ML20125A741
| ML20125A741 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/27/1979 |
| From: | NRC ATOMIC SAFETY & LICENSING APPEAL PANEL (ASLAP) |
| To: | |
| Shared Package | |
| ML20125A738 | List: |
| References | |
| NUDOCS 7908160531 | |
| Download: ML20125A741 (68) | |
Text
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.J UNITED STATES OF AMERICA NUCLEAR REGULATORY C0:@lISSION BEFORE Tile ATOMIC SAFETY AND LICENSING APPEAL BOARD
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-In the !btter of
)
VIRGINIA ELECTRIC AND POWER COMPANY
)
Docket Nos. 50-338 OL
)
50-339 OL (North Anna Nuclear Power Station,
)
Units 1 and 2)
)
fiRC STAFF TESTIM 0t!Y REGARDIrlG PUMPHOUSE SETTLEt'EtiT By L. Heller, R. Kiessel, J. Lenahan, J. tiemiel, and A. Oromerick APRIL 27, 1979 Detd
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TABLE OF CONTENTS Page A.
Background and Introduction................
1 8.
. Responses to Specific Appeal Board Concerns........
7 1.
Relationship to Public Safety 8
2.
Settl ement Hi s to ry..................
11 3.
Soil Mechanics....................
16 4.
Dewatering......................
20 5.
Mo n i t o ri n g......................
32 6.
Stress Analysis 35 7.
Other Concerns.................... 43 8.
Response to Mrs. Allen's Concerns 49 C.
Attachments
r-4 O.
It0RTH ANNA 1 & 2 PUMPHOUSE SETTLEMENT A.
Background and Introduction The service water system for North Anna Units 1 and 2 is designed to provide cooling water to the safety-related plant systems for nonnal operating conditions, anticipated operational occurrences, and accident conditions.
Service water flow is provided to the charging pump coolers, control room air conditioners, instrument air compressors, and pipe penetration cooling coils for any of the above three conditions.
During nomal operation and cooldown, service water flow is also provided to the component cooling heat exchangers.
In the event of a loss-of-coolant accident, ser/ ice water flow will additionally be provided to the recirculation spray heat exchangers for cooling containment spray water during recircula-tion.
The service water system provides seismic Category I backup water supply for the spent fuel pit makeup and the auxiliary feedwater system, and backup cooling flow for the spent fuel pit coolers and the recirculation air cooling coils.
The service water system is shared by both Units 1 and 2.
It consists of two full capacity redundant trains, each of which supplies water to both units.
The normal service water is supplied from the service water reservoir by means of four service water pumps, of which two are required during all operational modes,
e.
- D while the other two pumps may be used for fast cooldown.
As a backup, if the service water pumps are not available, service water can also be supplied from Lake Anna by means of two auxiliary service water pumps, both of nhich would be required during emergenci es.
In summary, the service water pump requirements during power operation or under accident conditions can be met by either two service water pumps or two auxiliary service water pumps, or one of each.
The cold shutdown cooling requirements can be met by one service water pump or one auxiliary service water pump. All service water pumps are located in seismic Category I structures and are protected from tornado missiles as well as internal missiles.
The pumps are powered by redundant emergency electrical buses.
The entire system is designed to seismic Category I requirements.
Sufficient redundancy is provided to meet the single failure cri terion.
The following is a discussion of foundation material at the site.
Lake Anna has oeen created by the construction of an earth dam on the North Anna River five miles southeast of the site.
The North Anna River watershed has a drainage area of about 343 square miles.
The dam crest is 265 feet above mean sea level, plant grade is 271 feet above mean sea level, and the normal lake is 250 feet above t
b..
> mean sea level.
Lake Anna will normally be used to supply circu-lating water for plant operation and during shutdown.
The soil and foundation conditions at the site include residual saprolite soil composed predominantly of silty fine sand, severely weathered rock that is soft and friable, moderately weathered rock having more than 50 percent intact rock in core borings, and slightly weathered to fresh rock.
The North Anna site is underlain by metamorphic rocks, mainly medium to high grade gneisses and schists, and in the vicinity of the containment structures, the surficial weathered material was removed so that structures could be founded on sound, fresh rock.
Other important structures are founded on slightly weathered to moderately weathered rock, with the exception of the service water reservoir and dike, which are founded on saprolite.
Properties of the foundation material, as given in the Final Safety l
Analysis Report for Units 1 and 2 of the facility, indicate that the rock has a density of 165 pounds per cubic foot and a shear wave propagation velocity of 5000 to 6000 feet per second.
The shear wave propagation velocity of residual soil is 800 to 350 feet per second and for saprolites the velocity is 950 feet per second.
The dry density of saprolites (severely weathered rock and residual
^
soil) varies from 98 to 135 pounds per cubic foot with porosity m
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e a
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values ranging from 21 to 40 percent.
The average saprolite porosity value is 30 percent. The permeability of the foundation saprolite is 1 x 10-6 centimeters per second and the permeability of the compacted dike core and two-foot-thick pond liner is 1 x 10-0 centimeters per second, as reported in Table 3.8.4-1 of the Final Safety Analysis Report (FSAR). As stated in the FSAR, backffll under tanks and other structures is select granular material placed to a density of not less than 95 percent of Modified Proctor Compac-tion, in accordance with Anerican Society of Testing and ifaterials, Specification ASTM 0-1556.
tiore detailed investigations described in the licensee's latest reports on geotechnical investigations and interpretation reveal that the dry density of the sampled saprolites underlying the spray pond dikes and pump house varies from about 66 to 106 pounds per cubic foot and that the permeability of the saprolite is 2 x 10-4 centimetars per second. The pond liner permeability is 2 x 10-7 centimeters per second.
Additional laboratory tests on undisturbed saprolite were conducted to estimate its compressibility under foundation and dike loadings.
A comparison of the properties of the saprolite as reported in the FSAR and as determined by a later detailed investigation in the vicinity of the dikes and pumphouse, reveals that the capability of t
i
J
. the saprolites under these facilities is less than was originally expected; the dry densities are considerably less and the permea-bility is considerably greater.
Because of these differences in saprolite properties, the foundation perfonnance of structures and facilities supported by these saprolites might be expected to differ from that anticipated during their design.
The dikes used to impound the service water reservoir are a few to forty feet high and some 3000 feet long, with a crest elevation at about 320 feet above mean sea level.
Dikes are composed of com-pacted earth fill, with an upstream slope of one vertical on three horizontal, arid a downstream rock fill shell with a slope of one vertical on two horizontal.
A sand layer serves as a filter to separate the earth fill from the rock fill.
The dikes are supported on residual soil.
The service water pumphouse for Units 1 and 2 is located within the dike that impounds the spray pond reservoir.
It is founded on a 64-foot by 61-foot mat on residual soil, at an elevation of 297 feet above mean sea level. The foundation loading is 3,050 pounds per square foot and the allowable bearing value based upon labora-tory tests is 4,200 pounds per square foot.
The main reservoir screenwell on Lake Anna is founded on a 64-foot by 187-foot mat on residual soil, at an elevation of 218 feet above mean sea level.
t 9
. The foundation loading is 3,330 pounds per square foot and the allowable bearing value based on laboratory tests is 8,000 pounds per square foot.
The compacted earthfill main dam impounding Lake Anna has an up-stream slope of one vertical on 2.75 horizontal and a downstream slope of one vertical on 2.5 horizontal. At its maximum section, it is about 90 feet high with a crest elevation of 265 feet above mean sea level.
Drainage features include a central chimney drain, a blanket drain, and relief wells along the ' downstream toe of the dam.
A gated concrete spillway, which is founded on rock, occupies the center portion of the dam.
Foundations for the embankment sections of the main dam consist of residual soils and saprolites which were stripped of surficial vegetation.
The properties of these materials are expected to be similar to those beneath the service water pond, dikes, and pump house.
The necessary reliability of a source of service water to safely shut down the plant in the event of the design basis earthquake is based on the existence of the service water reservoir and Lake Anna.. We believe that the dikes for the service water reservoir and North Anna dam together have an adequate degree of stability, and resulting reliability, under the seismic effects of the postulated safe shutdown earthquake.
Our review of 'lEPCO's infonna-tion on the main dam on Lake Anna, and its foundations, indicates t
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.that this dam has considerable seismic resistance and could survive the effects of the safe shutdown earthquake.
We thus conclude that the foundations and earthworks features of these two service water sources combined have adequate reliability, under seismic conditions.
1 In April 1975, VEPC0 informed the NRC Staff that the average settle-ment of service water pumphouse for North Anna Units 1 and 2 exceeded that predicted in the PSAR.
An inspection of the situation at the site indicated that the PSAR predicted settlement had been exceeded since December 1972.
The matter of pumphouse settlement, and its safety significance, has been under continuing review and evaluation by the NRC Staff since April 1975.
This evaluation has led the Staff to conclude that operation of the facility was acceptable provided that the settlement was monitored so that any necessary corrective action could be taken in time.
B.
Responses to Specific Appeal Board Concerns The following parts of this testimony are in response to the specific requests for testimony contained in ALAB-529 regarding pumphouse settlements. As suggested by the Appeal Board, the Staff and VEPC0 divided up the responsibility for responding to the areas of concern contained in ALAB-529.
Under this agreement, the Staff has principal responsibility for providing testimony regarding subject numbers 4 (dewataring) and 6(a)-(c) (stress analysis).
As to the remaining i
m.
f a
8 matters, VEPC0 has principal responsibility.
VEPC0 has provided draft testimony to the Staff on all questions raised by the Appeal Boa rd.
The Staff has reviewed this draft testimony, and in addition to its own testimony on questions where it has principal responsi-bility, has provided comments on the VEPC0 draf t testimony, and where appropriate, additional independent testimony.
1.
Relationshio to Public Safety ALAB Ouestion: The Appeal Board asks for information that furnishes a perspective of the potential seriousness of the pumphouse settlement problem from a safety standpoint.
It asks what would happen if the subsidence of the land were to lead to a failure of the service water system.
It asks for (a) the upper limits of functional requirements and system capability of the service water system (e.g., the pump and pipe flow requirements and capacity) both during normal opera-tion and under accident conditions; (b) which service water systems or components could fail as a result of further settle-ments; (c) where and how might they fail and what leak rates might be expected; (d) how such failures would be detected and what actions would be taken; and (e) how failure of the service water system affects other plant safety systems under normal operation and accident conditions.
_g.
Response
Section 8.1 of ALAB-529 raised a number of questions concerning the continued settlement of the service water pumphouse (SWPH) and its relationship to public safety.
Those were addressed by VEPC0 in Section III of his direct testimony.
Based on a review of this and other information available to the Staff, we made the following observations :
a.
Information available from the expansion joint manufacturer indicates that the joints were designed for a 3-inch (0.25 foot) lateral displacement, b.
Because of the conservatisms inherent in the design of all piping system components, it is reasonable to expect that the expansion joints can withstand lateral displacements in excess of the design value without failure.
c.
The slow manner of the settlement, coupled with the proposed technical specification reporting requirement at 75 percent of the design value, provides assurance of ample time to bring the plant to a safe condition before the design value of an expansion joint is reached.
d.
Because of the ductile nature of the material used in the bellows of the expansion joints, it is reasonable to
expect that, should failure occur, it would be in the form of cracks
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as opposed to a complete severance.
e.
The licensee has perionne~d a failue e analysis for the service water system piping expansion joints.
It is our understanding that the analysis is based on the service water pumphouse having reached its Technical Specification limit for setticmant and, therefore, the plant is in the cold shutdown moda.
Continued settlement is assumed to occur resulting in failure of the expansion joints. The licensee submitted evaluations for the follouing events:
(1)
Ccmplete failure of one expansion joint in a return header.
(2)
Ccaplete failure of one expansion joint in a supply header.
(3)
Simultaneous failure of all four expansion joints.
Since the service water system cooling water has performed its design function prior to being returned to the se,rvice water reservoir in
~
the return header, a failure of the expansion joint in the return header would only result in a reduction of the level of the water in.
the reservoir.
There is an ample supply of water in the reservoir to allcw for detection of the failure, and realignment of the system to use the auxiliary service water pumps at Lake Anna before the service water system function would be affected. 11e, therefore, agree with the licensee that plant safety is assured by use of the auxiliary service water pumps.
The complete fai' lure of one expansion joint in a service e
11
- tater supply header would result in isolation of the a'ffected hedder
- and the redundant supply header would be placed in service. We again agree with the licensee that plant safety is assured as the redundant train of service water is available.
If the expansion joints in the four service water lines were to fail, the plant would again have to resort to using the auxiliary service water pumps at Lake Anna, circu-lating cooling water through the system and returning the cooling water back to Lake Anna. He agree with the licensee that the plant safety is assured by the auxiliary service water pumps even after postulating this worst' case decurrence, and, therefore, the health and safety of the public will not be affected.
Based on the above, the Staff concludes that the health and safety of the public is protected through a multilayer defense in depth.
2.
Settlement History ALAB Ouestion:
The Appeal Board asks for bio separate charts, one for the pumphouse and one for other relevant points (e.g., exposed pipe
' ends and any other monitoring points on the pipes) each showing the amount of settlement that has taken place with the passage of time.
~
The span of time involved should be labeled not only by date but also in terms of the construction activities that were taking place at various e
. points (including, especially, such foundation-related activi-ties as excavation and backfilling, building of the pumphouse, laying the service water lines between pumphouse and reactor buildings, dewatering for reactor or other major building construction, building of the cooling pond and dikes, and dewatering of the ground under the pumphouse and service water lines.)
'b
Response
[
The licensee informed IE Region II, by telephone on April 16, 1975, that' the average settlement of the SWPH had exceeded the values predicted in the PSAR.
An inspection of the SWPH settlement was perfomed ori April 29, 1975.
Based on the results of this inspec-tion, it became apparent to IE Region II management that resolution of this problem would require extensive additional testing and design analysis.
Because of this, the lead responsibility for resolution of the SWPH settlement problem was transferred to NRR on May 13, 1975.
IE's role after May 13, 1975 was to provide to NRR the. information obtained during the various inspections conducted during construction of the plant pertinent to the SWPH settlement, and to provide' inspection and enforcement for any additional requirements defined by NRR actions.
e
After May 13, 1975, IE Region II received copies of correspondence between the licensee and NRR, but did not participate in technical evaluation of the SWPH settlement.
d summary of the inspections performed by IE Region II pertaining to the SWPH settlement and horizontal drain installation, related to this testimony, is attached as Appendix A.
IE Region II did not make any independent settlement measurements.
All settlement measurements (surveys) were made by the licensee's contractors.
The licensee notified IE Region II on April 28, 1978 that the SWPH average settlement exceeded the value required by the Technical Specifications for reporting, i.e., 75 percent of the maximum allowable value of 0.15 feet.
IE Region II transferred the lead responsibility for evaluation of the licensee's special report required by the Technical Specifications to NRR on May 15, 1978.
The licensee submitted the special report to NRC on May 31, 1978.
In response to allegations that the licensee had knowledge of SWPH settlement in excess of the Technical Specification limits in August 1977 but withheld the information from NRC for seven months until April 28, 1978, IE Region II conducted a special inspection on December 6-8, 1978 and a special inspection and inquiry on March 5-15, 1979. The results of these inspections and the inquiry are contained in IE Report Number 50-338/78-44 (December 6-8, 1978
. inspection; previously sent to Appeal Board) and IE Report Number 50-338/79-13 (March 5-15,1979, inspection and inquiry).
Al though the inspection reports relate to enforcement matters, which are not within the scope of the issues raised by the Appeal Board, they contain information regarding settlement of the service water pumphouse. Accordingly, these reports are attached to this testi-many as Appendices B and C, respectively.
The allegations were not subs tantiated.
IE Region II has reviewed Part V, entitled, " Settlement History",
of the April 27, 1979 testimony prepared by Virginia Electric and Power Company.
This review was limited to verification of the accuracy of the time versus settlement data stated in Part V and Figures 7A through 7G and Figures 25A and 258.
The data presented appears to be accurate except for the following:
a.
There are several minor errors in plotting of the magnitude of average SWPH settlement on Figures 7A through 7G. These errors are on the order of.002 to.004 feet which results in the data plotted on the figures indicating slightly less average settlement than has actually occurred.
b.
The scale on the ordinate on the right side of Figures 7D, 7F and 7G labeled, " Average Settlement since December 75-Ft", is
, - - ~
. plotted incorrectly.
The numbers shown on the scale should be increased by.005, i.e., 0 should read.005,.02 should read
.025,.04 should read.045, etc.
Figures 1 and 2, attached to this testimony, show a cross section of the service water pumphouse and embankment with an identifica-tion of construction sequence and the time versus settlement of the northwest corner of the service water pumphouse.
VEPCO's testimony, Figures 7A through 7G, provide the time versus average pumphouse settlement along with the labeled construction sequence.
VEPCO's testimony, Figures 25A and 258, provides the time versus settlement of the exposed ends of the service water pipes buried in the dike fill.
