Regulatory Guide 1.127

Inspection of Water-Control Structures Associated with Nuclear Power Plants

ML003739392
Person / Time
Issue date:	03/31/1978
From:	Office of Nuclear Regulatory Research
To:
References
RG-1.127 Rev 1
Download: ML003739392 (3)

Revision 1 U.S. NUCLEAR REGULATORY COMMISSION March 1978 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 1.127 INSPECTION OF WATER-CONTROL STRUCTURES ASSOCIATED

WITH NUCLEAR POWER PLANTS

B. DISCUSSION

Paragraphs (a)(4) and (b)(4) of §50.34, "Contents The National Dam Safety Act (Public Law 92 of Applications: Technical Information," of 10 CFR 367) requires, in part, that the Secretary of the Army, Part 50, "Licensing of Production and Utlilization acting through the Chief of Engineers, carry out a na Facilities," require each applicant for a construction tional program of inspection of dams' for the purpose permit or operating license to provide an analysis and of protecting human life and property. To determine evaluation of the design and performance of struc whether a dam (including the waters impounded by tures, systems, and components of the facility for the the dam) constitutes a danger to. human life or prop purpose of assessing the risk to public health and erty, the Secretary is required to take into considera safety resulting from operation of the facility. Gen tion the possibility that the dam might be endangered eral Design Criterion 45, ."Inspection of Cooling by overtopping, seepage, settlement, erosion, sedi Water System," of Appendix A, "General Design ment, cracking, earth movement, earthquakes, failure Criteria for Nuclear Power Plants," to 10 CFR Part of bulkheads, flashboards, gates on conduits, or other

50 requires that the cooling water system be designed conditions that exist or that might occur in any area to permit appropriate periodic inspection of important in the vicinity of the dam. As soon as practicable components to ensure the integrity and capability of after inspection of a dam, the Secretary is to notify the system. Paragraph (c)(3) of §50.36, "Technical the Governor of the State in which such dam is lo Specifications," of 10 CFR Part 50 defines surveil cated of the results of such investigation. The Secre lance requirements as those relating to test, calibra tary is required to notify the Governor immediately of tion, or inspection to ensure that the necessary qual any hazardous conditions found during an inspection ity of systems and components is maintained, that and to advise the Governor, on request, of timely re facility operation will be within safe limits, and that medial measures necessary to mitigate or obviate any the limiting conditions of operation will be met. hazardous conditions.

This guide describes a basis acceptable to the NRC

staff for developing an appropriate inservice inspec SSection 2 of the Act specifically excludes from the inspection tion and surveillance program for' dams, slopes, can program (1) dams under the jurisdiction of the Bureau of Recla als, and other water-control structures associated with mation, the Tennesse Valley Authority, or the International

• emergency cooling water systems or flood protection Boundary and Water Commission, (2) dams that have been con of nuclear power plants. Guidelines for the design structed pursuant to licenses issued under the authority of the Federal Power Act, (3) dams that have been inspected within the and construction of these structures will be presented 12-month period immediately prior to the enactment of this Act in separate guides. The Advisory Committee on by a State agency and that the Governor of such State requests Reactor Safeguards has been consulted concerning be excluded from inspection, and (4) dams that the Secretary of this guide and has concurred in the regulatory the Army determines do not pose any threat to human life or position. property. The Secretary may inspect dams that have been licensed under the Federal Power Act on request of the Federal Power Commission and dams under the jurisdiction of the Inter

• Lines indicate substantive changes from the previous issue. national Boundatry and Water Commission on request of such Commission.

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission, US. Nuclear Regu.

Regulatory Guides are issued to describe and make available to the public methods latory Commission, Washington, D.C. 20555, Attention: Docketing and Service Branch.

acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or postulated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. I. Power Reactors 6. Products Methods and solutions different from those set Out in the guides will be accept- 2. Research and Test Reactors 7- Transportation able if they provide a basis for the findings requisite to the issuance or continuance 3. Fuels and Materials Facilities 8. Occupational Health of a permit or license by the Co-mi~ion. 4.

