SALEM
SALEM STUDY SYSTEM
Systems > Radiation Monitoring

Radiation Monitoring

⚠️ DRAFT

Radiation Monitoring

Function

Radiation monitoring systems detect and measure radiation levels throughout the plant for personnel protection, effluent control, and post-accident monitoring. Process radiation monitors provide automatic actuation of safety functions (e.g., containment vent isolation) and alarms. The radiation protection program ensures that occupational radiation exposures are maintained as low as reasonably achievable (ALARA) and within 10CFR20 limits. (UFSAR 7.6, UFSAR 12)

Process Radiation Monitors

Exam — 2023 Q49
SGBD radiation monitor (1R19A) check source test: when the check source pushbutton is pressed, counts rise then return to the original reading (not held high while button is pressed). During the check source, interlocks are NOT expected to actuate. (Ref: S1.OP-ST.RM-0001)
Exam — 2023 Q62
1R1A (Control Room Area) radiation monitor in alarm: does NOT automatically actuate CAV in AP Mode. Requires manual actuation — press ACCIDENT PRESSURIZED pushbutton at 1RP2 to actuate BOTH units' CAV into AP Mode. Emergency intake dampers open on the unaffected unit.

Plant Vent Effluent Monitor (R41)

Exam — 2018 Q83
Gas Decay Tank (GDT) release path: 11 GDT discharges to the plant vent. An unplanned gaseous radioactive release from the 11 GDT will alarm on 1R41D (Plant Vent Noble Gas Release Rate) — NOT on 1R12A-B (Cont or Vent Gas Effluent/Iodine). Crew performs AB.RAD-0001 Attachment 1 (Process Radiation Monitors) to stop the release. Trap: R12A-B IS a gaseous process radiation monitor, but it monitors containment vent gas, not the plant vent. Also, Attachment 2 (Process Filter Radiation Monitors) applies to filtered systems — the GDT release path to the plant vent is unfiltered.
Exam — 2019 Q25
2R41 has 4 channels (A, B, C, D). 2R41 Channel D is the ONLY control room indication that reads out in µCi/sec and can be used to determine if a radiological release is in progress for notification to State and Local Agencies. Channels A, B, and C do not read out in µCi/sec — only Channel D provides release rate information.

Steam Generator Blowdown Radiation Monitors (R19)

Exam — 2018 Q23
R19 SGBD radiation monitor WARNING setpoint — unit difference confirmed: Unit 1 has NO automatic functions when R19 goes into WARNING (automatic functions only occur when the monitor goes into ALARM). Unit 2 has automatic functions on R19 WARNING — GB185 (Blowdown Discharge to Condenser) valves automatically close. Trap: do not confuse WARNING vs ALARM actions, and remember the unit difference at the WARNING level. Unit 1 warning is early warning only; Unit 2 warning closes blowdown valves.
Exam — 2020 Q51
R19 SGBD radiation monitor WARNING setpoint: Unit 1 — NO automatic actuations (warning is early warning only). Unit 2 — automatically closes ALL GB10s, GB185s, and 2GB50. Trap: R19 WARNING and ALARM actions differ. The ALARM setpoint on Unit 1 closes ALL GB4s, GB8s, GB10s, GB185s, and 1GB50. On Unit 2, ALARM isolates blowdown from the affected SGs by closing the associated GB4. Do not confuse warning vs alarm actions, and remember the unit difference at the warning level.

Liquid Effluent Radiation Monitor (R18)

Exam — 2020 Q90
2R18 (Radioactive Liquid Effluent Monitor) response to detector failure: R18 failing LOW will NOT cause 2WL51 (Liquid Release Stop Valve) to automatically close — only a HIGH alarm closes WL51. Per S2.OP-SO.WL-0001, if 2R18 is inoperable, 2FR1064 (Radwaste Overboard Discharge Flow Recorder) must be OPERABLE AND two independent samples, independent release calculations, and independent discharge valve lineups must be performed. Trap: ODCM 3.3.3.8 allows flow rate estimation if 2FR1064 is inoperable, but the release procedure prevents BOTH R18 and FR1064 from being inoperable simultaneously.

Fuel Handling Building Radiation Monitors

Exam — 2020 Q23
2R32A (Fuel Handling Crane area radiation monitor): when the monitor fails to its alarm setpoint, ONLY crane hoist-up operation is prevented. Lowering the hoist is still allowed (conservative — allows the assembly to be lowered back for increased water shielding). There is no BYP INT pushbutton to defeat this interlock, and crane trolley operation is NOT affected. Note: 2R5 and 2R9 (FHB area rad monitors) cause FHB exhaust to shift to 22 HEPA plus Charcoal but have NO interlocks with the fuel handling crane.
Exam — 2019 Q33
Confirms 2R32A behavior: with 2R32A failed high, ONLY crane motion other than downward movement of suspended load is locked out. FHB ventilation transfer to HEPA and Charcoal does NOT occur on 2R32A — FHB ventilation auto-shifts only on 2R5 and 2R9 alarms.