The Staff believes that the settlement history of each corner of the pumphouse and piping supports is significant because the differential movement across the expansion joint, the settlement-induced pipe stress, and the tilt of the pumphouse which could affect operability of the pumps, are directly influenced by the settlement of each measurement point.
Recent settlement data for corners of the pumphouse are given in attached Table A.
This table also gives the settlement of marker ASM-5 on top of the service water reservoir dike.
Table B, i
l
attached, gives settlement values for pipe hangers H584 and H569 which are located within the spray pond.
As shown in VEPC0's Figure 6 of the draft testimony, settlement points SM-7, 8, 9 and 10 are located, respectively, at the NE, SE, SW and NW corners of the pumphouse.
Settlement points H569 and H584 are located on pedestal-supported pipe hangers within the spray pond.
These hangers, H584 and H569, support the ends of water supply pipes from the pumphouse to the spray header system for Units 1 and 2, respectively.
Settlement markers SM-15,16,17 and 18 are located on the crown of exposed pipes to the north of the pumphouse, as shown in VEPCO's Figure 6.
3.
Soil Mechanics ALAB Question: The Appeal Board asks for a discussion of the current understanding of the engineering properties of the soils underlying the pumphouse, the reservoir dikes and the service water lines.
It asks precisely what the term " secondary consolidation" is intended to mean, and asks that the discussion include an indication of how the parties' knowledge of this subject has developed in terms of the timing of the studies and investigations that have led to their current understanding.
Response
Engineering Properties of Soils:
Our understanding of the engineering properties of the soils underlying the pumphouse and reservoir dikes has developed from our review of information docketed by VEPC0 in support of their license application, from inspections of compacted soil exposures in trenches adjacent to the pumphouse, from an examination of tested laboratory soil specimens performed by VEPC0's consultants (Ref.14), and from the results of the laboratory soil tests performed by our consultants, the U.S.
Army Corps of Engineers (Ref.15).
Although there has been no detailed program to detennine the specific properties of soil underlying the service water lines, it is reasonable to expect that they are consistent with the soils at other locations on the site.
Our review of docketed information concerning soil properties in the pumphouse and dike area began in the spring of 1975, shortly after unexpected settlement of the pumphouse was brought to our attention. From the docketed information available, we and our consultants were unable to conclude that the dikes and their foundation possessed adequate stability under all loading con-di tions. We asked VEPC0 to confirm their design assumption by performing additional soils exploration and sampling.
As a result of VEPC0's investigation and report of in situ soil conditions, we asked VEPCO to reassess the static and seismic stability of the
o
. dikes.
Based on the results of these investigations, tests, and analysis, we then asked VEPC0 to provide toe drains at the critical dike section and to control groundwater levels under the pumphouse to improve the long-term functional reliability of these safety-related facilities.
Our current understanding of the properties of the soils underlying the pumphouse and dike may be summarized as follows.
The dominant overburden soils are saprolites.
These are residual soils which consist of fine-grained material near the ground surface and grade to coarse-grained material with depth.
The residual soils are underlain by weathered and unweathered rock.
Soil depths vary, depending on the weathering processes which produced the soil from the parent rock, a-granite gneiss.
Engineering properties of the soils are quite variable, depending on the degree of weathering, orientation of relic jointing with respect to applied stresses and, to a lesser degree, the mineralogy of the soil constituents.
Since 1975, VEPC0 has performed a number of investigations to I
establish the occurrence and engineering properties of the saprolitic foundation soils in the vicinity of the reservoir dikes l
and service water pumphouse.
These investigations include ccm-pressibility, mineralogy, shear strength, and resistence to cyclic loads, such as those induced by earthquakes.
The results of these
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]
investigations are described on pages 3 and 4 of this testimony (see also Ref.14).
In 1976, the Corps of Engineers was asked by the Staff to independently assess the cyclic resistence of these-saprolitic soils because little infomation is available on the dynamic behavior of these soils.
The objective of the Corps investigation was to detemine the resistance to earthquake effects of undisturbed samples of saprolites by perfonning cyclic triaxial tests on these materials.
As a result of their tests, the Corps made the following observations:
"a.
...the specimens tended to expand when they were extruded from the tubes, resulting in a lower density; however, the after-consolidation density was close to but generally higher than the in-tube density.
This might suggest that the samples expanded during the sampling process and that the in situ density was greater than the in-tube density, b.
All samples achieved 100 percent pore water pressure response, i.e., initial liquefaction with cyclic stress values similar to those for medium dense sands (e.g., at 10 cycles R = 0.25 to 0.37).
The strain response of the specimens... was also similar to that of sands, c.
...the shape of the nomalized pere water pressure response is concave downward whereas that for most sands tends to be concave upward.
d.
The strength, strain, and pore pressure responses of a specimen consolidated for approximately 2 days...
were virtually identical to those of a specimen consolidated for approximately 30 minutes....
It may be noted that these two " specimens", were adjacent 6-in segments taken from the same boring and sample....
e.
...the results of three tests perfomed by Geotechnical Engineers, Inc., on similar undisturbed samples taken
1.
-from adjacent borings at similar depths, are very similar to the results of specimens tested in this investigation."
(Ref.15, pp.19, 20)
The agreement of the laboratory test results obtained by VEPC0's consultants and the Army Corps of Engineers indicates that the earthquake resistance of the saprolite soils supporting the dikes and pumphouse would be adequate. We would expect these soils to develop excess pore-pressures during the occurrence of the postu-lated safe shutdown earthquake, and that some residual shear strain of the fouadation soils would occur.
We would not expect the soils to strain sufficiently to cause a breach of the service water reservoir dike or the main dam that impounds Lake Anna.
In addition, the tests confirms the ability of the saprolites to support the pumphouse in the event of the postulated safe shutdown earthquake.
4.
Dewatering ALAB Question:
The Appeal Board asks for (a) the bases upon which the staff requirements for groundwater control were developed, and (b) the safety factor normally required, with appropriate supporting references, to protect against seismic induced soil liquefaction.
Response
w
[NEXTPAGEIS23]
9 O
-o Bases for Position We required VEPC0 to bring the probable cause of rapid foundation settlement under control before a license could be granted and that a program to monitor groundwater levels be~ established.
The bases for this requirement are as follows:
a.
Changes in groundwater levels in the saprolite supporting the pumphouse can cause settlement of the pumphouse.
b.
Unexplained rapid settlement of the pumphouse had occurred coincident with unusually heavy rainfall and it is known that l
j l
. seasons of heavy rainfall result in a rise of groundwater levels.
c.
There is a potential for leakage of reservoir water into the saprolite supporting the pumphouse, d.
Future groundwater levels are likely to change beneath the pumphouse due to a number of other factors.
e.
Future changes in grcundwater levels may be greater than that which probably caused the rapid pumphouse settlement between November 1974 and February 1975.
f.
We judged that this safety-related structural foundation, which had settled at the rapid rate of one inch in three months and has the potential for greater rates of settlement, did not meet the safety and performance requirements of an operating nuclear power plant.
g.
Groundwater control seemed the most practical remedial measure for reducing the potential for rapid settlement.
. These bases are discussed sequentially in the following paragraphs:
a.
The first basis of our position is information communicated to the Staff from VEPC0 in a letter dated May 16,1975 (Ref.1).
The second paragraph of page 2 of the attachment to Reference 1 (dated 5/15/75) reads:
4
" Heavy rainfall during the last winter has saturated the dike materials and resulted in additional settle-ment...."
Figure 6 of VEPC0's testimony indicates that an inch of settle-ment occurred from mid-November 1974 to mid-February 1975, a period of 3 months.
The Staff could not agree with VEPCO's interpretation that the cause of the inch of pumphouse settlement was due to dike saturation because 1) the dike material is relatively impervious, and 2) the filters placed over the dike fill should have conducted rainfall away from the dike and pumphouse before it could soak into the fill.
On this basis we believed that another cause of rapid settlement seemed more likely.
b.
The second basis of cur position is information contained in a letter from VEPC0 to the Staff dated February 5,1976 with an attached letter from Ralph Peck to VEPC0 dated January 17,
. 1976 (Ref. 2).
The last paragraph on page 3 of the Peck letter reads:
" Unusually great rainfall occurred in September 1974) as shown also in Figure 2, and appears to have produced further settlement.
A second acceleration of settlement occurred in January 1975, following relatively heavy December and January rains."
The referenced Figure 2 is reproduced as Figure 1 in this testimony. The first paragraph on page 5 of the letter reads:
"A substantial part of the total settlement of the NW corner (about 0.12 feet) that has actually been experienced appears not to be associated with increase in load.
Probably, as suggested by Stone and Webster, it can be attributed to rainfall."
In addition to the above, Dr. Peck, on page 5 of his letter, suggests that one conceivable mechanism causing settlement is the:
" weakening of the bonds between particles of the saprolite due to an increase in moisture content."
He also indicates that the increase in weight of the embank-ment fill by saturation appears to play a minor role in the potential mechanism for settlement.
In addition, he states:
"Beneath the dike, where stresses have been appreciably increased, added moisture might activate further settlement...."
7.
27 -
In the last paragraph on page 5 and the discussion on page 6 i_
of his letter, Dr. Peck indicates that reactivation of settle-ment under unchanged ambient conditions might occur in subsoils that had achieved a state of secondary consolidation after a reduction in applied loading.
In the Staff's view, changes in groundwater levels 'beneath the pumphouse might contribute to the realization of these phenomena and result in additional pumphouse settlement.
Accordingly, we attributed the unexplained rapid settlement that occurred from November 1974 to February 1975 to changes in groundwater levels in the saprolite supporting the pump-house because such changes 1) cause changes in effective stresses in the saprolite and 2) could cause a weakening of the bonds between particles of the saprolite.
c.
The third basis of our position is information obtained from our site visits.
On October 1,- 1975, members of the Staff visited the North Anna plant in company with our geotechnical engineering consultant, the U.S. Army Corps of Engineers. We viewed two inspection trenches cut into the embankment fill adjacent to the east and west walls of the pumphouse foundation.
The trenches were cut to examine the integrity of the contact 1
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, between the wall of the pumphouse and the fill; a crack at this interface could allow water to leak from the reservoir to the downstream filter. A crack at this interface might be expected because of the differential settlement and tilt of the pumphouse with respect to the adjacer.t fill.
Such differential movement was evident from cracked wingwalls attached to the pumphouse.
Our observations did not reveal any evidence of cracks opening along the foundation - fill interface, but we noticed two conditions which caused concern and which influenced our judgments regarding the need for control of groundwater levels under the pumphouse.
First, there was no visible evidence of a three-foot thick clayey liner (select fill) between the dike fill material and the pumphouse, as shown, for example, on NIF 3.8.4-15 of the FSAR, Part B, Volume II and NIF Figure S2.20-1 and S2.20-2 (Ref. 6).
The absence of this liner could allow more water to seep from the reservoir to the saprolite underlying the pumphouse than was expected.
Second, there was visible evidence of the presence of organic matter in the dike fil l.
Eventual decomposition of this organic matter with time could increase the amount of water leaking from the reservoir into the saprolite beneath the pumphouse.
a f: a On July 8,1975 and again on October 1,1975, before the reservoir was filled, we noticed plants growing in the soil on the bottom of the reservoir.
The roots of these plants pene-trate into, and perhaps through, the liner of the reservoir.
Eventual decomposition of these roots could provide paths for leakage of water from the reservoir into the saprolite under-lying the reservoir.
Leakage of water from the reservoir into the saprolite under-lying the service water pond and pumphouse in amounts greater than was anticipated in the design of the facility could lead to a rise in groundwater levels, and to saturation and soaking of portions of the saprolite which might again trigger unantici-pated high rate of pumphouse settlement. Control of groundwater-levels, by means of pumps or drains, appeared necessary to alleviate this cause of rapid pumphouse settlement.
d.
The fourth basis of our position has been mentioned previously under the heading Dewatering - Background. We believe that thi groundwater levels under the service water reservoir and pumphouse are likely to be affected and changed with time by a number of factors that include 1) changes in topography and surface drainage due to construction of the ' plant, 2) changes due to impounding Lake Anna, 3) changes due to construction i
. activities (dewatering, etc.), for Units 3 and 4, and
- 4) seasons of unusually plentiful or sparse rainfall.
Our bases e, f, and g express the Staff's concerns, judgments and logic leading to the requirement for groundwater control beneath the service water pumphouse.
The Staff considered that the potential for recurrence of rapid settlement of the pumphouse, without groundwater level control or some other remedial measure such as replacing or underpinning the founda-tion of the pumphouse, would be present throughout the useful life of the nuclear plant, and that rapid pumphouse settlement could stress safety-related piping beyond design and Code values before being detected or corrected by VEPCO.
Conclusion Because of the potential effect of groundwater level on the behavier of saprolite soils, i.e., that soaking these soils could soften them and that changes in effective stress could consolidate them, the Staff required a system and program to measure and record the groundwater levels in the vicinity of the dikes and pumphouse.
The Staff also required that a system to control the groundwater levels under the settlement-sensitive pumphouse and the critical section of the dike for the service water reservoir; control could be attained by drains.
The Staff believes that drains which limit
. groundwater levels and large fluctuations in groundwater levels can significantly reduce the possibility of rapid settlement of the pumphouse.
The data obtained from the settlement monitoring program, the groundwater monitoring program, and the drain flow measurements will, in time, either confirm or discount the effect of groundwater levels on the behavior of the saprolite.
In any case, the settle-ment monitoring program and the provisions of the Technical Speciff-cations give an advance notice of settlement effects such that a reasonable assurance of the availability of service water for plant shutdowns is attained.
Safety Factor The Staff has not established a generic or site specific safety factor for soil liquifaction. The reason for this is that the Staff does not believe that information about soil conditions and required soil and foundation performance can be reduced to a unique safety factor which represents, in any meaningful way, the functional reliability of these foundations when they are subjected to earth-quake effects.
It should be pointed out that, although applicants present safety factors for soil liquefaction in their license applications, the Staff does not consider these factors as the basis for acceptance. The bases for our acceptance, for safety-related facilities, are the foundation performance requirements,
. the degree of hazard involved, and the level of confidence in the knowledge of site conditions.*
We believe that a sufficient and appropriate investigation of the soils in the vicinity of the service water dikes has been conducted to demonstrate that these dikes and their foundations have a reason-able assurance of functionally surviving the effects of the safe shutdown earthquake assigned to this plant.
We base this judgment mainly on the results of cyclic loading tests performed on the saprolite soils by VEPCO's consultants and by the Staff's consult-ants. The results of the Army Corps' work has been described previously under the heading Soil Mechanics - Rescanse.
Our confi-dence in the data base supporting our judgments has been enhanced by our examination of the VEPC0 contractor's laboratory, and raw test results obtained in this laboratory.
Our confidence in the data base supporting our judgment is also enhanced by the agreement of test results obtained by VEPCO's consultant and by our consultant.
5.
Monitoring ALAB Ouestion:
The Appeal Board asks (a) for a description of the type of instruments and methods by which settlement of Class I structures are monitored, together with an evaluation of the accuracy of such monitoring and (b) for information as A discussion of soil liquefaction along with a number of references is contained in Reference 7.
. to how the movements of buried service water pipes are monitored or estimated.
They also ask whether the "47 degree elbows" in the service lines near the pumpho'use have been monitored and how much these elbows settled before and after dewatering.
Response
With regard to part (a) of the Board's question, IE Region II has reviewed paragraph a of Part VII, entitled, " Monitoring," of the April 27, 1979, testimony prepared by VEPCO.
The settlement moni-toring program and data for the SWPH and other Class I structures were reviewed in detail by IE Region II during special inspections conducted on December 6-8, 1978 and March 5-15, 1979. The results of these inspections, contained in Inspection Report Numbers 50-338/78-44 and 50-338/79-13, are in substantial agreement with the statements contained in paragraph a of Part VII of the licensee's testimony. These inspection reports are attached as appendices to this testimony.
With regard to part (b) of the Board's question, the only part of the service water piping being monitored is the exposed ends of the pipes located north of the service water pumphouse and expansion joints which are within the expansion joint enclosure structure.
e
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. The buried service water piping has not been monitored.
His-torically, such pipes are not monitored since access to them is not readily possible.
Our analysis, described'in Section 6, assumed that the 47 degree elbow has not settled.
This is a conservative assumption as settlement of the elbow results in a decrease in the differential settlement between the elbow and markers 15, 16, 17 and 18.
Thus, any settlement of the elbows would result in an increase in the allowable settlement of markers 15,16,17 and 18.
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. 6.
Stress Analysis ALAB Ouestion: The Appeal Board asked for a discussion of the topic of stress analysis, and to indicate the impact of varying amounts of settlement. They asked for a description of_ the types of loads assumed and methodology used in analyz-ing stress limits for service water piping and whether stresses due to the apparently greater settlement of pipes relative to that of the pumphouse are included in the analysis.
They asked the staff to (a) provide a full justification for selecting the differential motion limit of 0.22 feet between corners of the north side of the pumphouse and the expansion joint, and explain how this satisfies the staff's concerns on stress limits in the flexible couplings, (b) explain how limiting the absolute elevation of the exposed ends of the expansion joints to 0.22 feet (measured from August 3,1978) satisfies the staff's concerns on stress limits in the buried pipes, and (c) set forth the basis for choosing 75% of the limit as the level which triggers the reporting requirement for all estabitshed limits.