5. Environmental andSiting 9. Antitrust Materials and Plant Protection 10. General Review Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides lwhich may be reproduced) or for place times, and guides will be revised, as appropriate, to accommodate comments and meet on an automatic distribution list for single copies of future guides in specific to reflect new information or experience. This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission, substantive comments received from the public and additional staff review. Washington, D.C. 20555, Attention: Director, Division of Document Control.

I I

This legislation was developed as an expression of ally high uplift pressure noted at Hoover Dam (Ref.

public and congressional concern over the safety of 5). Construction defects have been found, such as dams in the United States. On August 28, 1974, the soft materials left in the abutments of a gravity dam, Corps of Engineers published "Proposed Guidelines inadequate provisions for heat di-ssipation of mass for Safety Inspection of Dams" in the FederalRegis concrete structures, or impervious fill misplaced in the ter (39 FR 31334). These guidelines propose proce shell of a zoned earthfill dam (Ref. 6). Foundations dures for inspection and evaluation of dams to deter may need further treatment after a period of opera mine if they constitute hazards to human life and tio'n, e.g., the foundation at Hoover Dam, which was property. The proposed inspection procedures are treated by providing additional drainage and grouting similar to the procedures discussed in this guide. to reduce uplift pressure and seepage. To detect such behavioral deviations, regular surveillance is Dams, slopes, canals, and other water-control essential.

structures and associated facilities are used to im pound, retain, and divert water sources for the emer Some dams may become weaker with advancing gency cooling operations of nuclear power plants. years, and expert professional care is then needed.

Failure to perform their functions could endanger the Examples of this phenomenon are concrete dams that plant and cause an undesirable release of radioactive were weakened by a chemical reaction between the material to the environment, thus affecting the public alkalies of the cement and the silica of the aggregate health and safety. The design and construction of (Ref. 6) and dams that experienced progressive fail these facilities, therefore, require a high degree of ure in earthfill embankments (Ref. 7). The weaken professional engineering performance. The founda ing of a dam or its foundation may become apparent tion of the dam should be stable under all conditions only after many years of safe operation. Painstaking and should be capable of carrying the weight of the monitoring and analysis of performance data are structure. The dam should impound its reservoir necessary to ensure detection of adverse conditions, water without undue strain and should be safe under including peripheral phenomena such as subsidence the application of external forces such as those result and landslide (Refs. 7 and 8). Each structure, as well ing from earthquakes. The reservoir area should be as each site, has its own characteristics and its own water retentive and free of the possibilities of susceptibilities to problems, and the surveillance pro dangerous slides. Dams and associated facilities gram should be tailored to account for these.

should be maintained in good working condition

.throughout their lives. Operation and surveillance Thorough physical examination is an essential part through the years should be conducted in such a of the surveillance program. The optimal frequency manner that any change in their structural, hydraulic, of inspections depends on the size, age, and condi and foundation conditions can be detected promptly tion of the facilities; the character of the foundation;

and corrections made. the regional geological setting; and the proximity of the facilities to populated areas.

Statistics of dam failures, based on the sum of op eration years of a regional group of dams (Ref. 1), The search for superficial signs of distress such as show a frequency of one failure every 1500 to 1800 longitudinal and transverse cracks is only one phase dam years. Causes of latent danger inherent in such of the examination. Possible internal disorders may works arise from site conditions, hydrologic and hy be probed by various portable instruments (Refs. 9 draulic features, types and qualities of the structures, and 10) such as soniscopes, hydrophones, television, operation and maintenance, and influence of the envi and bore-hole cameras. It is important that these ob ronment. Of these causes, the majority lie within the servations be correlated closely with measurements boundaries of modern technology and can be from embedded devices.

avoided. Most failures have resulted from gradually Particularly vulnerable areas that should be moni worsening defects (due to design, construction, oper tored are those where embankments have been placed ation, or lack of maintenance) that were either undis against or are covered by structures. There may be a covered or misjudged. The Nashville Masonry Dam high susceptibility to internal erosion at the planes of in Tennessee failed because of the saturation of con contact. Dams have failed because of piping along cealed clay seams (Ref. 1); the South Fork Dam in abutments and underneath superimposed structures Pennsylvania failed because of the overgrown vegeta such as fish ladders and spillways (Ref. 11).

