ML20154C049
| ML20154C049 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/28/1998 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20154C039 | List: |
| References | |
| NUDOCS 9810060125 | |
| Download: ML20154C049 (6) | |
Text
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8.7 WIRE, CABLE AND RACEWAY FACILITIES
'8.7.1 Design Bases 8.7.1.1 Functional Requirements device, these facilities must be of a type and b function during all postulated accident conditions.
8.7.1.2 Design Criteria The electricalloading of conductors does not exceed, a; d is generally ampacities recommended by American Institute of Electrical Engineers - ins publications S-135-2 and P-46-426,1962), and in maintained spacing in between cables the ampacities recommende'd of Electrical and Electronics Engineers (IEEE), joint publication, IPCEA P 440, and National Electrical Manufacturers Association (NEMA) Pub. N The percent cross-section fill of wireways is governed by the allowable cable ampacities.
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the National Electrical Code,1971.The physical support of wireway lEEE 279,1971, Sections 4 and 5 of IEEE Standard 3 and 18 of Appendix A of 10 CFR Part 50. Electrical penetration assembli 1 2 3 4 17 i
IEEE 317,1971.
8.7.2
System Description
8.7.2.1-System Cable types required to operate inside the containment after ari accident a an environment more severe than that expected in service. All cables have degree of flame resistance to obviate the need for flame retardant coati extinguishing systems.
listed below. The ' ower supply for this detector sy p
these areas, an annunciator in the control room displays tion type detector heads are as follows: protection is provided as d
. Additional fire Computer room Control room ventilating ducts le.
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rifiec Revision.js4Cd Main exhaust equipment room
' nitial.11 Date._tl.h!L i
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MNPS-2 FSAR
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Fuel handling area
- Auxiliary building and radwaste ventilating room b
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Cable spreading room Electrical penetration rooms Cable vault Medium voltage switchgear rooms 4
1.ow-voltage switchgear rooms
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Cable chases 8.7.2.2 Components The raceway system is made up of cable trays, conduits and undergroun the electrical cables contained therein.
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Cable trays are of galvanized steel, ladder type or solid bottom, with solid required. Hangers for trays carrying vital circuits are designed to withstand se disturbances as described in Subsections 5.8.1 and 5.8.1.1.
slabs. The duct banks going to the intake structure a withstand a seismic disturbance, as noted in Subsection 5.8.2.3.
All in-line splices of conductors are made only in metal enclosures such as term boxas and junction boxes or in designated splicing areas of the cable racewa e,
Table 8.7-1 lists the physical and electrical characteristics of the cables that are and indicates the qualification tests. The certified results of such tests are availa 1
inspection.
The electrical penetration assemblies through the wall of the containment structur form part of the containment pressure boundary, as described in Subsection 5.2 The low-voltage power and control modules are mounted in a stainless steel heade plate and are designed to meet or exceed all requirements of iEEE Standard 3 The medium-voltage power penetrations are designed to meet or exceed all re ments of IEEE Standard 317,1971.
demonstrated the suitability of the assemblies for operation under t service conditions. These tests include leak integrity, current carrying capacity (continuous, short-time overload, and fault current) dielectric strength, insulation
' therein meet all criteria applying to each class of service
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terminate in a stress cone and lug. Low-voltage power cables larger than 4/0 AWG
- o age conductors terminate in lugs rigidly fixed in a terminal box at each end of the penetration ass All other power, control, and instrumentation cables except for Class 1E instrumenta-the penet' ration assembly. The Class 1E instrumentati containment are made with qualified in-line splices. Coaxial cables terminate in connec-tors mounted in terminal boxes at each end of the penetration assembly. All terminal boxes are designed for NEMA IV service.
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A leak rate test is performed on each penetration assembly following its installation.
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.This test is cassable of detecting a leak rate of 1 x 10-8 cc/sec of dry nitrogen at L
ambient temperature when maximum design pressure is applied across the penetration L
assembly barrier. To effact this test, each assembly is fitted with a gage to monitor the.
l pressure, and is then charged with 30 psig of nitrogen. The assembly is so designed that all seals, including conductor seals, are monitored by the gage.
8.7.2.3 Cable Arnpacities Maximum ampacities for various installation conditions are given in Tables 8.7-2 and i
i 8.7-3, the actualloading being always below these limits. In all cases,90 C insulation and 50 C ambient air values are used. All ratings are based on those given in AIEE-IPCEA " Power Cable Ampacities," joint publication S-135-2 and P-46-426,1962, and for open-top cable trays without maintained spacing in between cables in IPCEA lEEE, j
joint publication, IPCEA Pub. No. P-54-440 and NEMA Pub. No. WC 51-1972.
