NUREG-1537, Part 2 - NRC

CHAPTER 13
* With natural-convection air cooling, the analyses show that the peak fuel )
temperature will not exceed x OC in = hr, which is below the temperature
necessary for fuel cladding to maintain fuel integrity.
* With the emergency core cooling system functioning as designed, the
analyses show that the peak fuel temperature reaches no more than xx 'C,
which is below the temperature necessary for fuel cladding to maintain fuel
integrity.
* As the primary coolant escapes and the reactor core becomes uncovered,
the decay fission products constitute an unshielded gamma-ray source near
the bottom of the pool. This source could expose personnel above the
pool to direct gamma radiations and personnel on the floor of the reactor
room to scattered gamma radiations. The applicant has analyzed both
locations, including the potential doses to facility staff and the public in
unrestricted areas. The delay time while the water is escaping from the
reactor pool allows the facility staff to take cover and avoid doses larger
than xx mrem. The maximum potential dose rates in the unrestricted area
would not exceed r mrem/hr, which provides sufficient time for protective
action, if required, so that no doses would exceed acceptable limits.
* To determine the maximum potential consequences for fuel integrity and
personnel, the applicant has analyzed a loss-of-coolant scenario in which all Kprimary
coolant is lost instantaneously (ifapplicable). The other
assumptions are the same as for the slower loss evaluated above. Although
the assumptions for this scenario exceed those discussed above, fuel
integrity should be ensured and personnel doses would not exceed
acceptable limits.
Los of Coolant Flow
The reviewer should select one of the two findings that follow:
(1) The applicant has discussed possible methods by which coolant flow
through one or more fuel channels could be interrupted while the reactor is
operating. The postulated initiating events range from total loss of forced
flow as a result of pump or normal electrical power failure to blockage of
fuel channel(s) by a foreign object. The scenario assumes that the
reactor has been opeating at full power and fission product decay rates
have reached equilibrium.
When the pump stops, a conservative assumption is that forced flow stops
instantly (pump coasidown can be used in the calculations if appropriate).
The coolant-flow scram shuts down the reactor within the technical
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