An investigation of scramming the outer shutdown rods of the ANS with no reversal of flow in the manifold inlet lines

Technical Report · Thu Oct 01 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/6990836· OSTI ID:6990836

Morsk, K ^[1]

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1. Royal Inst. of Tech., Stockholm (Sweden)

This report provides calculations and calculation checks on the outer shutdown system, consisting of eight shutdown rods located on the outside of the core. The function of the system is to scram the reactor, or to break the chain reaction of the fission process. The shutdown rods are clad with a neutron-absorbing material (i.e., hafnium) to achieve scram. During normal operation, the outer shutdown rods (Fig. 1) are in a nonscram, withdrawn position. This means that they are not close enough to the core to absorb a significant number of the neutrons that cause the fission process. In the case of a malfunction or an emergency, the outer control rods are moved to a position near the core. The outer shutdown system is operated with the use of springs and hydraulics. During normal operation, a constant flow of heavy water is circulated through the reflector vessel. A part of this flow provides a pressure high enough to keep the rods in their withdrawn or upper position, a nonscram status. If any signs of abnormal operation occur, the valves in the hydraulic system cut off the flow, and the springs push the rods into the scram position, stopping the chain reaction. Once the flow is restarted, the rods can be withdrawn to the nonscram position. Calculations of the mass of the outer control rod, the scram spring data, and the hydraulic pressure to hold the rods in the withdrawn position have been checked. In the case of a malfunction of the flow/pressure relief valves, a calculation was needed to show that the scram time would not exceed the time allowed. The scram time has been determined based on different values of the rod insertion length and the outside radius of the annulus was calculated. The effective force pushing the rod into the scram position, the rate of acceleration, and the actual scram time was then determined.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6990836
• Report Number(s): ORNL/M-2259; ON: DE93002858; TRN: 92-038111
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
RESEARCH AND TEST REACTORS
REACTOR CONTROL SYSTEMS
FLUID FLOW
HYDRAULICS
MATHEMATICAL MODELS
REACTOR SAFETY
SCRAM
VALVES
CONTROL EQUIPMENT
CONTROL SYSTEMS
EQUIPMENT
FLOW REGULATORS
FLUID MECHANICS
MECHANICS
REACTOR SHUTDOWN
REACTORS
SAFETY
SHUTDOWN
220400* - Nuclear Reactor Technology- Control Systems
220600 - Nuclear Reactor Technology- Research
Test & Experimental Reactors
220900 - Nuclear Reactor Technology- Reactor Safety
990200 - Mathematics & Computers