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March 19, 1970 L. Squires Chairman Midland Plant Subconnittee MIDLAND PLART, DRL M ETING ON THE SUBSIDENCE QUESTION Dr. James T. Wilson and I attended a meettog held by SEL on March 12, 1970 with Consumera Power Company to discuss the potential problem of subsidence I have asked Dr. Wilson to provide us with a at the Midland Plant site.
letter report of his opinion as to whether this is a real er paper problem.
The meeting resulted in DEL asking for more informatten and the applicant DRL eeked for some agreeing to provide part of the information desired.
micro seismic measurements and the applicant objectdd to obtaintag them since he could not see hee they would be useful.
It appeared that a general sub-sidence could occur but not an abrupt of feet. Bechtel thought the plant could tolerate a tilt of 2 or more inches in 500 feet and general or regional subsidence would not be a problem. An abrupt of feet er scarping could not be tolerated.
l A copy of my notes is attached for your information. Copies are being provided to the other ACRS members for their information.
J. C. McKinley Staff Assistant
Attachment:
Minutes of DRL Meeting on Midland Plant Bethesda, Md., March 12, 1970 cci ACRS Members w/ attachment ACR$ 8taff w/ attachment James T. Wilson W/ attachment p e.o 's ffp 050WO
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DRL (A. T. Cardone) is concerned that there may be a embaidence problem under the Midland plant site. To help alley this concera EEL held this meeting to request additional informaties from the applicant, imeloding:
I Does the applicant have basic survey data to show that es subsidence 1.
has occurred to date and from which future subsidence may be measured?
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If so, the applicant should provide the survey data.
The applicant should make a literature search for esbsidence history f
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over mining operations of comparable depth. A bibliography of case l
histories should be compiled.
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l N applicant should provide structural property data for the various 3.
strata overlying the salt beds, including information en bedding, i
joining and fracturing.
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N applicant should provide information regarding the amount of material removed from each cavity, the envity size and configuration.
There should be a statement regarding the intereenmection er lack l
thereof of tly various cavities and the basis for these eenetustoms.
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5.
The applicant should smalyse potential subsidence based on a family 1
of cavity ceafigurations and on the interaction of adjacent cavities.
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The applicant should censider the of facts of seismic events en the esvities and the ceasequences at the grenad surface.
7.
The applicant should state the tolerable limits of subsidence, tilt l
and offset for this reactor plant design.
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The applicant should state his intent regarding measures that could be taken to stabilise the salt formation in the vicinity of the cavities.
9.
The applicant should consider the installation of tastruments to detect movement in the reek strata (stere-setente lastruments and slope indi-sators).
- 10. The appliesat should analyse the of feet of draw down in the brine wells en the sepppre of the overlying beds.
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- 11. The appliesat should obtain a statement of Dov's intent regarding future hloride mining operations teclustna pesettle mistas et the potassium e
......hedathatpieabout-8,400-. feet.belem the surfose.
The statement-should -
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Br. J. T. Wilson suggested that the applicant provide the equations end saloale-tiens used by usedward-Clyde desociates in preparias their report en enheidence l
l that was submitted as part of Amendment No. 7 to the PSAR.
ll The representative frea Dow thought the detailed boring lege from one well would be representative of all of the welle since the site is located over a very Es stated that Dow had set up a survey J
unifore and flat geologie formation.
grid to measure any subsidence but had met observed any ever the 11 years that i
The mells used for mining are essented and cased to a they have been mining.
depth of 3950 feet and have never required maintenance for anything other than i
No casings in the entire region have failed due to rock movement corrosion.
In response to a question of possible plastic flow of i
above the salt beds.
the salt beds,,the Dow representative stated that a well had been drilled but After 120-130 days the bore ses jumagsil' not put into production for some time.
l and no change in diameter la the salt beds was observed; thus Saw does metPlastic flo if, believe that plastic flow of the beds will be ebeerved.
to become appreciable below about 7500 feet.
