ML20154R743
| ML20154R743 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 03/25/1986 |
| From: | Whittier G Maine Yankee |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| References | |
| GDW-86-77, IEB-80-11, MN-86-48, MN-86-487, NUDOCS 8603310169 | |
| Download: ML20154R743 (19) | |
Text
s MAIRE HARHEE ATOMICPOWERCOMPARHe ,uausray,TaQ3s (207) 623-3521 e
March 25, 1986 MN-86-48 GDW-86-77 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of Licensing
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) NRC IE Bulletin No. 80-11, Masonry Wall Design, dated May 8, 1980 (c) MYAPCo Letter to USNRC dated June 30, 1980 (WMY-80-103)
(d) M7APCo Letter to USNRC dated November 4, 1980 (WMY-80-149)
(e) MYAPCo Letter to USNRC dated October 21, 1982 ,
(MN-82-207) !
(f) MYAPCo Letter to USNRC dated April 22, 1985 (MN-85-78)
Subject:
Additional Masonry Walls Evaluated in Accordance with l IE Bulletin 80-11 Gentlemen: i In response to Reference (b), Maine Yankee performed a survey of the masonry walls at Maine Yankee in order to identify those which "
should be classified as safety related. The walls which were classified as safety related were identified in References (c) and (d).
In References (e) and (f), the list of safety related masonry walls was revised to include additional masonry walls which had been i classified as safety related. I In February, 1986, Maine Yankee performed a detailed review of our IE Bulletin 80-11 records. We were unable to locate the records documenting the initial masonry wall survey performed in 1980. As a result, a more comprehensive plant survey was performed by two independent teams of engineers to identify safety class masonry walls. A revised list of safety class block walls is provided in Table 1 (Attachment A). Additions to Table 1 are delineated by a bracket in the right hand margin of the page. A draft copy of Table 1 was provided to Mr. A. Varela, NRC Region I, on March 7, 1986. gl 7367L-GDW G603310169 g60325 PDR G
ADOCK 05000309 pon lll J
_ --- = = .
, =
M AINE YANKEE ATOMIC POWER COMPANY
! s United States Nuclear Regulatory Commission page Two I Attention: Mr. Ashok C. Thadani, Director MN-86-48 Attachment B provides a description and evaluation of each.of the newly identified walls listed in Table 1. For completeness, we have included walls which are in proximity to safety class equipment which is not required for safe shutdown or accident mitigation. As
~
l noted in Attachment B, most of the newly identified walls were l either not in existence or not in the proximity of safety related equipment at the time of the 1980 survey. We have concluded that the additional walls would either have withstood design loads or their failure would not have prevented adjacent safety class -
equipment from performing its intended safety function.
Four of the walls were modified to provide an additional margin.
of safety in lieu of performing a rigorous analysis of each wall.
Based upon questions posed by Mr. Varela and others during our February 18, 1986 conference call, an independent assessment of these walls was performed by Mr. John McWilliam, Structural Section Manager, Impell Corporation (Attachment-C). Impell's assessment confirms our conclusions that the recent masonry wall modifications, while prudent, were not required to ensure that the affected systems could perform their intended safety functions, and safe operation of the plant was not jeopardized. ;
As a result of our recent survey, we have determined that l additional design controls were necessary with respect to masonry l walls. Accordingly, we have implemented controls to ensure IE Bulletin 80-11 concerns are taken into account for design changes i associated with masonry walls or safety class equipment in proximity j to masonry walls, please contact me if you have any questions in this matter.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY c
hjhAV G. D. Whittier, Manager Nuclear Engineering and Licensing GDW/bjp Attachments: 3 cc: Dr. Thomas E. Murley l Mr. pat Sears Mr. Cornelius F. Holden Mr. Anthony Varela 7367L-GDW
MAINE YANKEE ATOMIC POWER COMPANY s
we ATTACHMENT A i
l 7367L-GDW !
l l
i 9
TABLE 1. Masonry Walls Evaluated for NRC IE Bulletin 80.-11 Page 1 of 4 Category 1: Walls which will withstand design basis loads and not affect safety class equipment.
Category 2: Walls whose collapse will be contained and not affect safety class equipment.
Category 3: Wils whose collapse will not affect safety class equipment.
- Denotes walls which have been analyzed.