tion at the spillway (Ref. 1); and the Waco Dam slide in Texas that occurred during construction is attrib Attention should also be focused on the slopes of uted to the low residual strength, high pore pressure the reservoir behind the dam where unstable terrain buildup (Ref. 2), and highly anisotropic behavior of may be a problem (Ref. 7). The early stages of slope the shale (Ref. 3). failure may be manifested in various ways: buckling Dams and associated facilities have not always per of concrete and asphaltic linings, leaning of trees and formed as expected, as exemplified by excessively poles, and cracking and bulging of walls (Ref. 12).

high pressure buildup discovered in the foundation Thorough surveillance of suspected unstable areas is soil at West Branch Dam in Ohio (Ref. 4) and unusu- essential when disturbance could jeopardize the

1.127-2

safety of the dam (Ref. 11). These areas require care Inspection personnel should be selected carefully.

ful and frequent inspection, sometimes supplemented The inspector and the analyst should be practical, by periodic measurement of precise level and triangu dedicated diagnosticians who examine thoroughly lation nets, reading of slope indicators or tiltmeters, every clue during their scrutiny of the behavior of and study of aerial photographs. these structures. A person who becomes uninterested, Before filling a reservoir, records of piezometric complacent, or overwhelmed when surrounded by voluminous collected data should not be assigned to levels, ground elevations, and background seismic ity 2 at the site should be compiled so that comparison this demanding duty. On the other hand, an analyst concerned with quantity rather than quality of data or can be made with the effects of water loading. As soon as filling begins, the inspection and mainte fascinated with overly sophisticated techniques may nance program for structures and operating equip overlook obviously adverse trends apparent by scan ning data or by simple charting. The key to striking a ment should be initiated. This includes regular patrol proper balance is the selection of a person who knows of the dam and its abutments and observations of what to look for and is perseverant in his search, dis seepage flows, piezometric levels, and structural and cerning in his interpretation, and communicative of foundation movements. These readings should be plotted and correlated with concurrent reservoir water his findings.

levels. An increase in seepage flow and turbidity is a A list of references used in developing this regula common symptom of piping as a result of impounded tory guide is included. An additional bibliography water penetrating and flushing out foundation open that may be useful to the licensee in developing an ings (Ref. 1). inspection program is also included. However, the listing of these references does not constitute a blan Although the most critical time in the life of a re ket endorsement of their contents by the NRC staff.

servoir may be during its first filling when the design is checked against actual performance, several years

C. REGULATORY POSITION

may pass before the foundation and structures have fully adjusted to the loads. Thereafter, deformation This guide applies only to water-control struc will continue in response to cyclical load variations. tures (e.g., dams, reservoirs, conveyance facilities)

Attention should be focused on inspection and data specifically built for use in conjunction with a nu collection during relatively rapid changes in reservoir clear power plant and whose failure could cause I

water surface elevations. Year-to-year conditions at radiological consequences adversely affecting the high and low seasonal levels should be compared. public health and safety. In addition, the structure Data should also be collected on changes occurring was built, wholly or in part, for the purpose of con since project construction that may influence safety trolling or conveying water for either emergency and function of the facilities. It is important that ab cooling operation or flood protection of a nuclear normalities affecting facility safety be met with quick power plant. Such a structure may be located on or corrective action. off the site. The NRC staff may consider the recom mendations of this guide fulfilled by the applicant or The service water channels should be examined for licensee if the structure is regulated by another any conditions such as channel bank erosion, aggra agency or State that enforces a comparable inspection dation, or degradation that may impose constraints on program, e.g., a hydroelectric pumped-storage proj the function of the cooling system and present a po ect built as part of a nuclear power plant and regu tential hazard to the safety of the plant. Submerged lated by the Federal Power Commission (Department dams and emergency canals (e.g., artificially dredged of Energy).

