GCRE-I HAZARD SUMMARY REPORT Page: 4 of 13
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This addendum has been prepared to answer questions raised by the
Reactor Hazards Evaluation Branch as transmitted in a letter dated 4
March 1959 from V. V. Hendrix to A. T. Biehl. This addendum supplements
the GCRE-I Hazard Summary Report (IDO-28506) in the following areas:
geometry and operation of the steam cooling system and the reactor
coolant by-pass and by-pass valving; the means by which by-passed cir-
cuits are preven rom re unintentionally disabled; design
and details of procedure for core flooding operations.
1. Steam Cooling System
This is the "last resort" cooling system. It is used only
when the reactor is shutdown and generally only as outlined in Section D
of ANSOP 5717. Its use in conjunction with reactor flooding is authorized
in ANSOP 5718. In this case, steam cooling is permitted during the por-
tion of -th'e flooding operation where the introduction of steam will not
force water up into the core proper. In addition, the water level in the
lower plenum is maintained at a low enough point to accommodate the water
displaced from the steam line without raising the water to the lower tube
sheet. This conservation increases the time required for flooding but
is felt to be a safe method of controlling the reactivity addition in
The schematic arrangement of the steam cooling system and
main control valves is shown on Figure 1. Figure 2 shows the details of
the piping arrangement under the lower plenum.
2. Reactor Coolant By-Pass Loop
This is an 8 in. line which by-passes the reactor from the
outlet side of the fired heater to the inlet side of the gas-to-water
heat exchanger. Both terminations of the line are on the compressor
side of the main coolant loop block valves as shown in Figure 3. Flow
through the by-pass loop is controlled by a single manually operated
valve in the heater pit (GNL-V-54).
This piping is designated as Class D (Type 347 Stainless
steel, schedule 80 seamless butt-welded fabrication) and has been
hydrostatically and leak tested (see Section MS-1, Process & Utility
Piping Specifications, Invitation No. AT(10-1)-945). The valve is a
900 lb, type 347 stainless steel gate valve with double packing, butt-
welded into the line.
The control valve in this loop is normally padlocked closed
and will be operated normally only when the reactor is shutdown. Any
situation requiring by-pass coolant flow during reactor operation will
be covered by a special procedure under ANSOP Section 9.
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GCRE-I HAZARD SUMMARY REPORT, report, March 1, 1959; United States. (https://digital.library.unt.edu/ark:/67531/metadc1054055/m1/4/: accessed March 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.