Resoonse:
The Staff reviewed VEPCO's proposed testimony regarding the assumed loads and methodology used in analyzing stress limits for service water piping.
The Staff does not disagree with these aspects of VEPCO's testimony.
The objectives of the staff's evaluation of allowable settlement limits were to assure during the period of plant operation, that the stress levels in the service water piping did not exceed the allowable values defined by the ASME Boiler and Pressure Vessel Code,Section III, and that the movement of the expansion joints in the service water if nes did e
~
a
.. not exceed the design values of the expansion joints. The following paragraphs address the Appeal Board's specific questions and contain the staff's explanation of the basis for satisfying the stated objectives.
a)
Justification of Differential Motion Limit In the following discussion, the staff uses the term differential motion to mean differential motion between either corner of the north side of i
the pumphouse and the exposed ends of the pipes that are buried in the gravel filter portion of the dike fill.
The limiting value for differential settlement after July 1977 (0.22 ft.) was developed in the manner described in this and the following paragraphs. Although VEPC0 has indicated other dates, we have conser-vatively assumed that the flexible joints were installed in December 1975, thereby setting that date as the initial reference point for settlement of the north wall of the pumphouse.
The July 1977 date was chosen as the first measurement of the pipes because this is the date that marks SM-15,16,17, and 18 were established on the pipes; no settlement readings were made on these pipe ends prior to July 1977.
Accordingly, no computations of the differential settlement between SM-7 or 10 and SM-15 through 18, based on direct measurements, could be made for the period December 1975 to July 1977.
The approximate settlement of SM-15 through 18 can be established, however, by assuming that the top of the dike near these markers settled the same amount as the exposed ends of the pipes embedded in the dike. The settlement values for the top of the dike near these pipes (ASM-5) and for SM-7 and SM-10 are given in Table A.
-O e.
During the period December 1975 to July 1977, the top of the dike settled 0.079 feet (the locations of SM-15 through 18 were assumed to have settled the same amount), SM-7 settled 0.046 feet and SM-10 settled 0.089 feet. Thus, the estimated differential settlement across the joint that occurred during this time period was between 0.033 feet (0.79-0.046) and -0.010 feet (0.079-0.089). A value of 0.03 feet was conservatively chosen to represent the differential settlement of SM-15, 16,17 ard 18 with respect to the north side of pumphouse during this periot of time.
Information from the flexible coupling manufacturer indicates that the l
coupling is designed for a lateral movement of one end with respect to 3,.
the other end of 0.25 feet (neglecting twist about the axis of the coupling and rotation of the ends of the coupling in the axial plane).
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(Ref.11, p.4).
The limiting differential settlement between markers SM-7 or SM-10 and any marker SM-15,16,17 and 18', after July 1977 is the joint design
^
limiting differential. settlement (0.25 feet) when the flexible joint was installed (December 1975) less the differential settlement estimated to 4
have. occurred (0.03. feet) during the period December 1975 to July 1977.
This difference (0.25-0.03) is 0.22 feet.
In summary, then, because the expansion joints were designed to accommodate 0.25 ft. of movement withcut exceeding stress and fatigue limits in the l
Joints, and because we conservatively estimate 0.03 feet of differential settlement has occurred since the joints were installed, the staff's c
i
. concerns about stress limits in the flexible coupling are satisfied with the differential limit of 0.22 ft.
b)
Stress in Buried pices The staff assumes that the Board's question refers to the absolute settle-ment of the exposed ends of the expansion joint rather than their absolute elevation. On August 2,1978, VEPC0 informed the staff that it had concluded that 0.33 feet of additional settlement since December of 1975 would not overstress the buried pipes (Ref.10, p.10). As a rough check of this conclusion, the staff made the conservative simplifying assumption that the pipes could be modeled as being rigidly anchored in the soil at a point 60 feet from the exposed ends and that the deflected shape of the pipes due to dike settlement is the same as a cantilever beam with a concentrated load at its end.
For such a model, the maximum moment and deflection are (Ref.18):
M = P1 3
y = P1 /3EI where M = maximum bending moment, lb-in P = concentrated load, lb 1
= length of beam, in y = maximum deflection, in E = modulus of elasticity (Young's modulus), psi I = moment of inertia, in#
The maximum bending stress is defined by the following (Ref.18, p.513):
c = Mc/I where c = maximum bending stress, psi e = distance from netural axis to extreme fiber (outer surface), in
o
. Combining the above equations yields an expression for the maximum deflection of a cantilever beam, with a point load at the end, as a function of the maximum bending stress at the section with the maximum bending moment:
2 y = cl
/3Ec Although the value of the modulus of elasticity varies with the compo-sition of the material and the temperature, a commonly used value for carbon steel (such as the SA-155 used for the service water piping) at 6
normal temperatures is ;29 x 10 psi.
The distance between the neutral axis and the extreme fiber for 36 inch (3.0 ft.) pipe with a 3/8 inch (0.03 ft.) wall thickness is 18.375 inch.
Using these values and the 60-foot (720 in.) length of the pipe yields:
y = cr/3084 For the SA-155, Grade C5, material used in the service water pipe, Table I-7.1 and ND-3652.3 of Section III of the ASME Code would-permit an allowable stress of 41,100 psi for the effect of any single nonrepeated anchor movement.
Stresses in the pipes due to friction forces of the fill on the pipe were estimated at about 4,000 psi by assuming the pipes were buried 12 feet deep in a fill with a unit weight of 120 pcf and a friction co-efficient (with steel) of 0.6.
Allowing 4,000 psi for friction loads in the pipe leaves a limiting stress of 37,100 psi which equals a maximum deflection of 12.03 inches or 1.00 feet. The pipe stress caused by the friction forces along the deflected pipe were conservatively neglected in this rough check.
. The next step in estimating the limiting additional displacement of the end of the buried pipes was to determine the displacement that had occurred since the pipes were buried in the fill. We conservatively assumed that the pipes were rigidly connected to the pumphouse at the elevation shown in the FSAR (Ref. 8), that this elevation was correct as of August 25, 1972, and that no pumphouse settlement had occurred prior to the time the pipes were connected.
The center line of the horizontal portion of the exposed pipes is at an elevation of 320 ft. - 10 inches (320.83 feet) (Ref. 8). The elevation of the top of the pipes would be 322.36 ft. (320.83 + 1.50 + 0.03) at the time they were attached to the pumphouse. VEPC0 provided the follow-ing elevations for the pipe ends, as measured on August 3,1978:
SM-15:
321.658 ft.
SM-16:
321.661 ft.
SM-17:
321.778 ft.
SM-18:
321.591 ft.
Settlement of pipe SM-18 (the one that apparently settled the most) between the time it was assumed to be buried and attached to the pumphouse and August 3, 1978 was thus 322.36-321.59 = 0.77 ft.
Thus, settlement of the ends of the pipes at markers SM-15 through 18 necessary to reach code allowable stresses was estimated at about one foot and past settlements accounted for 0.77 ft. Therefore, the ends could settle an additional 0.23 ft. (1.00-0.77) without exceeding code allowable stresses in that portion of the service water pipes buried in the dike fill just to the north of the service water pumphouse.
t The above steps led us to recommend that the allowable absolute settle-ment of the ends of these pipes, after August 3,1978 be limited to 0.22 ft. to keep the buried pipe stresses below code allowable values. The staff believes this value of 0.22 ft. is conservative.
New information in VEPCO's Testimony or. Service Water Pump House Settle-ment indicates that the service water lines were embedded in the coarse dike filter on August 27, 1973 (Figure 78).
Therefore, stresses _ induced in the service water pipes due to settlement of the dike would have started on August 27, 1973 rather than, as we had previously understood, aan August 25, 1972. According to information provided by VEPC0 to the Staff in a letter dated September 8,1978 (Table 1 of Reference 3), the northeast corner of the pumphouse had settled 0.15 ft. by August 23, 1973. Assuming that the dike settled as much as the least settlement recorded on the northeast corner of the pumphouse between August 25, 1972 and August 23, 1973, the allowable settlement of these pipes might be increased to 0.37 ft. (0.22 + 0.15) without exceeding code limits for stress in the service water pipes. Accordingly, the staff believes that there is additional basis to believe that the 0.22 ft. limit is conservative.
In summary, then, we have conservatively estimated the stresses in buried pipes induced by the settlement of the service water reservoir dike. We have found that additional settlement of the dike and embedded pipes in the amount of 0.22 ft. after August 3,1978 can be sustained without exceeding Code Allowable stress values. We believe that the technical specification for plant operation, which gives the allowable
, limits of settlement of the exposed ends of these buried pipes, is adequate to satisfy staff concerns regarding stress in these pipes.
c)
- 75 Percent Reporting Requirement The requirement that VEPCO report to the staff when settlement reaches 75% of the limits set in the technical specifications was proposed by
-VEPCO.- It was accepted by the staff because it was judged to provide adequate time for remedial safety-related actions prior to reaching settlement values that would affect safety or plant operations. The staff would probably have accepted reporting values ranging from 60 to 80 percent, because the same objective would have been attained with those limits, d).
Frecuency of Monitorina Settlement of Service Water pumphouse The Technical Specifications for Unit I require that the Category I safety related structures be surveyed every six months to assess settle-ment. ' VEPCO, however, is continuing to monitor the settlement of the Service Water Pumnhouse every month.
The staff concurs with VEPCO's practice. The Unit 1 Technical Specifications for monitoring groundwater elevations near the pumphouse and beneath the service water reservoir dikes call for monitoring every month for the first five years of plant operation.
The staff believes that the frequency of monitoring settle-ment near the pumphouse should be the same as that now prescribed for measuring groundwater levels and drain flow rates. Accordingly, measure-ments on settlement markers SM-7, 8, 9,10,15,16,17,18, H-569, and H-584 should be made at least once every 31 days until Unit I has been
. in operation at least five years.
Based on the past record of rates of pumphouse settlement and the expectation that the drains will reduce the potential for rapid settlement, a one-month interval is often enough to provide adequate warning that settlement limits given in the Technical Specifications are being approached. At the end of the 5-year period, an engineering study will be made by VEPC0 to determine the need for and frequency of continued monitoring of settlement, groundwater and drain flow rates.
7.
Other Concerns In its January 9,1979 submittal to the Appeal Board, the staff identified certain items of concern with respect to service water pumphouse settle-ment effects.
These items are addressed in the following sections.
a)
Differential Movement and Tilt of Pumphouse - Effects on Pipes This item is discussed in Section 6 of this testimony.
b)
Tilt of Pumphouse - Effect on Pumps 1
The second concern, pumphouse tilting effects on the service water i
pumps, is addressed in the response to question P3.6 of the Final Safety l
Analysis Report. VEPC0 has stated that the pumps will be shimmed, as 1
necessary, to correct for any pumphouse tilt so that the pump alignment i
is within the 0.011 inches per foot recommended by the pump manufacturer.
l This corresponds to a total allowable displacement of 0.29 inches for the 26-foot long vertical pump.
The manufacturer has also indicated that a total displacement of 0.5 inches would not adversely affect pump operability.
. In addition, VEPC0 is measuring differential pressure, flow rate and vibration amplitude every 30 days as required by Article IWP-3000 of Section XI of the ASME Code.
These pump performance parameters are to be maintained within the tolerances specified in Table IWP 3100-2 of Section XI, except that for the flow rate parameter, a tolerance of 18 percent is acceptable.
If necessary, corrective action will be taken as required by paragraph IWP-3230 to assure the required pump performance.
Maintaining the pump performance parameters within the specified tolerances provides adequate assurance that the pump will maintain its operability and that any effects of tilt will be accounted for, c)
Stress in Buried Service Water Pipes This matter is also discussed in Section 6 of this testimony.
d)
Leakage of Service Water Throuah Shears With respect to the fourth concern, the Final Safety Analysis Report indicates that the bottom of the service water reservoir was lined with compacted cohesive soil to impede leakage of reservoir water into the underlying saprolite.
The FSAR indicates that the pumphouse foundation is supported by the compacted liner material. As the pumphouse settles with respect to the liner, it punches into the liner material, as evidence by the past relative movement of the pumphouse with respect to the wi ngwall s.
A VEPC0 letter to tne staff dated September 8,1978, includes an analysis of reservoir leakage potential due to bending of the liner, We have concluded that the lack of potential for leakage has not been
L l
l i demonstrated and would be difficult to demonstrate and, therefore, have conservatively postulated that leakage will occur during the plant l
li fetime.
- Leakage of the reservoir liner will contribute to the quantity of water collected by the underdrain system and will change groundwater levels measured by piezometers.
Technical Specification 3/4.7.13, which gives the present groundwater level monitoring program and limiting ground-t water levels in the vicinity of the service water reservoir, is closely related to Technical Specification 3/4.7.12.
Groundwater monitoring as presently required by the Technical Specification is to be conducted l
monthly for the first five years after the issuance of the Unit 1 Operat-ing License. Adequate assurance that leakage will not be undetected and affect safe operation of the plant can be attained by changing Technical Specification 3/4.7.13 to require:
(a) measuring and recording the i
quantity of groundwater flowing from the underdrains on a monthly basis for five years; if flow rates for any month become more than three times the average annual flow rate, an engineering evaluation of the cause of the changed flow rates should be conducted and a report filed with the NRC; (b) monitoring and recording groundwater elevations on a monthly basis for a period of five years; and (c) at the end of the five-year period, requiring an engineering report to be filed by VEPC0 to determine if further measurements of groundwater levels are needed. A required
- As discussed in Section 4 of this testimony, we could not visually confirm the presence of a liner along the sides of the pumphouse (p.29). However, because we have postulated leakage of the liner under the pumphouse, the existence of the liner is not critical.
i
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! revision to Technical Specification 3/4.7.13 covering the above matters is presented in the proposed technical specifications included as an attachment to VEPCO's testimony.
e)
Potential for Cracking of Pumphouse The potential for significant cracking of the reinforced concrete pumphouse structure due to future differential settlement across the structure is likely to be preceded by warping of the pumphouse foundation. Available measurements and visual inspection by the licenseeindicates that very little, if any, warping has occurred to date and that only nominal l
cracking is now evident.
Because of the relatively soft foundation l
provided by the clay liner and underlying saprolite and the stiffness of i
the pumphouse foundation slab, significant differential settlement l
across the structure is unlikely. However, an out-of-plane distortion
[
l of any corner of the pumphouse foundation of about 0.06 feet would I
i indicate the onset of additional cracking in the structure. The potential
{
for crack development can be interpreted by analyzing measurements at l
l settlement points SM-7, 8, 9, and 10. We have concluded that the out-4 l
of-plane distortion of any corner of the pumphouse foundation should not l
exceed 0.06 feet in order to limit the width of cracks. A required revision to Table 3.7-5 of the Technical Specification is presented in the proposed technical specifications attached to VEPCO's testimony.
l The 75 percent Technical Specification reporting criteria would apply to this limit.
k
i
. f)
Effect on Spray Piping Connections l
The effect on spray piping connections at the service water pumphouse from further settlement of the pumphouse has been reviewed with VEPCO's technical personnel and representatives of the Stone & Webster Engineer-ing Corporation.
The staff understands that one end of the four 35-foot long pipes supplying the spray system was rigidly connected to the pumphouse wall with concrete above the reservoir bottom in the spring of 1975.
During June of 1975. the other end of the 24-inch-diameter pipes was supported above the reservoir bottom by a hanger and footing resting on the clay liner of the reservoir. To reach the American Society of Mechanical Engineers Boiler and Pressure Vessel Code allowable stress in these pipes the differential settlement (as calculated by VEPC0 and reviewed by the staff) between the southeast corner of the pumphouse and the hanger would need to be 0.175 feet.
Tables A and B. attached to this testimony, show that the differential settlement between marker SM-8 and either H569 or H584 has been essentially zero during the period of time from early August 1976 to late April 1978.
This evidence suggests that the differential settlement between the ends of the pipes has been negligible since June of 1975. when the ends of the pipes were tied down.
Accordingly, in order to assure that future pipe stresses will not exceed Code allowable values the differential settlement between marker SM-8 at the southeast corner of the pumphouse and markers H-569 and H-l 584 at the pipe support hanger should not become greater than 0.175 feet since the hangers were installed in June 1975.
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. g)
Inservice Testing of the Auxiliary Water pumps Our January 9,1979, submittal to the Board indicated that we had pre-viously granted VEPC0 a 20-month relief from the inservice testing of the auxiliary service water pump for Unit 1.
This relief was based on the fact that: 1) testing would result in untreated (Lake Anna) water being discharged into the service system; 2) four similar pumps (the service water pumps) would be tested monthly;
- 3) VEPC0 committed to perform a study of methods to permit testing; and 4) the pre-operational testing of the pumps was successful.
We concluded our January 9,1979, presentation to the Board by indicat-ing that the staff would require VEPC0 to provide an acceptable method of inservice testing of the auxiliary service water pumps at the end of the 20-month period of relief.