canals at the river bed or the bottom of the reservoir)

should be examined for any conditions, e.g., block Inservice inspection should be performed at age caused by sedimentation, debris, or instability of periodic intervals to check the condition of the slopes, that may impair the function of the canals water-control structures and evaluate their structural under extreme low-flow conditions. safety and operational adequacy. A detailed, systema tic inspection program should consist of, but not Operation of a dam tends to become routine in the necessarily be limited to, the following:

course of time and, without enforced requirements to 1. Engineering Data Compilation the contrary, emergency equipment may be put aside, even forgotten, and may be defective when an emer Engineering data related to the design, construc gency arises. At Kaddam Dam in India, the failure of tion, and operation of the water-control structures the power supply for the electric, drive of the spillway should be collected and, to the extent practicable, in gates (Ref. 1) occurred for this very reason. cluded in the initial inspection report. 3 These data Most engineering data are information presented in PSAR and I2The need for earthquake monitoring should be established in FSAR reports. To aid the inspectors, this information should be either incorporated into the report or referenced in detail as to its the design phase.

SAR location.

1.127-3

_L_

should include the following items, where available 2. Onsite Inspection Program and appropriate: The onsite inspection program of water-control a. General Project Data structures should be established and conducted in a systematic manner to minimize the possibility of

(1) Regional vicinity map showing the project overlooking any significant features. A detailed location and the upstream and downstream drainage checklist should be developed and followed for the areas. project structures to document the observations of

(2) As-built drawings of important project fea each significant structural and hydraulic feature, in tures, ihcluding details such as instrumentation, cluding electrical and mechanical control equipment.

internal drainage, transition zones, or relief wells. Particular attention should be given to detecting evi

(3) Construction progress and as-built photo dence of leakage, erosion, seepage, slope instability, graphs of concrete surfaces, points of contacts undue settlement, displacement, tilting, cracking, de between structures or structures and earth embank terioration, and improper functioning of drains and ments, foundation conditions, etc. relief wells; to verifying the adequacy and quality of maintenance and operating procedures; and to observ b. Hydrologic and Hydraulic Data ing significant postconstruction changes.

(1) Drainage area and basin characteristics. The use of photographs for comparison of previous

(2) Storage and surcharge capacities, including and present conditions, documentation of new or dead storage. progressive problems, and inspection records should be included as a part of the inspection program.

(3) Elevation of the maximum design pool and freeboard height. The inspection should include appropriate features

(4) Spillway characteristics (location, type, and items, including but not limited to the following:

width, and crest length and elevation). a. Concrete Structures in General

(5) Location and description of flashboards, (1) Concrete Surfaces. The condition of the fuse plugs, and emergency spillways. concrete surfaces should be examined to evaluate the c. Foundation data and geological features, includ deterioration and continuing serviceability of the ing boring logs, geological maps, profiles and cross concrete. Descriptions of concrete conditions should sections, and reports of foundation treatment. conform with the appendix to the American Concrete Institute publication, ACI 201, "Guide for Making a d. Properties of embankment and foundation mate Condition Survey of Concrete in Service" (Ref. 13).

rials, including results of laboratory tests, field tests, (2) Structural Cracking. Concrete structures construction control tests, and assumed design mate should be examined for structural cracking resulting rial properties. from overstress due to applied loads, shrinkage and e. Concrete properties, including the source and temperature effects, or differential movements.

type of aggregate, cement used, mix design data, and (3) Movement-Horizontal and Vertical test results during construction. Alignment. Concrete structures should be examined for evidence of any abnormal settlements, heaving, f. Electrical and mechanical equipment type; rat deflections, or lateral movements.

ing of normal and emergency power supplies, hoists,

(4) Junctions.The conditions at the junctions of cranes, valves, and valve operators; and control and the structure with abutments or embankments should alarm systems that could affect the safe operation of the water-control structure. be determined.

(5) Drains--Foundation, Joint, Face. All g. Pertinent construction records, including con drains should be examined for the purpose of ensur struction problems, alterations, modifications, and ing that they are capable of performing their design maintenance repairs. function.

