ML20003A440
| ML20003A440 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 01/30/1981 |
| From: | Stephen Burns, Cyr K NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | |
| Shared Package | |
| ML20003A437 | List: |
| References | |
| ISSUANCES-SC, NUDOCS 8102030689 | |
| Download: ML20003A440 (11) | |
Text
1/30/81 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
)
)
DAIRYLAND POWER COOPERATIVE
)
Docket No. 50-409 SC (La Crosse Boiling Water Reactor)
)
(Show Cause)
NRC STAFF'S PROPOSED FINDINGS OF FACT, CONCLUSIONS OF LAW AND PROPOSED FORM 0F ORDER Pursuant to 10 C.F.R. 2.754, the NRC Staff hereby submits its proposed findings of fact, conclusions of law and proposed form of order with respect to the issues addressed in the evidentiary hearing in the above-captioned proceeding held in La Crosse, Wisconsin on December 16 and 17,1980.
PROPOSED FINDINGS OF FACT 1.
The La Crosse facility is founded on loose to medium dense sand deposits and hydraulic fill.
(SER, p.1, licensee's testimony, p. 3.)1/
[
2.
A typical soil profile at the La Crosse site consists of the following: about 20 feet of hydraulic fill, a brown medium to coarse sand, l
1/
"SER" refers to the " Safety Evaluation by the Office of Nuclear Reactor Regulation Relating to Liquefaction Potential at the La Crosse Site",
admitted into evidence at Tr. 96.
" Licensee's Testimony" refers to the
" Testimony of Dairyland Power Cooperative on the Risk Issue Identified in the Licensing Board's Memorandum and Order of November 12, 1980,"
admitted into evidence at Tr. 306.
Transcript references are to the transcript of the evidentiary hearing held on December 16 and 17,1980, in La Crosse, Wisconsin.
810 203 0M underlain by about a 5 foot layer of dark gray clayey silt and very silty sand. This dark gray soil was removed from under the containment and stack foundation during construction excavation.
Beneath the silt and fine sand layer is 100 to 130 feet of gray to brown, fine to coarse sand with traces of gravel.
Below these deposits the bedrock consists of nearly flat-lying sandstones and shales. (SER, pp. 1-2; licensee's testimony, p. 3.)
3.
The type of soil found at the La Crosse site may be subject to liquefaction during strong seismic loading.
(SER, p. 2; licensee's testi-mo ny, p. 3. )
4 Loose sands tend to compact under cyclic loading which can cause an increase in the pore pressure, and if saturated, a reduction in shear s treng t h.
(SER, p. 2; licensee's testimony, p. 3.)
5.
When subjected to strong vibratory motion and high pore pressure development, loose sands can undergo complete loss of strength and lique-faction occurs. (SER, p. 2; licensee's testimony, p. 3.)
6.
Evaluation of liquefaction potential involves comparison of induced shear stress (loading) due to vibratory ground motion with the available shear stress (strength) in a soil which will resist liquefaction.
(SER, p. 2; licensee's testimony, p. 3.)
7.
Induced shear stress (loading) is evaluated based on the peak ground acceleration, earthquake magnitude, epicentral distance, and duration of strong motion, coupled with the site soils' ability to transmit the imposed vibratory motion.
(SER, p. 2; licensee's testimony, pp. 3-4; Tr.
181-184.)
e Cyclic shear strength of the soils is evaluated based on consider-8.
ations of the soil type, density, confining pressure, degree of saturation and drainage characteristics.
(SER, p. 2; Tr. 251-254.)
Two methods are commonly used to evaluate the cyclic strength of a 9.
a laboratory / analytic approach and an empirical saturated sand deposit:
Both approaches are considered important by the Staff in deter-approach.
mining soil resistance to liquefaction.
(SER, p. 2; licensee's testimony, pp. 3-4.)
The laboratory / analytical approach involves modeling the site soil 10.
conditions in the laboratory, correcting for known differences between lab and field conditions, and establishing cyclic shear strengths over a range of vibratory loading cycles.
(SER, p. 2; licensee's testimony, p. 4.)
The empirical approach utilizes the results of observations for 11.
sites where liquefaction occurred or did not occur in past earthquakes.