. Wall Room Reference Safety Class Building ID Location Drawing Wall Location Equipment to be Protected Category 1 Catecorv 2 Category 3 Containment C -2 Refueling Canal 11550-Frt-1B, C Block Shields at North Assorted Safety Class x* ]
1 End of Canal Piping and Equipment C 20 (Ref. EDCR 82-05) 2-3 Containment C -2 EL -2'-0" 11550-Frt-1C Southwest Annulus Containment Liner xe ]
2 Containment C -2 E l -2 '-O" 11550-Frt-1C North Annulus Containment Liner xe ]
3 Containment C 0.5 Elevator 11550-FA-5B South Wall Pressurizer Instrumentation xe 1 Er. closure . (PT-104, LT-106) and Tubing EL 0*-6" C 'O 20'-C" to 46 '-0" 1.
Containment C 46 Elevator 11550-F&58 North, West, and South Steam Cenerator Suppressors. xe 1-2 Enclosure . Walls and Tubing
.. El 46 '-O" to C 61 70'-6 1/2" 1-3 7367L-GDW
- w. _ _. . _ _ _ _ _ _ _ . _ -_ _ _ -
o e
TABLE 1. (ContinuedJ Page 2 of 4 i
Wall Room Reference Safety Class Building ID Location Drawing Wall Location Fguipment to be Protected Category 1 Category 2 Category 3 Fuel FB 44 Spent Fuel Pool 11550-FA-12A South Wall Spent Fuel Spent Fuel Purification Xe 1 EL 44'-6" Building and Cooling Return Lines and Containment Elec, Pen No. 14 Primary PAC 11 EL !!'-0" 11550-SK-MT-66A Shielding Blocks Around CVCS Letdown Line and he Auxiliary 2 11550-Ff5-2 A Letdown Lines Associated Valves Primary PAB 21 Boric Acid 11550-FA-11A Betseen Lines 7 and 9 Boric Acid System (Heat Tracing Xe ]
Auxiliary 1-t, Storage Area and Columns F and H Panel, Valves BA-M-36, 37, EL 21 *-O" FL-10) Auxiliary Steam HELB Isolation valve AS-P-78 Primary PA8 21 Demerator Vent 11550-FA11A East h il Degasifier D &lB XN ]
Auxiliary 7 Condenser Cubicle EL 21'-0" Primary PA8 35 Degasifier Vent 11550-F&11 A South and East Wall Containment Purge Line is Xe Auxiliary 1-2 Condenser Area Around PA8 Non-Nuclear Attached to Block h ll (Evaporator Safety Class Charcoal 6" VCT Relief Line and 3" Cubicle) Filter Hydrogen Vent Header are EL 36 *-0" Near Wall 1 and Above Wall 2 Primary PAB 36 Waste Gas' Surge 11550-F M 11A Removable Shield Wall Gas Decay Drums, Waste Gas Xe Auxiliary 3 Drum Area East Wall Surge Tank, Waste Gas EL 36'-0" Manifolds Service SB 21 Corridor Along 11550-FA-1A Between Column 4 and PCC/ SCC Piping, Cables From Xe ]
4 C-Line Elevator Main Feedwater Block EL 21*-0" Valves (MOV-1201A, 1201B, 1201C), PCC Surge Line 1
4 7367L-CDW
...__...m_._.. ___m_ .- . _ _ __ _ _ . . . . . _ _ ._.. . _ _ . .m _ . _ . _ _ _ _ _ _ _ _ . _ _ _ _ . . - _ .m_ . _ - _ _ . .. . _ - . - . . . . . -
o a
J
}
}
1 j' T__ABLE 1. (Continued) Page 3 of 4 Wall Room Reference Safety Class Building ID Location Drawing Wall Location Equigunent to be Protected Category 1 Category 2 Category 3 Service SB 71 Control Room 11550-FA-1A Toilet, South, West, and Control Panel Containing AFWS X#
17-19 EL 21'-0" East Wall Controls, Main and Bypass Feede ter Valve Controls, Containment Recirculation, Fan Controls, Reactor Coolant Loop Indication, Reactor Coolant Pump Bearing Lift, j-Lube Pressure Indication.
