ML19221A976
| ML19221A976 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-02.5.3, NUREG-75-87, NUREG-75-87-2.5.3, SRP-02.05.03, SRP-2.05.03, NUDOCS 7907120111 | |
| Download: ML19221A976 (5) | |
Text
[pm REcg NUREG.75/087 o
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.A U.S. NUCLEAR REGULATORY COMMISSION I )F i S hp/
OFFICE OF NUCLEAR REACTOR REG
\\....
SECTICN 2.5.3 SURFACE FAULTING REVIEW RESPONSIBILITIES l
Primary - Geosciences Branch (GB)
Secnnd y - None I.
AREAS OF REVIEW GB reviews information in the applicant's safety analysis report (SAR) related to the l
existence of a potential for surface faulting affecting the site. The information presented in this section results largely from detailed surface and subsurface geological and geophysical investigations performed in the site and vicinity. Tne following specific subjects are addressed: the structural and stratigraphic conditions of the site and vicinity (Subsection 2.5.3.1), any evidence of fault offset or evidence demonstrating the absence of faulting (subsection 2.5.3.2), earthquakes associated with faults l
(Subsection 2.5.3.3), determination of age of most recent movement on faults (Subsection 2.5.3.4), determination of structural relationships of site area faults to regional faults (Subsection 2.5.3.5), identification and description of capable faults (subsection 2.5.3.6), and 2ones requiring detailed fault investigations (Subsection 2.5.3.7).
II.
ACCEPTANCE CRITERIA The data and analyses presented in the SAR are acceptable if, as a minimum, they describe and document the information required by References 1 and 2, and other data that are necessary, dependinc the complexity of the site. The GE0-Reference File (Ref. 3) is used by the staff as tne principal reference guide to judge whether or not all of the pertinent references have been consulted. References 4 through 9 are also used by the staff.
Subsection 2.5.3.1 is considered acceptable if the discussions of the stratigraphy, methods of fault dating, structural geology, and geologic history of the site are complete, compare well with studies conducted by others in the same area, and are supported by detailed investigations performed by the applicant. Site and regional geologic maps and profiles constructed at scales adequate to illustrate clearly the surficial and bedrock geology, structural geology topography, and the relationship of the safety related foundations of the nuclear power plant to these features should be included in the SAR.
Subsection 2.5.3.2 is acceptable if sufficient surface and subsurface information is provided and supported by detailed investigations, either to confirm the absence of USNRC STANDARD f4LVIEW PLAN Stendeed rev e. piene are prepared for the eu sence of tne Office of Nuceeer Reector Reguistion start responsihie f or the review of apphcetions to coneiruci and operate nucleer power plaate These docuenente err mode aveatab'e to the pubhc as part of t'se Commise.ca e pobcv to inform the auctees industry and ebe generet pubsec of requietory procedures and pohtees $iendard rev.ew pleas are not subsistutes for **guietory guideo or rho Comm.se<on a requiersono end compbence ereth them es aos coquered The etenderd review plea sectione are keyed to Revie oo 2 of the Standerd Format end Coritent of Sa'ety Aasavais Reports for hvocar Power Plante Not sol eartsome of the Standard Formet have e conospondeng eeview plan Pubbehed evenderd rev5ew piens well be rev eed periodiceHv. es appropriete to accommodate commente and to reflect new anf ormation and esperieare Commeate and suggeettone for improvement we6l be cons.dered and shouad be seat to the U S Nucsoer Reguietory Commise*on O'f.co of Nuclear Reorf or A*)u letten. Washington. D C 20M6 l
7907120in
faulting or, if faulting is present, to demonstrate its If faulting is present in the site vicinity, it must be defined as to fault geometry
. mount and sense of movement.,
and age of latest movement. In addition to geologic evidence which may indicate fault-ing, linears interpreted from toaographic maps, low-altitude aerial photographs and Environmental Resource Technology Satellite imagery should be documented and investigated.
Evidence for absence of faulting is obtained by conducting site surface and subsurface investigations in such detail and areal extent to ensure that undetected offsets are not likely to exist. These investigations will vary in detail according to the geological comple.ity of the specific site.
Subsectior 2.5.3.3 is acceptable if all historically reported earthquakes within fi w miles of the site or near faults which trend within five miles of the site, as discussed in Section 2.5.2, are evaluated with respect to hypocenter accuracy and source origin.
