ML19263D276
| ML19263D276 | |
| Person / Time | |
|---|---|
| Issue date: | 03/14/1979 |
| From: | Snaider R Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-12, REF-GTECI-EQ, TASK-A-12, TASK-OR NUDOCS 7903270241 | |
| Download: ML19263D276 (3) | |
Text
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NUCLEAR REGULATORY COMM!sslON jj WASHINGTON, C. C. 20555
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March-14, 1979 MEMORANDUM FOR: Darrell G. Eisenhut, Deputy Director Division of Operating Reactors v.
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Don K. Davis, Chief, Systematic Evaluation Program Branch, DOR FROM:
Rich:;rd P. Snaider, Systematic Evaluation Program Branch, DOR
SUBJECT:
STATUS OF A-12 NEUTRON SHIELD TANV, NDTT SHIFT INVESTIGATION '40 rCCOMMENDATION FOR FURTHER EFFORT By letter dated April 24,197E, OIE transferred lead responsibility to D0R foa 2n issue reported inder 10 CFR 21 by Virginia Electric Power Compe,y (VEPCO). VEPCO reported that its architect-engineer, Stone and Webster Corporation (S&W), utilizing reactor neutron flux data supplied by the reactor vendor, Babcock and Wilcox Company (B&W), nad predicted an abnormally high NDTT shift for the neutron.
shield tank, which is water filled and acts as the reactor vessel support. The magnitude of the NDTT shiff, was such that the fracture toughness of the tank material could be in question after several years unless n.eans of mitiga':ing this eff t ct (e.g. ancillary heating) were employed. The derivatian of the exc4ssive NDTT shift was based in part on the use of damage functions for neutrons of energy less than 1 mev.
At an NRC/NRL/S&W meeting st.bsequent to the transfer of lead responsibility, two major p oblems anticipated in the resolution of this issue were discussed. The first involved verification of the reactor flux spectrum at the shield tank.
Brookhaven National Laboratory (BNL) assistance was utilized under an existing technical assistance contract. However, while BNL was in the process of verifying the information from B&W whicn had led S&W to its conclusions, VEPCO notified us that the original data had been based on the wrong core geometry and that they had contracted B&W to perform an updated study based on the correct geometry. The revised results were forwarded by VEPCO letter dated January 10, 1979, (copy of cover letter attached).
N0te that VEPC0 still believes the data to be conservative for shield tank damage calculations and has requested that we delay until final fuel calculations are perfomed prior to operation.
Meanwhile the North Anna 3/4 Project Manager has informed me that VEPC0 has requested an eight year cc,.atruction permit extension. Such a delay in resolving any generic aspects of the transfer of lead responsibility would be excessive.
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Darrell G. Eisenhut March 14, 1979 The second problem is that of acceptance of the low energy neutron damage function calculations used by S&W in the analysis. As you are aware, this subject has wider importance than that of the shield tank materials alone. However, C. Serpan of Research has a program at Oak Ridge National Laboratory to determine the actual damage caused by low energy neutrons. Engineering Branch has initiated a user's request to ensure that the program is tailored to provide the information we require to assess this potential problem.
Meanwhile, I would suggest that, because of the status of Generic Technical Activity A-12 (near generic completion with the exception of lamellar tearing), this issue be taken out of the A-12 program and be given appropriately high priority for at least the initial determination of the existence (or non-existence) of an important safety concern.
I request that you meet with me and the following personnel at the earliest opportunity:
Engineering Branch.
Reactor Safety Branch W. Hazelton, R. Johnson, S. Weiss, B. Morris V. Noonan Standards Research N. Randall C. Serpan 4--
Richaro P. Sn er Systematic Evaluation Program Branch Division of Operating Reactors
Attachment:
As stated
VzsorntA Ex.zcTaze Axo Powra COMPANT Racax ono.Vraorwr4 20200 MACWQ January 10, 1979 Mr. Harold R. Denton, Director Serial No. 002 Office of Nuclear Reactor Regulation LQA/RMN: jab Attn: Mr. O. D. Parr, Chief Light Water Reactors Branch No. 3 Docket Nos.
50-404 Division of Project Management 50-405 U. S. Nuclear Regulatory Comission Washington, DC 20555
Dear Mr. Denton:
In response to a telephone request by Mr. R. P. Snaider, a member of your staff, we have attached to this letter a tabulation of the neutron flux levels at the inside surface of the neutron shield tank. These flux levels are based on the following general assumptient:
Power Level - 2763 MWt Power Distribution - Cycle 3 T=150 days, 6 x 6 PDQ model Model 0 ANISN (Slab)
Cross Section Data - DLC-47/ BUGLE Babcock & Wilcox recomends an axial peaking factor of 1.15, an
' azimuthal peaking factor of 1.7 and an uncertainty factor of 1.25.
We believe that these flux levels are still too conservative and are inappropriate for computing damage to the neutron shield tank.
Mere realistic data will be available when detailed fuel cycle calcu-lations are made prior to operation, yrytrulyyours,
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- 5.'C. Brown, Jr.
Senior Vice President-Power Station Engineering and Construction Attachment
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NOTE TO: Accessions Unit 3//6/79 Room 050 Date:
Phillips Building FR0tt:
R P SJ All)FA TASK N6 NAGER, A -/2
$5542) Ext 284I4 RE:
NRR Generic Technical Issues (GEN TEC IS)
Please file the attached docunent(s) in Central Files and the Pu Room.
It should be filed under Generic Task No. A-M.
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