7 Service SB 35 Cable Tray 11550-FA-1B Battery Room 3 and 4 Area Battery Groups 3 and 4 and , X#
1-4 Room, EL 35'-0" South, North and West Wall Misc. Safety class Cables
} Service S8 35 Elevator 11550-F A-1B Elevator Enclosure East PCC Temperature Controller Me 1
- 7 Enclosure 115504 A-5A Wall - North Side PCC Surge Line EL 35'-O" Service S8 39 Vent and Air 11550-FA-1B Wall Along 7-Line Between Control Room Breathing Air Xe 1 Condition Columns E and F Supply Fans FN-7A, FN-78, Equipment and Ventilation Ducts
! EL 39'-O"
' Service SB 39 Cable Tray Area 1155044-1B South Wall Along Line 7 Cables From Main Feedwater. Me xe ]-
i 2 EL 35'-O" Between Columns D and E Regulation and Bypass Valves (HCV-1212, 1222, 1232, and FCV-1211, 1221, 1231) Cables for Control Room Breathing j Air and PAB HELB Isolation valve, exhaust duct for protected SWGR Room.
i
a e
TABLE 1. f Continuedl Page 4 of 4 Wall Room . Reference Safety Class Building ID Location Drawing W3 11 Location Equipment to be Protected Category 1 Category 2 Category 3
~
Service SS 45 Switchgear 11550-FE-27B Battery No. 2 and 1 Area Reactor Trip Breaker SWGR, Xe 1-3 Room, EL 45'-6" 11550-FA-18 South and West Wall and EMER MCC (NCC-8A), DC Dist Safety class SWGR Room Cab 4, DC Dist Cab 3, DC Dist cab 2, DC Dist Cab 1, 30, 22.5 MVA Inverter 5, 480 V Emergency SEG, Bus 8, 10 10 KVA Inverter 2, Battery Charger No. 2. 10 10 NVA Inverter 1 ,
Battery Charger No. 3, Battery Groups 1 and 2.
Service SB 45 Switchgear Area 11550-FA-18 East Wall PCC Surge Line, One-Inch Chemical X# ]-
6 EL 45'-6" Add. Lines for PCC and SCC Service S8 61 Elevator 11550-FM-3K Elevator Shaf t and PCC Surge Tank, TK-5, and Xe 2 Enclosure 11550-FA-1B Equipment Room - South SCC Surge Tank, TK-59 SB 77 EL 61*-0" Wall 2 EL 77'-4" Turbine TB 21 Corridor Along 11550-FM-3C Adjacent to PCC Hu E-4A, PCC Ha E-4A, E-4B Xe 2 C-Line Columns 7 E-4B to 9, EL 21*-O" Vent VE 21 EL 21'-O" FO-21J Walls hear Entrance to SCC Line to Penetration Xe ]
Equipment 1-4 Containment Spray Building Coolers and Spray Building Area Fans and Filter Yard Y 20 Refueling Water 11550-FY-1B RWST Shielding Blocks Refueling Water Storage Tank X* ]
Storage Tank 7367L-GW L
MalNE YANKEE ATOMIC POWER COMPAP$Y I
i j
L ATTACHMENT B
{
Walls C-1 (1). C-20 (2-3): Refuelino Canal Shields i These three " walls" are actually stacks of unmortared solid i shielding blocks which have been installed at the north end of the j refueling canal to reduce radiation levels in the containment during the transfer of spent fuel. The blocks were installed in the spring of 1984 along with protective shields which ensure that tre blocks l cannot collapse and damage any safety class equipment.
j i A brief description of the three " walls" and the safety class equipment in the vicinity of the shielding blocks is provided below.
Wall C-2 1 consists of shielding blocks stacked on the west side
- of the refueling canal, around column 4, between Elevation -2'-0" j and the bottom of the Elevation 20'-0" slab. Structural steel and i steel grating ensure that the blocks cannot collapse and possibly
, damage nearby safety related equipment. Equipment being protected 4
by the shields include valve HCV-335K, instruments PT-331 and -
LT-331, and several safety class pipes.