1 Mr. Allen of Consumers Poser suggested that the experte determine the else cavity the overlying rock can safely spam and see if may of the mined cavities approach I
If they don't then there is no problem and if they de then the effect that size.
of cavity collapse will have to be evaluated further.
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The applicant believes that regional subsidence is not a problem because they do not believe it will egeur and if it does occur it will cause ne distress la the Tilting of at least 2 inches la 500 feet can be tolerated. s The auclear plant.
l applicant believes that the only situation that could raise a dafety geestion would be the possibility of an of fset (scarping) accurring moder the plant.
'They believe the overlying geologic formations preclude such scarping.
The nearest salt well is No. 10 which is mov sealed and capped, the mest nearest l
is No. 17 which is in standby status and not being mined.The cavity under No. 17 is The Dow representative t
said that No.17 could possibly be abandoned.
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co be about 600 feet in diameter while the one moder No.10 is believed to be l
considerably smaller.
e Mr. Allen said that he expects strong intervention on the Midland Plant applicatio l
and he hoped the AEC would not raise theoretical issues that would feed the inLrveoors without having any real significance to the protectica of the health and safety of the public.
.Mr. Alles and his censultants could met see any use for stere-seismie data er a Mr. Allam~dsee statement that they did not intend to stabilise the cavities.
est intend to reply to inquires in these areas.
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1 BEL and the applicant agreed to meet again te discuss progress em thia (sees en
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Dr. ttison obtained a copy of "Investigaties of the Influence of Certain su d er 6ahles.am..tha.Subaidame=.Aheme..m mad. Areas"...pcepared..by. Woodward MW&
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Caple,s of this report l
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Attendees C--umsrs Power Causesy R. D. Allen J. T. Wilson, Consultant W. E. Kessler J. C. McKinley, Staff Bechtel Corseration DRL F. A. Martines F. Schroeder R. Cray, Censultant D. Muller E. Collesa F. Howe J. Murphy Dow Chemical D. Nunn F. J. Maddez A. T. Cardone
- 1. Holton H. Waldron, Consultant (USGS)
Meeting of AEC Personnel and Consultants Mr. Muller described the purpose of the meeting as an attempt to define th status and scope of the problem of subsidence at the Midland site.
Dr. Wilson thought the primary problem was the applicant did not know the l
configuration of the solution cavities produced b the salt mining operatio Es i
He noted that there is'very little published information on subsidence.
td wanted same more information from the applicant regarding when minius star e f
l spacing of the wells, if hydrofracturing was performed, the amount of sa t recovery, and if channeling was thought to have occurred.
Se felt the Mr. Waldron (USGS) felt that the more data available the better.
ities.
applicant should assume a single large cavity rather than maltiple sma He was not so concerned with a gradual subsidence as w displacement.
A tendency for plastic flow weeld reduce the beds at this depth (4300 feet).
He knew of only one case of of fset possibility for offset type of subsidence. subsidence and that w some rather shallow solution mining cavities.
Be could be required to cease and desist mining in the vicinity o tiona Mr. Neue thought that the AEC should give the applicant some gnidance area.
Dr. Wilsoa needed to know some of the basic assumptions seek as; scrity heripental span, height, amount of material removed to date and fu h
that chanetna the eseity shape affects the type of se -
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e ogeace seen en thy surface (th Le also depends en the prop fat."'%"Es gested 'n"serits ef"calculattims-for vertous shaped-seescies......
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I Dr. Wilsea considered the Woodward-Clyde & Associates report (submitted d6 i
haendosat No. 7) to be fairly credible but he wanted to see the calemlettees and equations used. Be thought the sesumption of a cylindrical sovityJens 4
conservative from a scarping ef fect but not adequate for other ef fects.'.M ^
was not alarmed at the subsidence potential because of the depth of the savities (over 4.000 feet down). He thought the surve) nata would be very important ta identifying and saeasuring any subeidence that had er might occur.
Cardone listed the additiemal information he thought the applicant should He agreed to obtain copies of a U. S. Bureau of Mines report %ethods Mr.
