ML23009B720
| ML23009B720 | |
| Person / Time | |
|---|---|
| Site: | Idaho State University |
| Issue date: | 01/20/2023 |
| From: | Xiaosong Yin NRC/NRR/DANU/UNPL |
| To: | Joshua Borromeo NRC/NRR/DANU/UNPL |
| References | |
| Download: ML23009B720 (1) | |
Text
License Amendment Request (License R-110, Docket No. 50-284)
The request
- Remove low power scrams for nuclear safety Channels 2 and 3
- Channel 2 currently has one low power scram to be removed
- Channel 3 has low power scrams in each linear range, but only low scrams in low power ranges (where detector does not function) and in startup range to be removed
Why?
- Old BF3 neutron detectors used in Channels 2 and 3 must be replaced
- BF3 detectors no longer available
- Replacement detectors have less sensitivity at low power levels; therefore no current to control console at low power levels
- Lack of detector current at low power causes Channels 2 and 3 to scram
Safety implications
- None
- No impact on assessment of maximum credible reactivity accident (ISU AGN Safety Analysis Report Section 5.5)
- Estimated power increase has stable period of 1 sec
Overview of scrams with amendment SAFETY CHANNEL SET POINT FUNCTION Nuclear Safety Channel No. 1 Unit A) 5% Full Scale Scram at levels (Startup Count Rate Channel)
Low Power OR Below the set points 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 3.0 x 10-13 amperes Scram at source levels (Log Power Channel)
< 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)
(for ranges above startup < 5% of Full Scale Low Power range)
Manual Scram ---- Scram at operator option From Table 3.1 of Facility License R-110 Docket Number 50-284 Amendment 7 Technical Specifications
Comparison with scrams for other AGNs Idaho State University Texas A&M University University New Channel Scram (ISU) (A&M) Mexico (UNM) 5% of full scale Channel 1 - Low or 10 counts per second NA 0.5 counts per second Channel 2 - Low 3.0 x 10-13 amps 1.0 x 10-12 amps NA Channel 2 - High 6 watts 10 watts 6 watts Channel 3 - Low 5% of scale 1.0 x 10-12 amps NA Channel 3 - High 6 watts 10 watts 6 watts