Walls C-20 (2-3) are similar to C-2 1 except that they are ,
stacked between Elevation 20'-0" and just below Elevation ~46'-0" on the west and east sides of the refueling canal. The protective shields are similar to the one installed at the lower level, and the safety class equipment being protected includes instruments'PI-332 and 333 and several pipes and valves.
l Walls C-2 (2-3):
Shieldino Blocks Stored in Lower Annulus
" Wall" C-2 2 identifies solid shielding blocks which are being stored in the southwest annulus (between columns 17A and 20). One i stack is four feet wide and five feet high while the second is one j foot wide and five feet high. There is no safety class equipment in the vicinity of these blocks except the containment liner. Our evaluation has concluded that these blocks cannot damage the'3/8" j steel liner backed by 4'-6" of heavily reinforced concrete.
! C-2 3 identifies two stacks of shield blocks stored in the. north-l annulus area (Elevation -2'-0"). One str.ck is one foot high and
- 2'-6". wide located adjacent to the crane wall, while the second i stack is five feet high and is.near Column 5. The only safety
- related " equipment" near these blocks is the containment liner which we.have concluded cannot be damaged by the stacked blocks.
W311s PAB 21 (1-6): Boric Acid Area a
! Six wall panels form the perimeter of the Instrument and Control j Hot Shop. The walls are 8'-0" high and free at the top (interior i i- drop ceiling was ignored). In lieu of block and mortar testing, l minimum properties were assumed in our analysis (f'm = 1350 psi,
- mortar Type N, mo = 750 psi). Based upon these minimum properties, j it was' concluded that the wall panels might collapse during an SSE j event with the following consequences
! 7367L-GDW
l M AINE YAP 5KEE ATOMIC POWER COMPANY o
I Wall PAB 21 1 could hit the base of Electrical Panel 6 CH-B (boric acid heat tracing, Train B). However, its collapse is acceptable since a redundant Train A, which is not near the block wall, provides this safety function. Wall PAB 21-2 is approximately 80" from Auxiliary Steam Isolation Valve AS-P-78. This valve is one-of two independent valves designed to mitigate the environmental consequences of a High Energy Line Break (HELB). This valve was not considered safety class in 1980. To ensure that a wall collapse would not impact the valve, a horizontal steel brace was installed j near the top of the wall to ensure that it can not collapse as a ;
cantilever. We are confident that block and mortar testing, coupled )
with more detailed analysis, could have demonstrated this wall j panel's ability to withstand the SSE accelerations (since the conservatively calculated tensile stress was less than 23 psi).
This low a stress would be acceptable providing the mortar i compressive strength, mo , was shown to be in excess 1,200 psi.
l This 1,200 psi is considerably below the 2,500 psi mo value obtained from the mortar sample tested from the battery rooms.
In our judgement, collapse of this wall would not prevent the j auxiliary steam isolation valve AS-P-78 from performing its intended safety function. Even if this valve is assumed to be rendered 1 inoperable, the redundant auxiliary steam isolation valve would l still have been able to isolate auxiliary. steam if required. i
~ ;
Wall PAB 21 3 has no safety class equipment in its vicinity. l l
Wall PAB 21 4 has the following safety class boric acid system ,
components located within 96" of the wall: MOVs BA-M-36, 37; check valves BA-38, 39 and CH-ll4 and their associated piping. Located between this equipment and the subject masonry wall are two Non-Nuclear Safety Motor Control Centers 9B and llc (NNS-MCCs).
The base anchorages of these MCCs were analyzed and upgraded to ensure that it could withstand the impact of the collapsing block panel, thus protecting the boric acid system components. It should be noted that the base anchorage upgrade would not have been required if credit was taken for the strength of the numerous conduit and cables exiting from the top of the MCCs. Assuming credit for the strength of these cables guarantees that the safety l class components shielded by the MCCs would not have been damaged by the postulated block wall collapse.
Walls PAB 21 5-6 are in the vicinity of the drain from Filter FL-10, the boric acid mix tank funnel, the handle for Valve BA-33 and 2" - CH-42-152. This equipment was evaluated and determined not to be required for safe shut down or accident mitigation.
7367L-GDW l
M AIRE YONKEE QVOMIC POWER COMPORV PAB 21-7: East Wall of Deaerator Vent Condenser Cubicle This wall' panel consists of a 3'-0" by 7'-0" doorway which has been solidly filled (18" thick) with masonry. Degassifier DA-1B and some associated piping are located approximately 22" west: of the blockout.