In conjunction with these discussions, a plot of the earthquake epicenters superimposed on a map showing the local tectonic structures as defined in Section 2.5.1 should be provided. Estimated error reginns of the earthquake epicenters should be shown.
Subsection 2.5.3.4 is acceptable when every fault, any part of which is within five miles of the site, is investigated in sufficient detail usinc geological and geophysical techniques of su'ficient sensitivity to demonstrate the age of most recent movement. An evaluation of the sensitivity and resolution of the exploratory techniques used shouid be given.
Subsection 2.5.3.5 is acceptable when a discussion is given of the struc ural and genetic relationship between site area faulting and the regional tectonic framework. In regions of active tectonism it may be necessary to conduct detailed geological and geophysical investigations to demonstrate the structural relationships of site area faults to regional faults knnwn to be seismically active. Both a theoretical and an observational basis for the conclusions reachec hould be given.
Subsection 2.5.3.6 is acceptable when it has been demonstrated tha+ the investigative techniques used have sufficielt sensitivity to identify all faults greater than 1000 feet in length wit hin five miles of the site and when the geometry, sense of movement, and amount of offset is given for each.
Subsection 2.5.3.7 is judged acceptable if the zone designated by the applicant as requiring detailed faulting investi ation is consistent with the description of such a g
zone in Reference 1.
Subsection 2.5.3.8 must be pr ented by the applicant if the aforementioned investiga-tio" reveal that surface displacement must be taken into account. No nuclear plant has ever been constructed on a cap 3ble fault and it is an open question as to whether it is pursible to design for surface or near-surface displacement with cor'idence that the integrity of the safety-related features of the plant would remain intact should displace-ment occur. It is, therefore, staff policy to recommend relocation of plant sites found Rev. 1 2.5.3-2
to be located on capable faults as determined by the detailed faulting investigation.
If in the future it becor:es possible to design for surface faulting, it will be necessary to present the decign basis for surface faulting and supporting dat; considerahie 9
detail.
III. REVIEW PROCEDURES The staff review procedure involves an evaluation to determine that the applicant has followed the in/estigations outlined in Reference 1.
The U.S. Gaological Survey (USGS) acts as staff advisor in reviewing this section of the SAR, on a case-by-case basis. On request, the USG5 provides expertise in numerous earth science disciplines and often is able to provide first-hand knowledge of the site. A literature search is conducted concerning the regional and local geology. The staff also contacts State geological surveys and universities to obtain additional R.11 Generally, the steps that applicants must follow it: metermining the presence and extent of faulting, and whether near-surf ace faulting (if present) represents a hazard or not, is outlined in the seismic and geologic siting criteria (Ref. 1).
Specific..westiga-tive techniques are not given in the criteria, however. The site area must be investi-gated by a combination of exploratory methods which may include borings, trenching, seismic profiling, geologic mapping, and geophysical investigations. The results of these explorations are cross-compared and evaluated by the staff.
It has been the policy of the staff to encourage applicants to avoid areas where there is a possibility for surface faulting. As the question of whether or not a surface faulting condition exists is so critical in determining wnether a particular site is suitable, this consideration is usually addressed very early in the review, Exceptions are those cases in which a fault, the existence of which was previously unknown, is revealed in excavations during construction or is discovered during the course of other investigations in the area.
When faults are identified in the site vicinity, it must be demonstrated that the faults are not capable. This is accomplished by determining the ages of the faults by absolute age dating (radiometric), associating the faulting with regional tectonic activity of known age, stratigraphic or geomorphic evidence, etc.
In such cases the staff will carry out limited site observations and investigations of its own such as examinations of excavations, and selecting and dating samples taken from shear zones. Applicants are usually required tc trench in the areas where major facilities are to be located.
Subsection 2.5.3.1 is evaluated by conducting an independent literature search and cross-comparing the results with the information submitted in the SAR.
The comparison should show that the conclusions presented by the applicant are based on sound data, are consistent with the published reports of experts who have worked in the area, and are consistent with the conclusions of the staff and its advisors. If the applicant's con-clusions and assumptions conflict with the literature, substantive investigative results to support those conclusions must be submitted to the staff for review.
jf 2.5.3-3
Subsection 2.5.3j is evaluated by first determining through a literature search that all known evidences of fcult offset have been considered in the investiga+'co. The results of the applicant'> site investigations are studied and cross-compared in detail to see if there is evidence of existing or potential displacements. If such evidence is found, additional investigations such as field mapping, geophysical inve,tigations, borings, trenching, etc., must be carried out to demonstrate that there is no offset or to define the characteristics of the fault if it does exist.