Eis Itst of additional provide.
and Equipment for Measuring Subsidence" by Louis A. Fanek.
information included:
1.
Subsidence survey data
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2.
Literature search for case histories
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3.
Structural properties of the overlying strata Cavity shape and sise 4.
Additional instrumentation to detect movement la the rock (micre. seism 5.
devices and slope indicators)
Radioactive tracer injected into ese cavity and monitored in another 6.
Dov's intent regarding potassium chloride beds 8.000 feet belee the 7.
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Tolerable strain limits of the nuclear plant c
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Actions planned to stabilise the area
- 10. Seismic considerations Meeting with Consumers
- Power Company and Consultants Mr. Waldron emplained that he had started to write his report'to DEL saying subsidence was met a problem but then relised that he could not defend that No felt that he needed more information
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position for the lifetime of the plant. He admonished the applicant te make the to provide assurance of a safe destga.
worst assumptions possible in performing the analysis.
p Mr. Kessler asked if DRL had any evidence of a problem is areas with steller t/
Me asked if there was any data available and what approach
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geologic formations?
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would show their assumptions valid?
Mr. Allen pointed out that his orga61sation was attempting to came to gripe with He wondered if it was a matter of the applicant this 11th bour problem.
substantiating his conclusions or if DRL had some evidence of a probleef Mr. W 11er assured him that DEL did not have any calculatises that show emb-sidence will be a problem.
Mr. Waldron pelated out that Woodward-Clyde & Associates had assumed a savity We wanted the shape varied to see the ef fects, if any, en the geomed shape.
as aska4 ewe 5ppTYD Es se surface and to detormine which $s the worst a ase.
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Mr. Betten (Dew) said that information had been provided to Moedverd-Clyde as as did est well as bore loss and data from ese well to a depth of 4500 feet, have as estensive data from other wells but did have good 11thelegical less and production data. Ne felt the detailed data from the one well wee representa-Es tusev tive of the others because of the very uniform geological structure.
ef no fractures er faults in the area. We. pointed out that there are esteatly eeven levels of salt interlayered with delomite. Because of this he thought the cavities would be more searly cylindrical than "nornias glory" shaped.
(The " morning glory" shape results from imseluables saattas the salt surface l
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end inhibiting dissolution).
Mr. Waldron noted that the Woodward-Clyde report issored potential time effects l
(plastic flow) on the cavities. Ne felt that this should be senaldered staae the plant has a potential life of around 50 years.
Mr. Melton said that plastic flow becomes appreciable at deptha below about Dow had dettled a well into this salt bed (4300 feet) and had not t f
7500 feet.
put it into production right away. About 120 days ! ster they gausedI the hele 7 f
and found no reduction in diameter so they conclude there is se plastic flow.
l Mr. Cardone suggested the cavities might have fingers extending is dif ferest
'r directions and that flow might be significant in that case.
i Mr. Holton thought fingering would improve cavity stability. Ne noted that he had assumed a 50 feet thick salt layer 50% dissolution leavlsg a cavity 25 to 30 feet high. He also pointed out that Dow removes only about 101 of the salt i
from a given field and that 907,le left la place, Mr. Cardone questioned interaction of adjacent cavities en the poteettel for subsidence.
Mr. Molton stated that Dow knew which envities were intercommected and which The two nearest the site were not. Me based this statement en the were not.
ability to pressurise either cavity to 1000 pet and not detect any flew into
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any other cavity, Dr. Wilson pointed out the concern for scarping or an abrupt of fset of the t
ground surf ace. Ne noted that a this cavity was less likely to casse a scarp them a thick cavity.
Mr. Betten replied that they had salentated the sovity womid have a diameter of ahest 636 feet. For analyets purposes they then deobled the disaster. pnseted shot in theory if one removed one cubic yard of material from any depth ymm seuld eventually see some ef fect at the graued surf ace but to praettee it was l
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but had Mr. Esites said they had/been unsuccessful in obtaining intercommeetisms.'-Re' said that he had some additional background information as the New wetla that had not been included in the Woodward-Clyde report. Be challenged the theory that cavity collapse would be seen on the surf ace and pointed out the bulking offeet of 'ragmenting rock. This bulking would soon fill the sovity.
