ML20040F452
| ML20040F452 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 02/05/1982 |
| From: | Chen W, Hood D ENERGY, DEPT. OF, NRC, Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20040F437 | List: |
| References | |
| ISSUANCES-OL, ISSUANCES-OM, NUDOCS 8202090216 | |
| Download: ML20040F452 (15) | |
Text
L' g
W 02/05/82 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
)
)
CONSUMERS POWER COMPANY
)
)
)
(Midland Plant Units 1 and 2)
)
TESTIMONY OF W. P. CHEN & JARL HOOD FOR THE NRC STAFF REGARDING UNDERGROUND SEISMIC CATEGORY I PIPING My name is Wellington Paul Chen.
I am manager of the Stress Analysis Unit of the Systems Engineering Department of.the Energy Technology Engineering Center (ETEC).
ETEC is a'U. S. Department of Energy (DOE) laboratory which is operated by the Energy Systems Group (ESG) of Rockwell International (RI).
A resume of my professional qualifications is attached hereto (Attachment 1).
I have served since September 1979 as Principal Investigator of the Mechanical Engineering Case Reviews III contract between the U.S. Nuclear Regulatory Comission (NRC) and ETEC.
In aadition to, and as a result of, serving as Principal Investigator of this contract, I have been directly involved since January 1980 in the technical reviews of the effects of soil settlement on the underground, seismic Category I piping at the Midland Plant, Units 1 and 2, as requested by the Mechanical Engineering Branch (MEB) of the NRC.
In particular my review has been restricted to the adequacy from a mechanical engineering perspective of the' Consumers Power Company (CPC) responses to Questions 16 through 20 of b
DESICJATTP ORICI"AL B202090216 820205 PDR ADOCK 05000 y
5
. " Responses to NRC Requests Regarding Plant Fill" (10 CFR 50.54(f)
Request) and related materials, as requested by the MEB.
My name is Darl Hood.
I am a Senior Project Manager in the Division of Licensing, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission.
I am the Project Manager for the Midland Plant application for operating licenses.
I have served in that position since August 29, 1977, when the application for operating licenses was tendered to the NRC for acceptance review. My responsibilities include management of the Staff's environmental and radiological safety reviews.
I am responsible for that part of this testimony c'escribing the function of the service wate.r system.
The purpose of this testimony is to provide technical support for the NRC Staff on (1) the soils settlement problem as delineated above, and (2) Stamiris Contention Numbers 4A(4) and 4C(f), and Warren Contention Number 3, as they relate to underground seismic Category I piping.
The seismic Category I piping to be addressed is founded in the plant fill area and identified in the response to Question 17 of the 10 CFR 50.54(f) Request, and includes piping for the service water system (SWS), borated water system (BWS), and emergency diesel fuel system (EDFS). The nominal pipe size for these lines vary between 8 inches to 36 inches (SWS), 18 inches (BWS), and 1-1/2 to 2 inches (EDFS),
respectively.1/
1/
Some, but only a small portion of non-seismic Category I lines affected by soils settlement are identified in the responses to Questions 13 and 19 of the 10 CFR 50.54(f) Request. The nominal outside diameter for these lines vary between 3 inches and 96 inches.
. The 26 and 36 inch diameter pipes consist of ASTM A-155, Class 2 Grade KC-70 carbon steel while the 8 and 10 inch diameter pipes are ASTM A-106
-Grade B carbon steel, and both types are constructed in accordance with the requirements (f the ASME B&PVC Section III, Class 3.
Depth of cover for these lines varies between approximately 6 feet for the 8 to 36 inch lines, and 2 feet for the 1-1/2 to 2 inch lines.
The service water system, of which the Service Water System piping is a part, is a shared system for both Midland Unit 1 and Midland Unit.2.
It consists of two redundant Essential Service Water trains and two turbine building service water trains.
In addition to providing treated cooling water for various components during normal plant operations, the-system also provides cooling water to engineered safety features equipment, and provides a backup water supply for several safety-related systems during a design basis accident. Each Essential Service Water train serves half the safety-related cooling components of both Midland units.
