Power Ascension

Fission counters are used extensively for both out-of-core and in-core measurements of neutron flux in nuclear flux in nuclear reactors. In out-of-core situations, they monitor the neutron population during the early stages of power ascension when the neutron flux level is very low. For in-core measurements, fission counters are used for flux mapping (and consequently, determination of the core power distribution). They are manufactured as long thin q lindrical probes that can be driven in and out of the core with the reactor in power. Typical commercial fission counters for in-core use have diameters of about 1.5 mm (0.06 in), use uranium enriched to at least 90 percent in as the sensitive material, and can be used to measure neutron fluxes up to 10 neutrons/(m s) [10 neutrons/(cm s)]. 

If the control system meets all requirements defined in the design speeifieations, the time courses of the status variables vector x(t) achieved at the power ascension testing must be equal to those aequired in analyses provided by the manufacturer. A deficiency of this procedure is the fact that the above shown formalized notation is impossible with complex process systems and that not all status variables are measurable. 

The check of the design is performed during the power ascension stage of the commissioning by means of special tests a part of which will be evaluated from the point of view of the major control circuits quality. 

INCREASE IE SCRUTINY OF POWER ASCENSION TEST PROGRAM... 

The overall objective of the commissioning is to demonstrate that the plant has been constructed as designed, that the systems performance is consistent with the plant design, and that activities which culminate in operation at full licensed power are performed in a controlled and safe manner. These activities include initial fuel load, initial criticality and power ascension. 

Initial fuel loading and subsequent initial criticality and power ascension to full licensed power are performed during the start-up commissioning. Prior to the initiation of these operations, the systems and conditions necessary to bring the plant into compliance with the Tech-Specs (Chapter 16 of the EDCD, Reference 10.3 must be operable and satisfied. These operations are performed in a controlled and safe manner by using test procedures that specify ... 

After the operating characteristics of the reactor have been verified by low-power testing, a power ascension programme brings the unit to its full rated power level in successive stages. At each successive stage, hold points are provided to evaluate and approve test results prior to proceeding... 

During the power ascension programme, tests are performed at various power levels as follows ... 

Stage C power ascension tests and power tests. 

M. L. McCormick-Barger, Experiment Data Report for LOFT Power Ascension Test L2-2. NUREG/CR-0492, TREE-1322, February 1979. 

The procedure for latching the control rods to the actuator tower extension rods shall include an independent verification, that the latch is engaged. An independent verification shall also be done at the first hold point on power ascension. (DB-3.4 of the 1988 Savannah River Site K-Reactor Restart Strategy) (Reference 2.)... 

The Westinghouse Savannah River Corporation (WSRC), Reactor Operations Management Plan (ROMP), WSRC-RP-89-368 (Reference 1), required that a controlled, formal, and deliberate program be established for K-Reactor design testing/data control and restart/power ascension. The plan to be developed shall have the following characteristics ... 

Westinghouse Savannah River Company (WSRC) committed to developing a plan that will establish a controlled, formal, and deliberate program for K-Reactor restart and the subsequent reactor power ascension. This program will include very deliberate and controlled startup core testing relating to criticality, rod worth, temperature coefficients of reactivity, poison buildup, axial and radial power distributions. 

The criteria for determining the adequacy of the SRS power ascension testing program for restart are described below. 

The staff reviewed the Startup Test Program document (Reference 1), which contains a plan for the development and approval of procedures associated with startup and power ascension for K-Reactor. The staff determined that this document was acceptable. Subsequently, WSRC issued the Startup Test Program Manual (Reference 2), which establishes procedural requirements for test scope development, test writing, test conduct, and test closeout. The staff determined that the controls contained in the STPM were, in general, satisfactory. 

The Power. Ascension testing regime is described in Restart Test Identification Report (RTIR) 4 (Reference 3). Test procedures are under development and will be submitted to DOE for approval. This is an open item. 

Based on the above evaluation, the DOE staff concludes that WSRC has prepared an acceptable plan for the development and approval of power ascension test procedures. The exact scope of power ascension testing and the techniques to be used for the K-Reactor Restart and Power Ascension Test Program are not completely developed at this time. The staff will review the procedures developed for power ascension testing when they have been completed and made available for review. The closure of the open item specified above will be adequate to satisfy the restart criteria. 

WSRC, RTR-2710, "K-Reactor Restart Strategy and Power Ascension Program", February 16, 1990. 

WSRC, WSRC-TR-90-29-004, "RTIR 4, Power Ascension Restart Test Identification Report," April 1990. 

One manipulation shall be an approach to criticality and the other manipulation shall be a power ascension after criticality. These manipulations shall be evaluated by personnel other than his/her immediate supervisor and the evaluation documented. 

The minimum criteria established for restart shall be two evaluated control manipulations within 6 months prior to restart. One manipulation shall be an approach to criticality and the other manipulation shall be a power ascension after criticality. Evaluations will be performed of a Supervisor s direction and oversight of control manipulations. Supervisors will not be required to actually perform manipulations. These manipulations shall be evaluated by personnel other than his/her immediate supervisor and the evaluation documented. 

DPSOP 38 requires certified Control Room Operators to perform two control manipulations within 6 months prior to restart as specified in the restart criteria. One of these manipulations is an approach to criticality the other is a power ascension after criticality. These manipulations must be evaluated and documented by personnel other than the immediate supervisor. The purpose of these manipulations is to demonstrate operator proficiency at control rod movements after a prolonged period of inactivity due to shutdown conditions. 

---