ENS 52342
ENS Event | |
|---|---|
14:34 Nov 2, 2016 | |
| Title | Unanalyzed Condition for Control Rod Drop Accident at Low Power |
| Event Description | On November 2, 2016, while performing a re-evaluation of the radiological consequences of the Fermi 2 control rod drop accident (CRDA), DTE Electric Company (DTE) identified a non-conservatism in the current Fermi 2 design and licensing basis of the CRDA. As described in the Updated Final Safety Analysis Report (UFSAR) Section 15.4.9, the current design and licensing basis assumes that the post-CRDA release pathway consists of carryover with steam to the turbine condenser. The re-evaluation has identified that a forced release from the gland seal exhausters (GSEs) could also occur which could result in post-CRDA radiological consequences that exceed the current 10 CFR 100.11 offsite dose limits and Standard Review Plan 6.4 (General Design Criterion 19) main control room dose limits when operating at low power conditions.
The unanalyzed condition described above only applies to low power operating conditions (i.e. less than 10% power) since the fuel damage postulated as a result of a CRDA is only credible under low power operating conditions when an individual control rod worth is high. Fermi 2 is currently at 97% power and, therefore, the plant condition is currently bounded by the design and licensing basis such that the condition currently does not exist and no immediate actions are required. However, Fermi 2 has operated at low power levels several times in the past three years. Those periods of operation at low power represent unanalyzed conditions that significantly degraded plant safety since the occurrence of a CRDA during those periods could have resulted in offsite and main control room doses exceeding regulatory limits. Therefore, this 8-hour notification is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B). There was no adverse impact to public health and safety or to plant employees. The licensee has notified the NRC Resident Inspector. |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+0.52 h0.0217 days <br />0.0031 weeks <br />7.12296e-4 months <br />) | |
| Opened: | Greg Miller 15:05 Nov 2, 2016 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Nov 2, 2016 |
| 52342 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (97 %) |
| After | Power Operation (97 %) |
WEEKMONTHYEARENS 552312021-05-03T13:30:0003 May 2021 13:30:00
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