Site dependent standard penetration test (SPT) hammer blow values are used Hammer to address the dynamic performance characteristics of site soils.
blows measure soil penetration resistance which is indicative of soil (SER, p. 2; licensee's characteristics such as density and shear strength.
testimony, p. 4; Tr.118-119, Tr. 324-326.)
The earthquake loading at the La Crosse site can be adequately and 12.
conservatively characterized as a magnitude 5 to 5.5 event at a distance of less than 25 Di producing a peak ground acceleration of.12g and an equiva-lent duration of 5 cycles. (SER, p. 2-3; Tr.185, 203, 396-397; Exh. 4,
- p. 16 & Fig. 10; Exh. 8).
- 13. A magnitude 5.5 earthquake is the very lower bound where lique-faction has ever been experienced and recorded. (Tr. 113,246-47.)
14 In July,1980, Dairyland Power Cooperative and Dames & Poore performed four test borings directly beneath pile supported structures at the La Crosse site to assess the increase in density under those structures due to the vibrations during driving of displacement piles under the struc-tures. (SER, p. 4; licensee's testimony, p. 5; Tr. 94,110, 268.)
- 15. These borings taken under the turbine and stack foundations are representative of the soil conditions below pile-supported structures, including the containment building. (SER, p. 5; licensee's testimony, p. 5.)
16.
The results of the Standard Penetration Tests (SPT) harmer blow values taken under the turbine building and the stack foundation indicate a significant increase in soil density compared to the SPT results from the free field borings.
(SER, p. 5, Figures 5 through 8; licensee's testimony,
- p. 5.)
17.
The SPT results for the turbine building and stack clearly show that the piles produced an improved condition (greater. soil density) over earlier free-field subsurface conditions and indicate a low liquefaction potential for the turbine and reactor buildings.
(SER, p. 5.)
18.
The soil density gradient which radiates laterally outward from pile groups, and from a single pile, was taken into account in assessing the liquefaction potential under pile supported structures. (Tr. 120-124,363-364.)
L 1
l
- 19. Soil densification is a better measure than a dewatering system to preclude liquefaction. (Tr. 266-267.)
i i
t 20.
The Mississippi River water level is reflected in the water level below grade at the LACBUR site and the effect of this connection on soil properties at the La Crosse site is to saturate the sands at the level of the water table.
(Tr. 248.)
- 21. Ground water conditions affect liquefaction potential in that higher ground water conditions indicate lower margins of safety against liquefaction; deeper ground water level conditions indicate higher margins of safety against liquefaction.
(Tr. 248, 391. )
- 22. The liquefaction potential evaluation perfonned by the licensee, and evaluated by the Staff assumed a ground water level of 10 feet deep, which was on the high side of recorded nonnal conditions (13 feet). (Tr.
249-250.)
23.
However, even if flood conditions with water levels at the base of the buildings existed, and an earthquake which produced a ground accelera-tion of.12g occurred, liquefaction under pile-supported structures would not result. (Tr. 252,391-392.)
24.
Based upon review of the results of the test borings under the turbine building and the stack and the data presented by Dairyland Power Cooperative and Dames & Moore, the NRC Staff has concluded that the soils under pile-supported structures at the La Crosse site are safe against liquefaction in the event of an earthquake up to a magnitude of 5.5 with a peak ground acceleration of.12. (SER, p. 5; Tr. 97,112, 308.)'
9 25.
Neither the type of pile used to densify the soils under the foundations nor the structural support of the piles enters into the con-clusions reached on liquefaction potential under pile-supported structures
~.
at the LACBWR site.
It is the densification which results from the driving of the piles which is the significant factor. (Tr. 285-286.)
26.
The only structures for which liquefaction remains a concern are the crib house, located on the river bank, and the underground piping of the service water line. (SER, p. 5; licensee's testimony, p. 6.)
27.
A site dewatering system is unnecessary, however, to resolve the concerns about possible effects of liquefaction on the crib house and service water line.
Dairyland Power Cooperative is installing a dedicated safe shutdown system to preclude reliance on the crib house and piping in the event of an earthquake. This system is expected to be operable by the end of February 1981.
