ML20052D973
| ML20052D973 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/30/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04.D, TASK-02-04.F, TASK-2-4.D, TASK-2-4.F, TASK-RR NUDOCS 8205070354 | |
| Download: ML20052D973 (21) | |
Text
_
Consumem Power Company l
Generet oRces. 1945 West Parnell Road, Jack son, MI 49201
- 1517) 788 0550 April 30, 1982 Q
RECelVED 7
MAY8 1982> 32 9-n - nmu m Dennis M '.rutchfield, Chief 8MQEE 84 7
Operating Reactors Branch No 5 C>
Nuclear Reactor Regulation US Nuclear Regulatory Commission 4
g Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SYSTEMATIC EVALUATION PROGRAM - REQUEST FOR ADDITIONAL INFORMATION FOR TOPICS 11-4.D AND II-4.F By letter dated February 5, 1982, the NRC requested additional information concerning SEP Topics II-4.D and II-4.F for the Big Rock Point Plant.
Consumers Power Company (CP Co) had previously submitted SARs for these topics in letters dated October 5, 1981 and October 19, 1981, respectively. Attached are the CP Co responses to those requests.
Two items should specifically be noted in addition to the attached informa-tion.
First, we feel that the SARs and the drawings submitted previously are adequate to show that no significant slopes exist in the vicinity of the site.
Detailed topographical maps of the areas south and east of the plant, however, are not available in CP Co files.
Should the current reviewer of this topic need more detailed information, a site visit would be recommended.
Second, the plant is founded on a shallow layer of medium dense to very dense glacial till over bedrock (limestone).
This till is very stiff, particularly below the building foundations. The site conditions are such that no substantial settlement of structures would be expected. Since survey records which show total settlement are not available, however, it is necessary to rely on visual observation to assess settlement.
It has now been over twenty years since the plant was constructed.
In recent inspections conducted by both the NRC and CP Co, no signs of any significant settlement were observed. When this long time span is considered, we believe that these inspections are adequate in themselves to assess settlement of all plant structures and underground equipment, and that essentially no potential remains for additional settlement over the remaining life of the plant.
oc0482-0029al42 0
$b I
9205070354 020430 PDR ADOCK 05000 m
r--
8
- D M drutchfield, Chief 2
Big Rock Point Plant SEP. Topics II-4.D & II-4.F April 30, 1982 We trust that the attached information is sufficient to address remaining NRC-concerns on these topics.
ur k
(-
i Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point Attachments 4
?
i oc0482-0029a142
!~
REQUEST FOR ADDITIONAL IhTORMATION SEP TOPICS II-4.D AND II-4.F Big Rock Point Plant f
I i
I nu0482-0029d142 i
N.
SYSTEMATIC EVALUATION PROGRAM BIG ROCK POINT PLANT REQUEST FOR ADDITIONAL INFORMATION TOPICS:
II-4.D, Stability of Slopes II-4.F, Settlement of Foundations and Buried Equipment Topic II-4.D (TAC No 41272) 1.
Provide both longitudinal and cross-sectional details of the discharge channel.
Answer: Reference the following information:
Site Plan Clearing Rough Grading and Excavation - Drawing C-5* (Enclosed)
Plot Plan Finish Grading and Paving - Drawing C-7* (Enclosed)
D'Appolonia Report Seismic Safety Margin Evaluation; Screehouse/ Diesel Generator Room / Discharge Structure - Figures H-2 and H-4 (Submitted to NRC by CP Co letter dated August 26, 1981)
Letter, R A Vincent to D M Crutchfield Dated 12/21/81; CP Co Evaluation, SEP Topic III-3.C, Inservice Inspection of Water Control Structures, Big Rock Point (Enclosed) a.
This letter provides a description of the discharge canal and other related structures and equipment.
b.
This letter will be referenced as the Enclosure in our later discussion (s).
2.
Evaluate the stability of the discharge channel slopes for both static and dynamic (SSE) loading conditions.
Answer: D'Appolonia found in their review for the Seismic Safety Margin Evaluation of Big Rock Point that "no problems of slope stability will effect either the intake structure or the offshore intake line because there are no slopes of any consequences that exist near these facilities" (see Chapter 1.2.0 of D'Appolonia Report listed in Reference (4) of the Enclosure).
(Please note also the close proximity of the small discharge canal banks (slopes) with respect to the offshore intake line at the screenhouse/ diesel generator room / discharge structure).
Consequently, a postulated seismic event that could possibly disrupt the small discharge canal banks (slopes), causing blocking of the discharge canal, would not
- Actual dimensions of the discharge canal will vary from time to time because of dredging and riprap work that is conducted periodically; see our discussion in the Enclosure, nu0482-0029c142 J
r.
Big. Rock Point Plant.
2 SEP Topics'II-4.D & II-4.F affect the intake water supply supplied via the intake structure and off-shore intake line to the screenhouse/ diesel generator room / discharge structure.
The intake water supply is the essential water source to ensure the plant can be safely shut down and maintained in a safe shutdown _ condition. The discharge canal is not considered essential for safe plant shutdown or maintaining the plant in a safe condition.
Consequently, there is no need
- o evaluate the small discharge canal banks (slopes) for SSE loading
-conditions. Again, we would like to emphasize that, in our evaluation, there are no significant natural or man-made slopes on the site.
t 3.