Subsequent to our presentation, VEPC0 sumitted its inservice testing program for Unit 2.
This program, submitted with their letter of Janu-ary 31, 1979, did not request relief for the auxiliary service water pump on Unit 2.
Recent telephone conversations between the Staff and VEPC0 have indicated that they have determined that the chemical content of Lake Anna has changed sufficiently to permit the use of untreated Lake Anna water in the service water system during periods of inservice testing of the auxiliary service water pumps.
It is the staff's under-standing that this infornation will be confirmed in a forthcoming letter from VEPCO.
Thus, monthly inservice testing of the auxiliary service water pumps appears to be now feasible for Unit 1, also.
In addition to
O e
. providing the bases for the change in position, VEPC0 will also propose beginning the inservice testing for Unit I at the same time as it will begin for Unit 2. i.e. when it is licensed. The If censing of Unit 2 is currently scheduled for June 1979 and testing will be monthly thereafter.
Coupling the start of the two inservice testing programs will permit an I
orderly implementation of the procedure and is acceptable to the Staff.
If the issuance of an operating license for Unit 2 is delayed, we will require that monthly inservice testing of the Unit 1 auxiliary service water pumps be initiated during the first refueling of Unit 1.
The staff concludes that this resolves the previously noted concern with respect to the inservice testing of the auxiliary service water pump for both Units I and 2.
8.
Response to Mrs. Allen's Concerns ALAB Recuest:
The Appeal Board asked that the testimony pre-pared by the parties contain sufficient information to address the concerns that the North Anna Environmental Coalition (NAEC or Coalition) has posed in its written communications which the parties believe are legitimately significant and relevant to the pumphouse settlement issue (ALAB-529, Slip op.11, n.10).
These concerns as well as the responses to these concerns are set forth below.
Coalition Ouestinn: The Coalition has questioned the effectiveness of the drain system as a means of protecting the pumphouse.
Staff Response:
Section 4 of this testimony addresses this question in some detail.
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.m t
. Coalition Question: The Coalition asked whether any other nuclear plant had been required to install a comparable system of remedial drainage and if so, where is it located, and what has been its experience to date?
Staff Response:
Some nuclear power plants have proposed ground water con-trol systems for their sites.
For example, a ground water control system was proposed by the application and has been found acceptable for use on the Perry nuclear plant. We are not aware of the required installation of a groundwater control system at any nuclear plant that is comparable to the one proposed for the North Anna Power Station Units 1 and 2, service water pumphouse. Horizontal drains, based on the same principles as the proposed North Anna system, have been used for decades to reclaim swampy land for agricultural uses; clay tile is commonly specified for this purpose.
Coalition Question: The NAEC inquired about the length of time the staff specified as an adequate pre-operational testing period for the drainage system at North Anna.
Staff Resonnse: No pre-operational testing period has been specified for the above system because future environmental conditions over any speci-fled time period are not known.
Piezometers will be read at scheduled intervals and used to measure the effectiveness of the system over the life of the plant.
If the system is, or becomes inadequate, it can be i
replaced or supplemented with negligible risk to the heal *.h and safety of the public.
Pre-operational testing is thus unnecessary.
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. Coalition Question: The NAEC asked what soecific measures will NRC take l# the drainage system fails after the North Anna operating license is granted.
Staff Response:
If the drain system fails (becomes clogged), the NRC will require it to be purged or otherwise cleared so that it will again limit groundwater levels.
If the proposed drains transport fines from the saprolite, they can be abandoned and replaced with a redesigned system.
Coalition Question:
The Coalition asked if it had been experimentally determined yet at North Anna whether controlling groundwater levels will prevent settlement or ciuse settlement beneath the service water pumphouse.
Staff Response:
The explicit answer to the Coalition question is no, because the groundwater control system has not been in service long enough to predict its effect over the life of the plant (say 40 years).
In theory, if the water table is about 274 feet ele /ation when the horizontal drains
. are installed, the drains will lower the water table and cause an incre-ment of pumphouse settlement due to increased effective stresses.
- However, this increment of settlement would be no more than would be experienced by a natural seasonal decrease in water table elevation to an elevation of 274 feet.
In theory, if the water table is at or below 274 feet when the drains are installed the drains would not cause any change in effective stress and no increment of settlement due to the drains would be expected.
The drains should reduce the total settlement of the pumphouse over the l
11fe of the plant because seasonal fluctuation of groundwater levels will l
be reduced.
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Coalition Question: Coalition has asked how North Anna's design can with-stand possible lack of integrity in saprolitic foundation.
Staff Response:
Section 3 of this testimony addresses the Coalition's question in some detail.
As mentioned in Section 3, appropriate engineering tests have been per-formed on the saprolitic soils which exist at the North Anna site.
Labora-tory tests on undisturbed specimens (representative of in-situ foundation I
materials) and on reconstituted specimens (representative of engineered fill material used to construct the dikes and dams) of these saprolites i
show that this material has adequate strength to satisfy the design con-ditions imposed by the plant facilities.
The occurrence and compressibility of the in-situ saprolite and weathered rock beneath the pumphouse make future predictions of settlement and differential settlement of these structures complex and possibly imprecise.
Future settlement, however, will occur slowly and upper bound values of settlement rates and magnitude can be based on past and continuing settle-ment measurements. We believe that a conscientious, complete and diligent i
program of settlement monitoring, interpretation, and plan for remedial action will provide adequate safety from the effects of past and future I
3 settlement of the pumphouse.
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The design of the groundwater control system is compatible with the
{
1 properties of the saprolite such that piping of fines from the saprolite i
should not occur as water drains from it.
If piping of the fines begins I
some time in the future, a large increase in the turbidity and susoended I
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solids content of the effluent from the system would occur. As a pre-caution VEPC0 will monitor the effluent for suspended solids and turbidity.
Monitcring will provide sufficient warning on the onset of any piping so that remedial action can be taken before unsafe conditions can develop.
Coalition Question: The Coalition asked on what experiential or experi-mental basis can predictions be made about the future course of settlement at North Anna.
Staff Response:
The main basis for predicting the future course of settle-ment at the North Anna Power Station, Units 1 and 2, will be the record of past settlements.
Coalition Question:
The Coalition has asked what studies the NRC has done of the possible relationships between microseismic activity, regional faulting (Neuschel's Lineament. Stafford faulting et al), and the weakness of saprolite as a foundation material.
Staff Resoonse: Microseismic activity, and any regional faulting together with other geologic and tectonic factors have been taken into account in determination of the safe shutdown earthquake.
There is no evidence whatsoever to indicate that an earthquake would more likely occur in,
saprolites than other materials.
H,owever, any different behavior of saprolite during an earthquake has been taken into account in the design of the North Anna Power Station Units 1 and 2.
l L_
4 54 -
Coalition Question: The Coalition has asked if the North Anna dam is designed to withstand activity on a nearby fault or activity from the point where Neuschel's Lineament transects the reservoir.
Staff Response: The North Anna plant is designed to a reference acceleration of 0.12g based on an assumed intensity VII (Modified Mercalli). There are no known active faults near the dam that could localize an earthquake there.
The North Anna dam is expected to survive the ground motion effect of a safe shutdown earthquake with a peak acceleration of 0.12g on rock and 0.18g on saprolite. We believe our expectations are reasonable in light of the survival of similar California dams that were affected by the 1971 San Fernando earthquake which had a Richter magnitude rating greater than the magnitude of the SSE at North Anna.
9 Coalition Ouestion: The Coalition asked for our present day judgments on matters pertaining to laboratory tests and seismic design and foundation engineering that transpired in 1969.
They asked whether we considered the 1969 answers to questions were still accurate and, if not, when changes in soil profiles, bearing capacities, etc., were changed and by whom.
Staff Response: We would consider 1969 answers to questions to be accurate
- today, but incomplete.
The 1969 answer did not include a bearing value for the highly weathered saprolite (residual soil) nor did it indicate allowable bearing values based on settlement considerations. On October 6, 1976, we learned that the allowable bearing value used for the design of f
h
O o
. foundations on the highly weathered saprolite was about half of the value usgd for foundations on dense saprolite.
The FSAR for Units 1 and 2 has been amended by VEPC0 to include an allowable bearing value for this foundation material.
Our evaluation of the changed bearing value for the saprolite is stated on page 2-5 of Supplement Number 7 to our Safety Evaluation Report dated August 1977, wherein we condluded that the transient bearing value is acceptable.
In light of the limited information available at the time that the 1969 answer was filed, we still judge that the 1969 answer was a reasonable representation for the situation as known at that time.
A considerable amount of additional information has been developed and docketed by VEpCO during the past few years.
In our judgment, the new information provides a better interpretation of foundation conditions and dike stability than that provided by VEpCO in 1969 in anwer to question 5.
Thus, considering the new information, we would now judge that the margins of stability of the ultimate heat sink reservoir dike and foundation are somewhat less than indicated by the 1969 answer to question 5.
Nonetheless we have con-cluded that, considering the existence of Lake Anna, they possess adequate reif atility under seismic conditions. Our evaluation of the ultimate heat sink reservoir dike and foundation is stated on pages 2-12 and 2-13 of Supplement Number 2 to our Safety Evaluation Report dated August 1976.
l Coalitinn Question:
The Coalition has asked what the increased stresses are in the service water piping and whether these stresses have exceeded j
or are close to exceeding allowable safety limits.
r s
, Staff Response:
Section 6 of this testimony addresses the Coalition's questions and concerns in some detail.
Coalition Question: The Coalition asked whether we agreed with a statement that "no additional settlement has occurred since the installation of the groundwater control system", and with the statement that "the majority of the recent settlement resulted from the installation of the groundwater control systems"?
(
Staff Response:
The Coalition's questions can best be answered by referring to settlement data contained in Reference 11 and in Regerence 2.
These letters indicate that the average pumphouse settlement from December 1975 to October 1976 (10 months), was about 0.025 feet.
From October 1976 to September 1977 (11 months), the period when drains were installed and the reservoir filled three times and emptied twice, the pumphouse settlement increased from about 0.025 to 0.105 feet.
Of the 0.08 feet of additional pumphouse settlement that occurred during this 11 month period, about one third can be attributed to time effects (ordinary expected settlement),
one third due to the influence of drains (causing a drawdown of the water table) and one third due to repeated reservoir fillings (changing loading on soils). More recent settlement amounts are included in VEPCO's testimony and in Appendices B and C of this testimony. The Staff's interpretation of the recent settlement data would not indicate j
that the drains have not been a significant cause of settlement.
l l
. Coalition Question: The Coalition has asked why there is any necessity to double the allowable pumphouse settlement from 1.8 to 3.96 inches.
Staff Response: According to Techn1 cal Specification 3/4.7.12, if the average settlement of the pumphouse exceeds 0.15 feet since December of 1975, the plant would have to be shut down.
The pumphouse settlement is now approaching the specified limits. The Staff has proposed to increase the allowable settlement value for the pumphouse.
The bases for the new limits are set forth in Section 6 of this testimony.
Coalition Ouestion: The Coalition has asked the basis for the staff's validation of settlement predictions.
Staff Resconse: The staff is not attempting to validate predictions of pumphouse settlement as a basis for allowable settlement values.
- Rather, we are examining the consequences of increased pumphouse settlement values on the safety functions of service water system components.
Coalition Question: The Coalf tfon asked how the staff interprets the pattern of settlement reflected in VEPCO's reading of April 25, ffay 10, and May 15.(1978) and asked if June and July readings show a similar trend.
Staff Response:
The staff would avoid an interpretation of the pattern of average settlement from April 25 to May 15,1978 because the time period is very short and because the change in settlement (0.006 feet) is too small to be significant considering the required sensitivity of
. the measuring system.
The pattern of settlement after May 15,1978 is shown in Figure 7 of VEPCO's testimony.
Coalition Ouestion:
The Coalition has asked what remedial actions are being considered beyond those of changing allowable limits.
Staff Response: We will not consider immediate remedial measures until the limits for safe operation of the plant are approached.
If and when that time comes, we view possible remedial actions to include reworking or replacing the expansion joints, addition expansion joints to pipes between the pumphouse and reservoir spray system, and mud jacking the north side of the pumphouse.
Underpinning of the pumphouse foundation is another alternative remedial action.
Coalition Question:
The Coalition has expressed concern that the expansion joints constitute an unreviewed safety question.
Staff Response:
Expansion joints are commonly employed in the piping systems of fossil fuel and petrochemical plants and the technology assoc-f ated with the use of expansion joints is well known.
The use of such joints is familiar to staff reviewers and we have reviewed the expansion joint utilized at North Anna.
Thus, we do not feel that their use at North Anna constitutes an unreviewed safety question.
Coa'lition Question:
The Coalition has asked what caused the pumphouse to settle 0.66 inches in 50 days in late 1974 and early 1975.
t I Staff Response: This question is addressed in Section 4 (pp. 25-27) of our testimony.
i t
I Coalition Ouestion: The Coalition has asked what caused the pumphouse to settle 0.57 inches in 23 days between July 11 and August 2,1977.
I Staff Response:
It appears that the main cause of the settlement was significant lowering of groundwater levels by drain number 4 which was placed below adjacent drains and below the target elevation of 274.0 l
fee t.
i Coalition Ouestion: The Coalition ask whether the increased stresses on the service water piping are due to settlement and whether they exceed allowable limits.
Staff Resoonse: This matter was responded to in Section 6 of our testimony.
t Coalition Question: The Coalition asked if settlements during December I
of 1974 and July of 1977 had the same causal mechanism.
Staff Rosconse: We have no data to substantiate that the settlements had the same cause, l
Coalition Question: The Coalition asked, if the groundwater level was below I
the drains during their installation post drought in the summer of 1977 how were the drains able to significantly affect the groundwater level.
b 9
l
Staff Response:
Previous Piezemeter readings from which the groundwater levels were determined are now thought to be erroneous.
Because ground-water flowed from the drains when they were installed, we conclude that the drains were placed below the groundwater level.
Coalftfon Question: The Coalition has asked if it has ever been clearl/
established that changes in groundwater level were responsible for settle-ment at the North Anna Site.
Staff Resoonse: We are not aware of any direct evidence on the changes in groundwater levels during the period of rapid pumphouse settlement, except for the values reported during the period of drain installation.
The i
period of rapid settlement preceded the initiation of periodic monitoring of groundwater levels.
Coalition Question: The Coalition has asked whether or not the causes of rotation and tilt have been clearly established.
Staff Resonnse:
The staff has not made an attempt to establish the reasons for the tilt (rotation is another term for the same phenomenon) of the pumphouse, but it is likely due to the different loads and soil properties under and near the pumphouse.
Coalition Ouestion: The Coalition has asked for the safety rationale of basing remedial actions and reporting on " average settleront".
l l
1 l
o Staff Response: This question is addressed in Section 6 of the staff's testimony. Average settlements are not used 'as a limiting basis for report-ing in the proposed technical specification.
Coalition Question: The Coalition asked how the safety of the North Anna site is protected by changing the Technical Specifications to double the amount of settlement.
Staff Resoonse: The staff's proposed change to the Technical Specification does not propose doubling of the average settlement.
Staff testimony.
Section 6. addresses this question.
Coalition Ouestion: The Coalition has asked about the prompt surveillance and accurate reporting of settlements along with other chronological matters rotated to pumphouse settlement.
3 Staff Responset Settlement measurements and drain installation dates are given in VEPCO's testimony.
The staff's evaluation of VEPCO's surveillance practices are described in Section 2 and Appendices B and C of the staff's tes timony.
Coalition Ouestion:
The Coalf tfon asked the basis for future predictions of settlement and why the saprolites can be found suitable as foundation ma te rial.
Staff Rosconse The basis for future estimates of settlement will be the record of past settlement; the evidence for the suitability of saprolite
. as a foundation for the pumphouse is addressed in the staff's testimony.
Section 3.
Coalition Ouestion: The Coalition asked, if the causes of the settlement have never been firmly diagnosed, upon what basis can " remedial actions" be taken or a prognosis made regarding the 40-year foundation integrity.
Staff Response: The Technical Specifications for the North Anna plant prescribe a program of continual diagnostic procedures.
If future symptoms indicate the recurrence of unexpected and unacceptable settle-ment, then appropriate remedies, based on a diagnosis of the new symptoms, will be implemented to assure that adequate levels of safety are maintained.
Coalition Ouestion: The Coalition has expressed their belief that the staff has been inconsistent in their attempts to explain the cause of unexpected settlement of the pumphouse.
The Coalition cites the staff's statement that. " settlement has been empirically related to precipitation" and the staff's statement that, "there is no known reason for settlement based on factual data such as infiltration of rainfall and changes in groundwater lovels", as evidence of inconsistency.
Staff Responset Rates of rainfall and rates of settlement are the only available data.
There are no data for changes in groundwater levels during the periods of rapid pumphouse settlement.
An empirical correlation of settlement and rainfall has been observed.