(SER, p. 5-6; licensee's testimony, p. 6, Tr. 312.)
28.
The currently estimated return periods for an earthquake producing a peak ground acceleration of 0.129 at the La Crosse site are on the order of 1,000 or 10,000 years.
More likely than not the actual value is closer to the longer end of this range. (Testimony of Leon Reiter, p. 2, admitted into evidence at Tr. 85 (hereinafter Reiter's testimony); Tr. 124-126, Tr.
206.)
- 29. These return periods are based upon staff analysis of the results submitted so far in the Lawrence Livermore Laboratory--TERA Corporation Site Specific Spectra Program (SSSP).
In the SSSP, return periods were cal-culated for peak ground accelerations, peak ground velocities and response spectra at ten eastern and central U.S. sites, including the LACBWR site.
Experts on eastern seismicity were polled with respect to seismic zonation, frequency of earthquake occurrences, upper magnitude cutoff, and characteri-zation and attenuation of ground motion.
(Reiter's testimony, p. 2-3; Tr.
l l
128, Tr. 155-165.)
l t
,~
30.
Specific earthquakes such as those at Anna, Ohio, and New Madrid, Missouri, were taken into account in these analyses.
(Reiter's testimony,
- p. 3-4.)
The earthquake which occurred in Maysville, Ohio in July 1980, was of a type which was included in the assumptions made by the seismology experts.
The magnitude of the Maysville earthquake was within the range of the magnitude 5.0 - 5.5 earthquake which is being considered for La Crosse.
(Reiter's testimony, pp. 3-4; Tr.127-131. )
31.
Several attenuation models were used to calculate ground motion estimates for sites in the SSSP. At La Crosse, the peak accelerations associated with given return periods were similar for the various models used.
(Reiter's testimony, pp. 4-5.)
32.
The amplification conditions inherent in the seismic hazard analy-ses performed by LLL-Tera for the SSSP program are those which might result at average western sites.
Even if the amplification conditions are different at the la Crosse site from those at the average western site, the range of on the order of 1,000 or 10,000 years for the return period for an earth-quake producing a peak ground acceleration of.129 at the La Crosse site, would not be affected.
(Reiter's testimony, p. 6; Tr.145, Tr.139-144.)
- 33. The 10
- 10 probabilities specified in the Standard Review Plan, sections 2.2.3 and 3.5.1.6 are used as guidelines for the identifi-cation of design basis events, such as earthquakes, which must be considered in the design of a plant.
Accordingly, the effects of earthquakes are evaluated since potentially damaging earthquakes are considered to have
-7 annual probabilities greater than the 10 10 guideline.
=
l, While the annual probability of potentially damaging earthquakes 34.
(the seismic hazard) has been characterized as 10 to 10, the quantifi-
~
cation of seismic risk involves considerations of many factors including the a
probability of structural / mechanical failure and radionuclide dispersion as a function of various levels of ground notion or seismic hazard.
In general, seismic hazard cannot be equated directly to seismic risk since the hazard is a component of the risk (Testimony of Howard Levin, pp. 2-3, admitted into evidence at Tr. 90.)
In the particular case of La Crosse, the seismic hazard cannot be equated directly to seismic risk.
(Tr. 245.)
In order to quantify the overall level of risk from a seismic 35.
event at the La Crosse site, a long chain of events would have to be con-For example, first, there is the probability an event will occur; sidered.
given that event, there is a probability that liquefaction will occur; given the probability that liquefaction occurs, there is in turn an additional probability that there will be some pathologic response of the plant to that liquefaction.
(Tr. 231, 233, Tr. 406-409. )
The NRC Staff and the Licensee are not aware of any evidence that 36.
would indicate that liquefaction would occur for the seismic event of magni-tude up to 5.5 producing a peak ground acceleration of 0.129 (Tr. 233-234, Tr. 401. )
There is reasonable assurance that the soils under pile-supported 37.
structures at the LACBWR site are safe against liquefaction for an earth-quake with a magnitude 5.0 to 5.5 producing a peak ground acceleration of
.129 (SER, pp. 5-6; Tr. 97,112, 308.)
i i
9_
PROPOSED CONCLUSIONS OF LAW Based upon its evaluation of the NRC Staff's Safety Evaluation Report, the affidavits submitted by the NRC Staff and the Licensee in support of their respective Motions for Summary Disposition and responses thereto, the testimony of the Staff's and the Licensee's witnesses at the evidentiary hearings held at La Crosse, Wisconsin on December 16 and 17,1980, the Board makes the following conclusions of law:
1.