Analysis of the blockout, assuming minimum blocks and mortar properties shows that the 3'-0" span is acceptable for all loadings.
Service Buildino SB21-4: Wall West of Larce PCC/ SCC Lines This wall is part of the ground floor, C-line partition which separates the Turbine and Service Buildings. The wall is 11'-4" high, has a gap between its top and the bottom of the Elev. 35'-0" Service Building steel and spans approximately 28' horizontally between the 7 line and the concrete wall at the south end of the control room.
Assuming minimum block and mortar properties for this 12" thick wall, it was concluded that the wall might collapse but.that the nearby 20" PCC and 16" SCC lines have adequate strength to successfully withstand the postulated impact loads.
Service Buildino SB39-2: Line 7 Between Columns D and E This wall is essentially identical to the 7-line wall between columns E and F which was described in our November 4, 1980 submittal, Reference (d).
This wall panel acts as a partition separating the unprotected switchgear area from the ventilation and air conditioning equipment area. Refer to ll550-FA-1B for wall location. The wall is "
constructed of 12" thick hollow block and is thirteen feet four
~
inches high. It rests on the El. 45'-6" slab and is supported at the top by'a steel channel attached to the underside of a roof girder. The vertical joints at the columns are-caulked. The wall is unreinforced and is constructed of the same materials as the battery rooms.
This wall was added to our list of walls due to concerns about the cables for the Feedwater regulator and bypass valve trip solenoids, the power cables for the Control room breathing air fans, and the trip cables for the PAB auxiliary steam isolation valves.
These cables were either not installed or not classified as safety class at the time'of the original walkdown.
The safety class cables of concern are located in the third cable tray farthest from the wall with two other' trays and their cables acting as deflector and energy absorbing shields protecting the safety class cables from possible damage. With this geometry, it is questionable.whether these cables would be damaged by collapsing blocks.
7367L-GDW j
MAINE YANKEE ATOMIC POWER COMPANY 4.
Though hard to quantify, the tensile strength of the trays and I
cables and their ability to move slightly away from impacts, and the fact that masonry debris could not directly hit the safety class cables, provides a high degree of confidence that these cables would i have been able to perform their safety function in the event of a i block wall collapse. We are confident that a rigorous analysis would verify this. However, to avoid further rigorous analysis, Maine Yankee elected to modify the wall to ensure that this portion .
of the wall will not collapse. Three vertical steel ribs were )
installed to reduce masonry stress to allowable levels.
Service Buildino SB45-6: East Wall of Unprotected SWGR Room
~
This 12" thick, hollow block wall separates the unprotected SWGR Room from the Turbine Building. Refer to drawing ll550-FA-1B for the location of this wall. The wall spans vertically from the top of the Elevation 45'-6" slab to the bottom of the Elevation 61'-0" floor framing. The wall is unreinforced, single wythe and is constructed of the same materials as the battery rooms.
The pCC surge line runs vertically on the east side of this wall on its route to the PCC surge tank. If one were to assume that the 12" blocks could pivot about their top and bottom supports, the resulting angle of the failed wall panels at the point of contact with the pCC surge line would be quite small (approximately 4') and thus the impact force would be correspondingly small.
Considering that seismic piping at Maine Yankee is designed to an allowable stress of 1.8 SH for sustained plus seismic (SSE) loadings and that an allowable stress of 3.0SH can be justified !
for this one-time masonry impact loading, it is our opinion that the '
surge line would have been able to function through the event.
Nevertheless, in lieu of pursuing this line of analysis, we elected to install a protective shield between the pipe and wall to prevent any masonry debris from striking the surge line.
Vent Eonipment Area: Walls Near Entrance to Containment Spray Buildino "
l These walls are located just east of the containment spray building in the Vent Equipment Area at elevation 21'-0", adjacent to the fans and filters for the spray building. These components were not considered safety class in 1980. Also, two 2" safety class Secondary Component Cooling (SCC) lines are supported off of one of the wall panels (VE 21 4).
All four wall panels are constructed of two wythes of 8" grouted blocks separated by a 2" center core (total thickness =
18"). For the location and height of the walls, refer to drawing ll550-FC-21J. These walls have been evaluated and found to withstand design basis loadings.