Changes in groundwater levels can cause settlement, but there is no L
1 data during the period of rapid settlement to prove that sue'a changes 1
actually occurred.
r' For the above reasons, the shiff, does not believe the cited stat 5ments are contradictory, p '. /
t c
A Co.ilition Ouestion: The Coalitier has asked if the change from 1.8 to 3.9f inches of allowable averad s,ettlement of the pumphouse is a solution 1
to the problem.
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Staff Resoonse: The stc/f does~not believe that the change is a complete s'
solution. The staff's't.Npesed Techdtcal Specification chans explained q
in Shction 6 of the staff's testimony isc,hnsidered to be an adequate n
t solution to the problem of pumphouse setti,'eae'it values that ar3 approaching present Technict) Specificatiot limits.'
l' r
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(-
1 Coalition Questjn: T[.e Coalition noted that VEpCG's requested revision
, s.
t to the Technical SpecificitNn, allowing 0.33 ft average settfement since 1'
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/
December 1975, when added to the average settlement in December of 1975 I
when; added to t'nt average settlement in Aacomber of 19M (0.37 ft) is
),
l>
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i nea' ly the samn is the staff's proposed' 00cember 2r,1977 specification t.
(;
e (superseded) of 0.22 ft of allowable average settlement since July 1977, if 'm4 adds to this value the' average settlement measured in August of I
t 1917 (0.49,'t. ).
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. Staff Response: -The Staff's December 22, 1978 proposed specification was superseded by our January 9,1979 proposal.
In the January 9, 1979 proposed specification, the staff proposed a limiting value of 0.22 ft.
of differential settlement, whereas VEPCO proposed limit of 0.33 'ft. of averace, settlement.
The two figures cannot be compared by simply adding to the Staff's proposed limit the average settlement of the pumphouse prior to July 1977.
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- i,
1 REFERENCES 1.
Ltr dated 5/16/75 from S. Ragone (VEPCO) to D. Knuth (NRC) w/ attachment; ltr dated 5/15/75 from S. Ragone (VEPCO) to N. Moseley (NRC).
2.
Ltr dated 9/8/78 from S. Ragone (VEPCO) to B. Rusche (NRC) w/ attachment; ltr dated 1/16/76 from R. Peck to S. Ragone (VEPCO).
3.
Ltr dated 9/8/78 from S. Brown (VEPCO) to H. Denton (NRC).
4.
FSAR, Part B. Volume II, NIF, Figure 3.8.4-19 (dated 11/3/78).
5.
FSAR, Part B, Supplement, Volume I, NIF Figure p3.9-1 (dated 6/16/76.
6.
Ltr dtd 12/14/76 from S. Brown (VEPCO) to B. Rusche (NRC).
7.
" Evaluation of Soil Liquefaction Potential for Level Ground During Earthquake - A Summary Report" (NUREG-0026, September,1976).
8.
FSAR, Part B, Volume I, Figures NIF Figure 1.2-31 dated 3/31/77 and NIF 1.2-32 dated 7/8/77.
9.
FSAR, Part B, Volume II, NIF Figure 3.8.4-1 dated 11/3/78.
- 10. Ltr dated 8/2/78 from S. Brown (VEPCO) to H. Denton (NRC) w/ Enclosure.
- 11. Ltr dated 5/31/78 from C. Stallings (VEPCO) to J. O'Reilly (NRC) w/ enclosure.
I
- 12. Report on Geotechnical Investigations of Service Water Reservoir, North Anna Power Station Units 1 and 2, for VEPC0; Appendix E, NIF, December 23, 1975
- 13. Final Safety Analysis Report, Part B. Supplement Volume I, (e.g.,
I pages NIV P3.6-1 to P3.11-9).
- 14. Appendix L, Report on Laboratory Soil Testing North Anna Power Station, Service Water Reservoir, VEPC0 dated 7/14/76.
.15. Ltr from F. Brown, Corps of Engineers to W. Gammill, NRC dated March 8, 1977, with enclosures.
a J
k il 1
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REFERENCES
- 16. Terzaghi, K., and Peck, R., (1967) Soil Mechanics in Engineering Practice, 2nd Edition, pages 86,180, Wiley & Sons, New York
- 17. Lambe, T., and Whitman, R., (1969) Soil Mechanics, p.419, Wiley &
Sons, New York 18.
Eshbach, 0xid W. and Sounders, Mott, Handbook of Engineering Funda-mentals, John Wiley & Sons, 1975, page 518 e
l
TABLE - A (From Brown (VEPCO) ltr. to Denton (NRC) dtd. 9-8-78 and :: inspecticns)
SETTLEMENT - FT*
SM-7 SM-8 SM-9 SM-10 ASM-5 DATE NE SE SW NW NW 13 NOV 75 0.411 0.194 0.349 0.561 0.576 1 DEC 75 0.404 0.191 0.346 0.561 0.572 17 DEC 75 0.404 0.188 0.346 0.555 0.576 11 AUG 76 0.402 0.185 0.354 0.564 0.590 23 AUG 76 0.409 0.195 0.364 0.576 0.593 1 OCT 76 0.419 0.206 0.377 0.586 7 OCT 76 0.426 0.213 0.385 0.592 10 NOV 76 0.427 0.211 0.394 0.601 6 DEC 76-0.423 0.2 04 0.392 0.606 0.612 3 MAR 77 0.454 0.232 0.421 0.632 0.649 11 JUL 77 0.450 0.232 0.429 0.644 0.655 12 DEC 77 0.489 0.265 0.473 0.686 0.694 15 MAR 78 0.509 0.281 0.490 0.707 0.714 30 MAR 78 0.507 0.279 0.488 0.703 0.713 25 APR 78 0.495 0.265 0.475 0.693 0.702 10 MAY 78 0.493 0.269 0.480 0.699 0.709 15 MAY 78 0.496 0.274 0.484 0.700 0.706
(
1 JUN 78 0.485 ' 0.260
- 0. 473 ' ' '0. 691 ~
0.709
~ ~
~
~
30 JUN 78 0.498 0.280 0.488 0.701 0.709
-~
3 AUG 78 0.501 0.280 0.487 0.700
~0.708-6 SEP 78 0.504 ~0.200 0.495 0.705 0.709~~
~~
2 OCT 78 0.506 0.281 0.493 0.703' 0.713
~
6 NOV 78-~~0.508 0.288 0.498 0.710 '0.716 20 NOV 78 0.507 0.287 0.496 0.708 0.714 3 JAN'79- 'O.513 0.288 0.498 0.713 0.719 6 FEB 79 0.511 0.287 0.498 0.711 0.719 7 MAR 79 0.511 0.285 0.496 0.714
- The settlement values shown in the above table are based on addin9 the settlements measured by MH&C surveyors since 13 Nov. 1975 to the settlements measured by S&W construction surveyors through 13 Nov. 1975. The initial MH&C survey was performed on 13 Nov.1975.
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TABLE - B (from Brown (VEPCO) ltr to Denton (NRC) dtd 9-a-7f. and I&E)
SETTLEMENT OF UNITS 1 AND 2 SERVICE WATER SPRAY PIPING SUPPORTS SETTLEMENT SINCE 13 MAY 76 - FT DATE Hanger H569 Hanger H 584 10 Aug 76 0.01 0
6 Oct 76 0.06 0.05 10 Nov 76 0.08 0.07 28 Feb 77 0.06 0.06 12 Jul 77 0.06 0.05 14 Dec 77 0.08 0.08 25'Apr 78 0.07 0.07 I
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SETTt_EM:i M r or 3WPH (Frani vario:a 3?.W Onvq: T J93(i i:..* 2 ?.5
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SUtt1ARY OF INSPECTIONS PERFORitED BY IE ON SWPH SETTLEMENT RELATED TO Tills TESTIMONY Report Inspection Ir:spection Effort Number Dates Inspectors Relating to SWPil Settlement Results 50-333/77-56 November 16-18, 1977 McFarland Inspection of completed hori-Item closed:
339/77-35 zontal drain installation and cormni tments review of technical specifica-implemented tions related to horizontal drain.
50-338/78-11 March 27-31 and Kidd Reviewed Mil &C data collected April 3-6, 1978 through Dec.1977 on SWPil settlement.
50-338/78-44 Dec. 6-8, 1978 Bryant SWPil and service water lines Lenahan settlement data and unresolved item on settlement monitoring program.
50-338/79-13 March 5-15, 1979 Lenahan SWPil settlement and service Unresolved items Alderson water lines settlement data, on collection of performance of horizontal piezometer data drains, collection of piezometer data, and inquiry concerning handling and review of SWPil settlement data.
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APPENoix 8 l
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- ga 880 9'o, 0
UNITED STATES NUCtEAR REGULATORY COMMISSION 3 p)'"p([j }r REGloN ll 101 M ARIETTA STREET, N.W.
- j f
ATLANTA, GEORGIA 30303 s......
.ne In Reply Refer To:
RII:JCB 50-338/78-44 Virginia Electric and Power Company Atta:
Mr. W. L. Proffitt Senior Vice President, Power P. O. Box 26666 Richmond, Virginia 23261 Gentlemen:
This refers to the inspection conducted by Mr. J. C. Bryant of this i
office on December 6-8, 1978, of activities authori::ed by NRC License i
No. NPF-4 for the North Anna Power Station, Unit I facility, and to the discussion of our findings held with Mr. P. A. Slater at the conclusion of the inspection.
l Areas examined during the inspection and our findings are discussed in the enclosed inspection report.
Within these areas, the inspection consisted of selective examinations of procedures and representative records, interviews with personnel, and observations by the inspectors.
Within the scope of this inspection, no items of noncompliance were disclosed.
l We have examined actions you have taken with regard to previously j
reported unresolved items.
The status of these items is discussed in the enclosed report.
-In accordance with Section 2.790 of the NRC's " Rules of Practice",
Part 2, Title 10, Code of Federal Regulations, a copy of this letter and i
the enclosed inspection report will be placed in the NRC's Public l
Docucent Room.
If this report contains any information that you (or your contractor) believe to be proprietary, it is necessary that you make a written application within 20 days to this office to withhold such information from public disclosure. Any such application must include a full statement of the reasons on the basis of which it is o
I Ib
- Virginia Electric and Power Co..
claimed that the information is proprietary, and should be prepared so that proprietary information identified in the application is contained in a separate part of the document.
If we do not hear from you in this regard within the specified period, the report will be placed in the Public Document Room.
Should you have any questions concerning this letter, we will be glad to discuss them with you.
Sincerely,
/
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.m
/
$tt i i
r James P. O' Reil y Director
Enclosure:
Inspection Report No.
50-338/78-44 cc w/ enc 1:
Mr. W. R. Cartwright, Station Manager North Anna Power Station P. O. Box 402 Mineral, Virginia 23117 Mr. P. M. Perry, Senior Resident Engineer P. O. Box 38 Mineral. Virginia 23117 6
O Y
T
r A"C'IO UN!TED STATES g
o NUCLEAR REGULATORY COMMISSION y
g REGloN ll p, (
r tot MARIETTA STREET, N.W.
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[
ATLANTA, CEoRCIA *0303 Report No.:
50-338/78-44 Docket No.:
50-338 License No.:
NPF-4 Category:
B2 Licensee:
Virginia Electric and Power Company Post Office Box 26666 Richmond, Virginia 23261 Facility Name: North Anna Power Station, Unit 1 Inspection at: North Anna Power Station, Mineral, Virginia Inspection conducted:
December 6-8, 1978 Inspectors:
J. J. Lenahan J. C. Bryant Reviewed by:
.h,
iz[z.h7s w
es J. C. Bryant, Chikt v
Date Engineering Support Section No. 1 Reactor Construction and Engineering Support Branch Inspection Summarv Inspection on December 6-8, 1978 (Report No. 50-338/78-44)
Areas Inspected:
Special announced inspection of data collected on settlement of Units 1 and 2 service water pump house and of licensee action on previously identified item concerning settlement surveys.
This inspec-tion involved 40 inspector-hours onsite by two NRC inspectors.
Results:
Within the areas inspected, no items of noncompliance or deviations,were identified.
0 9
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RII Rpt. No. 50-338/78-44 I-1 DETAILS I Prepared by:
fd
/*/* 7/78 J. Jv LEnahan, Civil Engineer Date Engineering Support Section No. 1 Reactor Construction and Engineering Support Branch Dates of Inspection:
December 6-8, 197,8 Reviewed by:E l\\/l ( %
b i E/77!7(
J. C. Bryant, Chief f
Datd Engineering Support Section No. 1 Reactor Construction and Engineering Support Branch 1.
Persons Contacted a.
Virginia Electric and Power comoany (VEPCO)
- C. M. Robinson, Jr., Supervisor, Civil Engineering Services
- 0. Schultz, Supervisor, Survey Services
- R. C. Sturgill, Assistant Engineer, Unit 1 E. R. Bane, Supervisor, Construction QA
- P. A. Slater, Resident QA Engineer
- E. R. Smith, Jr., Supervisor, Engineering Services, Unit 1
- J. D. Kellams, Superintendent Station Operations
- W. F. Diehl, Engineer, Engineering Services
- D. C. Woods, VEPCO NRC Coordinator b.
Stone and Webster Engineering Corporation (S&W)
D. Barry, Resident Engineer B. McIver, Soils Engineer (telephone conversations)
R. Allen, Field Engineer (telephone conversations) c.
Moore, Hardee and Carrouth Associates (M H & C)
- M. Croker; Party Chief
- G. Robertson, d.
Nuclear Regulatory Commission Personnel (NRC)
- M. S. Xidd, Resident Inspector
- Denotes those present at the December 7,1978 exit interview.
- Denotes those present at the December 8,1978 exit interview.
- Denotes those present at the December 7 and 8,1978 exit interviews.
e t
6
RII Rpt. No. 50-338/78-44 I-2 2.
I,icensee Action on Previous Inspection Findings (Open) Unresolved Item (338/78-37-04):
Settlement of Class I Structures.
Settlement survey requirements of Technical Specification 3.7.12.1 and enclosed Table 3.7-5 have not been met due to either the need to reset survey points or due to establishment of some points prior to or after baseline dates. The inspectors examined survey field notebooks kept by Moore, Hardee and Carrouth Associates (engineering firm retained by VEPC0 to perform settlement survey), various settlement points, and settlement data. ' A review of the settlement data for points which have not been disturbed since the baseline date indicates that differ-ential and total settlements are well within the limits established in Table 3.7-5 for all structures except for the total allowable average settlement of.the service water pump house.
Differential settlements between structures founded on rock or on fill concrete placed on rock are on the order of.005 to.010 feet.
These apparent movements are a result of the limits of the accuracy of surveying.
After the baseline dates had past, NRC requested that the licensee establish additional settlement points.
Settlement of these points can not be referenced back to the Technical Specification baseline dates. Other settlement points were estab,lished by the licensee prior to Technical Specification baseline date.
Settlement of these points was. recorded prior to the baseline dates.
The licensee will submit a letter to NRC requesting permission to amend the Technical Specifications to clarify baseline dates.
Six points have been reset since Technical Specification baseline date.
This was either due to construction activities which resulted in points being destroyed or erection of permanent facilities which have made points inaccessible.
The licensee has reconstructed the settlement history of points which have been reset from the settlement records of other points on the same structure and from settlement points on adjacent structures which have similar foundation and loading conditions.
The licensee is evaluating methods to protect settlement points from construction and other activities.
The inspectors discussed requirements of a QA program with the licensee's representatives to audit the settlement survey program and the results of surveys performed by M H & C.
On occasions, up to 4 months have elasped between the time the M H & C surveys were made and data was transmitted to the licensee's engineers. The licensee was informed that the time lapse from making the surveys to analyzing the data must be reduced.
In cases where the limits approach 75*. of the allowable values listed in Table 3.7-5, this time lapse should be on the order of one to three days to insure prompt reporting as required by the Technical Specification.
This ites remains open pending NRC review of the licensee's final report.
RII Rpt. No. 50-338/78-44 I-3 3.
Unresolved Items No new unresolved items were identified during this inspection.
4.
Independent Inspection Effort There was no independent inspection conducted during this inspection.
5.
Scope of Special Inspection On April 28, 1978, the licensee notified RII that survey readings taken on March 30, 1978, indicated that the average settlement of the service _ water pump house (SWPH) exceeded 75%'of the maximum allowable value of 0.15 feet.
The licensee submitted a special report regarding the settlement of the SWPH to NRC RII on May 31, 1978.
This special
-inspection was performed to review the settlement data collected at the site and deter =ine the following:
When 75% of the' maximum allowable service water pump house settlement a.
was attained.
b.
If settlement surveys are being performed at frequency required in Technical Specifications.
If the licensee had reported to NRC within 60 days of when 75% of c.
the allowable settlement of the SWPH was detected.
d.
Amount of differential settlement between the SWPH and the north side of the flexible joint in the service water lines.
The inspectors attended a meeting held in Bethesda, Maryland on December 5, 1978, between NRR, VEPCO and Stone and Webster to receive background on settlement history of the North Anna Site.
6.
Findings a.