Reasonable assurance exists that for an earthquake up to magnitude 5.5 with peak ground acceleration of 0.12g or less, the soils under pile-supported structures at the LACBWR site are safe against liquefaction.
2.
Reasonable assurance exists that in the event that an earthquake of magnitude 5.0 - 5.5 with peak ground acceleration of 0.12g causes damage to the crib house and underground piping, emergency cooling water can be provided for safe reactor shutdown using a dedicated safe shutdown system.
3.
Reasonable assurance exists that continued operation of the La Crosse Boiling Water Reactor without a dewatering system for the site will not endanger the health and safety of the public, pending a final determina-tion by the Board on the merits of all remaining matters in controversy in this proceeding.
PROPOSED FORM 0F ORDER "The Board, having considered and decided all matters in controversy among the parties concerning the liquefaction potential of the LACBWR site in the event of a magnitude 5.0 -
5.5 earthquake producing a peak ground acct?eration of 0.12g at the LACBWR site, having satisfied its own concerns with respect to these matters, and finding that no basis exists for suspending operation of the LACBWR on February 25, 1981, as proposed in the Order to Show Cause, hereby concludes in accorda regulations that no action should be taken to suspend operation of the LACBWR pending a final detemination by the Board on the merits of all remaining matters in controversy in this proceeding.
Respectfully submitted, Stephen G. Burns Counsel for NRC Staff 1 % O Orv Karen D. Cyr Counsel for NRC Staff Datet at Bethesda, Maryland this.,0th day of January,1981.
UNITED STATES OF AMERICA NUCLEAR REGULATORY C0tt1ISSION BEFORE THE ATOMIC SAFETY & LICENSING BOARD In the Matter of DAIRYLAND POWER COOPERATIVE
)
Docket No. 50-409 SC (La Crosse Boiling Water Reactor)
)
(Order to Show Cause)
CERTIFICATE OF SERVICE I hereby certify that copies of the NRC STAFF'S PROPOSED FINDINGS OF FACT, CONCLUSIONS OF LAW AND PROPOSED FORM OF ORDER and related BRIEF in the above-captioned proceeding have been served on the following by deposit in the United States mail, first class, or as indicated by an asterisk, through deposit in the Nuclear Regulatory Commission's internal mail system, this 30th day of January,1981.
Charles Bechhoefer, Esq.*
- 0. S. Hiestand, Esq.
Chairman Kevin Gallen, Esq.
Atomic Safety & Licensing Board Morgan, Lewis & Beckius U. S. Nuclear Regulatory Comission 1800 M Street, N. W.
Washington, D. C. 20555 Washington, D. C. 20036 Dr. George C. Anderson Atomic Safety & Licensing Board Panel
- Department of Oceanography U. S. Nuclear Regulatory Comission University of Washington Washington, D. C. 20555 Seattle, Washington 98195 Atomic Safety & Licensing Appeal Panel
- Mr. Ralph Decker U. S. Nuclear Regulatory Comission Route 4, Box 190D Washington, D. C. 20555 Cambridge, Maryland 21613 Mr. Frederick M. Olsen, III Coulee Region Energy Coalition 609 N. lith Street Attn: Ms. Ann K. Morse La Crosse, Wisconsin 54601 P. O. Box 1583 La Crosse, Wisconsin 54601 Docketing & Service Section U. S. Nuclear Regulatory Commission Fritz Schubert, Esq.
Washington, D. C. 20555 Staff Attorney Dairyland Power Cooperative l
l 2615 East Avenue, South La Crosse, Wisconsin 54601 I
Mr. Frank Linder General Manager Dairyland Power Cooperative Stephen G. Burns i
l 2615 East Avenue, South Counsel for NRC Staff La Crosse, Wisconsin 54601
-