of 1974, as amended and the Commission's Rules and Re321ations thereunder, Consumers Power Company submits our Proposed Seismic Evaluation Program and Basis for Continued Interim Operation in response to the Commission's lecter dated August 4, 1980.
Consumers Power Company's response is dated October 10, 1980.
CONSUMERS POWER COMPANY By R C Youngdahl (Signed)
R C Youngdahl, Executive Vice President Sworn and subscribed to_ before me this 10th day of October 1980.
Linda Carstens (Signed)
Linda Carstens, Notary Public (SEAL)
Jackson County, Michigan My commission expires June 10, 1981.
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