Dr. Wilson expressed his desire to see the Woodward-Clyde celestations and assumptions.
Mr. Cardone noted that Woodward-Clyde had made a finite plastic emelysis without considering bedding or joining effects of the everiytag strata.
Mr. Holton said that the rock properties had been obtained from one set of cores and sonic loggins of several bore holes.
I Dr. Wilson thought that agreement could be reached on the properties of the overlying rock formations.
Mr. Allen thoueht that an analysis should be made to see how large a sovity the rock would span and compare this with the conservatively estimated cavity l
sites.
Mr. Maddox noted that surface subsidence has never been noted where solution mining has been conduct.ed at depths greater than 2500 feet. Be potated out that Dow has 11 years of experience at this site and has set ebeerved any subsidence even at the top of the well casings.
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Mr. Cardone thought that there may be a hydrau11e connection between the salt beds and an underlying brine strata 5000-5300 feet below the ground surface.
m brine occurs in a sandstone formation. N current static pressure la this layer causes the brine to rise to within 1000 fecc of the surface in the brise wells. Mr. Cardone wanted to know the effects of pumptog this brine and redweing the static pressure supporting the overlying formations.
The applicant stated that be did not believe regional subsidence would pose a safety question. N problems arise 6f offset occurs. N worst offset described in the woodward-Clyde report enounts to about 0.06 inch, even ten timme that enount would not cause distress in the nuclear plant. N interaction and inter-connection of cavities might result in sebaidence of about 0.15 inch seer a mile area.
Mr. Alles did not went to espeed on the Woodward-Clyde report since it was prepared for Dow and not the appiteent. Es wanted Bechtel to de an independent smalyets i.
and to arrive at an independent conclusion. De does not believe that restenal
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'a f Midland Meeting Mr. Cardone reviewed his list of additional pieces of taformattee that SEL g)-v.
esold like to have submitted.
s The appliesat could see no use for the data obtained free the micro-estamte teatr aents. Mr. A11ensdaid that the applicant does not intend to tehn any mosaures to stabilize the salt formations. There are many things the ayy11eemt does met intend to do and he could see ne value in lieting them. Mr. 411em stated his intent to show that the plant is adequately safe and that he wt11 submit additional supporting information but will not eenduct the miere-seismic studies or state what he will not do.
Dr. Wilson was interesteJ in the well casing maintenance history as an indleatten of rock movement.
Mr. Holton said that the wells were cased and cemented to a depth of 3950 feet and that there were no cases of casing failures in the entire region.
Mr. Allen said that the applicant espects strong opposities to the Midland Plant and asked the AEC not to raise paper issuts that feed an intervenor but to be sure the issues raised are truly relevant to the health and safety of the public.
The applicant and DRL agreed to have another emeting on March 25, 1970. (This tnceting was subsequently postponed to an unspecified date).
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o37 JCN:bJh 4/6/70 frolact:
Midland Flaat Ag,g13gt Cemetruetten Fesult = first of two scheduled ACES usettage, no letter at this mosttag
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Backaroundt November 7,1964, Volumes 1 & 11 of F8AR reselved January 10,1M9, Preliminary EEL report reselved January 13, 1M 9, Applicaties formally isted January 22, 1969, site viett and subsemmittee meetles Josuary 23, 1969, BEL site report resolved February 4,1M9, subcommittee meettas February 6 8,1M9, ACR8 meettag en este related teaues March 6,1970, BEL report recatsed March 34, 1970, subcommittee *mset taa The Midland Float Umsta 1 and 2 are two loop (4ppumps) Babeeck and W11ses FWRe with design power levele of 2432 seit. The plant ta owned and will he operated by Consumare Feuer Company with the techtel Corporation as the A.E.