(6) Water Passages. All water passages and h. Water-control plan, including regulation plan other concrete surfaces subject to running water under normal conditions and during flood events or should be examined for erosion, cavitation, obstruc other emergency conditions. tions, leakage, or significant structural cracks.

i. Earthquake history, including a summary of sig (7) Seepage or Leakage. The faces, abutments, nificant earthquakes in the vicinity. and toes of the concrete structures should be examined for evidence of seepage or abnormal leak j. Principal design assumptions and analyses, in age, and records of flow of downstream springs cluding hydrologic and hydraulic analyses, stability should be reviewed for unusual variation with reser and stress analyses, and seepage and settlement voir pool level. The sources of seepage should be de analyses. termined, if possible.

1.127-4

(8) Monolithic Joints-ConstructionJoints. All designed to release reservoir water below the spill monolithic construction joints should be examined to determine the conditioni of the joint and filler mate way crest through or around the dam.

rial, any movement of joints, or any indication of dis (1) Control Gates and Operating Machinery.

tress or leakage. The structural members, connections, hoists, cables, and operating machinery and the adequacy of normal

(9) Foundation. The foundation should be visu and emergency equipment should be examined and ally examined to the extent possible for damage or tested to determine the structural integrity and verify possible undermining of the downstream toe. the operational adequacy of the equipmen

t. Where

(10).Abutments. The abutments should be cranes are intended to be used for handling gates and examined for signs of instability or excessive bulkheads, the capacity and operating condition of weathering. the cranes and lifting beams should be ascertained.

b. Embankment Structures Operability of control systems and protective and alarm devices such as limit switches, sump high

(1) Settlement. The embankments and water alarms, and drainage should be ascertained.

downstream toe areas should be examined for any evidence of unusual localized or overall settlement, (2) Unlined Saddle Spillways. If unlined saddle depressions, or sink holes. spillways are used, they should be examined for evi dence of erosion and any conditions that may impose

(2) Slope Stability. Embankment slopes should constraints on the functioning of the spillway.

be examined for irregularities in alignment and var iances from originally constructed slopes, unusual (3) Approach and Outlet Channels. The ap changes from original crest. alignment and elevation, proach and outlet channels should be examined for evidence of movement at or beyond the toe, and sur any conditions that may impose constraints on the face cracks that indicate movement. functioning of the spillway and the outlet works.

(3) Seepage. The downstream face of abut (4) Stilling Basin (Energy Dissipators). Stilling ments, embankment slopes and toes, embankment basins, including baffles, flip buckets, or other structure contacts, and the downstream valley areas energy dissipators, should be examined for any con should be examined for evidence of existing or past ditions that may impose constraints on the ability of seepage. The sources of seepage should be investi the stilling basin to prevent downstream scour or ero gated to determine cause and potential severity affect sion that may create or present a potential hazard to ing dam safety under all operating conditions. The the safety of the dam. The existing condition of the presence on slopes of animal burrows and vegetative channel downstream of the stilling basin should be growth that might cause detrimental seepage should determined.

be examined. (5) Intake Structure. The structure and all fea

(4) Drainage Systems. All drainage systems tures should be examined for any conditions that may should be examined to determine whether the systems impose operational constraints on the outlet works.

can freely pass discharge and ensure that the dis Entrances to the intake structure should be examined charge water is not carrying embankment or founda for conditions such as silt or debris accumulation that tion material. Systems used to monitor drainage may reduce the discharge capabilities of the outlet should be examined to ensure that they are opera works.

tional and functioning properly. (6) Conduits, Sluices, Water Passages, etc. The interior surfaces of conduits should be examined for

(5) Slope Protection. The slope protection erosion, corrosion, cavitation, cracks, joint separa should be examined for erosion-formed gullies and tion, and leakage at cracks or joints.

wave-formed notches and benches that have reduced the embankment cross section or exposed less-wave (7) Drawdown Facilities. Facilities provided for resistant materials. The adequacy of slope protection drawdown of the reservoir to avert impending failure against waves, currents, and surface runoff that may of the dam or to facilitate repairs in the event of sta bility or foundation problems should be examined for occur at the site should be evaluated. The condition any conditions that may impose constraints on their of vegetative or any other protective covers should be functioning as planned.

evaluated, where pertinent.

