ML060470374
| ML060470374 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/09/2006 |
| From: | Humphrey J - No Known Affiliation |
| To: | Dyer J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML060530276 | List: |
| References | |
| TAC MD0041, Y020060034 | |
| Download: ML060470374 (5) | |
Text
Original Due Date: 03/17/2006 Ticket Number: 020060034 Document Date: 02/09/2006 NRR Received Date: 02/14/2006 From:
TACs:
MD0041 John Humphrey To:
- YELLOW ***
J.E. Dyer For Signature of:
Routing:
==
Description:==
Mark I BWR Delta P Method That the NRC Has Successfully Used to Regulate Operating Plant Safety Assigned To:
Contact:
HANEY, CATHERINE Special Instructions:
YT - bo R.L feC..~-1S 25967 Mar Vista Court Los Gatos, CA 95033 January 16, 2006 Mr. James Dyer, Director Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Congratulations on the 30th Anniversary of the Mark I BWR Delta P Method That the NRC Has Successfully Used to Regulate Operating Plant Safety
Dear Mr. Dyer,
I am writing this letter to offer my congratulations to the NRC on the upcoming 2/14/2006 30h Anniversary of the adoption of Mark I BWR Drywell Pressurization used to successfully regulate Mark I operating plant safety and to request confirmation of the current status of Delta P use in the operating Mark I BWR plants.
Background
Thirty years ago while working as a Senior engineer at the General Electric Nuclear Energy division on the Mark I containment program, I invented the Drywell Differential Pressure method to dramatically reduce the vent clearing loads on the wetwell for a postulate DBA. In late 1975 subscale tests at GE had discovered that the downward force on the wetwell was approximately equal to the pressure at the vent exit when the vents cleared (and the pressurized drywell air first entered the torus wetwell) applied over the projected area of the wetwell.
Following this downward load, the resulting expanding air bubble accelerated the suppression pool upward, compressed the wetwell air volume and led to a transient upward load on the wetwell.
When the magnitude of these potential DBA pool swell loads became understood and analyzed for the Mark I plants, I recall Vermont Yankee voluntarily shut down on 1/26/76 and other plants were considering similar actions.
I had joined GE two years earlier from aerospace. Whereas the standard approach in power plant design is to design for existing loads, my training in aerospace was to modify the phenomena to reduce the loads. This mindset led me to search for ways to mitigate the postulated Mark I DBA pool swell event. The simplest way to reduce vent clearing pressure would be to reduce the water leg in the downcomers. However reducing the length of the downcomers could also affect their pressure suppression function. At this point the "blowing bubbles with a straw" phenomena occurred to me. Simply creating a small positive differential pressure between the drywell and the wetwell would maintain a reduced water ]leg in the downcomers which should result in a significantly earlier and lower pressure vent clearing with a substantial mitigation of the pool swell event.
I presented my proposed "phenomena fix" and my fellow GE engineers running the subscale test agree to conduct one "unofficial" test at the end of their current test series. That test with full delta P (zero water leg inside the downcomer) showed a 4:1 reduction in wetwell downward load
and very substantial reduction in upward load. The technical understanding that flowed from that single test and subsequent confirmatory delta P tests allowed GE to document to the NRC that Delta P operation could assure safe short term operation of the Mark I plants. As recorded in the following article from the San Jose Mercury News of Feb 14, 1976, Vermont Yankee was allowed to restart under delta P operation.
6A Sat., Feb. 14, 1976. t 4hBt~ !
d{tE tBll r11 19AFETY MOVE OKAYED
§>^4 Yankee A-Plant
.Fires Ip Again AVERNON, Vt. (AP) -
The Vermont Yankee Nudle-ariPower Corp. plant began firing up its reactor Fri-do. afternoon, after being idled for more than two icks by safety problems.
ihe 540-megawatt reactor was started immediate-lyDafter the federal Nuclear Regulatory Commission abnzounced it had approved the company's plans to bdlter a safety system that had been questioned.
sWe're starting back on immediately. We'll be back oftine in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and at full power in two days,"
s#. Vermont Yankee spokesman Lawrence Keyes.
Be commission approved Vermont Yankee's pro-pisRl to instaU steel supports around a large dough-.,.
niihshaped chamber that's designed to contain radio-apfve steam in an emergency.
- x addition, the commission said the plant could op-er;te for 30 days while the supports were being erect-edifby simply changing the air pressure in its reactor.
Tfi pressure change was proposed by Vermont Yan-kiW as a temporary method of eliminating the poten-ti safety hazards in the chamber.
I recall that the NRC subsequently directed the Mark I plants to institute a 1 psi drywell differential pressure as a condition of continued short term plant operation.
As a result, I believe of my Delta P invention, I was appointed Task Manager of the GE's new %
Scale Mark I pressure suppression test facility (QSTF). For the next several years I first directed the design and construction of this facility. The picture below shows the fully constructed QSTF
prior to testing with the key program personnel from GE (I'm second row on the right), Nuclear Services and Aerotherm. I then had the opportunity to direct a comprehensive series of both standard plant and plant unique tests that following NRC review confirmed: 1) that this large scale test facility generated loads defendable for full scale plant analysis and 2) that the plant unique loads (mostly mitigated using positive drywell differential pressurization) provided adequate operating margins.
Now 30 years later the NRC is to be congratulated on this successful regulatory action that restored plant operating margins and enabled these plants to continue providing America's energy needs.
REQUEST: I am now 60 and partially retired. As I look back on my career, I am proud of my contributions to the continued safe operation of the Mark I BWR plants through the invention of the delta P method and its verification in the Mark I QSTF. I asked some of my friends who still work in the nuclear industry how many of the Mark I plants that adopted delta P in 1976 were still operating under delta P. They understood that all but Millstone were still operating and that all those adopting delta P were still using thai operating method.
For my career accomplishment records I am requesting the NRC to confirm for me the list of Mark I BWR plants that are still operating with drywell differential pressure.
Thank you again for the NRC's role in assuring safe nuclear power to meet America's energy needs and in advance for providing me this requested information.
Sincerely, 2 4 John M. Humphrey CC: Mr. Bruce Boger, Associate Director of Operating Reactor Oversight and Licensing By separate original