L' 8.7.3 Availability and Reliability v
8.7.3.1 Separation 1
The raceway systems are so designed that any one raceway channel may be physically sacrificed under accident conditions. The layout drawings in Figure 8.7-1 show typical examples of the separation of raceways serving different channels.
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~ The separation of redundant cables is accomplished by spatial separation of their cable.
trays. This spatial separation is normally not less than four feet vertically and 18 inches horizontally to guard against damage from external fire, missile, or other accidents.
Where these spacings between trays of redundant systems cannot be maintained (physical obstructions, points of n' ecessary convergence, crossovers, etc.), barriers are provided to preserve the physical and electricalintegrity of the cables, Vertical stacking of separate redundant trays is avoided where possible.
b-Where separate redundant trays must be stacked with less than four-foot vertical separation, their horizontal separation is less than 18 inches, or they crossover with less than six inches clear space vertical separation, rated fire barriers or a combination of rated fire barrier / suppression system must be used.
10-9 Typically, rated fire barrier material employed to enhance raceway separatiori is one-half inch Marinite 36, or equivalent. Installation will be as follows:
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Mc La iel Maaration. A vertical barrier, one foot above and one foot below the a.
trays, or to the ceiling or floor, b.
Vertical Seoaration. A horizontal barrier between trays extending one foot each side,of the tray system.
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w2S7.w2 8.7-3 October 1994 l
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MNPS-2 FSAR vn29 Cross-overs. A horizontal barrier extending out one foot from each side of each c.
tray, and -five feet along each tray from the crossover.
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in lieu of the above, conduit or a totally enclosed tray may be used and the two channels do not touch each other.
Generally, no more than one channel of separate redundant systems is run through a compartment containing machines with flywheels. Where this cannot be avoided, each case is evaluated for additional protection. Similarly, no more than one channelis generally routed through an area containing high pressure (275 psi and over) piping.
Where necessary, the redundant raceway will be run at least ten feet from such Where this spacing cannot be achieved, pipe restraints are provided and each case is evaluated for additional protection.
Where routing is unavoidable through an area subject to a possible open accumulation of quantities (gallons) of oil or other combustible liquids as a result of rupture or leak of a fluid system, a single separation channel only is routed through this area. Further-more, the cables are protected from dripping liquids by conduit or covered tray.
Raceways (exposed conduits, trays, penetrations, etc.) are generally stacked vertical in the following relative order:
a.
6900-volt power b.
4160-volt power c.
480-volt load center subfeeders d.
'480-volt power and general control
' Shielded control and instrumentation e.
(" Shielded control and instrumentation cables may be run with un-shielded control and instrumentation for short distances such as risers into equipment).
Within each of these classifications, nonvital cable may be run with vital cables.
However, a nonvital cable is never routed in raceways of more than one separation channel.
Vital circuits, components, and equipment are those that are safety related. That is, the safe operation and shutdown of the nuclear system is dependent on them. Vital systems meet the single failure criterion and therefore are redundant and separate.
Where indicators and other devices are not essential for the safe functioning of a vital system, current and potential transformer secondaries or other low energy circuits feeding such devices are considered nonvital circuits.
Equipmb t, devices, cables and raceways have an assigned number that indicates if they are in vital service or not, and also indicates the channel. These designations are shown on one-line and three-line diagrams, schematics, circuit and raceway schedules, and the instrument index.
MP28-7.MP2 8.7-4 October 1994
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" v tal system. The absence e8 vital se ce Thefi of n
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p fix s called he a i Code, and its use is further ex iain d in Ta y
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e 8.7-Vital power and control cables fall mainly into two redundancy classifications; Ch nel Z1 and Channel 22. In a few cases there is also a Channel 25, which is a s that can be transferred from one source to another, and is run as described below t
Cables such as those in reactor protection service are assigned to Channels 21 and Z4. As shown in Table 8.7-4, nonvital Channel 1 may be routed with vital Channel Z1, and Channel 2 with Channel Z2. Low level butfered signal outputs fro 23 and 24 channels of a four-channelinstrument system may be run with nonvital channels 1 and 2 respectively. Where the system lacks a current limiting feature and 24 are run separately.