VEPC0 Service Water Pump House Settlement Surveillance Program-The licensee contracted with MH&C to perform the surveys for the settlement surveillance program required by Technical Specification 3.7.12.1.. Settlement survey requirements of the Technical Speci-fications are to determine elevations of points listed in Table 3.7-5 to the nearest 0.01 foot at least once every six months.
The elevation of the points is to be determined by precise leveling (surveying) with second order Class accuracy as defined by U. S. Department of Commerce, National Oceanic and Atmospherie Administration (NOAA).
The inspectors reviewed MH&C survey field data and field data reductions and discussed survey techniques used in the settlement surveys with MH&C personnel.
The inspectors e
e
o 4
9 t
RII Rpt. No. 50-338/78-44 I-4
)
4.
examined the settlement points in the service water pump house -
(SWPH) and on the north side of the expansion joint in the service water lines, and benchmarks (Reference Monuments A and B) used in the settlement survey.
Reference Monuments A and L consist of steel casing drilled and grouted into rock.
Settlement points in the SWPH are brass markers grouted into the concrete floor.
j Settlement points on the service water lines are painted on the pipes.
~
i The procedure used by MH&C in the settlement survey for the SWPH
.is to run a level line from Reference Monument A along the dike i
of the service water reservoir to Reference Monument B, estab-lishing a temporary benchmark (T3M) in the vicinity of the SWPH.
i
[
The TBM is usually either settlement marker 5 er 6.
A level line is then run into the SWPH to check the elevations of settlement points.
i MH&C employs Precise Level Rods (solid one piece yard rods) and a j.
Zeiss NI-2 self leveling level in the survey.
These instruments i
seet the requirements specified by NOAA for second order, Class 2 surveys.
Examination of survey methods, equipment and reduced l
field data indicated that the survey accuracy attained is equal to that required for second order, Class 2.
Surveys are being -
l performed at the frequency required by the Technical Specifi-l cations (at least once every six months).
t i
MH&C survey data indicated the following average service water pumphouse settlements.
(Note:
Complete NH&C data not tabulated i
i below.
Data shown is that which brackets readings when 75% of i
allowable SWPH settlement was attained.)
t j{
Percent of Allowable Settlement i
j Date Averste Settlement (Feet)
(0.15 Teet) t L
12/1/75
.000 0
7/11/77
.063 42 12/12/77
.303 69 j
3/15/78
.121 81 3/30/78
.119 79 4/25/78
.106 71 5/10/78
.110 73 8/3/78
.117 78 4
l The above data indicate that 75% of the maximum allowable total average SWPH settlement was exceeded on March 15, 1978, and i
j March 30, 1978.
However, NH&C su.veys made prior to March 15, 1
d v -
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e-p-mu.,-.,,,
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.--._.c.
y%,
t.
RII Rpt. No. 50-338/78-44 I-5 1978, indicated settlement was less than 75%.
Based on the above data, the licensee sent a Licensee Evint Report to NRC on April 28, 1978, that Sk?H settlement exceeded 75% of the allowable value.
A detailed special report was submitted to NRC on May 31, 1978.
b.
Construction Settlement Survey Program - Settlement of the SWPH along with other structures was monitored by Stone and Webster during construction.
This was not a requirement of the PSAR, FSAR, or the Technical Specifications but was done in accordance with standard engineering practice to confirm design assumptions.
The requirements of the S&W settlement surveillance program were determined by their Geotechnical Engineers.
This program was not a rigid project requirement, and at times surveys were not made due to higher priority work.
However, the frequency of the construction survey program was adequate to obtain a good settle-ment history of S*w?H.
From the results of the S&W surveys, the licensee determined and reported to h3C in April 1975 that the Sk?H settlement exceeded the PSAR estimates.
Additional design studies were made by S&W to investigate settlement of the SWPH and determine stresses in the service water lines at their connections tc the Sk?H.
As a result of these studies, S&W estimated that total averace addi-tional settle =ent of the S*a7H would be approximately 0.15 feet after December 1975 and flexible couplings were installed in the service water lines at their connection to the Sk?H.
The inspectors reviewed the survey field book in which the S&W SWPH settle =ent survey data was recorded and discussed survey techniques with S&W engineers.
S&W surveys were made from a variety of benchmarks, including Reference Monuments A and B, and several te=porary construction benchmarks.
S&W engineers stated that the procedure they used on their settlement survey was to run a level line from one of the benchmarks to the SWPH, establish a TBM in the vicinity of the Sk?H, and close the loop by either tying back into the originating benchmark or one of the other benchmarks on the project.
However, the survey loop closure was not documented in the field book for each S&W settlement survey.
Loop closures documented in the field book were closed within acceptable accuracy.
The rods used in the S&W survey did not meet the requirements of the type specified by NOAA for use in second order, Class 2 differential leveling.
There was some discussion that one of the l
S&W rods might have been slightly damaged.
The S&W engineer l
estimated errors of up to.01 foot.
S&W survey data was incomplete for readings made from August 3, 1977, through January 5, 1978, l
e i
RII Rpt. No. 50-338/78-44 I,6 because settle =ent point SM-8 was in' accessible to S&W surveyors though MH&C surveyors did record data for this point in December, 1977.
The missing data for point SM-8 can be interpolated from the other data to the nearest.01 foot.
In comparison of MH&C data vith S&W data, the inspectors noted that S&W data consistently indicated approximately.01 feet more settlement than the MH&C data.
From examination of the field data and the discussions with S&W engineers,.the inspectors concluded that the S&W survey did not meet the requirements of a second order, Class 2 survey, and that the SWPH settlements shown for the period from August 3,1977, through January 5,1978 were based on incomplete data.
The survey made for purposes of meeting the requirements of the Technical Specifications was that made by MH&C.
In cases of conflict between the MH&C data and the S&W data, the MH&C data would be accepted as correct since it was obtained from a survey which was better controlled and more accurate than the S&W survey, c.
Differential Settlement Between SUPH and North Side of Service Water Piping Expansion Joint - The inspectors reviewed the results of surveys performed by MH&C to mescure settlement of the service water lines north of the expansion joints.
Settlement of the service water lines was compared to the settlement of SWPH settle-ment point SM-7, which is located on the northeast corner of SWPH.
This is the location where the service water lines enter the pumphouse.
The settlement of point SM-7 versus the settlement of the service water lines is tabulated below.
Differential Differential Settlement Between Between Date of SM-7 SM-15 SM-7 & SM-15 eM-1E SM-7 & SM-15 7/11/77
.000
.000
.000 12/12/77
.039
.051
.012
.058
.019 3/15/78
.059
.071
.012
.081
.022 3/30/78
.057
.072
.015
.077
.020 4/25/78
.045
.060
.015
.066
.021 5/10/78
.043
.064
.021
.071
.028 8/3/78
.058
.066
.008
.069
.011 i
NOTES:
(1) July 11, 1977 is date when initial survey was performed on service water lines.
(2)
SM-15 is settlement point on east pipe.
(3)
SM-18 settlement point on west pipe.
1 r
O OO 9
RII Rpt. No. 50-338/78-44 I-7 (4), Complete MH&C data not tabulated in above table.
(5)
Settlements shown ~are in feet.
The above data indicate that differential settlements between the service water lines north of the expansion joint and the northeast corner of the SWPH has been insignificant since July 1977.
The data also indicate that the service water lines have settled more than the SWPH.
The expansion joints in the service water lines are located where the height of fill in the dike is the greatest.
The expansion joints in the service water lines were installed in March 1976.
An estimate of how much the service water lines have settled since the expansion joints were installed can be made by comparison of SWPH settlement data with the available service water line settlement data.
Settlement point SM-7 settled.046 feet between December 1975 and July 1977.
This is approximately the same magnitude SM-7 cettled between July 1977 and May 1978 when the largest differential settlement between the service water lines and the point SM-7 is indicated.
Therefore it is conceivable that an equal amount of differential settlement between SM-7 and the service water lines occured between March 1976 and July 1977 as occured between July 1977 and May 1973.
This would mean that a maximum of approximately one-half inch of differential settlement may have occured between the SWPH and the service water lines since the expansion joints were installed in March, 1976.
The expansion joints are designed to tolerate up to three inches of differential settlement between the SWPH and the service water lines. The inspectors examined the expansion joints during the inspection and detected no problems.
d.
Conclusions Based on the results of examination of settlement data and survey procedures and discussions with responsible engineers the inspectors concluded:
a.
The survey performed to meet the requirements of Technical Specification 3.7.12.1 indicated that the average pumphouse settlement exceeded 75% of the maximum allowable value in March, 1978.
b.
Settlement surveys are being made at the frequency required in the Technical Specifications.
. RII Rpt. No. 50-338/78-44 I-8 The licensee notified NRC within 60 days (time period specified c.
in the Technical Specifications) of when 75" of the allowable settlement of the SWPH was detected.
d.
The amount of differential settlement occurring between the SWPH and the service water lines is well within tolerance.
No deviations or items of noncompliance were-identified.
7.
Exit Interview The inspectors met with the licensee representatives denoted in paragraph 1 on December 7, 1978 and on December 8, 1978 to discuss the results of the inspection.
The inspectors summarized the scope and findings of their examination of data collected on settlement of the SWPH and of action on previous inspection findings concerning settlement surveys.
No deviations or items of noncompliance were identified.
t 8
9 4
4 4
APPENDIX C NOTE: Appendix C, IE Report No. 50-338/79-13, is attached since it contains recent settlement figures that were reviewed by IE inscectors. The Sucinary of Inquiry, which is a part of the Report, is not relevant to this proceeding as it pertains only to the enforcement / compliance aspect of the investigation.
However, it is being included for completeness since it is referred to in the earlier portions of the Report.
D
unirso stares
,#g ase jo, NUCLEAR REGULATORY COMMISSION ug RaoioN ii o
iot MAnisTTA sTResT.N.W.
ATLANTA. GEORGIA 3o3o3 5,
APO 2 51979 In Reply Refer To:
RII:JJL 50-338/79-13 Virginia Electric and Power Company ATTN:
W. L. Proffitt Senior Vice President, Power P. O. Box 26666 Richmond, VA 23261 Gentlemen:
This refers to the inspection conducted by J. J. Lenahan of this office on March 5-15, 1979, of activities authorized by NRC License No. NPF-4 for the North Anna Power Station, Unit 1 facility, and to the discussion of our findings held with W. R. Cartwright at the conclusion of the inspection.
Areas examined during the inspection and our findings are discussed in the enclosed inspection report. Within these areas, the inspection consisted of selective examinations of procedures and representative records, interviews with personnel, and observations by the inspector.
Within the scope of this inspection, no items of noncompliance were disclosed.
We have examined actions you have taken with regard to previously reported unresolved items. The status of these items is discussed in the enclosed report.
One new unresolved ites resulted from this inspection and is discussed in the enclosed report. This ites will be exasised during subsequent inspections.
In accordance with Section 2.790 of the NRC's " Rules of Practice", Part 2, Title 10, Code of Federal Regulations, a copy of this letter and the enclosed inspection report will be placed in the NRC's Public Document Room. If this report contains any information that you (or your contractor) believe to be proprietary, it is necessary that you make a written application within 20 days to this office to withhold such information from public disclosure.
Any such application must include a full statement of the reasons on the basis of which it is claimed that the information is proprietary, and should be prepared so that proprietary information identified in the application is contained in a separate part of the document. If we do not hear from you in this regard within the specified period, the report will be placed in the l
Public Document Room.
9
APR 2 syg Virginia Electric and Power Co. Should you have any questions concerning this letter, we will be glad to discuss them with you, i
Sincerely,
. _ f a h ta_
ses P. O'Reilly Dt ector
Enclosure:
Inspection Report No.
50-338/79-13 cc w/ encl:
W. R. Cartwright, Station Manager Box 402 Mineral, VA 23117 P. G. Perry Senior Resident Engineer P. O. Box 38 Mineral, VA 23117 9
e I' t S
UNITED :TATss
- g Megjo NUCLEAR REGULATORY COMMISSION
[
n REGION 11 3
j 101 M ARIETTA STREET.N.W.
e ATLANTA GEORGIA 30303
%*...*/
Report No. 50-338/79-13 Licensee: Virginia Electric and Power Company Post Office Box 26666 Richmond, Virginia 23261 Facility Name: North Anna Power Station, Unit 1 Docket No. 50-338 License No. NPF-4 Inspection at North Anna Site near Mineral, Virginia, VEPCO offices, Richmond, Virginia, and Stone and Webster Engineering Corporation (S&W) offices, Boston, Massachusetts Inspector:
ff.
//////
J. @'$7enahan Date Signed Accompanying Perso el:
C. E. Alderson Approved by:
b~4
/3'/M CT Br'ya K, Section Chief, RCES Branch
Date Signed
SUMMARY
Inspection on March 5, 6, 14 and 15, 1979, at North Anna site; March 7, 1979 at Richmond, Virginia; March 13, 1979 at Boston, Massachusetts Areas Inspected This special, unannounced inspection involved 21 inspector-hours on-site and 18 inspector-hours in the VEPCO and Stone and Webster Corporate Offices in the areas of settlement data collected on Units 1 and 2 service water pumphouse, performance of horizontal drains, collection of piezometer data and licensee action on previously identified items concerning settlement surveys.
In addition, an inquiry was conducted concerning handling and review of service water pumphouse settlement data. The inquiry involved 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> on-site and 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> in the VEPCO and Stone and Webster corporate. offices by an NRC investigator. The Summary of Inquiry is appended to this inspection report.
Results of the areas inspected, no apparent items of noncompliance or deviations were identified.
I
DETAILS 1.
Persons Contacted Licensee Employees C. M. Robinson, Supervisor, Civil Engineering Services
- 0. Schultz, Supervisor, Survey Services
- C. E. Sorrell, Civil Engineer
- J. W. Waddel, Manager, Power Station Engineering P. A. Slater, Resident QA Engineer
- E. R. Smith, Jr., Supervisor, Technical Services
- J. D. Xellaas, Superintendent Station Operations
- W. R. Cartwright, Station Manager R. C. Sturgill, Assistant Engineer T. Schreckenghast, Engineering Technician Other Organizations D. Barry, Resident Engineer, North Anna Site (S&W)
- 8. McIver, Geotechnical Engineer, Boston (S&W)
NRC Resident Inspector
- H. S. Kidd
- Attended exit interview.
2.
Exit Interview The inspection scope and findings were summarized on March 15, 1979 with those persons indicated in Paragraph I above.
3.
Licensee Action on Previous Inspection Findinas (0 pen) Unresolved Ites (338/78-37-04): Settlement of Class I Structures.
Technical Specifications are not clear on settlement survey requirements for reset survey points and baseline dates since several of the points were not required by NRC until after the baseline dates had passed.
Also, though some of the points were in existence prior t'o the appro-priate baseline dates, survey readings were not made on the baseline l
date. A typical example of this is point number 117 on the service l
building. The Technical Spe,cifications specify a limit on the settlement occurring af ter April 1,1977. However, settlement surveys were made on March 9, 1977, and not on April 1.
Therefore, it is necessary to j
extrapolate the post April 1 settlement for Point 117. Other examples of the need to clarify baseline dates are settlement points 206 through L
o
. 209 on the Boron Recovery Tank Dike. The technical specifications specify limits on settlement after completion of construction (i.e.,
"as built" settlement).
However, these settlement limit; were not required by NRC and initial settlement readings were not made until May 1976, more than one year after this structure was built.
Six points have been reset since the technical specification baseline date.
This was due either to construction activities which resulted in points being destroyed or erection of permanent facilities which have made points inaccessible to surveying. However, the licensee has a large redundancy in survey monitoring points and, therefore, was able to reconstruct the settlement history of reset points from other settlement points on the same structure or from settlement points on adjacent structures which have similar foundation and loading conditions.
A typical example of how missing data were reconstructed for reset points can be illustrated for point number 144 on Unit I containment structure.
In addition to point number 144, the licensee had estab-lished 5 other points, numbers 126, 127, 130, 143 and 149 on the Unit I containment structure. These additional points were surveyed at the same frequency as point number 144. Point number 144 was destroyed between the 10/8/76 and 7/7/77 readings; however, it is possible to reconstruct the missing data for point number 144 from data collected for the other points.
The readings collected for the other 5 points on the structure indicated an average of approximately 0.016 feet of rebound during the period 10/8/76 through 7/7/77.
Since all the points are on the same rigid structure, it is reasonable to conclude that point number 144 also rebounded 0.016 feet during this period. Point number 144 indicated 0.003 feet of settlement between 5/13/76 and 10/8/76 and 0.005 feet of settlement between 7/7/77 and 10/25/78. Therefore, the net apparent movement of point number 144 since May 1976 is actually.008 feet of rebound, not settlement.
The Unit I containment structure is founded on rock. The inspector concluded, based on the data, that the struc-ture most likely has not moved since May 1976, and the small apparent movements are a result of the limits of accuracy of surveying.
