ML15296A451

21C025, Rev. 0, Bloost Code Validation Report.

ML15296A451
Person / Time
Site:	05000704, Armed Forces Radiobiology Research Institute
Issue date:	04/20/2012
From:	Sherman R General Atomics, Hitachi America, Ltd, Marubeni Canada, Ltd, TRIGA Technologies
To:	Govt of Thailand, Office of Atomic Energy for Peace, Office of Nuclear Reactor Regulation
References
TAC ME1587 21C025, Rev. 0
Download: ML15296A451 (4)

Text

3. NUREG-1 537, Part 1, Sectioti 4.6 recommends that an application should justify the assumptions andmethods, and validate results. bi/scuss the BLOOST code transient analysis in additional detail includingthe quantitative values of the rfajor parameters that enter the analysis. This should include the fluxpeaking factors used to represehf the hottest fuel rod.Please see the attached "BLOOST Code Validation Report" which provides more detail regarding theassumptions and methods of th'e BLOOST code. The "BLOOST Code Validation Report" also discusses abenchmarking study performed at the Sandia TRIGA Annular Core Pulse Reactor (ACPR).3-t 5. NUREG-1537, Part 1, Section 13.1.2 provides guidance to the licensee to identfi,5 all potential methodswhereby excess reactivity could be accidentally inserted into the reactor to cause an excursion. Pleasediscuss these potential methods and evaluate those found to be credible. At a minimum, analyze a rampinsertion of reactivity of the most reactive control rod (not the transient rod) at its maximum insertionrate, starting from the most Jim iting power level. Evaluations should include discussion of the model,assumptions, and calculation results.A ramp insertion of reactivity resulting from the withdrawal of a control rod may be caused by operatorerror or instrument malfunction. In order to determine power as a function of time during a linearreactivity increase, a single delayed neutron group model with a prompt jump approximation is used:*where P(t) is the power at time t, P0 is the initial power level, f3 is the total delayed neutron fraction(0.007), X, is the one group decay constant (0.405 sec-'), t is time, and y is the linear insertion rate ofreactivity.Control rod data for the AFRRI TRIGA reactor is shown in Table 1.Table 1. Control rod data for the AFRRI TRIGA reactor in core position 500.Rod Total Worth Total Withdrawal Average Insertion($). Time (sec) Rate ($/sec)Transient 2.89 29.0 0.0997Safety. 2.65 39.4 0.0673Shim 2.74 36.1 0.0760Regulating 3.01 34.8 0.0865For the reactivity insertion accident, starring power levels of 100 W and 1.0 MW were considered. TheSCRAM set point was assumed to b~e 1.09 MW, and a 0.5 second delay time was assumed betweenreaching the SCRAM set point and of the control rods. In addition to the single controlrod withdrawal scenario, the simultaneous withdrawal of all four control rods was also analyzed as aworst case.

Table 2. Summary of ramp insertion of reactivity for AFRRI TRIGA control rods.'Rod Withdrawn Starting Power Time until Release of Total ReactivityControl Rods (sec) Inserted at SCRAM ($)Transient 100 W 9.77 0.93___________1.0 MW 1.23 0.13Safety 100 W 13.5 0.92___________1.0 MW 1.53 0.11Shim 100 W 12.23 0.931.0 MW .1.43 0.11Regulating "100 W 10.99 0.951.0 MW 1.32 0.12All Rods 100 W 3.51 1.161.0 MW 0.74 0.25In all cases, including the simultaneous withdrawal of all control rods, the total reactivity insertion is wellbelow the pulse reactivity insertion limit of $3.50 (2.45% Ak/k), thus safety of the reactor would not beadversely impacted.

6. NUREG-1537 Part 1, Section 13 provides guidance to the licensee to discuss potential accidentscenarios. Section 13.1.5 of the SAR presents the results oalan analysis al a reactivity insertion of $0.51.Justify the magnitude of this assumed reactivity insertion in comparison with the maximum reactivityinsertion associated with any sin~gle experiment.The following analysis will replace the reference to a reactivity insertion of $0.51 of the SAR:The failure of an experiment or experiments could result in instantaneous insertion of reactivity. Theworst possible case would be the prompt addition of $3.00 (2.1% Ak/k) within the reactor core. TheTechnical Specifications establish that the sum of the absolute reactivity worths of all experiments in thereactor and in the associated experimental facilities shall not exceed $3.00 (2.1% Ak/k). Theinstantaneous insertion of $3.00 (2.1% Ak/k) to the reactor core as a result of a worst case reactivityinsertion is bounded by the an~lysis of the $3.50 (2.45% Ak/k) pulse limit and would not result in anyadverse safety conditions withili the AFRRI TRIGA core.