d. Reservoirs c. Spillway Structures and Outlet Works The following features of the reservoir should be The spillway examination should cover the struc examined for any conditions that may impose opera tures and features, including bulkheads and tional constraints on the cooling system or that may flashboards, of all service and auxiliary spillways for be hazardous to the safety of the dam:

any condition that may impose operational constraints

(1) Shore Line. The landforms around the reser on the functioning of the spillway. The outlet works voir should continually be examined for indications examination should include all structures and features of major active or inactive landslide areas and for

1.127-5

their susceptibility at any later date to massive land devices should be examined to determine any change slides of sufficient magnitude to significantly reduce from the original position of the structures.

reservoir capacity or create waves that might overtop (3) Horizontal and Vertical Movement, Con the dam. solidation, and Pore-WaterPressure Instrumentation

(2) Sedimentation. The reservoir and drainage (Embankment Structures). The existing records of area shotild be examined for excessive sedimentation measurements from settlement plates or gages, sur or recent developments in the drainage basin that face reference marks, slope indicators, and other de could cause a sudden increase in sediment load, vices should be examined to determine the movement thereby reducing the reservoir capacity with attendant history of the embankment. Existing piezometer increase in maximum outflow and maximum pool measurements should be examined for the purpose of elevation. determining if the pore-water pressures in the em

(3) Potential Upstream Hazard Areas. The re bankment and foundation would, under given condi tions, impair the safety of the dam.

servoir area should be examined for changes with a potential for hazardous backwater flooding. (4) Uplift Instrumentatio

n. The existing records

(4) Watershed Runoff Potential. The drainage of uplift measurements should be examined for the purpose of determining if the uplift pressures for the basin should be examined for any extensive recent maximum pool would impair the safety of the dam.

alterations to the surface of the drainage basin such as changed agricultural practices, timber clearing, rail (5) Drainage System Instrumentation. The road or highway construction, or real estate develop existing records of measurements of the drainage sys ments that might adversely affect the runoff charac tem flow should be examined to confirm the normal teristics. Upstream projects that could have an impact relationship between pool elevations and discharge on the safety of the dam should be identified. quantities or to detect any changes that have occurred in this relationship.

e. Cooling Water Channels and Canals and Intake (6) Seismic Instrumentation. The existing rec and Discharge Structures ords of seismic instrumentation should be examined

(1) Channels and Canals. The water con to determine the seismic activity in the area and the veyance channels and canals should be examined for response of the structures to recent earthquakes.

channel bank erosion, bed aggradation or degradation and siltation, undesirable vegetation, or any unusual g. Operation and Maintenance Features or inadequate operational behavior.

(1) Reservoir Regulation Pla

n. The actual prac

(2) Intake and Discharge Structures. The struc tices in regulating the reservoir and discharges under tures and all features should be examined for any normal and emergency conditions should be conditions that may impose operational constraints on examined to determine if they comply with the de the cooling facilities such as silt or debris accumula signed reservoir regulation plan.

tion at the water intake or discharge.

(2) Maintenance. The maintenance of the operating facilities and features that pertain to the f. Safety and Performance Instrumentation safety of the dam should be examined to determine Instruments that have been installed to measure the adequacy and quality of the maintenance proce behavior of the structures should be examined and dures followed in maintaining the dam and facilities tested for proper functioning. The available records in safe operating condition.

and readings of installed instruments should be re viewed to detect any unusual performance or distress h. Postconstruction Changes of the structure. The adequacy of the installed in Data should be collected on changes that have strumentation to measure the performance and safety occurred since project construction that might influ of the dam should be determined. ence the safety of the project.

(1) Headwater and Tailwater Gages. The exist ing records of the headwater and tailwater gage

'measurements should be examined to determine the

3. Technical Evaluation relationship between these and other instrumentation measurements such as streamflow, uplift pressures, When findings of the engineering data review and alignment, and drainage system discharge with the onsite inspection indicate that significant changes upper- and lower-water surface elevations. have occurred, an evaluation of the existing condi

(2) Horizontal and Vertical Alignment In tions of the water-control structures should be made.

strumentation (Concrete Structures). The existing The evaluation should include the assessment of the records of alignment and elevation surveys and hydraulic and hydrologic capacities and the structural measurements from inclinometers, inverted plumb stability, based on the changes or affected bobs, gage points across cracks and joints, or other parameters.