The Essential Service Water t ains are designed to provide a cooling water supply for the Containment Recirculating Air Cooling Units, which act to remove energy from the containment after a steam line break accident or loss-of-coolant accident. A portion of the Service Water System is designed to provide cooling water supply for the Diesel Generator Coolers to permit continuous operation of Emergency Diesel Generators at required power during design basis accident conditions.
. Ths Essential Service Water train is designed to provide the supply of cooling water for the safeguard chillers which maintain air temperature of the control room, switchgear rooms, battery rooms, and engineered safety features equipment rooms below the room design ambient air temperature during operation under accident conditions. The Essential Service Water train is designed to provide the supply of cooling water to heat exchangers of the component cooling water systems which, in turn, provides cooling water to engineered safety features systems during a loss-of-coolant accident. The component cooling water system thus provides cooling water few removal of heat from the decay heat removal heat exchanger, decay heat removal pump seal coolers, reactor building spray pump coolers, reactor coolant pump seal coolers and makeup lube oil coolers. The Service Water System, operating in conjunction with the Decay Heat Removal System and the Component Cooling Water System, provides a means to cool the reactor core and reactor coolant systems following shutdown. The Essential Service Water train provides alternate water supplies to the Auxiliary Feedwater Pumps, Spent Fuel Pool, and the pressurized water storage tank of the Containment Penetration pressurization System.
The Borated Water System is described in the testimony of Hood, Singh and Kane offered for this hearing session.
The function of the Emergency Diesel Fuel System is of course to supply fuel to the onsite Diesel Generators in case of loss of offsite power.
The current condition of the piping is described in data supplied in (1) responses to Questions 17, 19, 34 and 45 of the 10 CFR 50.54(f)
. Request, and (2) various reports and meeting handouts. These data indicate that:
1.
Current invert elevations for lines profiled average 0.2 feet above to 1.8 feet below the design elevations. The current elevations are predominantly below the design elevations, and the difference between these elevations is variable both for given lines and from line to line.
All of the 26 inch and 36 inch diameter seismic Category 1 piping has been profiled to indicate the present condition of the pipe due to soil settlement.
2.
Current percentage ovality for lines inspected is nearly 2 percent for the 26 inch piping, nearly 3 percent for the 36 inch piping.
3.
Profile data indicate that-differences in invert-inside diameter profiles of up to 1/4 inch exist within 2 inches of either side of weld joints in the profiled 26 inch and 36 inch piping.
4.
Current rattlespace annulus dimensions vary considerably from the design dimensions.
5.
All of the 8 and 10 inch seismic Category I SWS piping in the vicinity of the Diesel generator building has been or will be rebedded, except the 8"-2HBC-81, 8"-2HBC-82, 8"-1HBC-310, and 8"-1HBC-311. Each of these lines is approximatly 30 feet long.
6.
Diameter verification pigging operations conducted on the four 8 inch SWS lines mentioned in (5) above indicated that the inside diameters are greater than 7.781 inches, and no obstructions are present.
7.
Local kinking 1.e., discontinuity in the slope of the pipes, at weld joints is apparent in the profiled 26 and 36 inch diameter SWS piping.
. 8.
Apparent local sagging is evident at four of the five locations where roadways or railways cross the profiled lines.
9.
Differential setticment stresses at the ends of some lines has been relieved by cutting and refitting of the ends.
- 10. The 18 inch diameter SWS piping is to be rebedded,
- 11. The 1-1/2 inch and 2 inch diameter EDFS piping was installed after the Diesel Generator Building surcharging, thus obviating any problems due to past settlements related to these pipes.
Tne eleven items cited above give rise to the following observations i'
regarding the seismic Category I underground piping:
1.
It is not known how much of the deviation in invert elevations is attributable to soil settlement per se. Though fabrication and installation tolerance on overall location was +2 inches, and no construction nonconformances related to this requirement were reported, there are no profiles to verify post-installation locations.
In view of Items 7 and 8, i.e., kinking at weld joints and sagging beneath roadways and railways, it would appear that part of the deviations are due to fabrication and installation and part to settlement.
2.