7367L-GDW
i M AINE' YANKEE ATOMIC POWER COMPANY
- u l
l 1 -S-l-
Yard Y 20 1: Shield Blocks Near RWST ..
This " wall" consists of an approximately 2'-0" high-stack of solid shielding blocks surrounding part of the Refueling Water t Storage Tank (RWST) base. .The blocks are one block thick (8") and
! rest on the RWST's concrete foundation. The blocks were noted and I- evaluated in June of 1983. The impact load that could affect the RWST was found to be acceptable.
f 6
5 7367L-GDW
-J
ATTACHMENT C O
IMPELL cORPORADON March 20, 1986 0570-042-NENR-001 j Maine Yankee Atomic Power Company
~1671 Worcester Road Framingham, Massachusetts 01701' ATTENTION: Mr. G. D. Whittier, Manager Nuclear Engineering and Licensing
SUBJECT:
Review of Modified Masonry Walls IE Bulletin 80-11 Maine Yankee Atomic Power Station
Dear Mr. Whittier:
At the request of !!r. W. E. Henries of Yankee Atomic Electric Company, an ,
independent walkdown and review of selected masonry walls was conducted at Maine Yankee on March 19, 1986 by Mr. John McWilliam, Impell's Structural Section Manager.
The masonry walls reviewed included four walls which either had not been previously identified or had not been formally reported (because their safety related status changed after issuance of IE Bulletin 80-11), and which have been recently modified. The four walls included:
Wall PAB 21 2 (PAB Boric Acid Area)
Wall PAB 21 4 (PAB Boric Acid Area)
Wall SB 39 2 (Service Bldg, 7 Line, Above El. 45'-6")
Wall SB 45 6 (Service Bldg, SWGR Room, Above El. 45'-6")
Although no rigorous analysis of these walls (or surrounding components) was performed to qualify the walls, Maine Yankee prudently implemented structural modifications as soon as preliminary reviews indicated a potential overstress condition. i I
The purpose of Impell's independent review was to determine if there existed a i high level of confidence in the ability of the safety systems, located in !
proximity to these walls, performing their required functions prior to modifications being installed.
l l
1 800 SOUTH STREET
- WALTHAM, MA 02154 * (617)893 2224 1
e Mr. G. D. Whittier Maine Yankee Atomic Power Company March 20, 1986
- 0570-042-NENR-001 Page Two 1
1 Conclusion The results of Impell's walkdown indicated several legitimate reasons why it was highly probable that each of the four walls either (1) would not fail, (2) in the event of failure, could not impact the safety system (s) in proximity, or (3) in the event of both failure and impact, would not adversely affect-the intended performance of the safety system.
Thus, Impe11 concludes that a high confidence did exist that the safety systems in question could have performed their required functions, and that safe operation of the plant was not jeoparized.
Summary of Results Below is a description of the findings from Impe11's walkdown of each wall and the associated reasons why the above conclusion was reached.
Wall PAB 21 2 (PAB Boric Acid Area)
This wall is an eight foot high wall free along the top edge. The safety component in question is 'the Auxiliary Steam Isolation Valve AS-P-78, which is located approximately 80 inches from the face of the wall. ;
In order to impact the valve, the wall (96" high) would have to fall in nearly .
a perfect arc, pivoting about the base of the wall. Given that the first l course of a masonry wall is usually mortared in place on a roughened concrete l surface resulting in ve'ry good bonding, the potential failure plane is likely to be at some level above the base of the wall. This would make it unlikely (or impossible) for any part of the wall to strike the valve.
Secondly, discussions with plant personnel revealed that a series of radwaste LSA storage bins are normally assembled along the east face of Walls PAB 21 1 and 21 2. These bins are approximately 42"x42"x68" high and have a 1000 pound capacity. They are lined up 10 or 11 end to end in a row nearly flush with the face of the wall. Should the wall start to fail to the east, the heavy J
bins will tend to hold them up, thus preventing a " perfect arc" failure which could impact the valve. Should the wall fail to the west, the consequences would be acceptable since no safety related equipment is in proximity in that direction.
l IN(PE.LL@
t l l
l
i Mr. G. D. Whittier Maine Yankee Atomic Power Company March 20, 1986
- 0570-042-NENR-001
- Page Three l Finally, to impact the valve, the mode of failure must result from a i significant overstress in the bed joint. The calculated stress in the joint i is relatively small, even though conservative assumptions were employed in the' analysis. These included (1) the assumption that the mortar used was Type N rather than the Type M identified in masonry wall testing at Maine Yankee (Type N has only approximately one half the tensile strength as Type M), and
, (2) the fact that no credit was taken for the dead load of the wall reducing 5 the tensile stress in the bed joint.