The reactors are stallar to the matte provided for the Rancho Seso Arkansas Nuclear One, and three Mile faland plante.
A weigue feature of the Itidiand Flast to the intent to supply apprealmstely 6.010,000 lb/br of procdes steam to the adjacent Dew Chemical Cegany plast.
The Committee made a preliminary este review La February 1M9 and semeluded at that:
"The Committee seasiders the site propeeed to be unacceptable for use with reaeter plante destaned and analysed as presently described in the PSAR. Bewever, it believes that the atte may be asseptable for use with reacter plante of the proposed power rating if t (1) The facility to s w ipped with ade wate eastasered safety features and protective systeest (2) the facility 16 analysed sufficiently son-servatively - particularly (a respect tot determinattaa of emefeates area and low populattoo oeoeg aneurance of les potential doses at short distances from the reactor la the unlikely event of a serious assident evaluatten of the number and locaties of peopy who sould he safely and geiskly evacuated la such an events and, use of assumptions, for example these related to meteorology, la dose sateu-1stions: (3) the facility is designed, sometructed, and utilised sufficiently senservativelyg and (6) the fas111ty to provided with thoroughly structured, effect-ive emergency plane, includies evacuatten plane."
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t M*.dland Status Report April 6,19M DEL Reviev l
BEL has concluded that the plant can be built without undee risk to the health and I
safety of the public if the following issues can be satisfactority resolved.
- 1) potentist for surface embsidence
- 2) stability of plant fill slopes 3) flood protection
- 4) meteorological monitoring program l
- 5) eentrol room protection against enterior hasards
- 6) vibration testing j
- 7) cooling pond dike design 1
- 8) diversity in ECCS initiation signals
- 9) pressuriser high level alare design
- 10) eentrol room shielding
- 11) monitoring of process staan j
- 12) coping with hydrogen I
l Sehecanittee Review 1
At the March 24. 1970 Subcommittee meeting and in emboequent diseuestems';the following topics were identified for discussion at the April M S meeting'.
- 1) Radioactivity in the process steam esported to Dow.
- 2) The differences is the Midland Plant and the Indian Point /Etos plaats including:
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distance vs dose calculations j
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pressure vessel cavity destga basis c.
Post less of ecoling accident protection (FIACAP)
- 3) Instrumentation and centrol systems and components.
- 4) Protection of the control room from the release of esternal temie meterials (ehlorine from Dow).
- 5) Coping with hydrogen fellowing a taA.
i-The following topies were identified for discussion at the May ACES meettag.
- 1) Failure to scram following anticipated transients
- 2) Seismic design
- 3) Subsidence
- 5) Flood level Another Subcedttee meeting is planned la April, prior to the May ACES meeting.
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b Excerpt fm 120t ACRS Meeting Meeting with Director of Regulation-(re MIDLAND) 50 (Control of radwaste effluents to levels' 3.
10 CFR Part 20 and Part "as low as practicable")_. - Mr. Price stated that the latest draf t re-vision of Parts 20 and 50 (draft dated March 3,1970) has been pub-This proposed revision requires that radwaste effluents lished for comment.
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from licensed facilities be held to values as " low-as-practicable."
Applications for water reactors would have to describe the facilities, The basic limits of procedures, etc., to be provided to accomplish this.
10 CFR Part 20 remain unchanged. A press conference was held, and the subject was covered by the press in a " mixed" fashion.
A discussion was hela of the implementation of " low.as-practicable" for Midland and for new applications for construction.
Mr. Price stated that, in the case of the Midland plant, Dow would have to obtain a materials license if the radioactivity in the S nce the steam being ex-i steam was not below the " exempt" limit.
ported to Dow is not actually being released to the environment, it is not clear that Part 20 limits or levels "as low-as-practicable" are applicable.
Mr. Price noted that the proposed revision of Part 20 is being used by the Staff for interim guidance in the systrit of the Commissions statement to minimize releases from water reactors. For example, the Tech. Specs. for the Monticello plant require plant operation to hold releases " as icw-as-practicable".
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