1.127-6

a. Hydraulic and Hydrologic Design Capacities significant earthquakes, hurricanes, tornadoes, in These should be evaluated in accordance with tense local rainfalls, or other unusual events.

applicable portions of Regulatory Guides 1.59, "De sign Basis Floods for Nuclear Power Plants;" 1.102,

5. Inspection Report

"Flood Protection for Nuclear Power Plants;" and

1.27, "Ultimate Heat Sink for Nuclear Power A technical report should be prepared to present Plants." All constraints on water control such as the results of each general inspection. These docu blocked entrances, restrictions on operation of spill ments should be kept at the project site for reference way and outlet works, inadequate energy dissipators, purposes, should be available for inspection by regu restrictive channel conditions and significant reduc latory authorities, and should be retired only on ter tion in reservoir capacity by sedimentation and other mination of the project. Any abnormal hazardous factors should be considered in the evaluation. conditions observed during the inspection should be reported immediately to the NRC staff in accordance with the Commission's regulations, as summarized in b. Stability Assessments Regulatory Guide 1.16, "Reporting of Operating These should use in situ properties of the struc Information-Appendix A Technical Specifica tures, as well as foundation and pertinent geologic tions.'"

information, to determine the existence of changes to or continuation of conditions that are hazardous, or The content of the report should consist of the that with time might develop into safety hazards, and following:

to formulate recommendations pertaining to the need a. Initial Report. In addition to a general descrip for additional investigations, analyses, or remedial tion of water-control structures, major elements of measures. References 14 and 15 provide generally the report should include:

acceptable methods for the analyses of structural sta bility. (1) Results of the visual inspection of each proj ect feature, including photographs, where appro

4. Frequency of Inspections priate.

The inspection intervals suggested below are for (2) Results of the instrumentation observations.

general guidance in developing projected inspection (3) Evaluation of operational adequacy of the schedules. These intervals in no way preclude more reservoir regulation plan and maintenance of the dam frequent inspections if deemed necessary or less fre and operating facilities, including the warning quent inspections (not to exceed each 5 years) for system.

those structures where conditions or structural integ

(4) Technical assessment of the causes of dis rity warrant such relaxation.

tress or abnormal conditions and evaluation of the a. Initial Inspection. The first general onsite in behavior, movement, deformation, or loading of the spection should be carried out immediately after top structure.

ping out for new earth and rockfill dams and prior to (5) Conclusions and recommendations for addi impoundment of reservoir water for new concrete tional investigations, remedial measures, or future in structures. For existing facilties that are now in oper spections, where appropriate.

ation, onsite inspection should be carried out as soon as practicable if no inspection comparable to that de b. Subsequent Reports. These reports should in scribed in this guide has been performed. clude information, as described in paragraphs 5.a(l)

through 5.a(5) above, relative to changes or continua b. Subsequent Inspections. The second inspection tion of abnormality in conditions noted since the pre of earth and rockfill dams should be performed at a vious inspection. Any extreme events that have oc reasonable stage of reservoir filling but in no case curred since the last inspection, such as floods, seis later than at the attainment of normal operating pool mic events, etc., should also be included.

level. The second inspection of concrete structures should be performed when the reservoir water attains The inspection should be conducted under the di the normal operating pool level but in no case later rection of qualified engineers experienced in the in than 1 year after initial impoundment has begun. vestigation, design, construction, and operation of Subsequent inspections should be made at 1-year these types of facilities. The field inspection team intervals for the next 4 years, at 2-year intervals for should include engineers, engineering geologists, or the following 4 years, and then may be extended to other specialists able to recognize and assess signs of each 5 years if the results of the previous inspections possible distress (e.g., structural joint movement, warrant this extension. piezometric fluctuations, seepage variations, settle ment and horizontal misalignments, slope movement, c. Special Inspections. Special inspections should cracking of concrete, erosion, and corrosion of be performed immediately after the dam has passed equipment and conduits) and able to recommend ap unusually large floods and after the occurrence of propriate mitigating measures.