Fuel Storage Area Monitor (2R9)

Exam — 2019 Q36
2R9 (Fuel Storage Area Monitor) alarm response: BOTH Fuel Handling Area Exhaust Fans receive an auto start signal (standby fan starts). 21 HEPA ONLY Filter Unit ISOLATES and 22 HEPA PLUS CHAR filter unit automatically aligns. After 2R9 alarm, both exhaust fans are running but only the charcoal filter unit is in service. Trap: 2R9 does NOT keep both HEPA units in service — the HEPA ONLY unit isolates and the HEPA PLUS CHAR unit takes over.

Containment High Range Monitors (R44A/B)

Exam — 2020 Q26
R44A/B containment high range monitors provide input to the Subcooling Margin Monitor for adverse containment determination. R44A/B > 1E05 R/HR triggers adverse containment conditions for the SMM. Note: >1E06 R/HR is the integrated dose value used in procedures — the SMM adverse threshold is >1E05 R/HR. R44A/B are also used in EOP-CFST-1 to determine entry into EOP-FRCE-3 when radiation exceeds 2 R/HR.

Shielding Design

  • Primary shielding: biological shield around the reactor vessel (concrete)
  • Secondary shielding: containment structure, auxiliary building walls
  • Designed to limit dose rates in normally occupied areas to levels consistent with 10CFR20 occupational limits
  • Shielding design considers both normal operation and post-accident conditions (UFSAR 12.1)

Ventilation for Contamination Control

  • Plant ventilation systems maintain appropriate pressure differentials to direct airflow from areas of lower contamination to areas of higher contamination
  • HEPA filters and charcoal adsorbers on exhaust systems remove airborne contamination
  • Containment purge system used to reduce airborne activity levels before personnel entry (UFSAR 12.2)

Radiation Protection Program

  • Dosimetry: personnel monitoring for external and internal exposure
  • Radiation surveys and monitoring
  • Contamination control and decontamination
  • Respiratory protection program
  • Radioactive material control and accountability
  • Training for all personnel with access to radiation areas (UFSAR 12.3)

ALARA Program

  • Design features to minimize exposure: remote operation, shielding, ventilation, decontamination capability
  • Administrative controls: radiation work permits, dose goals, pre-job ALARA reviews
  • Dose tracking and trending (UFSAR 12.4)

Key Regulatory Limits (10CFR20)

ParameterLimitSource
Total Effective Dose Equivalent (TEDE)5000 mrem/year10CFR20.1201
Lens of Eye Dose15000 mrem/year10CFR20.1201
Shallow Dose Equivalent (skin/extremity)50000 mrem/year10CFR20.1201
Declared Pregnant Worker500 mrem/gestation10CFR20.1208
General Public (fence line)100 mrem/year10CFR20.1301

Tech Spec LCOs

Exam — 2022 Q83
Fission Product Barrier Table (EP-SA-325-123) and R44A/B containment high range radiation monitors: with R44A and R44B both reading >2000 R/hr following a LBLOCA, the barrier assessment yields: FB2.L (fuel barrier loss, 5 pts) + RB1.L or RB2.L (RCS barrier loss, 5 pts) + CB2.P (containment barrier potential loss, 2 pts) = 12 points → General Emergency. Classification: GE with Loss of 2 barriers and Potential Loss of the 3rd barrier. This is NOT a loss of all 3 barriers — containment is a POTENTIAL loss (lowering pressure indicates containment is functioning).
JPM — 2022 RO-A4
Dose and stay time calculation for containment entry (RP-AA-300): from survey map, identify gamma and neutron dose rates at work location. Calculate stay time = (dose limit / dose rate) x 60 min/hr. Compare all limiting factors: gamma stay time, neutron stay time, and heat stress stay time. The lowest value is the controlling factor. At 22 CFCU area (130' CTMT): neutron = 40 mrem/hr → 12 min stay time (most limiting), gamma = 5 mrem/hr → 24 min, heat stress = 15 min.
JPM — 2018 IP-k
During liquid radwaste release (S2.OP-SO.WL-0001 Sec 5.5), 2R18 reads 105 cpm with High Radiation light illuminated at 104 panel during Step 5.5.8 data collection. Step 5.5.9: 2R18 Monitor ALARMS → direct NCO to CLOSE 2WL51 (LIQUID RELEASE STOP VALVE) to terminate the release.
JPM — 2022 IP-k
During liquid radwaste release (S2.OP-SO.WL-0001 Sec 5.5), 2R18 radiation monitor provides overwatch. At Step 5.5.8, operator reads 2R18 on 104 panel: 105 CPM with High Radiation light illuminated. Step 5.5.9: if 2R18 ALARMS, immediately direct NCO to CLOSE 2WL51 (LIQUID RELEASE STOP VALVE) to terminate the release.

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