The inspector examined installation of two additional permanent benchmarks which had been established in the main plant area. These benchmarks had been drilled and grouted into rock. Although the surveys made to date meet the requirements for U. S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA) Second Order, Class II accuracy, the survey results will be improved when these benchmarks are used since they are much closer to the plant than the benchmarks presently in use. According to NOAA standards, accuracy in leveling is a function of the square root of the distance surveyed. A reduction in the distance
_p t
p s
i
,/
g
,o
'j-p d
t- '
r 4
7 surveyed will lower the acceptable errors of closure, thus increasing survey accuracy. Also, a ru'uction in distance surveyed will reduce
?.he number of turning points, which will add to increased, survey 4 ccuracy.
+
'in inspector examined the licensee's revised procedure to be furnished to Moore, Hardee,iand Carrouth Associates (MH&C), the engineerit.g fire retained by the licensee to perform the settlement surveys. This procedure' lists requirements for collection and reduction of survey data, transmittal of the data ta the licensee, and QC require 3ents.
~
- The timeilapse beiween completion,of tne MH&C surveys and evaluation of the data by the licensee was up te four months in the past. This iravised procedure requires MEAC to;'.rztsait survey data to the licensee 5'eitnin seven working days after completica of the survey.
The-inspector.di: cussed with licensee management the need,to protect settlement points from being disturbed by construction srd other activities. The licensee is still evtluating methods to be used to accomplich this.
~
Based on revieu of the settlement data collected to date, it appears that the licensee has met the intent of Technical Specification 3.7.12.1, i.e., to monitor and eva'luai.e settlement of Cla'ss I structures. The licensee has requested a change to the Technical Specification to clarify baseline, dates and reset survey points. Unresolved item 338/78-37-04 remains open pending revision of the Technical Specifi-cation and NRC review of the licensee's corrective action and final report.
4.
Unresoli Items
(-
Unresolved items are matters about which more information is required to determine whether they are acceptiable or may involve noacompliance or deviations. Ne# unresolved ites identified during thic inspection are diacussed in Paragraph 7.e.
5.
Independent Inspection Effort The inspector examined the service water reservoir embsnkment, including slope protection, slope stability,.and downstreas embana;ent toe.
Nodeviationsoritemsofnoncompliancewerdident[Ified.
6.
Scope of Special Inspection On April it,1978, the licensee. notified NRC Region II that survey readings taken by MH&C on March 30, 1978, inMuted that the average settlement of the service water pump house (St.~rh) exceeded the value i.
-g
. required for reporting, i.e., 75% of the maximum allowable value of 0.15 feet. The licensee submitted a special written report regarding the SWPH settlement to NRC Region II on May 31, 1978.
This special inspection was performed to:
a.
Make a comparison of the SWPH settlement data collected by Stone &
Webster (S&W) with that collected by Moore, Hardee and Carrouth Associates (NH&C).
b.
Evaluate MH&C SWPH settlement data collected since November 1978.
c.
Evaluate differential settlement data between the SWPH and the north side of the service water piping expansion joints, and visually examine the expansion joints.
d.
Deteomine the performance of the horizontal drains.
e.
Review piezometer data.
In addition, an inquiry was conducted during the inspection by a Regional Investigator concerning the licensee's handling and review of SWPH settlement data. The Summary of Inquiry is appended to this inspection report.
7.
Findings Comparison of S&W and MH&C SWPH Settlement Data - S&W, the plant a.
designer and constructor, monitored settlement of the SWPH during its construction in accordance with standard engineering practice to confirm their design assumptions.
MH&C was retained by the licensee to perform the surveys required by the Technical Specification 3.7.12.1.
The inspector examined the S&W survey field book containing the SWPH data collected by S&W surveyors, reviewed calculations reducing the raw field data collected by S&W and MH&C to the computed SWPH settlement, made an independent check of these calculations, and compared the SWPH settlement calculated from the S&W field data to the settlement calculated from the MH&C data.
A comparison of MH&C and S&W settlement measurements is shown in the following table:
m
e
. MH&C DATA S&W DATA Average SWPH Average SWPH Date Settlement (ft.)
Date Settlement (ft.)
i 12/01/75 0.000 12/10/75 0.000 12/17/75 0.001 12/19/75 0.000 8/23/76 0.011 8/21/76 0.020 10/01/76 0.022 10/07/76 0.029 10/06/76 0.027 11/10/76 0.033 11/13/76 0.039 12/01/76 0.038 12/06/76 0.031 12/15/76 0.064 2/24/77 0.061 3/03/77 0.061 3/28/77 0.068 5/23/77 0.066 7/11/77 0.063 8/03/77 0.114 8/29/77 0.112 10/06/77 0.114 10/31/77 0.113 12/12/77 0.103 12/08/77 0.117 1/05/78 0.116 3/15/78 0.121 3/01/78 0.112 3/30/78 0.119 3/29/78 0.123 4/25/78 0.107 4/20/78 0.118 5/10/78 0.110 5/12/78 0.132
~
Notes (1) Settlement shown is in feet (2) S&W settlement values for 8/3/77 through 1/5/78 are based on incomplete data; i.e., no readings were made on settlement point SM-8 during this period. Missing data for SM-8 was interpolated from other data.
The Technical Specifications require that the licensee perform an engineering evaluation to determine the consequences of additional settlement when the average settlement of the SWPH exceeds 75% of 0.15 feet (0.1125 feet). The licensee is required to notify the Commission and submit a special report within 60 days of when this limit is detected. S&W data indicate that 76% of the allowable SWPH settlement of 0.15 feet occurred by August 3, 1977. However, the MH&C data indicates only 42% of the allowable settlement had l
occurred by July 11,11977, and that 69% had occurred by December 12, 1977.
S&W data of December 8, 1977 indicates,-for all practical purposes, no change from the. August 3 data. The difference, 69%
t h
g
. of 0.15 and 76% of 0.15, is less than 0.01 foot.
MH&C data did not indicate that the allowable settlement (75% of 0.15 ft.) was exceeded until March 15, 1978.
i The S&W data generally indicated approximately 0.01 foot more settlement than MH&C data. Examination of the data in the S&W survey field book disclosed that survey loop closures were not documented for the period between March 28, 1977 and March 27, 1978.
Since these loop closures are not documented, the accuracy of the S&W surveys for this period is questionable.
In addition, S&W did not make settlement survey readings on settlement point SM-8 (S&W point number 3) from August 3, 1977 through January 5, 1978. The settlement data for point SM-8 was interpolated from the data obtained for point numbers SM-7, SM-9 and SM-10.
Therefore, some of the S&W average settlements shown in the above table are based on suspect and/or incomplete survey data and in any case would not have the same degree of accuracy as the MH&C data.
The MH&C average SWPH settlement shown in the above table is based on complete data obtained from well controlled surveys which were made to Second Order, Class II accuracy.
The MH&C survey loops were closed with acceptable accuracy in all cases.
In cases of conflict between the MH&C data and the S&W data, the inspector-concluded that MH&C data would be accepted as correct since it was complete and was obtained from a more accurate and better con-trolled survey than the S&W surveys.
A more detailed discussion concerning MH&C and S&W survey procedures is contained in Region II inspection report number 50-338/78-44.
No deviations or items of noncompliance were identified.
b.
Evaluation of MH&C SWPH Data Collected Since November 1977 - The inspector reviewed MH&C SWPH data collected since November 1978.
Selected MH&C data is given below to show trends:
Average SWPH Percent of Allowable Date Settlement (Feet) Settlement (.15 Feet) 12/01/75 0.000 0
7/11/77 0.063 42 12/12/77 0.103 69 3/15/78 0.121 81 3/30/78 0.119 79 4/25/78 0.106 71 5/10/78 0.110 73 8/03/78 0.117 78
4
. Average SWPH Percent of Allowable Date Settlement (Feet) Settlement (.15 Feet) t 11/06/78 0.126 84 11/20/78 0.124 83 1/03/79 0.128 85 2/06/79 0.127 84 3/07/79 0.126 84 Notes December 1, 1975 is the baseline date for SWPH settlement in the Technical Specifications.
The data for Spring and early Summer 1978 indicate that average SWPH settlement was approximately 0.115 feet. Readings made in November 1978 through March 1979 indicate that average SWPH settle-ment was approximately 0.125 feet. This means that the SWPH settled an additional 0.01 foot between early Summer and early Winter 1978.
The licensee indicated that monitoring of SWPH settlement will con-tinue on a monthly basis until further evaluation indicates the frequency can be reduced.
No deviations or items of noncompliance were identified.
c.
Differential Settlement between SWPH and North Side of Service Water Piping Expansion Joints and Inspection of the Expansion Joints - The inspector reviewed the results of surveys performed by MH&C since November 1978 to measure settlement of the service water lines north of the expansion joints.
Settlement of the service water lines is compared to the settlement of SWPH settlement point SM-7, which is located on the northeast corner of the SWPH where the ser-vice water lines enter the pumphouse.
The settlement of point SM-7 versus settlement of point numbers SM-15 and SM-18 on the two outboard service water lines north of the expansion joints is tabulated below. Data are selected to show trends.
Settlement in Feet Differential Differential Between Between Point Point SM-7 Point SM-7 Date SM-7
,SM-15 and SM-15 SM-18 and SM-18 7/11/77
.000
.000
.000 12/12/77
.039
.051
.012
.058
.019 3/15/78
.059
.071
.012
.081
.022
4
- Differential Differential Between Between Point Point SM-7 Point SM-7 Date SM-7 SM-15 and SM-15 SM-18
'and SM-18 3/30/78
.057
.072
.015
.077
.020 4/25/78
.045
.060
.015
.066
.021 5/10/78
.043
.063
.020
.071
.028 8/03/78
.051
.066
.015
.069
.018 11/06/78
.058
.081
.023
.082
.024 11/20/78
.057
.083
.026
.083
.026 1/03/79
.063
.095
.032
.090
.027 2/06/79
.061
.101
.040
.090
.029 3/06/79
.061
.097
.036
.088
.027 Notes:
(1) July 11, 1977 is date when initial survey was performed on service water lines.
(2) SM-15 is settlement point on east pipe.
(3) SM-18 settlement point on west pipe.
The above data indicate that differential settlements between the service water lines north of the expansion joints and the northeast corner of the SWPH has been approximately 1/2-inch since July, 1977. The data indicate that the service water lines have settled more than the SWPH. The expansion joints in the service water lines are located where the height of fill in the dike is the greatest.
Monitoring of pipe settlement was not initiated until July 1977 while the expansion joints in the service water lines were installed in August and October 1976. However, conservative estimates of the total differential settlement which has occurred between the SWPH and the north side of the expansion joint can be made by comparison of SWPH settlement data with available service water line settlement data. Settlement point SM-7 on the SWPH settled 0.046 feet between December, 1975 and July, 1977. The maximum differential settlement between SM-7 and the service lines for this magnitude of settlement of SM-7 was 0.028 feet, occuring in May, 1978. Therefore it would be reasonable to conclude that the amount of differential settlement between SM-7 and the service
^
water lines in the time period August 1976 to July, 1977 was approximately 3/8-inch (0.03 feet). This amount, added to \\-inch which has occurred since July 1977 would mean that approximately 7/8-inch of differential settlement has occurred between the SWPH
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.g.
(point SM-7) and the service water lines since the expansion joints were installed in August and October 1976. The expansion joints are designed to tolerate up to three inches o,f differential settlement between the SWPH and the service water lines. The inspector examined the expansion joints during the inspection and detected no problem.
No deviations or items of noncompliance were identified.
d.
Performance of the Horizontal Drains - The licensee committed in an amendment to the FSAR to control the ground water level in the vicinity of the SWPH. The licensee had considered the use of deep wells, but this method was ruled out after the results of pumping tests indicated that, due to the low permeability of the insitu soils, large drawdowns and close well spacing would be required.
The licensee then elected to use drilled horizontal drains.
Drilled horizontal drains to control groundwater have been in use since the 1940's on numerous projects, including dams, highways, railroads, buildings, and other structures.
The initial drain, drain 0 was installed in August, 1976.
During installation of this drain the impermeable liner of the reservoir was punctured. The licensee reported this to NRC Region II as a 50.55(e) item. After repairs to the liner were completed and installation procedures were revised, horizontal drain number 1 was installed at North Anna in October, 1976 as a test drain. The data gathered from this drain was used to determine drain pipe size, drain spacing, and drain flow characteristics. Based on the data gathered from drain 1, the licensee determined that five additional drains were needed to control the groundwater level in the vicinity of the SWPH. The additional drains, drains 2 through 6, were installed in July and August of 1977. The drains were installed near the groundwater table elevation existing at time of installation.
The inspector examined field books containing records of the horizontal drain installation and discussed installation techniques with the responsible engineers. Examination of the records disclosed that after the problems with drain 0 had been resolved, installation of the remaining drains was carefully controlled. The location of the drains, both horizontal and vertical, was determined during installation using various types of instrumentation. Drain 4 was installed at elevation 272.5. The remaining drains were installed between elevation 274 and elevation 276.
The inspector examined records of periodic tests performed by the licensee to measure the volume of flow from the horizontal drains and to measure the turbidity and suspended solids in the effluent from the horizontal drains. Recordsexaminedwerethoseoftests
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\\ performed on April 7, 1978, July 7, 1978, and January 4, 1979.
Acceptance criteria for seasurement and analysis of flow from the horizontal drain are contained in PT-75.6, " Service Water Pump House Drain System - Turbidity - Suspended Solids", 'and Technical Specification 3/4.7.7.1., ',' Service Water System". The required frequency of testing is at least once every six months.
No deviations or items of noncompliance were identified.
e.
Review of Piezometer Data - The inspector examined records of l
piezometers located in the vicinity of the SWPH to determine the effect of horizontal drain installation on groundwater levels.
Prior to installation of the drains, piezometer number P-14 indicated ground water was at elevation 274.
Piezometer P-14 is angled to a point under the center of the SWPH.
Piezometer P-13 indicated groundwater was at elevation 276 prior to drain instal-lation.
Piezometer number P-13 is a vertical piezometer which was installed on top of the dike approximately 40 feet west of the SWPH. After installation of the drains, piezometer P-13 indicated a drop in groundwater from elevation 276 to elevation 274 while piezometer P-14 indicated a drop in groundwater from elevation 274 to elevation 270.5. Since this is below the level of the horizontal drains, the only explanation that S&W engineers could offer for the behavior of piezometer P-14 after drain installation was that the transducer for this piezometer was installed approximately 4 feet higher than previously believed.
The inspector examined monthly records of piezometer readings taken from June 1978 through February, 1979 to determine the ground water level of the service water reservoir. Acceptance criteria for measurement of the groundwater level are contained in 7
PT-75.7, " Service Water Reservoir - Groundwater Level", and Technical Specification 3/4.7.13, " Groundwater Level - Service Water Reservoir-Limiting Condition for Operaton."
Piezometer numbers P-13 and P-14 have indicated drops in ground-water level of approximately 1.5 feet since late November,1978.
The inspector questioned North Anna site personnel concerning the apparent drop in groundwater level. These discussions disclosed l
that site personnel compare the piezometer readings to Technical l
Specification (TS) requirements and if the data is within the TS limits, no further action is required. Results are then filed in the Document Control Unit (DCU) after distribution of copies of the data to various personnel in the Richmond VEPC0 and Boston S&W offices.
Site personnel do not perform and procedures do not require a trend analysis which would disclose variations in data t
i l
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p
. s from average monthly readings. Site personnel had no comment concerning the piezometer data, except to state that the data were within TS limits.
Discussions in the Richmond VEPCO offices with the VEPCO Supervisor of Civil Engineering Services and in Boston with the S&W Geotechnical Engineer disclosed that the apparent drops in groundwater levels in these piezometers are suspected to be either a result of errors by the individual making the readings or malfunction of the pore pressure indicator (instrument used to read the piezometers). The VEPCO Supervisor of Civil Engineering Services notified the site of the potential problem with the piezometer data in late February, 1979.
Further discussions at the site on March 14 and 15, 1979, with licensee management disclosed that the manufacturer of the pore l
pressure indicator will be contacted in the near future to send a representative to the site to service and calibrate the instrument, if required, review the procedure being used to read the instrument, and verify that the individual reading the piezometers is doing it correctly.
The inspector expressed concern over the delay in discovery of the potentially incorrect piezometer readings and questioned whether or not a trend analysis should have been performed to detect potential errors in readings. The apparent lack of adequate procedures to specify corrective action, e.g., perform a trend analysis, was identified to the licensee as Unresolved Item 338/79-13-01. This item is being evaluated by NRC to determine if adequate procedures have been established.
NRC will also review the report of the pore pressure indicator manufacturer in evalua-tion of this item.
The most current SWPH settlement survey data at the site on March 6, 1979, were the November 20, 1978, readings. The inspector verified
(
that these data were the most current available on site on this date by review of DCU files and discussions with the engineer responsible for review and analysis of SWPH settlement data.
During discussions with the VEPCO Supervisor of Civil Engineering Services and his staff on March 7,1979, the inspector questioned if any additional SWPH settlement surveys had been made since November 20, 1978.
The inspector was informed that surveys were made in January and February but that this data had not yet been received from MH&C. During a discussion of the effect of the apparent drop of groundwater table elevation on SWPH settlement, the licensee's representative indicated that they were not concerned l
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-. n,-.
