ML061890006
| ML061890006 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 04/14/2006 |
| From: | Duane Arnold |
| To: | Office of Nuclear Reactor Regulation |
| D. Spaulding LPL3-1 X2928 | |
| Shared Package | |
| ML061890004 | List: |
| References | |
| TAC MC8883 | |
| Download: ML061890006 (11) | |
Text
Dose Consequences Analysis for Control Rod Drop Accident without Automatic Trip of Mechanical Vacuum Pump at DAEC April 14, 2006
History
- DAEC submitted Full Scope Adoption of AST during Power Uprate dated 10/19/2000
- Used Gap Release Fractions from Draft Guide DG-1181 that were revised in RG 1.183
- CRDA analysis did not calculate TSC Dose - bounded by other events
- CRDA Ground Level Release Point assumed as Turbine Building Exhaust with slant range to CR and TSC
- In application DAEC committed to update calc when revised to full RG 1.183. NRC Reviewer concurred results were conservative.
- Amendment 240 was issued on 7/31/2001
History
- Subsequent review of original vendor analysis by DAEC personnel following training on RADTRAD code identified Release Timing was over one hour rather than instantaneous puff release
- New Calculation CAL-R02-001 was performed
- Revised GAP Release Fractions to RG 1.183
- Revised Release timing to 5 seconds
- Revised Release Point to Condenser
- Calculated TSC Dose
- Superseded applicable section of CAL-R00-PUP-008
- Results were acceptable under 10 CFR 50.59
History
- CAL-R05-001 prepared to support Amendment to eliminate MSL Radiation Monitors.
- Added Mechanical Vacuum Pump Release Path through Offgas Stack.
- Calculated Dose Consequences of manual trip of MVP at 10 minutes.
- Calculated Dose Consequences of failure to trip MVP as sensitivity case.
Elevated Stack Release while MVP operating Control Room 3150 cfm vent 155,000 ft^3 1.75 min holdup Technical Support Mechanical Vacuum Pump Center 1800 cfm 900 cfm vent Offgas Stack Condenser 68,300 ft^3 55000 ft^3 1%/day ground release leakage Exclusion Area after MVP secured or not running Boundary Source Term: Uprated Power 1950 MWt FTR T0802 Low Population Zone NUREG-1465 and RG 1,183 RELEASE RECEPTORS CRDA WITH/WITHOUT MVP OPERATION
Other Isolations from MSLRM
- Main Steam Line Drains
- Path also drains to condenser
- not modeled due to rapid transport of source term to the condenser through MSIVs in shorter time than valve stroke
- Recirculation System Sample Valves
- Small piping (0.5 in)
- Crack Arrest Verification System leak checked on startup, not a likely release path
- Inside secondary containment
New Assumptions since NRC Review of Amendment 240
- 1. Assumptions for the release of radioactivity from the fuel
- Release of Other (non-halogen or Noble Gas) fission products from the fuel is per RG 1.183 Table 3 for the gap release and from Table 1 (Early in Vessel) for the pellet release (fuel melt).
Gap Release fractions changed since previous NRC review to reflect RG 1.183 changes from Draft Guide 1181.
New Assumptions
- 2. All radiological nuclides released from damaged or melted fuel are assumed to be transported to the condenser within 5 seconds in accordance with the timeline in GNF Standard Application For Reactor Fuel (US) (reference 7.8) S2.2.3.1.1.
No credit for automatic or manual isolation of Main Steam Isolation Valves or Steamline Drains.
- 3. Per the US Supplement to the GESTAR II manual section S2.2.3.1.1 Sequence of Events, the gap release phase is conservatively modeled to begin at T = 0 seconds with a duration of 5 seconds and the fuel melt phase begins at T = 0 seconds with a duration of 5 seconds. Conservatively ignores transport time and assumes the full source term is transported to the condenser during the same period in which it is released from the fuel.
New Assumptions
- 4. Mechanical Vacuum Pump operation modeled at a constant 1800 cfm (design flow capacity).
New Transport Path
- Release point assumed from Main Condenser, previously assumed from turbine building exhaust point that used a slant range
- Added path for Mechanical Vacuum Pump discharge to offgas stack assumed design flow and 1.75 minute holdup.
- Post-accident meteorology atmospheric dispersion factors (X/Qs) from stack for the Control Room and TSC were calculated using inputs from CAL-R00-PUP-002 and the methodology described in RG 1.194 section C.3.2.2. The maximum X/Q using PAVAN or ARCON96 is used for the 0 - 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> interval. ARCON96 values are used for the intervals from 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The 1 - 4 Day and 4 - 30 Day intervals are calculated using a weighted average assuming 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at the PAVAN value and 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> at the ARCON96 value.
Control Rod Drop Accident Radiological Consequences Exclusion Area Low Population Control Room TSC Boundary Zone Accident Type (30 Day) (30 Day)
(2 hr) (30 day)
MVP Operating 7.0065e+00 3.3335e+00 8.5277e-01 6.6960e-01 Gap Release MVP Trip 10 Min 2.6990e+00 1.2172e+00 4.5996e-01 5.2669e-01 Dose MVP secured 6.3551e-02 3.8052e-02 3.5649e-01 5.1556e-01 MVP Operating 3.9007e-01 1.8532e-01 2.8787e-02 2.2001e-02 Fuel Melt MVP Trip 10 Min 1.5098e-01 6.7943e-02 1.5133e-02 1.6889e-02 Release Dose MVP secured 3.4575e-03 1.8803e-03 1.1413e-02 1.6316e-02 MVP Operating (Sensitivity Case) 7.3966E+00 3.5188E+00 8.8156E-01 6.9160E-01 MVP Manual Trip 10 Min (Proposed Total Dose Design Basis Case) 2.8500e+00 1.2851e+00 4.7509e-01 5.4358e-01 MVP secured (Expected Results Case) 6.7009E-02 3.9932E-02 3.6790E-01 5.3188E-01 6.25 (25% Of 10 CFR 6.25 (25% Of 10 CFR RG 1.183 Acceptance Criteria Guideline 5 5 50.67 Limit) 50.67 Limit)
Well Within 10 CFR Well Within 10 CFR Standard Review Plan Limit 5 5 50.67 Limit 50.67 Limit 10 CFR 50.67 Limits 25 25 5 5 Fraction of 10 CFR 50.67 Limit for No MVP Trip Case 29.59% 14.08% 17.63% N/A Numerical precision of results is shown based on results of software. Some inputs are only specified to 2 significant digits, therefore results are not considered to be accurate beyond two significant digits.