Channel 25 is associated with the spare units fed from 4160-volt emergency bu namely, service water pump P58, Reactor Building Closed Cooling Water (RBCCW) l pump P11 B, and High Pressure Safety injection (HPSI) pump P41B. The power circu and the control circuits for this equipment are all transferred simultaneously to Chan nel Z1 or Z2 sources. Thus, their circuits are routed together as Channel 25. The 25 control circuit and power circuit for the spare 480-volt charging pump P18B, are transferred to 21 or Z2 sources independent of the above circuits. Hence, the Z5 charging pump circuits are routed separately from those associated with bus A-5.
g Nonvital Channel 5 circuits are those associated with instrument loops or meterin circuits. Channels 5 and 25 circuits are routed together only where it can be demon-strated that their transfer to Channel 1 (Z1) or 2 (Z2) sources does not impair the separation of redundant safety related circuits.
Computer and annunciator circuits are considered nonvital. Their inputs are from nonvital Channels 1 and 2 that may be routed with vital circuits as shown in Table 8.7-
- 4. The Channel 1 and 2 segregation for the nonvital circuits is lost when they enter th final saceways at the computer or the annunciator terminal cabinets. The 480-volt' power supply to the computer is reduced to 120-volts by an uninterruptible power,
supply (preferred) or a regulating transformer (alternate). The intemal power supply provides 36 volts (fused one-half amp) to the digital inputs, and the analog inputs are 10-50 mA. The power supply to the annunciator is from two separate redundant AC to DC power supply systems which isolate the annunciator DC voltage from the AC sources and isolate the two AC power sources from each other.
The control element drive system (CEDS), including the CEDS logic cabinets, are also considered nonvital. Two separate feeders, one from each of the two nonvital 120 vac instrument buses, supply control power to the logic cabinets. The feeder cables are routed in separate raceway from the distribution panels to the cabinets, but are g.n ultimately bundled together within a common logic cabinet Separation of the nonvital gf 120 vac instrument buses is maintained, however, because separate double pole circ breakers installed in each of the nonvital distribution panels provide isolation between the two buses. No redundancy is intended, or required, for the CEDS logic cabinet power supplies.
ueme-7.ue 8.7-5 September 1995
e MNPS-2 FSAR 3
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All power supply equipment is identified with respect to its source. Odd first digits ar assigned to Channel 1; i.e., B1, B12, etc. Even first digits are assigned'to Channel 2; l
i.e., B2, B21, etc.
To assist in verifying proper separation, the jackets of all cables are color coded.
Table 8.7-4 indicates the physical separation applied to cables and raceways, and the cable jacket color for each case.
Apertures for entrance of redundant vital cables into control boards, panels and relay l
racks are separated by at least twelve inches of air space. Where this cannot be accomplished, the entrance is made with conduit or enclosed tray.
Redundant vital cables terminate on terminal blocks at least six inches apart. internal wiring of redundant vital circuits, and any associated devices, is separated by ayg[
minimum of six inches. Where the minimum spatial separation of six inches is not feasible, noncombustible barriers or conduit are used to provide separation. Nonvital i
channels may be wired to the same device, but their conductors are bundlec separately.
-C4 revicc h Whenever practicable, shipping splits and structural stiffeners are utilized as natura!
barriers. The barriers are comprised of two sheets of steel plates with one inch air space or insulating fire-resistant materialin between,if devices and/or
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f wiring are mounted on both facss of the barrier, if devices and/or wiring are mountec I
d on the barrier on only one face, a single sheet of steel plate for isolation is satisfactory provided devices and/or wiring on the other side are installed at least one inch away from the barrier. The barriers are properly supported for structural strength, and extend from top to bottom and front to back to a depth which provides a minimum of six l 97-W inches separation between channels.
1 Typical layouts illustrating the separation of redundant wireways are shown in Fig-ure 8.7-1.
8.7.3.2 Tests and inspections l-The various documents indicating the separate routing of rodundant cables are carefully l
cross-che'cked during the design of the system. The color coded jackets of the cables l
permit a visual inspection to verify that the separation criteria are observed.
insulation resistance of all power cabias is measured initially and spot checks are made I
at refueling periods. Such tests indicate significant trends in the unlikely event there has been deterioration of the insulation.
The pressyre gages on the electrical penetration assemblies are located in the auxiliary 1
building penetration rooms and are readily accessible. These assemblies remain charged with nitrogen throughout their life, and a pressure reading will be taken and recorded periodically.
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MP28 7.W2 8.7-6 September 1997
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