ML20216F622
| ML20216F622 | |
| Person / Time | |
|---|---|
| Site: | National Bureau of Standards Reactor |
| Issue date: | 06/22/1987 |
| From: | NATIONAL INSTITUTE OF STANDARDS & TECHNOLOGY (FORMERL |
| To: | |
| Shared Package | |
| ML20216F602 | List: |
| References | |
| NUDOCS 8706300898 | |
| Download: ML20216F622 (11) | |
Text
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Attachment I Requested Amendment to the NBSR Technical Specifications Change'Section 1,3 (2) to read:
All automatic isolation valves in ventilation, process piping and guide tubes are'either operable or closed.
Note: The only difference between the existing and' proposed specification I is the _ addition of " guide tubes "
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~7 8706300898 870622 PDR ADOCK 05000184 P- PDR
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l Attachment II i i
Facility Description and Safety Analysis l 1
I... Purpose-2
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.'The planned cold neutron facility will be a national center-for
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research using cold neutrons. Current 1f,~ there are no such centers in the United States. This facility takes advantage of the large NBS cold
- source- to' provide seven neutron beams ' guided by neutron guide ~ tubes
. into a large ' experimental hall (guide hall) that will house fifteen or more state-of-the-art neutron instruments. This facility will provide'
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the capabilities, not presently available to the United States, needed w to characterize-new materials, analyze chemical and biological
-f processes, develop advanced technologies, and explore fundamental physical concepts. It is a very high priority proj ect of 'the Department of Commerce in its drive to improve the international ,
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!" competitiveness of the Nation in areas of high technology and !
productivity.
II. Building Description
, A layout of the Cold Neutron Facility is shown in Figure 1. - The guide hall'is located contiguous to the reactor confinement building, but is not part of it and there is no direct access between the two. Seven neutron beams will be brought from the cold source in the reactor 1
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,1 through'the reactor confinement building north wall into the guide hall using neutron guide tubes. Neutron guides use the fact that low energy neutrons can be totally reflected by . flat surfaces of certain materials. Such guides make it possible to transport neutrons great distances with very little loss of intensity.
The guide hall will not have direct access to the reactor confinement building. Instead,.it can be accessed from the office wings. The
- present hot plug storage facility, loca't'ed on the north wall of the
' confinement building, will be relocated next to the lower level of the' '
guide hall building.
III. Heat Exchanger Room h In anticipation that it may be necessary to replace the existing reactor main heat exchangers, provisions are being made now to expedite the installation of new heat exchangers in the future. Rather than
. physically removing the existing heat exchangers, which are located
. deep within the process room, they would be left in place and' the new J heat exchangers will be located in a new, easily accessible room adjacent to the west wall of the process room. It will be below ground at the elevation of the existing ' process room and have direct access j I
for personnel.and piping as shown in Figure 2. Access for future heat ]
i: exchangers'will be through a large hatch in the roof of the room that
- can be removed by a crane.
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Detailed structural calculations show that the designed penetrations through the existing confinement building wall into the heat exchanger room will not reduce its structural integrity and that the new room will meet or exceed the original building objectives.
IV. Guide Tubes Penetrations The neutron guide tubes will penetrate the north wall of the reactor confinement bu'ilding as shown in Figure 3. The penetrations:are$
approximately 18 inches in diameter. The guide tubes are evacuated and.
so have gas tight seals at each end. They are mounted in pipes which penetrate the wall and are sealed to it with gas tight seals.
Automatic isolation valves are provided that serve two functions. The g.y primary function is to close automatically whenever a major scram calls for sealing the building. Thus, the confinement building will be sealed regardless of the condition of the guide tube windows. The second function is to act as beam tube shutters and to seal the building whenever maintenance work is being performed on the guide tubes. The function of these valves is the same as that of existing isolation valves in the confinement closure system.
Detailed structural calculations show that the designed penetrations through the confinement building wall will not affect the structural integrity of the confinement building.
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l V. Automatic Isolation Valves The guide tubes automatic isolation valve design is shown schematically in Figure 4. The major components are a shutter, two gate valves, a pneumatic piston to lift the shutter, and a section of neutron guide tube which is lif ted into place when the shutter is raised (opened).
All the components, except the pneumatic cylinder, are located within a vacuum jacket that,is penetrated only by the piston shaft. The vacuum is opened to and is part of the vacuum maintained inside the neutron guide tubes. As the shutter is lowered by the pneumatic cylinder, the j gate valve plates which are adjacent to but independent of the shutter !
are lowered along with the shutter until they are stopped in place by a l
mechanical stop. The shutter, however, continues moving down forcing j the gate valve plates against the sealing surf ace via the pivoting q 49 The shutter stops when its full weight is on the j lever arms shown.
arms which can't move out any further because the gate valve plates are in their full out, sealed position. Thus, the 0-ring vacuum seal is simply established and maintained by the weight of the shutter.
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The shutter is raised (opened) by the pneumatic cylinder until it hits j a mechanical stop. It is kept open by maintaining air pressure on the cylinder. It is lowered by closing the solenoid valve to the air supply and opening a bleed valve to let the air out of the cylinder.
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The bleed valve will be a fail open valve and the su'pply valve will be a fail closed valve. Thus, if the electric power, gas supply, or valve solenoids should fail, the shutter will close and seal by gravity.
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. VI . < Confinement Integrity and Performance All proposed penetrations of the existing confinement building are designed to maintain the structural integrity of the existing building.
Detailed . structural analysis show that the structural integrity of the building is not affected and that it will coati'nue to meet its original design objectives. In fact, the proposed penetrations ~are no different
' than existing;penetrat' ions. The possibility of bringing neutron. beams $
out of the confinement building was considered in the original Safety. -
Analysis Report and provisions were even made for one such beam.
The performance criteria and surveillance requirements for the confinement building established in the NBSR Technical Specifications
- p. are unchanged.
VII. Conclusions
' The proposed change in the NBSR Technical Specifications does not:
- 1. Involve a significant increase in the probability or consequences of an accident previously evaluated since the proposed confinement penetrations are similar to existing penetrations and will not af.fect confinement integrity or performance..
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- 2. Create the possibility of a new or different kind of accident from l l
any accident previously evaluated since confinement penetrations j f
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were considered in the original Safety Analysis Report and the proposal penetrations will not affect confinement integrity or performance.
3.. Involve a significant reduction in a margin of safety. Since both-confinement structural. integrity and confinement performance 4
requirements are not affected.
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