ML23045A320

14 Day Notification to Document Control Desk of Event 56331 Made to NRC Operations Center by UC Davis MNRC on February 1st at 1651 Est

ML23045A320
Person / Time
Site:	University of California-Davis
Issue date:	02/14/2023
From:	Frey W McClellan Nuclear Research Center
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
56331
Download: ML23045A320 (1)

Text

UNIVERSITY OF CALIFORNIA, DAVIS BERKELEY

• DAVIS

• IRVINE

• LOS ANGELES

• MERCED

• RIVERSIDE

• SAN DIEGO

• SAN FRANCISCO SANTA BARBARA

• SANTA CRUZ McClellan Nuclear Research Center UNIVERSITY OF CALIFORNIA Davis Davis (916)-614-6200 Tuesday February 14th 2023 Attn: Document Control Desk US Nuclear Regulatory Commission Washington, D.C. 20555-01

Subject:

14 Day Notification to Document Control Desk of Event #56331 Made to NRC Operations Center by UC Davis MNRC on February 1st at 1651 EST.

Summary of Event: During early summer of 2022 MNRC was working with the NRC staff to finalize the technical specification as part of the facilitys relicensing effort. MNRC staff proposed the limits on technical specification section 3.3 item number 4 as the limits set forth in 10 CFR 20 appendix B table 3. This limit was consistent with other similar research reactors and became part of MNRCs technical specifications on 11/21/22 when the new 20-year license was issued.

When proposing this new technical specification limit, MNRC Staff examined historical values for all non-tritium nuclides having half-lives greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. These nuclides are assayed at MNRC via high resolution gamma-ray spectroscopy. For these non-tritium nuclides, MNRC determined that the proposed limits could be satisfied. Separately, MNRC staff looked at the tritium concentration levels that are provided to MNRC via a private non-UC Davis laboratory. The latest result from this private laboratory was reviewed and confirmed MNRC would meet the new tritium limit of 0.01 uCi/ml by having a tritium concentration of approximately 1/40th of this value. Only this single tritium concentration report was checked as historical tritium levels were known to vary little from year to year.

On 1/31/2023 (while the reactor was shut down) it was discovered that the private laboratory results were incorrect and were mistakenly underreported by a factor of 100. As a result, MNRCs primary cooling water tritium concentration was determined to be approximately 2.5 times the new technical specification limit.

The exceeding of this limit was immediately reported to the NRC Operations Center (Event #56331) and reactor operations were suspended. A more extensive data review shows that MNRCs primary water tritium levels, during the past 10 years of 1 MW single-shift operation, were highly consistent ranging from a maximum of 0.026 uCi/ml to a minimum of 0.017 uCi/ml with an average concentration of 0.022 uCi/ml.

There has been no increase in the amount of tritium in MNRCs primary cooling water nor has any primary cooling water been released from the reactor tank since the new technical specification took effect.

Immediate Action: The UC Davis MNRC Director (level 2 management) instructed all licensed reactor operators that the reactor was not to be operated until further notice. Per MNRCs technical specification section 6.7.2 the NRC Operations Center was notified within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the discovery of having likely operated in violation of a limiting condition for operation from 11/21/22 until 1/30/23. The facilitys NRC program manager, backup program manager, inspector, UC Davis MNRC Nuclear Safety Committee chair,

and UC Davis MNRC license holder (level 1 management) where all notified of the event on 2/1/2023. It was determined that this event had no safety or security consequences and that no additional immediate actions were required by the MNRC staff.

Corrective Action and Event Resolution: As MNRC cannot lower the concentration of tritium in the primary cooling water, MNRC cannot operate under the conditions of technical specification 3.3 item 4. After consultation with NRC and MNRC staff, it was determined that a license amendment request (LAR) was the best option for resuming operation. A LAR was submitted to the NRC on 2/8/2023 and is currently under review. The LAR asks that MNRCs technical specification section 3.3 item number 4 be changed to allow for reactor operation so long as tritium levels in the primary cooling water do not exceed 0.05 uCi/ml. The current technical specifications require tritium concentrations under 0.01 uCi/ml (based on 10 CFR 20 appendix B table 3) in order to operate the reactor. The analysis provided in the LAR provides reasonable assurance that the proposed change does not represent any undue risk to the public or environment.

The event will reach final resolution when the license amendment is issued by the NRC. This event continues to have no adverse effect on safety or security.

Affirmation: I declare under penalty of perjury that the foregoing is true and correct executed on February 14th 2023.

Digitally signed by Wesley frey Wesley frey Date: 2023.02.14 13:13:45

-08'00' Wesley Frey PhD CHP MNRC Facility Director