}
l A rigorous analysis of this wall, possibly in conjunction with a confirmatory mortar test, is likely to show that the wall would qualify in the premodified condition.
Given the above arguments, Impell concludes the existing conditions of Wall PAB 21 2 did not jeopardize the safe operation of the plant prior to. wall j modification.
~
I Wall PAB 21 4 (PAB Boric Acid Area)
This wall is also an eight foot high single wythe wall free along the top edge. The safety components in question are MOVs RA-M-36 and RA-N-37; check valves BA-38, BA-39, and CH-il4 and their associated piping.
1 All are located approximately eight feet from the west face of the wall. In between the equipment and the masonry wall are two non-safety related motor control centers (MCC's 9B and 11C).
l The present analysis on the unmodified wall shows only a very small i overstress, conservatively assuming a Type N mortar. (See discussion on Type N versus Type M under wall PAB 212.) In addition, no credit was taken for any vertical support along the north or south wall edges, although mortared joints (and perhaps block interlock) exist along both edges.
Given these conditions it is very likely that a rigorous analysis of this
! wall, again possibly in conjunction with a mortar testing program, would show
! that the wall would have qualified prior to modification.
However, even if one conservatively postulated a wall failure, the wall would
! first impact the non-safety MCC's. The MCC's would then have to topple over
' before any safety component could be impacted.
1 f
e Mr. G. D. Whittier Maine Yankee Atomic Power Company March 20, 1986 0570-042-NENR-001 Page Four i
The MCC's are approximately 19" wide by 57" long by 90" high and weigh 2100 pounds each. Each MCC is anchored to the floor with four expansion anchors.
At the top of the MCC's are a total of thirty-four (34) 2 1/2" and 3" diameter rigid steel conduits running vertically from the MCC's to a cable tray overhead. The cable tray is supported from the ceiling directly over the MCC's. An additiopal 2 1/2" diameter rigid steel conduit runs horizontally above the length of both MCC's and is tied to several of the vertical conduits.
If the conduits at the top of the MCC's are conservatively ignored, and the MCC's are assumed to cantilever off the floor, the dead weight of the equipment alone is probably sufficient to prevent any overtuning due to its own inertia. This fact, coupled with the existing anchorage, indicates that a f
rigorous analysis of the equipment and anchorage would likely show that the consequences of the wall falling onto the MCC's would be effectively mitigated by the equipment.
If one should then take credit for the high ductile strength of the attached .
conduits and overhead cable tray and supports, effectively tieing the MCC's to the ceiling, it is very unlikely that a failed wall would cause the MCC's to topple over and impact the safety equipment.
Thus, given the reasons stated above, Impell concludes the existing condition of Wall PAB'21 4 did not jeopardize the safe operation of the plant prior to modification installation.
Wall SB 39-2 (Service Building, 7 Line)
Wall SB 39-2 is a 12" thick single wythe wall 13'-4" high. Positive archorage exists at the top boundary of the wall in the form of either clip angles or a channel welded to the steel roof beam, which encaptures the wall on both sides.
The safety related equipment in question include several cables located in one of three cable trays which run horizontally toward the south face of the wall near its top. The trays then turn vertical and run down the wall, with the closest tray less than nine inches from the south face of the wall. The second tray is approximately l'-9" from the wall and the third tray is i approximately 2'-6" from the wall. The three trays turn horizontally and run '
north below the bottom of the floor slab supporting the wall at its base. The trays are supported laterally just below the base of the wall and overhead by ;
several trapeze supports. l l
i Mr. G. D. Whittier Maine Yankee Atomic Power Company March.20, 1986 0570-042-NENR-001 Page Five The safety related cables.are located in the third tray, which is furthest from the face of the wall.
If full credit is taken for the existing boundary conditions and if Type M mortar is assumed (please note again that Type M mortar properties were identified in tests on masonry walls in the Battery Room), a rigorous analysis of the wall is likely to show the resultant stresses to be at or near the allowable values.