It is not known how much of the ovality of the 26 inch and 36 inch SWS piping is due to longitudinal bending due to differential soil settlement. The responses to Questions 19 and.45 of the 10 CFR 50.54(f)
Request show that at least one line (96"-2YBJ-4) was out-of-round with the vertical diameter larger tiian the horizontal, prior to surcharging of the Diesel generator building area. Though this 96 inch pipe is not strictly safety related, similar behavior may be exhibited by safety related piping. Since ovalization of this type will occur in flexible
. piping during placement of the fill material at the sides of the pipe, the current ovality measurements cannot be due solely to longitudinal bending of the pipe. Furthermore, the allowable manufacturing ovality tolerance is one percent for 26 and 36 inch ASTil A-155 straight pipe.
3.
Although the apparent 1/4 inch weld mismatch of Item 3 exceeds the 15/32 inch local and 13/32 inch overall mismatch allowed in fabrication and installation of the piping, it is not known how much of this apparent mismatch is due to nonsymetric weld shrinkage and the tolerance in profile measurement.
In view of the above described condition of the seismic Category I piping, the Staff believes thet the following criteria are necessary to assess the structural adequacy of the piping for its intended function over the life of the Midland plant:
1.
Strength Criteria: These criteria are intended to assure the strength of overall cross-sections of the piping to resist the forces nd moments due to all loads imposed upon the piping over the life of the plant. These loads include, pressure, thennal expansion, over burden and traffic, soils settlement and seismic loads.
2.
Buckling Criteria: These criteria are intended to guard against local buckling (which could lead to cracking of the piping) and gross collapse (which could lead to loss of function of the piping).
3.
Minimum Rattlespace Criteria: These criteria are intended to assure that both local and gross overstressing of the piping and gross overstressing'or distortion of piping components or attached equipment does not occur due to loads to be imposed during the life of '.he plant.
. 4.
Nozzle and Other Interface Loads Criteria: These criteria are intended to provide assurance that the structural adequacy or functional integrity of attached components (e.g., pumps, valves, vessah, supports, etc.) associated with the seismic Category I piping will not be compromised over the life of the pl6nt.
- 5. Criteria for Effects of non-Category I Piping:
Since both seismic Category I and non-Category I piping are founded in the plant fill, these criteria would ensure that failures of non-Category I piping-have no detrimental effects on Category I piping.
The above criteria have been discussed with the Applicant:
1.
Strength Criteria: The applicant had proposed the 3.0Sc criterion of sub paragraph ND-3652.3(b) of the ASME B&PVC Section III, Class 3 for bending stresses due to soil settlement. This criterion applies to "any single nonrepeated anchor movement (e.g., predicted building settlement)." The Staff would accept this criterion for application to soils settlement bending stresses.
Difficulties have been encountered, however, in verifying compliance with this criterion due to uncertainties regarding the maximum stresses in the piping over the life of the plant. These uncertainties relate to methodology of analyses for the current piping configurations and changes in those configurations due to additional settlements anticipated over the life of the plant. Several types of analyses are generally used to deal with the difficulties of verification. They are based upon the assumption thttt deviations in current invert elevations from design elevations are due solely to soils settlement, simple elastic analyses, which utilize displacements corresponding to the profile data as i:iputs.
T~
. indicate that the maximum stresses in the 26 and 36 inch lines are on the order of 200ksi. These exceed the proposed 3.0Sc allowable stress of 52.5 ksi. Analyses performed at ETEC, as well as by CPC and its consultants, showed that stresses due to current settlement were acceptable for all but localized areas. These analyses, however, contain limitations in that soil reactions are not modelled realistically. The reactions are not distributed along the length of the pipe but rather are concentrated at displacement input locations.
But, linear elastic analyses were performed by Structural Mechanics Associates (SMA) with refinements to account for 1) continuous soil reaction, and 2) variations in soil meterial property constants. These analyses yield results which do not differ much from those detailed by the simple elastic method of analysis described above.
Further analytical refinements were then introduced by SMA to include non-linear soil and piping properties. These yielded inconclusive results but identified problem areas not very different from those obtained in both the simple elastic and refined elastic methods of analysis.
Southwest Research Institute, another CPC consultant, then introduced analytical refinements to incorporate possible construction defects such as offsets and misalignnent, as well as continuous soil reactions. This analysis identified problem areas not too different from those obtained by SMA's simple elastic method of analysis.