1. 127-7

D. IMPLEMENTATION

method for complying with specified portions of the The purpose of this section is to provide informa Commission's regulations, the method described tion to applicants and licensees regarding the NRC herein is being and will continue to be used in staff's plans for using this regulatory guide. evaluating inservice inspection programs of water control structures until this guide is revised as a result This guide reflects current NRC staff practice. of suggestions from the public or additional staff Therefore, except in those cases in which the appli review.

cant or licensee proposes an acceptable alternative

1.127-8

REFERENCES

1. E. Gruner, "Classification of Risk," Proceedings Foundation Engineering Division, ASCE, Vol. 93, of International Congress on Large Dams, Madrid, No. SM4, July 1967, pp. 107-133.

1973, Vol, 1, pp. 55-68. 8. C. Jaeger, "The Vaiont Rock Slide," Water

2. R. R. W. Beene, "Waco Dam Slide," Journal of Power, Vol. 17, March 1965, p. 110.

Soil Mechanics and Foundation Engineering Divi 9. "Instrumentation of Earth and Rock-Fill Dams,"

sion, American Society of Civil Engineers (ASCE), Engineer Manual 1110-2-1908, Corps of Engineers, Vol. 93, No. SM4, July 1967, pp. 35-44. Dept. of the Army, Dec. 1971.

3. S. G. Wright and J. M. Duncan, "Analyses of 10. S. D. Wilson, "Investigation of Embankment Waco Dam Slide," Journal of Soil Mechanics and Performance," Journal of Soil Mechanics and Foundation Engineering Division, ASCE, Vol. 98, Foundation Division, ASCE, July 1967.

No. SM9, Sept. 1972, pp. 869-877.

11. A. 0. Babb and T. W. Mermel, "Catalog of

4. C. A. Fetzer, "Electro-Osmotic Stabilization of Dam Disasters, Failures, and Accidents," Bureau of West Branch Dam," Journal of Soil Mechanics and Reclamation, U.S. Dept. of Interior, 1968.

Foundation Engineering Division, ASCE, Vol. 93, 12. R. G. Chassie and R. D. Goughnour, "State In No. SM4, July 1967, pp.85-106. tensifying Efforts to Reduce Highway Landslides,"

5. K. B. Keener, "Uplift Pressures in Concrete Civil Engineering, April 1976, pp. 65-66.

Dams," Trans. American Soc. Civ: Engrs., 1951, p. 13. "Guide for Making a Condition Survey of Con

1128. crete in Service," ACI JournalProceeding, Vol. 65,

6. R. B. Jansen, R. W. Carlson, and E. L. Wilson, No. 11, November 1968.

"Diagnosis and Treatment of Dams," Proceedings 14. "Design of Small Dams," Bureau of Reclama of International Congress on Large Dams, Madrid, tion, U.S. Dept. of the Interior, 1973.

1973, Vol. IV, pp. 975-991. 15. "Stability of Earth and Rock-Fill Dams," En

7. L. A. Wolfskill and T. W. Lambe, "Slide in the gineer Manual 1110-2-1902, Corps of Engineers, Siburua Dam," Journal of Soil Mechanics and Dept. of the Army, April 1970.

BIBLIOGRAPHY

"Recommended Guidelines for Safety Inspection of National Dam Safety Act, Public Law 92-367, 86 Dams," Federal Register, Vol. 39, No. 168, Aug. Stat. 506 and 507, Aug. 8, 1972.

1974, pp. 31334-31346.

"Periodic Inspection and Continuing Evaluation of "Inspection of Project Works with Respect to Safety Completed Civil Works Structures," EM 1110-2-100, of Structures," Federal Power Commission Order Corps of Engineers, Dept. of the Army, 1973. 315, December 1965.

"Model Law for State Supervision of Safety of Dams and Reservoirs," U.S. Committee on Large Dams, "Guidance for Planning of Inspection Programs for

1969. Dams," USAEC Technical Guide I.H. I, Nov. 1971.

"Statutes and Regulations Pertaining to Supervision of Dams and Reservoirs," Dept. of Water Resources, "Inspection, Maintenance, and Rehabilitation of Old State of California, 1974. Dams," ASCE, 1974.

1.127-9