Evaluate the potential for liquefaction of the overburden soils under SSE condition, particularly with respect to possible blockage of discharge channel.
Answer: Please review our discussion of soils and liquefaction under Question 3, Topic II-4.F.
Postulated blockage of the discharge canal would not create any significant problem as discussed above.
Topic II-4.F (TAC No 41261) i 1.
Your assessment report mentions minor cracks in the foundation, but does not address either the magnitude of these cracks or their significance on the safety of the buildings. Your assessment should include an evaluation of the above and their relationship to settlement effects.
Answer: The minor foundation cracks observed during the November 1978 NRC-CP Co onsite inspection of Big Rock Point were apparently of no concern to the NRC-CP Co inspectors (see Reference (12) under CP Co evaluation of SEP Topic II-4.F).
The minor foundation cracks observed during late 1981 (see Section 5(d) under CP Co evaluation of SEP Topic l
III-3.C (Enclosure) were typical of minor (small) cracks one would expect j
to observe in any foundation where concrete is used. Minor foundation cracks are not unusual; consequently, these cracks would have no effect on the safety of our building (s).
As noted in Reference (12) under CP Co evaluation of SEP Topic II-4.F and Section 5(d) under CP Co evaluation of Enclosure above, there were no apparent foundation / ground settlements observed.
4 2.
Your assessment report does not evaluate settlement of the safety-related buried equipment. Provide a description and' construction details for the l-buried equipments and evaluate their settlement for both static and dynamic (SSE) loading conditions.
Answer: During our evaluation of SEP topics, we have found it difficult to define specific boundaries between plant structures, systems and l-components, and to provide design information that does not overlap with other SEP topics under the current program. This overlap, as expected,'is
{
nu0482-0029c142
. Big Rock Point Plant 3
SEP Topics II-4.D & II-4.F due to the broad coverage required of the SEP Topics and,to some extent, due to the uniqueness of the Big Rock Point Plant design.
However, we feel the safety objective, as defined for SEP Topic II-4.F in the Topic List / Definitions (reference NRC letter, D G Eisenhut to D A Bixel dated March 7, 1978), was met which states, "to ensure that safety-related structures, systems and components are adequately protected against excessive settlement." Our evaluation of this topic showed that the NRC staff and CP Co representatives toured the plant site and visually inspected foundations / ground settlements in areas around the containment building, turbine building, stack, screenhouse building and in areas where buried equipment was located. Nothing that was of significance was observed.
In our evaluation of SEP Topic III-3.C (Enclosure), we discussed CP Co inspections of the screenhouse using a diver and discussed that a later inspection was conducted (by topic writer) of the screenhouse and surrounding areas.
In the former inspect ion, no significant problems were observed and, in the latter inspection, no foundation / ground settlements were observed which included areas where buried equipment is located. From the above, we can conclude that foundation / ground settlements are not a problem of concern for structures or buried equipment.
Seismic qualification of buried equipment was not specifically defined in j
the safety objective of SEP Topic II-4.F; however, our evaluation of SEP l
Topic III-3.C (Enclosure) discusses D'Appolonia's Seismic Safety Margin l
Evaluation for Big Rock Point and discusses seismic qualification and describes buried equipment associated with the water control structure; for example, the buried offshore intake piping and the buried fire main piping.
Also, the D'Appolonia Reports discussed on Page 6 (and 7) and listed as references on the last page of the SEP Topic III-3.C (Enclosure) show a portion of the seismic qualification work covered by D'Appolonia.
Specifically, seismic qualification is analyzed and the buried I
structures / equipment are described in the Reports (see D'Appolonia Reports (4), (5), (6) and (7) referenced on the last page of the (Enclosure).
In the above Reports, the buried structure / equipment meet or exceed the seismic criteria specified.
As noted above, the D'Appolonia Seismic Safety Margin Evaluation was submitted to the NRC by CP Co letter dated August 26, 1982. Because of the large volume of this report a separate copy is not included herein, but it is available within the SEP Branch.
3.
Assess the liquefaction potential of the overburden soils at the site or provide justification for not performing the analyses.
Answer: The lakeshore near the site consists of scattered limestone outcrops which alternate with short stretches of beach. Beach soils are composed of granular materials ranging in site from sand to coarse boulders and limestone rubble. The small banks (slopes) of the discharge nu0482-0029c142
t Big. Rock Point Plant 4
SEP Topics II-4.D & II-4.F canal are lined with riprap as shown on the enclosed drawings. Modeling of the site soil-structure interaction was performed by D' Appolonia for the Seismic Safety Margin Evaluation of Big Rock Point using appropriate lumped parameter soll springs and dampers which are described in Chapter 7 of D'Appolonia Report listed in Reference (7) of the Enclosure. They reviewed the criginal soll subsurface investigation (including soil borings) and conducted their own geophysical investigation (drilling new test borings) to obtain the compression and shear wave velocities of subsurface materials at the site. They found the soils on the plant site well suited for 'our application. D'Appolonia specifically reviewed the liquefaction potential of foundation soils beneath the intake structure (potentially the worst case) and the associated potential ground damage and concluded this effect(s) is negligible (see Chapter I.2.0 of D'Appolonia Report listed in Reference (4)'of the Enclosure). From the above, it can be concluded that no additional analysis is necessary.
i i
nu0482-0029c142