Staff concludes, therefore, that the simple elastic method of analysis can be utilized as a screening tool to identify regions where stress criteria are exceeded due to soil settlement for lines for which
. profile data can be obtained, i.e., 26 and 36 inch diameter SWS piping.
This method of analysis can also be used to account for local effects due to misalignments, mismatch and weld shrinkage.
Future settlement effects can also be evaluated by this method of analysis if the distribution of such settlements along the lines can be defined.
Results of analyses for stresses due to overburden, traffic, and seismic loads on piping are still under review.
In summary, the status of Staff's review to assure that strength criteria have not been exceeded is as follows:
i) 26 and 36 inch SWS piping a) Current soils settlement problem areas have been identified.
b) Review of future soils settlement effects is incomplete.
c) Review of stresses due to other loads is incomplete.
ii) Rebedded 18 inch BWS and 8 and 10 inch SWS Piping a) Review of future soils settlement effects is incomplete i
b) Review of stresses due to other loads is incomplete.
i iii) Non-rebedded 8 and 10 inch SWS Piping s*
a) Current soils settlement problem areas have not been identified.
b) Review of future soils settlement effects is incomplete, c) Review of stresses due to other loads is incomplete.
l iv) 1-1/2 and 2 inch EDFS Piping a) Review of future settlement effects is incomplete.
b) Review of stresses due to other loads is incomplete.
- 2. Buckling Criteria
. CPC has previously proposed a five percent ovality criterion to preclude buckling. This criterion is predicated on adequate compaction of the pipe backfill. Since the adequacy of the Midland pipe backfill is i
l questionable, however, use of this criterion is precluded. CPC has nonetheless more recently proposed a less conservative criterion of eight l
percent. Since buckling of the piping could occur due to the combined effects of pipe bending caused by soil settlement and circumferential or ring type bending due to overburden and traffic loads, the buckling criterion for Midland should be determined considering the interaction of both types of bending. A review of the literature by Staff indicates that no data were available for bending with lateral restraints. Assuming that this restraint is negligible, because there is a lack of data on the degree of compaction of the backfill, the data for pure bending with no lateral restraint shows decreasing consistancy with increasing diameter to thickness ratio (D/t). Based on currently available data, the minimum critical ovality at buckling versus D/t plot is as shown in Attachment 2.
Based on the data shown in Attachment 2, Staff's position is that maximum permissible ovality values of 1-1/2 and 4 percent are satisfactory to preclude buckling for the 36 and 26 inch diameter piping, respectively. The margin of safety associated with these values is l
approximately equal to two provided that total ovalization is limited to these values.
Based on presently available data, as noted above, the 36 inch l
diameter SWS piping would be unacceptable. However, a search for additional data is underway, and the authors of the publications containing the current data have been contacted for assistance and
. interpretation of the findings. The 26 inch diameter piping is acceptable with respect to buckling. In addition, the effects of future settlements and seismic loadings anticipated over the life of the plant are still under evaluation.
i Buckling criteria for piping less than 26 inches in diameter are still under ieview, but Staff believes that a minimum of at let st four percent is acceptable.
CPC has proposed a pipe ovalization monitoring program for the 26 and 36 inch diameter SWS piping over the life of the plant. This program l
l addresses the functional capability of the piping only and is still under l
review. Final recommendations regarding acceptability will be made pending completion of this review.
- 3. Minimum Rattlespace Criteria These criteria are still under review. The effects of future settlement over the life of the plant on the degradation of existing clearance and movements under seismic loads have yet to be considered.
- 4. Nozzle and Other Interface Loads Criteria The status of these criteria are the same as that for the minimum l
rattlespace criteria.
- 5. Criteria for the Effects of Non-Category I Piping l
The effects of breaks in non-seismic Category I on Category I piping
~
where the former lies beneath the latter have been evaluated and found to be acceptable. Those evaluations were based on the worst-case condition of a washout sxtending to the surface.
Furthermore, potential hazards resulting in flooding due to a failure in the circulating water discharge
. piping near the Diesel Generator Building have been evaluated and have been shown to be negligible.
Response To The Stamiris And Warren Contentions:
i
- 1) Stamiris Contention 4A(4). The effects on seismic Category I piping of completed or proposed remedial actions by CPC are still under evaluation.