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3
. that additional SWPH settlement had resulted from a drop in the groundwater table since they assumed the piezometer data was incorrect.. At the request of the inspector, the licensee obtained copies of the January 3, 1979, and February 6, 1979, survey data.
The inspector and the licensee reviewed the data and verified that additional SWPH settlement had not occurred since November 20.
No deviations or items of noncompliance were identified.
e 9
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UNITED STATES
[{g ne%q#c,,
NUCt. EAR REGULATORY COMMIS310N REGloN il g
101 MARIETTA STREET.N.W.
E e
ATLANTA. GEORGIA 30303
%,...../
I
SUMMARY
OF INQUIRY
Subject:
Virginia Electric & Power Company (VEPCO)
North Anna Unit 1 Docket No. 50-338 Allegations that VEPCO had knowledge of significant safety information regarding foundation conditions (Service Water Pump House settlement) at the North Anna site in August 1977 and withheld the informa-tion from the NRC for seven months until April 28, 1978.
Dates of Inquiry:
March 5-13, 1979 Performed by:
O F
e n L-J 3-27 19 C. E.lAlderson Date Regional Investigator Office of the Director NO Reviewed by:
1 -- p 3-27 79 F. J. Long Date Acting Deputy Director Office of the Director
3,
. I.
INTRODUCTION In a letter to the Commissioners dated November 1, 1978, the North Anna Environmental Coalition (NAEC) stated that from information available to the NAEC it appeared that significant safety information regarding foundation conditions at the North Anna site had been withheld from the NRC for a period of seven months and was never reported to the Atomic Safety and Licensing Board (ASLB). The letter alleged that VEPC0 had been aware of abnormal and differential settlement in August 1977 and had not reported it to the NRC until April 1978. The letter further alleged that the matter was reportable under the Unit 1 Technical Speci-fications and had been reportable under the requirements of 10 CFR 50.55(e) prior to issuance of the Unit 1 operating license.
In a letter to the Advisory Committee on Reactor Safeguards (ACRS) dated November 3,1978, the NAEC stated that it would appear that VEPCO under-took no evaluation for months after becoming aware of the excessive settlement.
This letter to the ACRS included a copy of NAEC's November 1st letter to the Commissioners.
This inquiry and a special inspection were initiated under the authority provided by Section 1.64 of Title 10, Code of Regulations and were conducted jointly to:
(1) determine the specific reporting requirements pertaining to the Unit I and 2 Service Water Pump House settlement which were in effect at the various times in question; (2) review Stone and Webster (S&W) and VEPC0 procedures for the accumulation, evaluation and reporting of settlement data; (3) determine the specific handling of the data resulting from the survey performed by Stone and Webster in August 1977; and (4) determine if an investigation into the matter was warranted.
The results of the inquiry are presented below. Technical evaluation of the North Anna settlement monitoring program, including S&W surveys and Moore, Hardee and Carrouth Associates (MH&C) surveys is addressed in the report of the special inspection (IE Report No. 50-338/79-13) to which I
this Summary of Inquiry is appended.
(
II.
SCOPE l
This inquiry included the following activities:
a.
Review of 10 CFR 50.55(e) reporting requirements.
i b.
Review of North Anna Unit 1 Technical Specification reporting i
requirements.
c.
Review of:
(1) Correspondence between VEPCO and the NRC; (2) the transcript of the ASLB hearings for the Unit 1 operating license; l
1 l
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Mb.
. (3) the North Anna Unit I and 2 Safety Analysis Report; and (4) the North Anna Units 1 and 2 Safety Evaluation Report including supple-ments, to determine whether VEPCO had made any commitments beyond the settlement monitoring and reporting requirements of the Unit 1 Technical Specifications.
d.
Review of files related to settlement in the possession of the S&W Construction Group at the North Anna site and discussions with the S&W Site Construction Project Engineer on March 5, 1979.
Review of files related to settlement in the North Anna Station e.
Records (VEPCO) and discussions on March 6, 1979, with the engineer on the North Anna operating staff assigned responsibility to evaluate settlement data.
f.
Review of files in the possession of and interwiews with VEPCO's Supervisor of Civil Engineering Services and the Chief Surveyor at the Corporate Offices in Richmond, Virginia on March 7,1979.
Review of files in the possession of and interviews with S&W's Lead g.
Geotechnical Engineer for the North Anna project and a previous Engineering Project Engineer for North Anna Unit I at S&W's Corporate Offices in Boston, Massachusetts on March 13, 1979.
h.
Discussions with the current and prior Licensing Project Managers and the Leader of the Geotechnical Engineering Section in the Office of Nuclear Reactor Regulation.
i.
A telephone discussion with the official of the NAEC who had written the letters to the Commissioners and the ACRS.
III. DETAILS Review of Monitoring and Reporting Requirements and Effective Dates a.
Paragraph 50.55(e) of 10 CFR 50 was reviewed for applicability to the situation. Based on this review, it would appear that VEPCO's telephone notification to Region II on April 16, 1975 and their subsequent written report to the NRC dated May 15, 1975 concerning settlement of the Unit 1 and 2 Service Water Pump House satisfied the reporting requirements of 50.55(e). The purpose of 50.55(e) is to ensure that the NRC is made aware of any significant problems identified during construction of a facility so that the problems can be evaluated and monitored to assure appropriate resolution.
Periodic status reports are not required by 50.55(e) after initial notification is made.
F
. C) 4 The monitoring and reporting requirements of the North Anna Unit 1 Technical Specifications became operative on November 26, 1977 when the operating license was issued, and therefore, no report could have been required thereunder, before that date.
The question as to whether a sixty-day report on the S&W survey results of August 1977 would have been due on:
(1) the day the license was issued (since more than sixty days had elapsed since the surveys had been made), (2) sixty days following issuance of the license, or (3) sixty days from the time VEPCO became aware of the results, requires a legal interpretation of the Technical Specification. However, based on the information obtained during this inquiry, the answer to this question does not appear to have any bearing in this matter.
The investigator revi'ewed VEPCO/NRC correspondence on this issue and discussed it with both the current and prior NRR Licensing Project Managers, and the Geotechnical Engineer who had been involved to determine if any special reporting requirements had been imposed on VEPCO regarding settlement survey results. The review and discussions did not disclose any special requirements; however, a letter from VEPCO to the NRC dated July 11, 1975 was found to contain the following statement:
" Monitoring of the settlement will be continued on a monthly basis throughout the construction and initial operation of Units 1 and 2.
These observations will be reviewed at that time to determine if a less frequent monitoring sequence can be justified. The staff will be consulted prior to any change in the monitoring schedule."
This statement was contained in VEPCO's response to a question from NRR which requested a discussion of proposed Technical Specification i
limitations. The investigator was unable to locate any subsequent l
NRC/VEPCO correspondence regarding monitoring frequency until the proposed Technical Specification with a six-month surveillance frequency, was submitted in October 1977. This response was also discussed with the three individuals from NRR and none could recall the letter or a discussion of a one-month frequency. They further stated that there was never a requirement that surveys be accom-plished monthly.
It should be noted that between June 11, 1975 and the submittal of l
the proposed Technical Specification, additional structures had been identified as requiring monitoring for settlement. The Technical Specification which was eventually issued required a much more extensive program than was being considered when the earlier letter was written.
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A,
. -b.
Responsibilities for Performing Surveys The investigator interviewed several individuals to determine the relationship between S&W surveys and those performed by MH&C. The Supervisor of Civil Engineering Services (VEPCO) stated that monthly settlement measurements were initiated in December 1972 due to the appearance of cracks in the SWPH wing-wall. At that time S&W was instructed by VEPCO to perform the necessary surveys for what was believed to be a temporary program. However, the Supervisor said that in 1975 it became apparent to VEPCO that the NRC would require a long-term monitoring program, possibly lasting the life of the plant. The Supervisor explained that since S&W would eventually leave the site when construction was completed, VEPCO decided that it would be better to hire a local company to perform the surveys.
MH&C had been performing survey work for VEPCO in other areas since 1967 and VEPCO decided that they should perform the surveys required by the Settlement Monitoring Program being developed at that time.
The investigator reviewed the "open-ended" service contract between VEPCO and MH&C and determined that it had been entered into on September 1, 1967. The investigator also reviewed a letter from VEPCO to MH&C dated September 23, 1975 which authorized MH&C to initiate a survey program to monitor the North Anna Service Water Reservoir das and pump house under the service contract. The letter specified that upon completion of the original surveys, the alignment-settlement markers were to be monitored when the water-level in the reservoir reached certain specified levels and once each year after the reservoir was filled.
The investigator found several S&W and VEPCO letters in the various files reviewed which clearly establish that S&W was assisting VEPCO in the development of the Settlement Monitoring Program and the proposed Technical Specification, including the identification of structures and components to be monitored, the frequency of monitoring i
and the limits on differential settlement. The letters and various l
internal memoranda also indicate that it was VEPCO's intent to have I
a single monitoring program which satisfied the informational needs of VEPCO, S&W and the NRC, and that the surveys would be performed by MH&C.
The individuals interviewed were unable to state why the S&W pump house settlement surveys; continued after MH&C was contracted to perform the settlement' surveys; however, it was pointed out to the investigator that S&W' surveys did not include but five of the many points required by the. Technical Specifications and were never intended to satisfy those requirements.
b 4
I
6-c.
Procedures for Accumulating, Evaluating and Reporting Settlement Data The S&W Project Engineers for Construction (site) an'd Engineering (Boston), and the Lead Geotechnical Engineer were interviewed to determine the normal procedure for handling the settlement survey data within the S&W organization. At VEPCO's Corporate Office the Supervisor of Civil Engineering Services and the Chief Surveyor were interviewed to determine the normal procedure for handling the settlement survey data within the VEPCO organization. Discussions were also held with the engineer on the North Anna operating staff responsible for evaluating the survey data and discussions had been held previously with the S&W survey party chief who had been involved in the August 1977 surveys. These interviews and records reviews disclosed that prior to October 11, 1977 there were no formal written procedures within S&W or VEPC0 covering this area, but the descriptions provided by these individuals as to how the data was handled were all in general agreement.
With regard to S&W surveys, the S&W surveyors would make the surveys and enter the raw data in a field book. At some later time the survey party chief would transfer the raw data to a form which was then forwarded to S&W-Boston. The records indicate that from initation of the survey program in late-1972 until late-1975 this form with the raw data was sent only to one individual at S&W-Boston by telecopier.
In late-1975 (around August) a standard transmittal form was introduced and the distribution of the raw data was expanded to include several individuals, including VEPCO employees.
From this point in time on, the data was sailed to the recipients, except for special requests which were sometimes telecopied. The transmittal sheet was revised at least once and the distribution was changed. The transmittal sheets contained no data themselves and serely served as " routing" forms. For this reason, the trans-sittal sheets were not retained with the data sheets, if at all, and the investigator was unable to identify from the records those individuals who received any particular set of raw data or when they received it.
The records available did indicate that between February 1973 and mid-1975 the S&W survey data was being received by S&W-Boston within one to two weeks from the time the survey was made. After mid-1975, the records indicated a continuing trend of ideresse in the time between the survey and receipt of the data in Boston.
Beginning in late-1976 it appears that the S&W survey data was forwarded to S&W-Boston and other persons on distribution only after a data sheet was full; the time required being dependent on the frequency of surveys.
Generally, it appeared that S&W-Boston received the data within one to two months af ter the first survey on the data sheet was made.
e
7 Regarding MH&C data, normal flow of the raw survey data was from MH&C to VEPC0's Chief Surveyor, who passed it on to VEPCO's Supervisor of Civil Engineering Services. The Supervisor of C1,vil Engineering Services then forwarded copies of the data to S&W-Boston, and following issuance of the' operating license, to the operating staff at North Anna.
The various individuals interviewed indicated that prior to licensing of Unit 1, S&W's Lead Geotechnical Engineer was responsible for reducing and evaluating the survey data from both S&W and MH&c.
Within VEPCO, the responsibility for the Settlement Monitoring Program was assigned to the Supervisor of Civil Engineering Services.
Upon issuance of the operating license, responsibility for evaluating the data for compliance to the Technical Specifications was assigned to an engineer on the North Anna operating staff. This engineer only received and evaluated the MH&C data. He did not normally receive S&W data.
The Lead Geotechnical Engineer stated that raw S&W data would sometimes be received regularly, but that at other times, no data l
would be received for quite a while and then several sets of the raw data would be received at one time. He explained that it i
depended on the workload of the Survey Party Chief and when he l
could find time to transfer the raw data from the field book to the data sheets. At times, the Lead Geotechnical Engineer would call the S&W Survey Party Chief and request the data be forwarded. The Lead Geotechnical Engineer further stated that there was no specific schedule established for his to reduce the raw data and determine settlement and that he did it at irregular intervals.
f The Supervisor of Civil Engineering Services (VEPCO) stated that he normally received copies of the S&W data, but that he only glanced at it, as S&W was responsible for reducing the data and informing VEPC0 if any problems were encountered.
d.
Handlina of S&W Survey Data for August 1977 The Lead Geotechnical Engineer (S&W) stated that he did not believe that he received any S&W survey data from the field between May 1977 and January or February 1978. He explained that he had requested i
the data from the S&W Survey Party Chief several times, but that j
the Survey Party Chief was busy and had not gotten around to sending the data.
He stated that he was out of the office for three weeks in January 1978 and when he case back he started reviewing MH&C data and bringing his settlement plots up to date. He further
[
stated that around the end of February 1978 he was reviewing and plotting the data for the MH&C pump house survey of December 12 j
1977 and noticed a significant change, but did not know if it was l
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an actual settlement or a bad survey. He then notified VEPCO's Chief Surveyor of the possible probles and requested,that the Survey Party Chief send all S&W survey data not previously received by S&W-Boston from the field. An internal memorandue from the S&W Survey Party Chief to the Lead Geotechnical Engineer indicated that S&W survey data was forwarded to S&W-Boston on February 28, 1978.
A meno from the Lead Geotechnical Engineer back to the Survey Party Chief indicated that S&W surveyors performed an additional survey on March 1, 1978 and that the field books were reviewed to determine the validity of the bench marks. The memo also indicates that the Lead Geotechnical Engineer had reached the conclusion that the MH&C data for December 12, 1977 survey was valid.
The Lead Geotechnical Engineer stated that he prepared a letter to VEPCO and on March 6, 1978 he notified VEPCO's Supervisor of Civil Engineering Services that the MH&C data for December 12, 1977 indicated that the pump house had attained 65 percent of the average allowable total settlement and that S&W survey data confirmed the validity of the measurement.
VEPCO subsequently requested NH&C to perform additional surveys.
An MH&C survey performed on March 15. 1978 indicated that the pump house settlement had exceeded the 75 percent limit and a special report to the NRC was required within 60 days.
This required report was provided on May 31, 1978; however, the NRC had been notified of the settlement and sesbers of NRR had visited the site as early as April 13, 1978 to review the matter. A Licensee Event Report was submitted on April 28, 1978, e.
Discussion With NAEC Official In reviewing the draft of this summary, it was noted that the phrase "from information available to the NAEC" which appeared in the NAEC's letter to the Consissioners dated November 1, 1978, could imply that they had information beyond that which they addressed in the letter and which eight not be known to the NRC staff. The NAEC representative who had signed the letter was contacted by telephone on March 28, 1978, and was asked if the NAEC had any information that had not been made available to the NRC.
The individual stated that she did not believe they had any infor-sation beyond that available in the documents in the Public Document Room.
With regard to the allegation that VEPC0 was aware of the settle-ment on August 3, 1977, the individual stated that this was based on the information contained in VEPCO's special report dated May 31, 1978. Regarding reportability of the settlement, she stated that
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C).
. the NAEC had contacted the consultant to the ACRS after reading his report to the ACRS dated July 19,1978 and that he had said he felt the settlement should have been reported in August 1977.
IV. CONCLUSICNS The records available clearly indicate that VEPC0 intended that a.
there be one monitoring program and that VEPC0 expanded an existing costract with MH&C to accomplish the necessary surveys.
b.
Prior to issuance of an operating license, VEPCO relied on S&W to evaluate the survey data and forwarded the results of NH&C surveys to S&W.
Subsequent to issuance of the Unit 1 operating license, responsi-c.
bility for evaluating survey data to determine compliance with Technical Specifications rested with the plant operating staff and only MH&C data was forwarded for their evaluation.
However, VEPCO continues to forward the NH&C results to S&W for further evaluation.
d.
When reduced and evaluated, the results of the surveys performed by S&W on and af ter August 3,1977 indicated that the service water pump house settlement had exceeded 75 percent of the limit; however the investigator could not conclusively establish the date that S&W-Boston or VEPCO became aware of the August 3, 1977, and subse-quent S&W survey results, but there was no indication that either received the raw data for these surveys until near the end of February 1978.
There did not appear to be any significant differences in the e.
bandling and processing of S&W data of August 3,1977 and later, when compared to the handling and processing of earlier S&W data.
f.
The allegations are not substantiated and no further investigative effort is warranted with regard to this matter.
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