(2) Here's Dave Lochbaum's analysis of the under ground cable issue and
also his answer to me about whether the cooling tower collapse at Vermont
Yankee could happen at Hope Creek:
FW: Hope Creek Generating Station and Salem Nuclear Generating Station, Unit
Nos. 1 and 2 - Closeout of Generic Letter 2007-01 "Inaccessible or
Underground Power Cable Failures That Disable Accident Mitigation Systems or
Cause Plant Transients" (TAC Nos. -
There's a two-fold approach to this problem. The first part involves
increased awareness that installation configurations can cause
underground cabling to deteriorate faster than normal.
But since increased awareness is a catchy phrase but not a
guarantee, the second part involves testing and/or monitoring of
buried cabling. With cables in service, they can monitor the voltage
drop from one end of the cable to the other end. If the voltage drop
increases, it suggests the cable insulation is degrading. With the
cables not in service, they can run a test called "meggaring" that
measures how well the cable carries current.
I put most weight on this second part of the solution. If they are
testing enough of the cables often enough, they have reasonable
assurance that the deterioration is detected before it gets too bad.
It's nearly impossible to find out how many cables were
affected/checked. PSEG sent in a letter to NRC saying they've got it
under control. NRC inspectors can audit any and all records at the site
to confirm or refute that notion. But since PSEG didn't submit those
records, they are not publicly available.
VY's cooling towers are made of wood. Hope Creek has a concrete tower.
While more resistant to aging, concrete towers can also fall down if
load-bearing members degrade too much.
However, there's a big difference in the function of the towers at VY
and Hope Creek. Part of one of the towers at VY is needed to cool water
after an accident that is then used to cool the emergency diesel
generators, control room air chillers, and other emergency equipment.
The White River is not as large as the Delaware River and the pumps and
piping used at VY to fetch water from the White River is not designed to
survive earthquakes, etc. So, if the safety part of the VY cooling tower
collapses, the plant is without a reliable means of cooling vital
equipment. The cooling tower at Hope Creek only serves to assist the
plant generate electricity. If it were to collapse, making electricity
is impacted but none of the safety systems and the systems needed to
cool the safety systems are affected.
If I were a betting soul, I'd bet that the turbine electro-hydraulic
control (EHC) system, the generator stator and bus duct cooling systems,
and main transformers are likely to be Hope Creek's version of the
Vermont Yankee cooling towers.
The turbine EHC system uses oil pressure to control the valves that
admit steam to the turbine. With Hope Creek recently receiving a power
uprate, more steam flows to the turbine. More steam flow can cause
higher vibrations. Higher vibrations can cause fittings in the oil lines
to come loose and leak oil, allowing the turbine valves to move.
The generator stator cooling system removes the heat from the shell
around the generator rotor. With the recent power uprate, the generator
makes more electricity, creating more heat to be removed. The generator
bus duct cooling system is an air conditioning system for the three
electrical phases running from the main generator to the transformers.
With the recent power uprate, these phases carry more electricity and
dissipate more heat. The generator bus duct cooling system has to have
increased heat removal ability, otherwise electrical equipment runs
hotter and ages more quickly.
The main transformers are non-safety-related equipment - meaning they
don't get tested and inspected as often as the emergency diesel
generators. Transformers across the country are wearing out and
literally blowing up. One of the transformers at Diablo Canyon blew up
this past July, sending shrapnel into the adjacent office building.
Luckily, it happened around midnight when the office was empty,
otherwise people could have been killed.