In particular, the EDFS and SWS piping in the vicinity of the Diesel Generator Building are still under review.
However, since the EDFS piping was constructed after the surcharge program and most of the 8 and 10 inch diameter SWS piping has been or is going to be rebedded, the effects of completed remedial actions is negligible except for those 8 inch lines which have been pigged a'nd were discussed above.
- 2) Stamiris Contention 4C(f). The concerns regarding differential soil settlement and seismic effects on seismic Category I piping are currently being investigated.
- 3. Warren Contention 3.
The surcharge program did not affect the seismic Category I EDFS lines since those lines were constructed after the program.
CONCLUSIONS On the basis of the above, no conclusions regarding the adequacy of the seismic Category I piping over the life of the plant can be reached at this time. Areas where additional data are required or ongoing l
reviews are in progress have been identified.
Final conclusions will be made pending satisfactory disposition of all ongoing and/or additional reviews.
)
W. P. CHEN MANAGER, STRESS ANALYSIS UNIT, ENERGY TECHNOLOGY ENGINEERING CENTER (ETEC)
EDUCATION B. Eng.
Civil Engineering & Applied Mechanics, McGill University, 1959 M. Eng.
Civil Engineering & Applied Mechanics, McGill University,1962 Ph. D.
Theoretical and Applied Mechanics, University of Illinois, 1965 EXPERIENCE 1965-1971 Simon Fraser University, Burnaby, B.C.,
Canada Teaching and research in the Mechanics of Deformable Media with particular emphasis on problems of limit analysis and contained plastic flow of elastic-plastic media.
1972-1974 Basic Technology, Inc., Pittsburgh, Pa.
Thermal stress analysis of components.
1974-Present Energy Technology Engineering Center ASME B&PVC compliance analysis of piping and components.
NRC LWR licensing support and snubber research activities.
Technical support for Solar Central Receiver and Ocean Thennal Energy Conversion projects.
PUBLICATIONS 1.
A complementary Linear Theory of Plasticity for Plane Strain, Arch.
Mech. Stos., Vol 18, P. 731-749, 1966 2.
On Classes of Complete Solutions for Rigid Perfectly Plastic Truncated Wedges in Plane Strain, Arch. Mech. Stos., Vol. 21, P.
469-494, 1969 3.
On Uniqueness of the Limit Load for Unbounded Regions, Arch. Mech.
Stos., Vol. 21, P. 679-699, 1969 4.
On the Cdllapse of Rigid Perfectly Plastic Tapered Cantilever Beams Under End Shear, Acta. Mech., 1972 5.
On Torsion of Elastic - Perfectly Plastic Cylinders of Polygonal Cross Section (In Preparation)
_,_ A C H lk E N T 2.
7T i
CRITICnL Di/AUTY> f%
i
- s l
Q....._... M 4_.._.-
I i
Q.. _ _.
t i
t' l
l i
I i
,y a
,7
_-y._
VI, i
=
r f
1 e
y
..L__..._
\\. -n i
p o
s O
i
@j i
T\\-
ki r
v, t/l (p.
l.-- - - - - $---
m,. -
L i
i t
l.
g
_ ql - _ - - -
/
i
_.l. _ _. l _.
i 4
.+
. _. +._;
. g_
j.
g 7..
s
,o n
--e et
?
I D
i rb;p O G ;p t
l
.Th y
~
~ g'
_... n_L i
t t
}
i
+-
t
}
i l
. _... _ _ Q _
,... _. - p
...)
g g 4
._ _ _i ___
,,3
_ __. i J
e y,p' i
_. N I
. ___. j.. _. _ _ _.
o O
E' i
m p
_,!___.___.,..-..p_....__..
.. ~. _ _ _. _....
. _ _ _I _._
.4.._.
+
l i
}
}
}
I l
4 j
i
. l e
i 1
7.....
l l
l l
i j
i b
l A
?
t I
h I
I._ _.. L_ _ _. - _:
e i
t
. J
__- w _ _
+-__._.....i...___3..-_.-. ' _ _ _ -
i l-I i
I I
t t
i I
l l
{
e L
I
' d.____
I
.m______
vi sw,,,, i., o, i.., n
.-