However, even if a wall failure is postulated, the safety related cables would very likely not be impacted. This is due principally to the geometry of the trays and the wall. The fact that the horizontal run of trays is located near the top of the wall makes it very unlikely that any of the three trays could be impacted by a collapsing wall, since the positive anchorage at the top would result in the most likely failure plane located near the mid height of the vertically spanning wall. This would be at a location below the height of '
the horizontal trays. Also, in the unlikely event the horizontal trays were impacted, the two top trays would very effectively act as a ductile shield for '
the safety cables located in the bottom tray.
! Similarly, as the trays run vertically down the wall, the two inner trays act i as an effective buffer between the wall and safety related tray. The location of the inner tray (between six and nine inches from the wall face) is such that the wall would have to undergo significant diqplacement (six inches minimum on a 13'-4" span) to even " load" the inner tray, but conversely would limit " excessive" displacement (nine inches maximum or less than the block thickness). This makes it virtually impossible for even the inner tray to experience a dynamic impact from a block acting as a missile. Once again l please note that the safety cables are located in the most remote tray from the wall, thus reducing further the possibility of the cables being impacted by the wall.
The inner tray (actually all three trays) are additionally " supported" by a pair of one inch copper air lines which run horizontally between the first and second trays near the top of the vertical run. Although not attached to the trays, the two pipes would tend to act as a ductile mechanism supporting the trays in the event the inner tray started to deflect away from the wall, i
i
e Mr. G. D. Whittier Maine Yankee Atomic Power Company March 20, 1986 0570-042-NENR-001 Page Six The consequences of block failing on either side of the vertical trays is not considered significant since the block will fall directly vertically and could not impact the trays.
Thus, given these arguments, Impell concludes the existing conditions of Wall SB 39 2 did not jeopardize the safe operation of the plant prior to wall modification.
Wall SB 45 6 (Service Building, East Wall SWGR Room)
This wall is a 12" thick single wythe wall approximately 13 feet high and supported at the top and bottom. The safety related component in question is a four inch diameter PCC surge line running vertically along the full height and approximately six inches from the face of the wall. Below the bottom of the wall the PCC line turns horizontally to the north. The pipe is supported just below the bottom of the wall by a two way lateral steel support welded to ~
- structural steel. This support structure is also located directly above the
" exposed" portion of four inch pipe as it runs north.
Since the original analysis showed the wall to be marginally overstressed, a rigorous analysis of the wall should bring the calculated stresses to a value at or near the allowables.
Similarly, the four inch steel pipe is located so close to the wall (approximately one half a block thickness) that it would be very difficult for a failing wall to create much of a dynamic impact on the pipe. Conversely, to
" load" the pipe at all would require the wall to undergo a six inch displacement, a significant value over a 13 foot span. The strength of the pipe itself, along with its support geometry, indicate load carrying capabilities. It is thbs concluded that a rigorous analysis of the pipe itself would show stresses at or near the allowable values.
On an additional note, the wall has several one to two inch diameter non-safety steel conduits mounted on it in close proximity to the pipe. In j fact, there is a two inch conduit mounted vertically on the wall, exactly between the wall and the pipe, for the full height of the wall. These conduits would tend to act as " external rebars" as the wall tries to deflect outward toward the pipe. The ductile nature of the conduits would likely tend to hold that section of wall together, thus preventing any overall collapse in that area.
S S
Mr. G. D. Whittier Maine Yankee Atomic Power Company March 20, 1986 0570-042-NENR-001 Page Seven The section of horizontal pipe running north at an elevation below the bottom of wall physically cannot be impacted by postulated falling block due to the existance of the structural steel pipe support located directly above the exposed section of pipe.
Therefore, for the reasons stated above, Impell concludes the existing conditions of Wall SB 45 6 did not jeopardize the safe operation of the plant prior to installation of the modification.
~
We trust this independent assessment provides you with sufficient information for your response to the NRC. Should you require further detail or additional information, please contact Mr. John McWilliam at your convenience.
Very truly your
)
cyl,
{h '
Joh E', Roberts, Jr.
Vi ~ President JER/nc cc: P. Anderson W. E. Henries R. Shone I
l l
N W l
.