ML24137A309
| ML24137A309 | |
| Person / Time | |
|---|---|
| Site: | Idaho State University |
| Issue date: | 04/26/2024 |
| From: | Idaho State University |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24137A307 | List: |
| References | |
| Download: ML24137A309 (1) | |
Text
Specification
- a. The total scram withdrawal time of the safety rods and coarse control rod shall be less than 1 second.
- b. The average reactivity addition rate for each control or safety rod shall not exceed 0.065% k/k per second ($0. 0 0877 per second).
- c. The safety rods and coarse control rod shall be interlocked such that:
(1) Reactor startup cannot commence unless both safety rods and coarse control rods are fully withdrawn from the core.
(2) Only one safety rod can be inserted at a time.
(3) The coarse control rod cannot be inserted unless both safety rods are fully inserted.
- d. All reactor safety system instrumentation shall be operable in accordance with Table 3.1 with the exception that, with the approval of the Reactor Supervisor, Safety Channel No. 1 may be bypassed whenever the reactor control or safety rods are not in their fully withdrawn position.
- e. The shield water interlock shall be set to prevent startup and scram the reactor if the shield water level falls 10 inches below the highest point on the reactor shield tank manhole opening.
- f. The shield water temperature interlock shall be set to prevent reactor startup and scram the reactor if the shield water temperature falls below 15°C.
- g. The seismic displacement interlock sensor shall be set to prevent reactor startup and scram the reactor during a seismic displacement.
- h. A manual scram shall be provided on the reactor console.
- i. A loss of electric power shall cause the reactor to scram.
- j. An operable installed area radiation monitor capable of detecting gamma radiation shall be immediately available to reactor operating personnel whenever the reactor is not secured. When required monitors are inoperable, portable instruments may be substituted for any installed monitor for periods up to two weeks, while the installed monitor is being repaired.
Basis
The specifications on scram withdrawal time in conjunction with the safety system instrumentation and set points assure safe reactor shutdown during the most severe foreseeable transients. Interlocks on control and safety rods assure an orderly approach to criticality and an adequate shutdown capability. The limitations on reactivity addition rates allow only relatively slow increases of reactivity so that ample time will be available for manual or automatic scram during any operating conditions.
AGN -201 Technical Specifications, Amendment No. 8 9 The neutron detector channels (Nuclear Safety Channels Nos. 1 through 3) assure that reactor power levels are adequately monitored during reactor startup and operation.
Requirements on minimum neutron levels will prevent reactor startup unless Channel 1 is channels are operable and responding, and will cause a scram in the event of instrumentation failure. The power levels initiate redundant automatic protective action at power level scrams low enough to assure safe shutdown without exceeding any safety limits. The period scram conservatively limits the rate of rise of reactor power to periods which are manu ally controllable and will automatically scram the reactor in the event of unexpec ted large reactivity additions.
The AGN -201's negative temperature coefficient of reactivity causes a reactivity increase with decreasing core temperature. The shield water temperature interlock will prevent reactor operation at temperatures below 15°C thereby limiting potential reactivi ty additions associated with temperature decreases.
Water in the shield tank is an important component of the reactor shield and operation without the water may produce excessive radiation levels. The shield tank water level interlock will prevent reactor operation without adequate water levels in the shield tank.
The reactor is designed to withstand 0.6g accelerations and 6 cm displacements. A seismic instrument causes a reactor scram whenever the instrument receives a horizontal acceleration that causes a horizontal displacement of 1/16 inch or greater. The seismi c displacement interlock assures that the reactor will be scrammed and brought to a subcritical configuration during any seismic disturbance that may cause damage to the reactor or its components.
The manual scram allows the operator to manually shut down the reactor if an unsafe or otherwise abnormal condition occurs that does not otherwise scram the reactor. A loss of electrical power de -energizes the safety and coarse control rod holding magnets causing a reactor scram and thus assuring safe and immediate shutdown in case of a power outage.
An area radiation monitor must always be available to operating personnel to provide an indication of any abnormally high radiation levels so that appropriate action can be taken to shut down the reactor and assess the hazards to personnel.
AGN -201 Technical Specifications, Amendment No. 8 10 Table 3.1 Reactor control and safety systems set -point specifications.
SAFETY CHANNEL SET POINT FUNCTION Nuclear Safety Channel No. 1 Unit A) 5% Full Scale Scram at levels (Startup Count Rate Channel) OR B elow the set points Low Power Unit B) 0.5 counts/second Nuclear Safety Channel No. 2 6 watts Scram at power (Log Power Channel) (120% of licensed power) > 6 watts High Power Nuclear Safety Channel No. 2 -13 Scram at source levels (Log Power Channel) 3.0 x 10 amp ere s < 3.0 x 10 -13 amps Low Power Reactor Period 5 sec Scram at periods
< 5 sec Nuclear Safety Channel No. 3 6 watts Scram at power (Linear Power Channel) (120% of licensed power) > 6 watts High Power Nuclear Safety Channel No. 3 5% Full Scale Scram at levels (Linear Power Channel) < 5% of Full Scale Low Power
Manual Scram ---- Scram at operator option
Alarm at or below level Area Radiation Monitor = 10 mR/hr set to meet requirements of 10 CFR 20
3.3 Limitations on Experiments
Applicability
This specification applies to experiments installed in the reactor and its experimental facilities.
Objective
To prevent damage to the reactor or excessive release of radioactive materials in the event of an experiment failure.
Specification
- a. Experiments containing materials corrosive to reactor components or which contain liquid or gaseous, fissionable materials shall be doubly encapsulated.
- b. Explosive materials shall not be inserted into experimental facilities or the reactor or stored within the confines of the reactor facility.
AGN -201 Technical Specifications, Amendment No. 8 11