Suosection 2.5.3.3 is reviewed in conjunctiun with the consideratica of Section 2.5.2.
Historic earthquake data derived from the review of Section 2.5.2 are compared with known local tectonic features and a determination is made as t; whether any of these earthquakes can reasonably be associated with the local structures. This determination includes an evaluation of the error regions of the earthquake locations. When available, the earthquake source mechanisms should be evaluated with respect to fault geometry.
Subsection 2.5.3.4 is evaluated to determine if the age dating methodology used by the app'icant is based on accepted geological procedures. In some cases tnusual age dating techniques may be used. When such methods are employed, the staff will require exten-sive documentation of the technique and may treat it as a generic review item.
The resolution of all age dating techniques should be carefully documented.
Suasecticn 2.5.3.5 is evaluated by determining through a literature search that the applicant's evaluation of the regional tectonic framework is consistent and recognized by experts whose reports uppear in the published literature. The conclusions reached by the applicant should be based on sound geologic principles and should explain the available geologic 31 and geophysical data. When special investigations are cade to eterm:ne the structural relationship between faults which pass within live miles of the si a and regional faults, the resolution of the investigative techniques shoulc be given.
Subsection 2.5 3.6 is evaluated to determine if a sufficiently detailed investigation has been made by the applicant to define the specific characteristics of all capable faults located within 5 miles of the site. The fault characteristics requiring defiri-tion include-lencth, orientation, relationship of the fault to regional structures; the nature, amount, and geologic history of displacements along the fault; and the nuter limits of the fault zone established by mapping fault traces 10 miles along trends in both directions from the point of nearest approach to the site. The staff must be satisfied that the investigation covers a large enough area in sufficient detail to demonstrate that ther? is little likelihood of near-surface displacement hazards assc:i-ted with capable faults existing undetected near the site.
Subsection 2.5.3.7 Criteria for determining the zone requiring detailed faulting inve>tigation are clearly outlined in Reference 1.
The staff reviews the results of the applicant's faulting investigation together with the published literaturs. The investigative techniques employed by the applicant are evaluated to a'artain that they are consistent with the state of the art.
As part of this phase, experts in specific Rev. I 2.5.3-4 i46 026
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disciplines are asked to ceview certain arpects of the investigative program. The results of the investigation are analyzed to determine whether the o er limits of the zone requiring faulting investigation are appropriately conservative. If there is insufficient data to substantiate the outer boundaries, more conservative assumptiras are required.
Subsection 2.5.3.8 If the detailed faulting investigations reveal that there is a potential for surface displacement at toe site,'he staff recommends that the site be moved to in alternate location. In the future, when it may be possible to design a nuclear power plant for displacements, substantial information will be required to support the design basis for surface faulting.
IV.
EVALUATION FINDINGS After completing the review, the staff summarizes its conclusions regarding surface faulting in the SER. If after the staff completes a detailed review of the applicant's investigations and.cnclusions and it has been effectively demonstrated that near-surface displacement cannot occur at the site, the entire section of the SER can be summarized by a statement such as: "The staf f concludes that there are no surface or near-surf ace displacement potentialities existing at the site."
If it is determined that surface displacemeit cannot be precluded, the staff notifies the applicant of its conclusiens well in advance of publication of the SER.
V.
REFERENCFJ 1.
10 CFR Part 100, Appendix A, " Seismic and Geologic Siting Criteria for Nuclear Power Plants."
2.
Regulatory Guide 1.70, " Standard cormat and Content of Safety sis Reports for Nuclear Power r s," Revision 2.
3.
"GE0-
Reference:
Corrputerized File of Earth Science Titles," American Geological Institute, Washington.
4 M. R. Grey, R. McAfee, Jr., and C. L. Wolf, eds., "Glcssary of Ceology," American Geulogical Institute, Washington (1972).
5.
G. V. Cohee (chairman) et. al., " Tectonic Map of the United States," U. S. Geological Survey and American Association of Petroleum Geologists (1962).
6.
State geological maps and accompanying texts.
7.
U. S. Geological Survey 7.5-and 15-minute topographic and geologic quadrangle maps.
8.
U. S. Department of Agriculture and U. S. Geological Survey aerial photographs.
9.
Environmental Resources Technology Satellite photographs.
) k bev0i27 2.5.3-5